Showing papers in "Animal Science in 2002"

Independent effects of dietary linoleic and linolenic fatty acids on the conjugated linoleic acid content of cows’ milk

Abstract: It may be desirable to increase the level of conjugated linoleic acid (CLA) in milk as a health benefit in human nutrition. The purpose of this work was to separate the effects of linoleic and linolenic acids on CLA production in dairy cows and to determine to what extent endogenous synthesis contributes to cis-9, trans-11 CLA concentration in milk fat. Eight lactating cows and four non-lactating duodenal fistulated cows were used in a 4 ✕ 4 Latin-square design. All cows received a basal diet of grass silage that was supplemented with one of four concentrates, which were designed to differ in their linoleic and linolenic acid contents. The oil components of the concentrates were produced from mixtures of olive, linseed, rape, soya and sunflower oils to produce the four treatments: low linoleic/ low linolenic acid (LL), low linoleic/high linolenic acid (LH), high linoleic/low linolenic acid (HL) and high linoleic/ high linolenic acid (HH). Milk cis-9, trans-11 CLA contents were 0·8, 0·9, 0·9 and 1·1 g/100 g fatty acid methyl esters (P < 0·05) and yields were 5, 7, 7 and 8 g/day (P < 0·05) for the LL, LH, HL and HH treatments, respectively. The yields of trans-C18:1 fatty acids in milk were 19, 22, 21 and 23 g/day (P < 0·05), respectively. Taking the data for the cis-9, trans-11 CLA content and flow of duodenal fluid from the fistulated cows and representing this in terms of dietary intake by the lactating animals, the amounts of cis-9, trans-11 CLA produced in the rumen were calculated to be 0·8, 0·9, 1·2 and 1·1 g/day (P < 0·05) and for trans-C18:1 fatty acids 58, 58, 66 and 69 g/day (P < 0·05). Increasing linoleic and/or linolenic acids in the diet can increase the cis-9, trans-11 CLA content of cows’ milk. Only diets high in linoleic acid increased cis-9, trans-11 CLA production in the rumen. On all four diets, more than 80% of cis-9, trans-11 CLA in milk was produced endogenously by Δ9-desaturase from trans-11 C18:1 in the mammary gland. Cows on the same diet have different milk fat cis-9, trans-11 CLA concentrations that may be partially explained by differences in Δ9-desaturase activity between cows. Increasing the activity of Δ9-desaturase in the mammary gland may offer greater potential for enhancing the cis-9, trans-11 CLA content of milk fat than increasing cis-9, trans-11 CLA production in the rumen.

Influence of dietary fibre on digestive utilization and rate of passage in growing pigs, finishing pigs and adult sows

Abstract: Four experimental diets differing in the level and the origin of dietary fibre (DF) were studied: a control, low DF diet (diet C, 100 g total dietary fibre (TDF) per kg dry matter (DM)) and three fibre-rich diets (200 g TDF per kg DM) which corresponded to a combination of diet C and maize bran (diet MB), or wheat bran (diet WB), or sugar-beet pulp (diet SBP). During two successive experimental periods, each diet was offered to five pigs at a growing stage (35 kg body weight (BW)) and at a finishing stage (75 kg BW). In addition, four adult ovariectomized sows received successively one of the four diets according to a 4 ✕ 4 Latin-square design. Digestive utilization of energy and nutrients of diets and rate of passage parameters were determined using a pulse dose of ytterbium oxide followed by total faecal collection. Faecal marker excretion was quantified using an age-dependent, one-compartment model, from which the mean retention time in the gastrointestinal tract of pigs (MRT) was obtained. The digestibility of dietary energy and nutrients, especially the DF fraction, increased with the increase in BW from growing to finishing pigs (P < 0.01) and was still higher in adult sows; the difference between pig stages was more pronounced for diet MB. At each stage, the digestibility of energy or nutrients was lower (P < 0.01) for diets MB or WB than for diet SBP. Accordingly, the energy and DF digestibility of sugar-beet pulp was higher and increased much less with BW. The MRT was shorter for diets MB and WB in growing pigs and in sows. Sows had a longer MRT (81 h) than finishing pigs (37 h) and growing pigs (33 h); however, MRT was highly variable between sows. It is concluded that the degree to which different types of DF are digested depends, in part, on the botanical origin, and it may be improved by a longer MRT in the gastrointestinal tract of pigs. Some fibrous foodstuffs (such as maize-by products) will benefit more from a longer MRT than others.

Rumen metabolism and nitrogen flow to the small intestine in steers offered Lolium perenne containing different levels of water-soluble carbohydrate

Abstract: Lee, M. R. F., Harris, L. J., Moorby, J. M., Humphreys, M. O., Theodorou, M. K., MacRae, J. C., Scollan, N. D. (2002). Rumen metabolism and nitrogen flow to the small intestine in steers offered forage diets bred for elevated levels of water-soluble carbohydrates. Animal Science, 74, 587-596. Sponsorship: LINK Sustainable Livestock Production - MAFF/Milk Development Council / Meat and Livestock Commission/ Germinal Holdings Ltd.

Compensatory growth response in pigs, muscle protein turn-over and meat texture: effects of restriction/realimentation period

Abstract: The present experiment was designed to evaluate the effect of different time spans of ad libitum feeding of pigs prior to slaughter after a period of restricted feeding on performance and texture characteristics of the meat. Te n litters of five pigs (Duroc ✕ Landrace ✕ Large White crosses) were allocated to five feeding treatments (AA, R28A42, R43A27, R52A18 and R60A10) at the age of 70 days. AA-pigs were given ad libitum a concentrate diet from day 70 to slaughter at day 140 (approx. 100 kg live weight). R28A42, R43A27, R52A18 and R60A10 pigs were given food at a restricted level (0·6 of ad libitum) for 28, 43, 52 and 60 days, respectively, followed by ad libitum feeding for 42, 27, 18 and 10 days, respectively, until slaughter at day 140. All pigs that had been given food at a restricted level for a period (R28A42, R43A27, R52A18 and R60A10) showed a compensatory growth response in the subsequent ad libitum period. However, only pigs on ad libitum for a minimum of 27 days prior to slaughter (R28A42 and R43A27) had carcass weights and muscle mass similar to that of the control pigs (AA) at slaughter. The restricted feeding increased meat proportion, whereas the feeding strategies had no effect on technological meat quality traits (pH24, drip loss and CIE-colour traits: L*, a* and b*). During compensatory growth, protein turn-over was increased and positively related to the length of the ad libitum period as indicated by the concentration of elongation factor-2 (eEF-2) (P < 0·10), the activity of µ-calpain (P < 0·01) and the myofibrillar fragmentation index (MFI) 1 day post mortem in m. longissimus dorsi (P < 0·08) and the solubility of collagen (P < 0·01). Although not significant, the shear force at day 1 followed the same pattern of improvement as the MFI. The concentration of eEF-2 increased at a faster rate following transition to ad libitum feeding than did the activity of µ-calpain. This suggests that muscle protein synthesis increases at a faster rate after change to ad libitum feeding and reaches the same level as in the control pigs (AA) before muscle protein degradation. This time lag between the increase in protein synthesis and degradation could explain the compensatory growth response and it also suggests that in order to use the compensatory growth mechanism to improve tenderness, the optimal time of slaughter may not coincide with the period of highest growth rates, but may occur at a later stage, when muscle protein degradation is maximal. For pigs slaughtered at 100 kg live weight, we expect muscle protein degradation to be maximal some time beyond 42 days of ad libitum feeding prior to slaughter.

