Showing papers in "Animal Science in 2005"

Costs of the major endemic diseases of sheep in Great Britain and the potential benefits of reduction in disease impact

Abstract: The costs of three major endemic sheep diseases in Great Britain, gastro-intestinal (GI) parasites, footrot and scab, were estimated and compared with costs for other diseases from another study. Disease costs include lost performance, preventive measures and treatment of affected animals. The most costly disease, of those studied, for the British sheep industry is infestation with GI parasites, with estimated annual costs of £84 million. Annual costs for the other two diseases are £24 million for footrot and £8 million for sheep scab. This compares with literature estimates of £20 million for Chlamydial abortions and £12 million for toxoplasmosis. For sheep scab most costs are for preventive measures, therefore, short of eradication, a reduction in incidence will have a limited effect on costs. For GI parasites, costs are linearly related to the severity of the infestation and a reduction of the disease will have a proportional effect on the costs to the industry. For footrot about half the costs are for preventive measures, the other half is for lost production and treatment. A reduction in the incidence of footrot has a proportional effect on the £10 million associated with loss of production and treatment of infected animals. It is concluded that gastro-intestinal parasites and footrot are two sheep diseases in Britain for which a reduction of severity or incidence will have a large impact on costs of production.

Apparent ileal digestibility of amino acids in dietary ingredients for broiler chickens

Abstract: The apparent ileal digestibility coefficients of amino acids in 107 samples representing 22 food ingredients were determined using 6-week-old broiler chickens. The ingredients assayed included five cereals ( barley, maize, sorghum, triticale and wheat), two cereal by-products ( rice polishings and wheat middlings), four oilseed meals ( canola, cottonseed, soyabean and sunflower meals), full-fat canola, maize gluten meal, four grain legumes ( chickpeas, faba beans,field peas and lupins) and five animal protein sources ( blood, feather,fish, meat and meat and bone meals). The mean ileal digestibility coefficients of amino acids in wheat and maize were higher than those in sorghum, triticale and barley. However, variations observed in individual amino acid digestibilities among samples within cereal type were greater than those determined between cereals. Threonine and lysine were the least digestible indispensable amino acids in the five cereals evaluated. The most digestible indispensable amino acid was phenylalanine in wheat and, leucine in maize and sorghum. In the case of the wheat middlings and rice polishings, threonine was the least digestible indispensable amino acid and arginine was the best digested. In the oilseed meals assayed, amino acid digestibility was highest for soya-bean and sunflower meals, intermediate for canola meal and lowest for cottonseed meal. Ileal digestibility coefficients of amino acids in lupins were found to be slightly lower than those in soya-bean meal. The amino acid digestibilities of field peas, faba beans and chickpeas were considerably lower than those of lupins. Digestibility of arginine was the highest and that of threonine was the lowest of the indispensable amino acids in oilseed meals and grain legumes, except in cottonseed meal. Lysine was the least digestible amino acid in cottonseed meal. In the animal protein sources assayed, digestibility coefficients of amino acids in blood meal were high, intermediate in fish meal, and low in meat meal, meat and bone meal and feather meal. Variation in amino acid digestibility coefficients determined for blood meal samples was small. However, wide variations in amino acid digestibilities were observed for other animal protein sources, highlighting significant batch-to-batch differences. In particular, marked variations were determined for meat meal and meat and bone meal samples. Cystine was the least digested amino acid in animal protein meals, with the exception of blood meal in which isoleucine had the lowest digestibility. The limitations of using apparent digestibility values in diet formulations and the concept of the standardized digestibility system to overcome these limitations are discussed.

Inbreeding – lessons from animal breeding, evolutionary biology and conservation genetics

Abstract: Increased rates of inbreeding are one side effect of breeding programmes designed to give genetic progress for traits of economic importance in livestock. Inbreeding leads to inbreeding depression for traits showing dominance, and will ultimately lead to a decrease in genetic variance within populations. Here we review theoretical and experimental literature from animal breeding, evolutionary biology and conservation genetics on the consequences of inbreeding in terms of trait means and genetic and environmental variance components. The genetic background for these effects is presented and the experimental literature interpreted in relation to them. Furthermore, purging of deleterious alleles and the variable nature of effects of inbreeding on populations are discussed. Based on the literature, we conclude that inbreeding in animal breeding must be controlled very efficiently to maintain long-term sustainable livestock production in the future. The tools to do this efficiently exist, and much can be learnt on inbreeding from the literature in fields only distantly related to animal breeding.