Relationship between litter size and perinatal and pre-weaning survival in pigs

Abstract: The objective of this study was to analyse the relationship between direct and maternal genetic effects on litter size and piglet survival. The analyses were performed on records from 26 564 Landrace litters and 15 103 Yorkshire litters from first parity dams in Finnish herds. The trivariate model fitted total number of piglets born, proportion alive at birth and proportion survived from birth until 3 weeks as traits of the litter. The model included direct genetic and maternal genetic effects for all traits. In Landrace pigs, maternal heritabilities were estimated to be 0·11 for total number born, 0·06 for proportion alive at birth, and 0·08 for proportion survived from birth until 3 weeks. The corresponding estimates for the Yorkshire breed were 0·14, 0·06 and 0·01. All heritability estimates of direct effects were below 0·05. In the Landrace breed, there was a negative correlation of -0·39 between maternal genetic effects on total number born and maternal genetic effects on proportion survived from birth until 3 weeks and a negative correlation of -0·41 between direct and maternal genetic effects on proportion survived from birth until 3 weeks. These correlations were not significant in the Yorkshire breed. The results show that selection for number born in total alone will lead to a deterioration in the maternal ability of sows. Selection for pre-weaning survival could be achieved by selecting on direct and maternal components jointly.

A genetic evaluation of growth in sheep using random regression techniques

Abstract: Repeated measures of live weight in growing animals are used to describe the path by which they travel from birth to maturity. A family of growth functions-the Gompertz is one in particular-has been used successfully to describe this journey with relatively few parameters (most importantly mature size and a rate parameter). However, using these functions to differentiate the genetic merit of individual animals to grow is problematic since the estimates of these parameters are highly correlated and are obtained with varying precision among animals. An alternative is random regression (RR) methodology. It allows environmental effects specific to the time of recording to be accounted for and can accommodate genetic differences in the shape of each animal’s growth curve. At present, though, only linear models (polynomials) can pragmatically be fitted with RR. This may be limiting since a priori beliefs about the appropriate form of a growth function, such as the non-linear Gompertz equation, cannot be accommodated. This paper describes the application of RR techniques to describe growth on a population of Suffolk sheep and compares the genetic evaluation predicted from a RR model with that obtained from a more traditional method based on a Gompertz form. The RR model chosen as providing the best fit ( P < 0·01) included additive genetic and permanent environmental (between repeat records of an individual) effects fitted to a fifth order polynomial, and dam effects fitted to a third order polynomial. Measurement error was modelled as six classes. The heritability varied at different points along the growth trajectory (from 0·09 at 15 days to 0·33 at 150 days), suggesting that live weight early in a lamb’s life is a different trait to live weight later in life. There was genetic variation in the growth curves of individual animals, which was accounted for by fitting a RR model. Breeding values obtained by RR and a Gompertz approach were moderately to highly correlated (0·81 at 56 days, 0·91 at 150 days). If breeding value for live weight at 150 days of age were the selection criterion, similar individuals would be chosen with both methodologies. The ‘better’ properties and greater flexibility of the RR approach are discussed.

Feeding strategy for young rabbits around weaning: a review of digestive capacity and nutritional needs

Abstract: The digestive maturation of the young rabbit is reviewed. It indicates that their nutritional needs and those of lactating females are antagonistic in many aspects. Energy requirements of lactating females are very high, whilst a low starch, high fibre diet around weaning improves the health of the young after weaning. To solve this problem, several feeding and management strategies are presented and discussed. If weaning occurs between 28 and 35 days of age, feeding the young with a specific diet, different from the female’s, seems an effective solution. Otherwise, it is necessary to find a compromise between the needs of the litter and of the doe. Early weaning (< 26 days) could be also a promising way to provide adequate feeding for the young as soon as they begin to eat solid food.

Responses to selection for lean growth in sheep

Abstract: This paper reports the selection responses achieved, and related results, following 9 years of index selection for lean growth in Suffolk sheep. The breeding goal of the index used comprised carcass lean weight and carcass fat weight at a constant age, with relative economic values of + 3 and ‐1 per kg. The selection criteria were live weight (LWT), ultrasonic fat depth (UFD) and ultrasonic muscle depth (UMD) adjusted to a constant age of 150 days. By year 9, responses in LWT, UFD and UMD in both sexes, as judged by the divergence between selection and control line performance, amounted to 4·88 kg, ‐1·1 mm and 2·8 mm respectively ; these responses are between 7 and 15% of the overall means of the traits concerned. Although selection was originally on index scores based on phenotypic records, the retrospective analyses reported here used the mixed model applications of residual maximum likelihood to estimate parameters and best linear unbiased prediction to predict breeding values. The statistical model comprised fixed effects plus random effects accounting for direct additive, maternal additive and temporary environmental variation. Estimated genetic trends obtained by regressing estimated breeding values on year of birth were similar to annual responses estimated by comparing selection and control line means. Estimates of direct heritabilities were 0·054, 0·177, 0·286, 0·561 and 0·410 for birth weight (BWT), weaning weight (WWT), LWT, UFD and UMD respectively. Corresponding estimates of maternal heritabilities were 0·287, 0·205, 0·160, 0·083 and 0·164. Phenotypic correlations between all pairs of traits were positive and usually moderately high. There were low negative direct additive correlations between BWT and WWT, and between BWT and LWT, but higher positive maternal additive correlations between all other pairs of weight traits.

A description of the growth of sheep and its genetic analysis.

Abstract: The Gompertz is one of a family of growth functions that, when the environment (e.g. food, housing) is nonlimiting, provides a useful description of growth as a comparatively simple, single equation. It has three parameters of which the important ones are mature size, A , and the rate parameter, B . Estimates of A and B , however, are highly correlated and defining their separate values for individual animals is problematic. This problem was explored using five methods for estimating the parameters, or transformations of them, to describe the growth of two genotypes of Suffolk sheep kept under non-limiting conditions. One genotype was under selection for high lean growth rate and the other was its control. Live weights that were collected at least fortnightly from near birth to 150 days of age over a 9-year period on 1934 lambs were used. The Gompertz form adequately described the growth of the great majority of the lambs evaluated. When considering A and B as a lumped parameter, Z = A·B , and fitting Z , B and an initial condition (a transformed birth weight) as the parameters, the problems in estimation were substantially overcome as shown by a low correlation of Z with estimates of B both within and across animals. Usefully Z has a biological interpretation in that Z /e is the maximum daily growth rate. Since the Gompertz form adequately described growth in these sheep, the extent of genetic co-variation for the growth parameters values ( A, B, Z ) was estimated to determine if they were amenable to selection. A weighted univariate animal model was fitted. Mature size, A , and the rate parameter, B , were moderately heritable (0·37 (s.e. 0·04) and 0·38 (s.e. 0·05), respectively) as was live weight at 150 days of age (0·31 (s.e. 0·06)). However there was a substantial negative genetic relationship between A and B (‐0·48). Z was highly heritable (0·72 (s.e. 0·05)). After 9 years of selection, the genotype selected for high lean growth rate was heavier ( P < 0·001) at 150 days of age (5·2 kg) and at maturity (6·6 kg), with a maximum growth rate ( Z /e) that was 1·12 times that of the control. Our lumped parameter Z , in effect a rate parameter scaled for mature size, avoided problems in estimating A and B and, in so doing, offers a general and robust description of lamb growth amenable to selection.

Ovarian follicular dynamics and endocrine profiles in Polwarth ewes with high and low body condition.

Abstract: In this investigation we tested the hypothesis that static body condition (BC) of the ewe affects oestradiol and FSH with implications for subsequent follicular growth and turn-over. Sixteen Polwarth ewes were selected from a flock according to their BC score (scale: 1 emaciated; 5 obese). High BC (HBC) ewes (no. = 8) had a BC score of 4·1 (s.e. 0·1) and low BC (LBC) ewes (no. = 8) had a BC score of 1·9 (s.e. 0·1). Daily ultrasound examinations were performed and blood samples for progesterone, oestradiol and follicle-stimulating hormone (FSH) determination were collected. All HBC ewes (8/8) exhibited three waves of follicular development, while four LBC ewes (4/8) had two waves and the other four (4/8) had three waves of follicular development (P ≤ 0·05) during the interovulatory period. Overall, the emergences of 33 out of 44 follicular waves were preceded by significant increases in FSH concentrations. Maximum FSH concentrations were detected 0·9 ± 0·2 days before wave emergence. Oestradiol concentrations increased significantly during the growing phase in 38 out of 44 large follicles. A negative correlation between oestradiol and FSH was observed in HBC ewes. A similar inhibitory effect of oestradiol on FSH was observed in LBC ewes, irrespective of whether they developed two or three follicular waves. However, a longer period with high FSH was needed to promote the emergence of the second follicular wave in two-wave LBC ewes. Four HBC ewes had twin ovulations but no LBC ewes did (P ≤ 0·05). In HBC ewes, the follicular phase was characterized by lower oestradiol (6·5 (s.e. 1·0) pmol/l) but higher mean FSH concentrations (2·4 (s.e.0·4) μg/l) than in LBC ewes (8·9 (s.e. 1·2) pmol/l and 2·0 (s.e. 0·3) μg/l, respectively; P ≤ 0·05). The present results suggest that BC influences the pattern of follicular dynamics through changes in the endocrine milieu. Higher FSH concentrations during the follicular phase in HBC ewes, which allowed an extended period of follicular recruitment from a significantly larger pool of small antral follicles could explain the higher ovulation rate observed in this group.

Visible/near infrared reflectance spectroscopy for predicting composition and tracing system of production of beef muscle

Abstract: Muscle chemical analysis and muscle identification both were attempted by using visible and near infrared reflectance spectroscopy (NIRS). Seventy-eight beef muscles (m. longissimus dorsi) from Hereford cattle were used. The samples were scanned in a NIRS monochromator instrument (NIRSystems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced muscle presentation to the instrument were explored. Predictive equations were made using ISI software (Infrasoft International, Port Matilda, PA, USA) and muscle identification was performed by Principal Component Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA). The coefficient of determination in calibration (R-CAL(2)) and standard error in cross validation (SECV) for the intact sample presentation were 0.09 (SECV. 15.6), 0.89 (SECV. 46.9), 0.48 (SECV. 23.9) for moisture (M), fat and crude protein (CP) on g/kg fresh weight basis respectively. R-CAL(2) and SECV for minced sample presentation were 0.41 (SECV: 16.1), 0.92 (SECV. 43.4), 0.71 (SECV. 20.5) for M, fat and CP on g/kg fresh weight basis respectively. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

The use of X-ray computer tomography for measuring the muscularity of live sheep

Abstract: Jones, H. E., Lewis, R. M., Young, M. J., Wolf, B. T. (2002). The use of X-ray computer tomography for measuring the muscularity of live sheep. Animal Science, 75, (3), 387-399 Sponsorship: DEFRA; SEERAD; BBSRC

Effect of growth rate on tenderness development and final tenderness of meat from Friesian calves

Abstract: The present study was conducted to determine the effect of growth rate of calves on the activity of the calpain system post mortem, post mortem desmin degradation, myofibrillar fragmentation index and meat tenderness of m. longissimus lumborum (LL) and m. supraspinatus (SS). Twenty-four Friesian heifer calves were allocated to two treatment groups: MM and HH. The MM calves were given food to achieve a moderate growth rate (678 g/day from 5 days of age to 90 kg body weight (BW) (period I) and 770 g/day from 90 kg BW to slaughter at 250 kg BW (period II)) and the HH calves were given food to achieve a high growth rate (period I: 895 g/day and period II: 1204 g/day). The myofibril fragmentation index (MFI), desmin degradation and the activity of µ-calpain, m-calpain and calpastatin were measured in LL and SS at slaughter, and 1 and 7 days post mortem. Shear force was measured in LL and SS after 1 and 7 days of ageing and a sensory panel evaluated the eating quality of the loin aged 7 days. MFI (P < 0·01) and tenderness (P < 0·01) were higher and shear force was lower (P < 0·001) in meat from HH calves compared with meat from MM calves. However, growth rate did not affect the activity of µ-calpain, m-calpain or calpastatin or the degradation pattern of desmin at any time post mortem. Besides growth rate and MFI at day 7 post mortem, which both correlated positively with meat tenderness (P < 0·001 and P < 0·01, respectively), fibre type traits and DNA or RNA concentrations were not generally related to final tenderness. Thus, it was concluded that increased growth rate of calves before slaughter increased the ease of fragmentation (MFI) of the meat and improved the tenderness but these findings could not be related to any changes in the activity of the calpain system.