Effect of forage type and proportion of concentrate in the diet on milk fatty acid composition in cows given sunflower oil and fish oil

Abstract: Based on the potential benefits of cis-9, trans- 11 conjugated linoleic acid (CLA) for human health there is a need to develop effective strategies for enhancing milk fat CLA concentrations. In this experiment, the effect of forage type and level of concentrate in the diet on milk fatty acid composition was examined in cows given a mixture of fish oil and sunflower oil. Four late lactation Holstein-British Friesian cows were used in a 4 x 4 Latin-square experiment with a 2 x 2 factorial arrangement of treatments and 21-day experimental periods. Treatments consisted of grass (G) or maize (M) silage supplemented with low (L) or high (H) levels of concentrates (65: 35 and 35: 65; forage: concentrate ratio, on a dry matter (DM) basis, respectively) offered as a total mixed ration at a restricted level of intake (20 kg DM per day). Lipid supplements (30 g/kg DM) containing fish oil and sunflower oil (2: 3 w/w) were offered during the last 14 days of each experimental period. Treatments had no effect on total DM intake, milk yield, milk constituent output or milk fat content, but milk protein concentrations were lower (P = C20 (n-3) polyunsaturated fatty acids (PUFA) and lower (P = C20 (n-3) PUFA content, but reduced (P 0.05) on total milk conjugated linoleic acid (CLA) (2.7 and 2.8 g/100 g fatty acids, for M and G, respectively) or cis-9, trans-11 CLA content (2.2 and 2.4 g/100 g fatty acids). Feeding high concentrate diets tended (P<0.10) to decrease total CLA (3.3 and 2.2 g/100 g fatty acids, for L and H, respectively) and cis-9, trans-11 CLA (2.9 and 1/7 g/100 g fatty acids) concentrations and increase milk trans-9, cis-11 CLA and trans-10, cis-12 CLA content. In conclusion, the basal diet is an important determinant of milk fatty acid composition when a supplement of fish oil and sunflower oil is given.

How do the nature of forages and pasture diversity influence the sensory quality of dairy livestock products

Abstract: This review summarizes the recent developments in understanding of the relationships between the diet of animals and the sensory quality of dairy products. Feeding dairy cattle with maize silage by comparison with hay or grass silage leads to whiter and firmer cheeses and butter and sometimes to differences in flavour. Major differences in sensory characteristics were observed between cheeses made with milk produced by cows on winter diets (based on hay and grass silage) or turned out to pasture in the spring. Conversely, preserving grass as silage, by comparison with hay, has no major effect on cheese sensory characteristics, except on colour, the cheese being yellower with grass silage. Several recent experiments have shown a significant effect of grass botanical composition on cheese texture and flavour. These effects are due to the presence in milk of specific molecules directly introduced by feeding (carotenes, terpenes) or produced by the animals (plasmin, fatty acids) under the effect of specific diets.

The development of harmful social behaviour in pigs with intact tails and different enrichment backgrounds in two housing systems

Abstract: The present study compared the performance and development of adverse behaviours of pigs with intact tails, when housed in a straw-bedded system or a part-slatted system enriched with a commercial device. The pigs had previously received different enrichment treatments (rooting box, liquid dispenser, straw bedding or none), either in the farrowing crate or with their lactating dam or post weaning. The pigs were mixed in groups at 10 weeks of age and from then on, every 2 weeks, behavioural observations were performed, focusing mainly on harmful social behaviour and enrichment use. The study showed that pigs with undocked tails can be at high risk of tail biting in part-slatted systems, whereas the straw bedding prevented the development of tail biting. The immediate effects of the environment seemed to exert a greater influence on the development of adverse behaviour than early life enrichment and adding a simple enrichment device could not compensate for the deficiencies in the barren environment of the part-slatted system. In order to prevent vice, functional design of environmental enrichment is required.