The effect of a neighbouring conspecific versus the use of a mirror for the control of stereotypic weaving behaviour in the stabled horse

Abstract: Weaving behaviour involves the repetitive lateral swaying of the head, neck, forequarters and sometimes hindquarters of the horse and is generally believed to be indicative of poor welfare. The behaviour of six known weavers was recorded three times a day for 5 days in each of three different stable designs. These were a conventional loose-box, a conventional loose-box with a 1 m2 acrylic mirror and a conventional loose-box in which there was a grilled 1 m2 side window separating the resident horse from a non-weaving conspecific in an adjacent stable. Weaving and other stereotypic behaviours were significantly higher in the unmodified stable and during the late afternoon observation period. There was no significant difference in the amount of stereotypic behaviour recorded in the two modified stables. Significant differences in the behaviour patterns and location of horses during the study suggest that activity engaging with either a visual image of a horse or a hay net is associated with a reduction in weaving and other repetitive activities in the stabled horse.

Effect of non-starch polysaccharides on production and absorption of indolic compounds in entire male pigs

Abstract: In order to study the effect of feeding non-starch polysaccharides (NSP) on the production and absorption of the malodorous compounds skatole and indole, eighteen male pigs, representing nine littermate groups, were used. One pig from each litter was assigned to either a low-NSP diet (87 g/kg of NSP) or a high-NSP diet (160 g/kg of NSP). Faecal samples and blood samples from vena jugularis were collected during a three-day period. The production of indolic compounds in different sections of the gastro-intestinal tract of six littermate groups was measured at slaughter (after 1 month on the diets). To investigate the absorption of indole and skatole, three catheterized pigs, acting as their own control (2 weeks on each diet) were used. Parallel determinations in portal blood, peripheral blood and in faeces of skatole and indole were conducted. Faecal, intestinal and blood samples were analysed for indolic compounds by high-performance liquid chromatography (HPLC). The production of indole and skatole in the proximal and distal part of the hind gut, respectively, was significantly reduced in pigs given the high-NSP diet. Similarly, both blood and faecal samples revealed that dietary NSP-inclusion reduced skatole concentration, whereas a dietary effect of NSP on the indole concentration was reflected in blood samples only. The absorption of skatole and indole was significantly lower in pigs given the high-NSP diet compared with those offered the low-NSP diet. The skatole concentrations in blood and faeces were highly correlated when measured within the individual animal, suggesting that a proportional amount of the skatole produced was absorbed. In contrast, only weak correlations were demonstrated when determined between animals. This emphasizes the great impact that individual hepatic clearance rate would have on the level of skatole in backfat, and consequently the importance of applying cross-over designs, when studying the absorption of indolic compounds.

Effect of high ambient temperature on protein and lipid deposition and energy utilization in growing pigs

Abstract: The effects of high ambient temperature (T) on protein (PD) and lipid deposition (LD) and energy utilization were studied on 36 Pietrain ✕ (Landrace ✕ Large White) barrows according to a factorial design including two temperatures (23oC for thermoneutrality and 30oC for the high temperature) and four feeding levels. One feeding level corresponded to the voluntary food intake (VFI) at each temperature. Expressed as proportion of VFI at 23oC, the actual feeding levels were 1·00, 0·90, 0·80, 0·70 at 23oC and 0·80, 0·73, 0·68 and 0·62 at 30oC. Animals were offered a wheat, maize and soya-bean meal based diet containing 187 g crude protein per kg and 0·95 g ileal standardized digestible lysine per MJ of net energy. Pigs were housed individually and had free access to water. The experiment started at 24 kg live weight and animals were slaughtered at 65 kg live weight and their body composition was measured. Slaughter of nine control pigs at the beginning of the experiment allowed calculation of the composition of gain (nutrients and energy) according to the comparative slaughter technique. Reduction of metabolizable energy (ME) intake resulted in a reduced live-weight gain at each T: the maximum gain was 1052 g/ day in pigs offered food ad libitum at 23oC and the minimum (760 g/day) at the lowest intake at 30oC. Visceral organ mass was lower at 30oC than at 23oC but was not affected by feeding level within T. Growth responses were described as polynomial or broken-line functions of ME intake (linear-plateau for PD). Both the slope and the plateau were influenced by T. At 30oC, PDmax (143 g/day) was reached at 22·8 MJ ME per day, while at 23oC PDmax (165 g/day) was reached at 28·4 MJ ME per day. In both cases, PDmax was reached at 0·88 of VFI at this temperature. Also the marginal response of PD to ME intake before the breakpoint was affected by T (5·9 and 4·5 g PD per MJ ME at 23oC and 30oC, respectively). At identical high ME intake (e.g. 0·80 of VFI at 23oC), PD was greater at 23oC than at 30oC. In contrast, severe food restriction reduced PD at thermoneutrality more than an identical food restriction obtained at high ambient T. The results indicate that heat stress has a direct negative effect on PD and affects the partitioning of energy gain between protein and fat deposition.

Comparison of microbial markers (15N and purine bases) and bacterial isolates for the estimation of rumen microbial protein synthesis

Abstract: The first objective of this experiment was to investigate the effect of using different bacterial isolates on the estimation of microbial protein production in semi-continuous fermenters (RUSITEC) given four diets, and to test whether a ‘mixed’ bacterial pellet was representative of the whole bacterial population in the fermenters. A second objective was to compare two different microbial markers (nitrogen-fifteen (15N) and purine bases (PB)). Diets consisted of neutral-detergent fibre from grass hay (10 g/day) and sugar-beet pulp (2 g/day) and 280 mg/day of one of four N forms (isolated soya-bean protein, soya-bean peptides, amino acids blended to profile soya-bean protein and NH4Cl). Two 14-day incubation runs were carried out and in each run each of the four different diets were given to two vessels. On days 12 and 13, total digesta (effluent plus nylon bags residues) was collected for analyses of non-ammonia N, 15N enrichment and PB concentration, and for isolation of total mixed bacterial pellets (TB). On the last day of each incubation run, the system was stopped for isolation of liquid- (LAB) and solid-associated (SAB) bacteria. Microbial N flow was estimated from the 15N enrichment and PB concentration in both total digesta and in the three different bacterial pellets (TB, LAB, and SAB). For all diets, LAB presented a greater (P < 005) 15N enrichment and PB: N ratio than SAB, with TB having an intermediate value. For both markers, the use of LAB produced the lowest (P < 005) estimates of microbial N flow and the use of SAB produced the greatest (P < 005) estimates. The use of TB produced intermediate values with all diets, suggesting that TB consisted of SAB and LAB. For all bacterial pellets, PB produced greater (P 005) values of microbial N flow than 15N. However, there was a positive relationship (r = 0·883; P 0001; no. = 15) between the values of microbial N flow determined with the two markers when TB were used as reference.