The route of absorbed nitrogen into milk protein

Abstract: A database reviewing the metabolism of nitrogen (N) compounds from absorption to milk has been compiled from 14 published and unpublished studies (33 treatments) that measured the net flux of N compounds across the splanchnic tissues in dairy cows. Apparent N digestibility averaged 0·65, with this then partitioned between 0·34 excreted in urine and 0·31 secreted as milk.Nitrogen metabolites are absorbed from the lumen of the gut into the portal vein, mainly as free amino acids (AA) and ammonia; these represented 0·58 and 0·57 of digested N, respectively. All of the ammonia absorbed was removed by the liver with, as a result, a net splanchnic flux of zero. Detoxification of ammonia by the liver and catabolism of AA results in production of urea as an end-product. Hepatic ureagenesis is a major cross-road in terms of whole body N exchange, being the equivalent of 0·81 of digested N. Therefore, salvage of a considerable part of this ureagenesis is needed to support milk protein synthesis. This salvage occurs via transfer of urea from the blood circulation into the lumen of the gut. On average, 0·47 of hepatic ureagenesis was returned to the gut via the portal-drained viscera (equivalent to 0·34 of digested N) with 0·56 of this then used for anabolic purposes e.g. as precursor N for microbial protein synthesis. On average, 0·65 of estimated digestible AA was recovered in the portal vein. This loss (0·35) is due to oxidation of certain AA across the gut wall and non-absorption of endogenous secretions. The magnitude of this loss is not uniform among AA and varies between less than 0·05 for histidine to more than 0·90 for some non-essential AA, such as glutamine.A second database (six studies, 14 treatments) was constructed to further examine the subsequent fate of absorbed essential AA. When all AA are aggregated, the liver removed, on average, 0·45 of portal absorption but this value hides the considerable variation between individual AA. Simplistically, the AA behave as two major groups: one group undergoes very little hepatic removal and includes the branched-chain AA and lysine. For the second group, removal varies between 0·35 and 0·50 of portal absorption, and includes histidine, methionine and phenylalanine. For both groups, however, the efficiency of transfer of absorbed AA into milk protein decreases with increasing supply of protein. This loss of efficiency is linked directly with increased hepatic removal of AA from the second group and, probably, increased catabolism by peripheral tissues, including the mammary gland, of AA from the first group. Therefore, we must stop using fixed factors of conversion of digestible AA to milk in our predictive schemes and acknowledge that metabolism of AA between delivery from the duodenum and conversion to milk protein will vary with nutrient supply. New information evolving from re-analysis of the literature and recent studies will allow better models to be devised for the prediction of nutrient-based responses by the lactating cow. Consideration of biological efficiency, rather than maximal milk yield, will lead to systems that are economically more sensible for the farmer and that have better environmental impacts.

The effect of concurrent corticosteroid induced immuno-suppression and infection with the intestinal parasite Trichostrongylus colubriformis on food intake and utilization in both immunologically naïve and competent sheep

Abstract: The nutritional cost of both the acquisition and maintenance of immunity to gastro-intestinal nematodes was investigated using immunologically naive 5-month-old lambs and immunologically competent 17-month-old ewes. Within each age cohort, animals were either infected with the equivalent of 80 L3 Trichostrongylus colubriformis larvae per kg live weight (LW) per day (IF), similarly infected and concurrently immuno-suppressed with weekly injections of 1·3 mg/kg LW of the glucocorticoid methylprednisolone acetate (ISIF), immuno-suppressed only (IS) or remained as controls (C). Body composition of all animals was estimated using X-ray computer tomography on days -14 and 76 relative to the start of infection. Body weight and faecal nematode egg counts (FEC; eggs per gram of fresh faeces (e.p.g. )) were taken weekly and blood samples for serum proteins and antibodies were obtained every 2 weeks. FEC in IF lambs peaked at 1250 e.p.g. before a typical decline as immunity developed to less than 100 e.p.g. by day 75. FEC of less than 100 e.p.g. in IF ewes indicated immunity was maintained. Successful immuno-suppression in ISIF lambs and ewes was indicated by FEC of 4000 e.p.g. on day 75 and was confi rmed by comparative worm burdens and serum antibody titres. The typical reduction in voluntary food intake (VFI) as a consequence of infection was observed in IF lambs (proportionately 0·30, P < 0·001) but not in IF ewes, ISIF lambs or ISIF ewes. Gross effi ciency of use of metabolizable energy for net energy deposition was reduced by proportionately 0·20 in lambs during acquisition of immunity and by 0·16 in ewes maintaining an established immunity. Infection in immuno-suppressed animals reduced effi ciency by 0·05 and 0·15 for lambs and ewes, respectively. These fi ndings allowed the hypothesis that the reduction in VFI and loss in performance in young parasitised sheep is caused by physiological signalling associated with the acquisition phase of the host immune response to infection, rather than simply the damage caused by the parasite per se.