The influence of cow genetic merit for milk production on response to level of concentrate supplementation in a grass-based system

Abstract: The objective of this study was to investigate if there is a genotype ✕ feeding system interaction for milk production in Holstein-Friesian dairy cows. For this purpose, 48 high genetic merit (HM) and 48 medium genetic merit (MM) dairy cows, were used in a two (genotypes) ✕ three (levels of concentrate feeding) randomized-block design experiment in three consecutive years. In year 1, all animals were in their first lactation, while in year 2 and year 3, 18 and 12 first lactation cows replaced animals culled at the end of the previous lactation. A total of 66 cows remained in the study in the same feeding system for the 3-year duration of the study. Concentrate feeding levels were 376, 810 and 1540 kg per cow per lactation; these were identified as the LC, MC and HC feeding systems respectively. There was a separate farmlet for each feeding system; farmlets were managed so that pre-grazing and post-grazing herbage height were similar for all three feeding systems. When compared on treatment means there was a significant genotype ✕ feeding system interaction for fat yield, while for mean solid-corrected milk yield the interaction was close to statistical significance (P = 0·07). However, regression coefficients of both milk and protein yield on pedigree index for milk and protein yield were significantly different between the LC and the HC. The interaction between feeding system and the regression of both on pre-experimental milk and protein yield were close to statistical significance (P = 0·08 and P = 0·09 respectively). Outputs of milk, fat, protein and lactose were greater for the HM than the MM cows. Feeding system had a significant effect on milk, fat, protein and lactose yields. There was a significant genotype ✕ feeding system interaction for body condition score (BCS) at the end of lactation; the MM cows had a higher rate of body tissue repletion than the HM cows especially in the HC system. The results suggest that there is a genotype ✕ concentrate feeding level interaction and that feeding systems developed in the past for animals of lower genetic merit may require adaptation if they are to be optimal for higher genetic merit animals.

Ovulation of the first dominant follicle arising after day 21 post partum in suckling beef cows

Abstract: The effects of body condition score (BCS) of 2·0 or 3·0 units at calving (low v. moderate), post-partum energy intake at 0·6 or 1·0 MJ metabolizable energy (ME) per day per kg M0·75 (low v. high) and unrestricted or restricted (once daily) suckling on the ability of cows to ovulate were studied in a 2 ✕ 2 ✕ 2 factorial design with each treatment replicated eight times. Calf isolation and restricted suckling were imposed shortly after selection of the first dominant follicle (DF) to emerge after day 21 post partum. The episodic release of LH (sampled at 15-min intervals for 10 h) was determined 48 h before and 48 h after the day calf isolation and restricted suckling commenced. Additional blood samples were collected weekly for plasma insulin determination. The mean interval from calving to first ovulation was shorter for cows in moderate than low BCS at calving (47·8 v. 57·1 days, s.e.d. = 4·50, P 8 mIU per l). There were indications of interactions between suckling treatment and BCS (P < 0·08), and suckling treatment and plasma insulin concentration (P < 0·06), on LH pulse frequency, which suggested that calf restriction could alleviate the suppressive effects of under nutrition on episodic LH release. Amongst cows suckling once daily, the non-ovulating animals had fewer LH pulses prior to restricted suckling and smaller, slower growing DF, indicating an inability of the DF to respond to increased LH pulse frequency following calf restriction. Cows of moderate BCS, particularly those with moderate to high levels of plasma insulin (³ 5 mIU per l), responded favourably to restricted suckling. In contrast, excessively thin cows with low plasma insulin concentrations (<5 mIU per l), that had most to gain from restricted suckling, responded poorly.

Genetic control of resistance to gastro-intestinal parasites in crossbred cashmere-producing goats: Responses to selection, genetic parameters and relationships with production traits

Abstract: This paper investigates the genetic control of the resistance of goats to nematode parasites, and relationships between resistance and production traits. The data set comprised faecal egg counts (FECs) measured on 830 naturally challenged (predominant species Teladorsagia circumcincta ), crossbred cashmere-producing goats over 5 years (1993-1997) and production traits (fibre traits and live weight) on 3100 goats from the same population in Scotland, over 11 years (1987-1997). Egg counts comprised repeated measurements (4 to 11) taken at 12 to 18 months of age and production traits, i.e. live weight and fibre traits, were measured at approximately 5 months of age. The goats for which FECs were available were subdivided into a line selected for decreased FECs, using the geometric mean FEC across the measurement period and goats not selected on the basis of FECs, acting as controls. The selected line had significantly lower FECs, compared with the control, in 4 out of 5 years (back transformed average proportional difference of 0·23). The heritability of a single FEC measurement (after cubic root transformation) was 0·17 and the heritability of the mean FEC was 0·32. The heritabilities of the fibre traits were moderate to high with the majority in excess of 0·5. The heritability of live weight was 0·22. Genetic correlations between FECs and production traits were slightly positive but not significantly different from zero. Phenotypic and environmental correlations were very close to zero with the environmental correlations always being negative. It is concluded that selection for reduced FEC is possible for goats. Benefits of such selection will be seen when animals are kept for more than 1 year of productive life.

Effect of pre- and post-weaning management on subsequent pig performance to slaughter and carcass quality

Abstract: The aim of this study was to assess the effect of weaning weight and post-weaning diet on the performance of weaned pigs. In experiment 1, 30 litters with more than 10 pigs born alive per litter were selected. At 11 days of age, pigs of average weight for the litter were removed from 15 litters so that eight pigs remained per sow. These litters were given access to creep food (16·5 MJ digestible energy (DE) per kg and 18·7 g/kg lysine). The remaining litters were left complete and were not given creep food. Pigs were weaned at 28 days of age and pairs of pigs (a male and a female littermate of similar weight) were formed from each litter (no. = 54 pairs). Pairs were blocked on the basis of litter origin and weight and assigned at random to one of the following treatments: (1) 10 kg starter diet (16·1 MJ DE per kg and 17·4 g/kg lysine) followed by link diet (15·3 MJ DE per kg and 15·0 g/kg lysine) to 27 days (high dietary regimen; HDR); or (2) 4 kg starter diet, 10 kg link diet and weaner diet to 27 days (low dietary regimen; LDR). Thereafter pigs were given common diets to slaughter at about 95·6 kg live weight. On experiment 2, four pigs (two light and two heavy) were taken from each of 32 litters (no. = 128 pigs; age = 22 days), blocked on sex, litter origin, and weaning weight and within weight category individually assigned at random to two dietary treatments: (1) high density diet (16·1 MJ DE per kg and 17·4 g/kg lysine); and (2) low density diet (15·1 MJ DE per kg and 15·7 g/kg lysine). The duration of the experiment was 26 days. In experiment 1, reducing litter size and creep feeding increased weaning weight by 0·6 kg (P 0·05). This weight advantage at weaning was lost by day 14 post weaning (P > 0·05). From day 0 to day 27 post weaning daily gain was 472 and 427 g/day (s.e.12·8; P 0·05) and food conversion efficiency was 1·26 and 1·36 g/g (s.e. 0·026; P 0·05) for HDR and LDR, respectively. In experiment 2, weaning weight was 7·1 and 5·8 kg (s.e. 0·08; P 0·01) and pig weight at day 26 post weaning was 17·5 and 15·4 kg (s.e.0·23; P 0·01) for heavy and light weight categories, respectively. In the period from day 0 to 26, food intake was 440 and 396 g/day (s.e. 8·0; P 0·01) and daily gain was 389 and 355 g/day (s.e. 8·0; P < i 0·01) for heavy and light weight categories, respectively. Weaning weight was found to be a good determinant of weight at day 26 when terms for litter origin were included (R2 = 0·67; P 0·001 for the high density diet and R2 = 0·77; P 0·001 for the low density diet). It is concluded that weaning weight can be increased by pre-weaning management but that this weight advantage is lost in the early post-weaning period. Where weaning weight was naturally higher the weight advantage was still evident at day 26 post weaning.

Effect of dietary energy source on the performance and perirenal fat thickness evolution of primiparous rabbit does

Abstract: Seventy-four New Zealand ✕ Californian females were used to determine the influence of dietary energy source on the performance and perirenal fat thickness (PFT) change measured by ultrasound of primiparous rabbit does. Three highly concentrated diets were designed with different dietary energy sources: animal fat (diet F), vegetable oil (diet O) and cereal starch (diet S), and does were fertilized by artificial insemination after parturition (AP group) or around weaning (AW group), litters being weaned at 28 days of age. There were no significant differences in live weight and food intake of females throughout gestation, but does given diet S showed a higher increase in their PFT until 28th day than those given diets F and O (P < 0·01), although all females had a similar PFT at parturition. Rabbit does given diets S and O showed a significantly higher dietary energy intake than those given diet F (P < 0·01) during the first weeks of lactation, and similar thereafter until the second parturition. Milk yield and litter weight gain were significantly higher with fat-enriched diets (P < 0·05), and milk composition of rabbit does given diet F showed a higher total solids content (P = 0·01), fat (P < 0·001) and energy (P < 0·01) than milk of does receiving diets O or S. Although pups on fat diets showed a higher weaning weight (P < 0·05), dietary treatment during lactation did not have any effect on the performance of pups during the subsequent growing period. PFT always decreased during lactation for does given fat-enriched diets, while it increased for does given diet S and fertilized after parturition. Live weight of AP does was significantly higher at 21st day of lactation (P < 0·01) and at weaning (P < 0·001), and they showed a significantly lower food intake during the final week of lactation. The period from weaning to parturition was too short for AP does, which showed a decrease of their PFT, while AW does showed an increase of their PFT and a greater number of pups alive at birth (P < 0·05). Due to the lower milk yield of rabbit does fertilized AP, their pups showed a significantly higher solid food intake (P < 0·001), resulting in a similar value for the live weight of pups in both groups at weaning. The earlier promotion of solid food intake significantly affected the food intake of litters during the subsequent growing period, presenting higher values for pups coming from AP does. In conclusion, the addition of dietary fat, especially from animal origin, seems to improve the utilization of energy for milk production, while the use of a high level of starch could decrease the negative balance of primiparous rabbit does during lactation.

Effects of level of concentrate supplementation on grazing behaviour and performance by lactating dairy cows grazing continuously stocked grass swards

Abstract: The effect of level of concentrate supplementation on the grazing behaviour of lactating Holstein-Friesian cows was examined over three periods on continuously stocked grass swards maintained between 7 and 8 cm sward surface height (SSH). A dairy concentrate containing 180 g crude protein per kg fresh weight was offered at 0, 1·2, 2·4, 3·6, 4·8 or 6·0 kg fresh weight per day in two equal feeds during milking. Grazing and ruminating behaviour was recorded automatically over 24 h using sensors to measure jaw movements. Intake rates were calculated by weighing cows before and after approximately 1 h of grazing, retaining the faeces and urine excreted and applying a correction for insensible weight loss. Details of jaw movements were also recorded during these grazing periods. Level of supplementation did not significantly affect short-term intake rate of herbage or total eating time during grazing over the day, which varied between 15 and 21 g organic matter per min and between 530 and 600 min/day respectively. Supplementation had no effect on ruminating behaviour. Increasing the level of supplementation produced a significant linear increase in milk yield. The results show that at the level of grass intake achieved on continuously stocked swards maintained at 7 to 8 cm SSH, daily intake of up to 6 kg concentrates does not significantly affect grazing behaviour or lead to substitution of the grazed herbage.

Genetic parameters of pathogen-specific incidence of clinical mastitis in dairy cows

Abstract: The objective of this study was to estimate heritabilities for and genetic correlations among different pathogen-specific mastitis traits. The traits were unspecific mastitis, which is all mastitis treatments regardless of the causative pathogen as well as mastitis caused by Streptococcus dysgalactiae, Escherichia coli, coagulase-negative staphylococci (CNS), Staphylococcus aureus and Streptococcus uberis. Also groups of pathogens were investigated, Gram-negative v. Gram-positive and contagious v. environmental pathogens. Data from 168 158 Danish Holstein cows calving first time between 1998 and 2006 were used in the analyses. Variances and covariances were estimated using uni- and bivariate threshold models via Gibbs sampling. Posterior means of heritabilities of pathogen-specific mastitis were lower than the heritability of unspecific mastitis, ranging from 0.035 to 0.076 for S. aureus and S. uberis, respectively. The heritabilities of groups of pathogen ranged from 0.053 to 0.087. Genetic correlations among the pathogen-specific mastitis traits ranged from 0.45 to 0.77. These estimates tended to be lowest for bacteria eliciting very different immune responses, which can be considered as the overall pleiotropic effect of genes affecting resistance to a specific pathogen, and highest for bacteria sharing characteristics regarding immune response. The genetic correlations between the groups of pathogens were high, 0.73 and 0.83. Results showed that the pathogen-specific traits used in this study should be considered as different traits. Genetic evaluation for pathogen-specific mastitis resistance may be beneficial despite lower heritabilities than unspecific mastitis because a pathogen-specific mastitis trait is a direct measure of an udder infection, and because the cost of a mastitis case caused by different pathogens has been shown to differ greatly. Sampling bias may be present because there were not pathogen information on all mastitis treatments and because some farms do not record pathogen information. Therefore, improved recording of pathogen information and mastitis treatments in general is critical for a successful genetic evaluation of udder health. Also, economic values have to be specified for each pathogen-specific trait separately.

Genetic variances, trends and mode of inheritance for hip and elbow dysplasia in Finnish dog populations

Abstract: The aims of this study were to assess genetic variances, trends and mode of inheritance for hip and elbow dysplasia in Finnish dog populations. The influence of time-dependent fixed effects in the model when estimating the genetic trends was also studied. Official hip and elbow dysplasia screening records of 42 421 dogs from seven breeds were analysed with REML. To investigate the mode of inheritance of hip and elbow dysplasia, trait distributions, genetic variances and regressions of offspring phenotypes on parental predicted breeding values were studied separately in males and in females. Genetic trends for hip dysplasia between the years 1983 and 1998 were favourable only in the Rottweiler. In elbow dysplasia, the trends were favourable after the year 1992 in all the four breeds studied but the overall changes were small. The reason for this seemed to be negligible selection pressure against these traits. Time-dependent fixed effects in the model had an influence on the estimated genetic trends, resulting either in a more negative or more positive genetic trend compared with the model from which the time-dependent effects were removed. Mitochondrial or sex-linked inheritance did not seem likely in the expression of hip and elbow dysplasia in the populations studied. Regression coefficients of offspring phenotypes on estimated parental breeding values were approximately equal to their expected value in a situation with equal parental contribution. Furthermore, the phenotypic frequency distributions of hip and elbow dysplasia grades were similar among males and females in each breed studied. No indication of major genes was found in the offspring frequency distributions within individual sires. According to these Finnish data, mode of inheritance for both hip and elbow dysplasia is polygenic (quantitative) with equal expression of the genes from both parents, although the estimates of heritability for hip dysplasia in the Rough Collie and for elbow dysplasia in the German Shepherd and the Golden Retriever were somewhat different in males compared with females.

Effect of rumen degradable protein with or without fermentable carbohydrate supplementation on blood metabolites and embryo survival in cattle

Abstract: High intakes of dietary protein, particularly rumen degradable protein (RDP), lead to elevations in systemic concentrations of ammonia and (or) urea and these may be increased further if associated with inadequate fermentable energy intake. High systemic concentrations of ammonia and urea have been associated with reduced reproductive performance in cattle. The objective of this study was to examine the effect of RDP and fermentable energy intake on a range of blood metabolites and on embryo survival in heifers. Oestrous synchronized, nulliparous beef heifers (no. = 162) were randomly assigned in a 2 ✕ 2 factorial designed experiment to two levels of RDP and two levels of fermentable energy. Grass silage-based diets were supplemented with either 0 (0U) or 240 (240U) g dietary urea (460 g/kg N) and these in turn with either 0 (0P) or 3 (3P) kg dry matter of molassed sugar-beet pulp pellets (MSBP) per day. The four treatments were, therefore, (1) 0U + 0P (no. = 43), (2) 0U + 3P (no. = 44), (3) 240U + 0P (no. = 40) (4) 240U + 3P (no. = 35), respectively. Systemic concentrations of ammonia, urea, insulin, glucose and progesterone were measured. Heifers were given artificial insemination (AI) and embryo survival measured by ultrasonography at 30 and again at 40 days after AI. Systemic ammonia and urea were elevated (P 0·05). Plasma glucose was not affected by urea or MSBP treatment (P > 0·05) but was affected by day and time of sampling (P > 0·05). Plasma concentration of insulin was not affected by urea or MSBP supplementation or by day or time of sampling (P > 0·05). Plasma concentration of progesterone was not affected by diet or time of sampling (P > 0·05). The overall embryo survival rate was 62% and was not affected by dietary urea or fermentable carbohydrate or by systemic concentrations of ammonia, urea, glucose, insulin or progesterone (P > 0·05).

Polyethylene glycol in concentrate or feedblocks to deactivate condensed tannins in Acacia cyanophylla Lindl. foliage. 1. Effects on intake, digestion and growth by Barbarine lambs.

Abstract: Thirty young male sheep were given air-dried foliage of Acacia cyanophylla Lindl. ad libitum and 400 g oat hay. Animals were divided into five equal groups each of which was supplemented with either 300 g concentrate with (C PEG ) or without (C) 20 g polyethylene glycol 4000 (PEG) or urea-containing feedblocks with (BU PEG ) or without (BU) PEG. One other treatment was PEG-containing feedblock without urea (B PEG ). PEG was used to preferentially bind A. cyanophylla condensed tannins (CT). Feedblocks (BU, B PEG and BU PEG respectively) were made from olive cake (395, 376 and 353), wheat bran (263, 250 and 235), wheatfeeds (132, 125 and 118), quicklime (88, 83 and 78), salt (44, 42 and 39), mineral and vitamin supplement (12, 10 and 10), urea (66, 0 and 59) and PEG (0, 114 and 107 g/kg). These diets were used in growth (60 days) and metabolism (7 days) studies. Ureacontaining feedblocks, as compared with concentrate, were higher in crude protein (CP; 235 v. 116 g/kg DM) and lower in metabolizable energy (6 v. 10 MJ/kg DM). The type of supplement (i.e. concentrate v. feedblocks) had no effect ( P > 0·05) on A. cyanophylla DM intake, CP and neutral-detergent fibre (NDF) digestibilities and nitrogen (N) retention. However, concentrate-containing diets exhibited higher DM and organic matter (OM) digestibilities ( P < 0·05), urinary excretion of allantoin ( P < 0·05), microbial N supply ( P < 0·001) and average daily gain ( P < 0·001). PEG supply increased DM intake of A. cyanophylla , CP digestibility, N retention, allantoin voided in urine, microbial N supply and lamb growth. PEG-containing feedblocks enriched (BU PEG ) or not (B PEG ) with urea had similar effect on A. cyanophylla intake, DM, OM and NDF digestibilities, allantoin in urine, microbial N supply and average daily gain. These findings suggested that urea inclusion in feedblocks are not necessary and thus the feeding cost may be reduced. The higher amount of microbial N and daily gain in lambs given concentrate as compared with those on feedblock-supplemented diets was ascribed to the level of energy which was low in the latter diets. Enrichment of feedblocks with energy-rich ingredients such as molasses or cactus fruits could be a solution. This work confirmed that tannins depressed the nutritive value of this shrub species and lamb growth. However, the reduction was not drastic in the absence of PEG in the diet. Feedblock diet (BU) matched maintenance requirements of lambs while lambs on concentrate-supplemented diet (C) grew at a rate of 78 g/day. The choice between these two supplements will depend upon farm conditions and objectives.

Out-wintering pads for finishing beef cattle: animal production and welfare

Abstract: The objective of this experiment was to evaluate the performance and well being of animals accommodated outdoors over the winter period on out-wintering pads (OWPs), relative to animals housed indoors in conventional slatted floor sheds. One hundred and twenty-six steers were assigned at random to one of seven treatments. The first six treatments were accommodated on OWPs. These six treatments were arranged in a three (6, 12 and 18 m2 per head space allowance) by two (wind sheltered or exposed) factorial design. A seventh treatment group (control) was housed indoors in a slatted-floor shed at a space allowance of 3 m2 per head. All animals were offered silage ad libitum and 5 kg concentrate per day. All animals were slaughtered at the end of the 151 day experiment. Animal production and indices (climatic energy demand (CED), behaviour, cleanliness, hoof condition and immune function) of animal welfare were evaluated. There was no significant effect of stocking density outdoors or sheltering on live-weight gain, carcass gain, fat score, fat score per 100 kg carcass, kidney plus channel fat (KCF) as a proportion of carcass, carcass conformation score, killing-out proportion, food intake or food efficiency. Relative to animals housed indoors on slats, animals accommodated outdoors on OWPs had higher daily live-weight gain (F < 0·001), carcass gain (F < 0·05), and food intake (F < 0·05). However, animals on the OWPs had less KCF per kg carcass and lower fat scores per 100 kg carcass. There was no effect of shelter on the CED of animals out-wintered, which was higher (P < 0·001) than their counterparts wintered indoors on slats. Animals housed on slats were cleaner than animals housed at 6 or 12 m2 per head (F < 0·05) but not 18 m2per head. There was no effect of treatment on physiological measures. Animals confined on the OWP with or without shelter, had a greater number of lying bouts per 24 h (F < 0·076), had a greater synchronized lying frequency (F < 0·082) and displayed less hesitation prior to lying when compared with animals housed on slats. Indoor animals had more white line disease (F < 0·01) and under-run (F < 0·001) on their front hoof, when compared with outdoor animals. Animals accommodated outdoors at 18 m2per head had more (F < 0·05) claw erosion while the indoor animals had a greater (F < 0·001) degree of under-run present on their hind hoof. There was no evidence to suggest that out-wintering compromised animal welfare. Further studies are required to determine the reason for the increased carcass growth and leanness of the cattle on the OWPs.

Meal patterns of dairy cows consuming mixed foods with a high or a low ratio of concentrates to grass silage

Abstract: With the aim of testing the effects of food quality on meal patterns 127 213 visits by 22 lactating cows to 12 computerized feeders supplying two foods, high forage (HF) and high concentrate (HC) consisting of grass silage and concentrate were analysed. The foods were composed of the same ingredients but the proportion of concentrate dry matter (DM) in the food DM differed between HC (0·59) and HF (0·27). Each of the foods was offered ad libitum to 11 cows from the start of lactation until 156 (s.e. 9) days after calving. Mean daily fresh food intake (49·2 kg) was not affected by treatment. Mean daily intake of DM differed between HC (23·6 kg) and HF (17·8 kg). After estimating individual meal criteria, visits were grouped into meals. The mean daily number of meals was 6·6, the mean fresh food intake per meal was 7·6 kg and neither was affected by treatment. Cows consuming HF had longer meals (41·4 v. 31·3 min) but a lower feeding rate than cows consuming HC (233 v. 337 g of fresh food per min and 78 v. 156 g DM per min). Pre- and post-prandial correlation coefficients were sometimes statistically significant but always low (R2 from 0 to 0·05) and not affected by treatment. Food intake per hour of the feeding cycle (defined as the intake during a meal divided by length of the meal plus the duration of the preceding between-meal interval) showed a diurnal pattern in the shape of a sine-wave with low values of about 1·5 kg/h for cycles starting just after midnight and high values of more than 3·0 kg/h for cycles starting just after noon. Neither the mean, nor the amplitude, nor the shift of the sine-wave were affected by treatment. The data suggest that similar mechanisms are responsible for the short-term intake regulation of HC and HF. No evidence was found to suggest that the diurnal meal pattern of cows consuming HF deviated from that of cows consuming HC as a result of differences between foods in constraints related to their physical properties.

Partial replacement of poly- with monounsaturated fatty acids and vitamin E supplementation in pig diets: effect on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness

Abstract: The effect of partial replacement of poly- (PUFA) with monounsaturated (MUFA) fatty acids in pig diets on fatty acid composition of subcutaneous and intramuscular fat and on fat and lean firmness was studied. No effect of dietary fat was observed on total saturated fatty acid concentration in any of the backfat layers or intramuscular lipid fractions. No significant effect of dietary fat was observed for the MUFA concentration in the outer layer, but a marked effect was evident for the inner layer (P < 0·001). A linear effect of dietary MUFA was observed for MUFA (P < 0·001) and PUFA (P < 0·001) in polar lipids. No significant effect of dietary treatment was observed on total concentration of n-3 fatty acids in any lipid location but a marked effect was observed for total n-6 fatty acid concentration. The response of pig fatty acid n-6 concentration was different depending on the lipid location. The neutral lipid fraction showed significantly lower n-6/n-3 fatty acid ratio than the subcutaneous fat. Intramuscular polar lipids showed no significant response of n-6/n-3 ratio. A linear effect of dietary MUFA concentration was observed on the melting point on the inner backfat layer (MP = 34·4 (s.e. 2·51) + 0·15 (s.e. 0·07) ✕ dietary MUFA (g/kg dry matter) (R2 = 0·24, P < 0·05)), indicating that the partial substitution of dietary PUFA by MUFA produced a fat of higher consistency. No response of the melting point of the outer layer to dietary treatment was observed. A marked effect of dietary fat was shown for backfat hardness (P < 0·001), gumminess (P < 0·001) and chewiness (P < 0·001). No effect of dietary fat was observed on the rheological properties of longissimus lumborum muscle.