The effect of cereal type and exogenous enzyme supplementation in pig diets on nutrient digestibility, intestinal microflora, volatile fatty acid concentration and manure ammonia emissions from finisher pigs

Abstract: A 2 × 2 factorial experiment was conducted to investigate the interaction between cereal type (wheat v. barley) and an exogenous enzyme supplement (with or without) on nutrient digestibility, large intestinal microflora, volatile fatty acid profile and in vitro manure ammonia emissions from finisher pigs. The enzyme supplement used contained endo-1, 3-β-glucanase (EC 3·2·1·6) and endo-1, 4-β-xylanase (EC 3·2·1·8). The diets were formulated to contain similar concentrations of net energy (9·8 MJ/kg) and lysine (10·0 g/kg). Urine and faeces were collected over seven consecutive days from 16 boars (four boars per treatment, 80·0 kg live weight) that were housed in metabolism crates. After collections, the pigs were slaughtered and the contents of the intestinal tracts were removed for analysis. There was a significant interaction between cereal type and enzyme inclusion in the apparent total tract digestibility of dry matter (DMD), organic matter (OMD) and nitrogen. The inclusion of an enzyme supplement in barley-based diets increased (P < 0·05) DMD, OMD and nitrogen digestibility compared with unsupplemented diets, however there was no effect of enzyme supplementation in wheat-based diets. There was a significant interaction between cereal type and enzyme inclusion in selected components of the gut microflora. Pigs offered unsupplemented barley-based diets had higher populations of bifidobacteria (P < 0·05) in the caecum and colon than those on the enzyme supplemented barley diet, however, there was no effect of enzyme supplementation on bifidobacteria in wheat-based diets. There was a significant interaction between cereal type and enzyme inclusion in volatile fatty acid production and in in vitro ammonia emissions. In the absence of an enzyme supplement, barley-based diets reduced the proportion of isovaleric acid (P < 0·05) and isobutyric acid (P < 0·05) in the caecum and colon and also reduced manure ammonia emissions during storage from 0 to 240 h (P < 0·05) compared with the wheat-based diet, however there was no effect of cereal type in enzyme-supplemented diets. In conclusion, the inclusion of an enzyme in barley-based diets increased nutrient digestibility but also increased ammonia emissions.

Factors identifying pigs predisposed to tail biting

Abstract: Approximately 5% of pigs slaughtered in the UK have been tail-bitten, leading to welfare and production issues. Tail biting is sporadic and not all pigs tail bite. The aim of this study was to identify factors that are common in pigs that perform tail-biting behaviour, and that might be used in a predictive way to identify such animals.The behaviour of 159 pigs was observed in the post-weaning period. Pigs were weaned at 4 weeks of age. In the week prior to weaning and at 6 weeks of age each pig was individually tested in a tail chew test (tail chew test 1 and 2, respectively). The tail chew test involved recording the pig's behaviour directed towards two ropes, one of which had been soaked in saline solution and the other not. The production performance of the pigs was recorded from birth to 7 weeks of age. Time spent performing tail-biting behaviour correlated positively with time in contact with the rope in tail chew test 2 (r = 0·224, P 0·05).The results suggest that pigs that tail bite have some nutritional deficiency that results in performance of foraging behaviour that is expressed in intensive housing as ear/tail biting.

The effects of fish oil supplementation on rumen metabolism and the biohydrogenation of unsaturated fatty acids in beef steers given diets containing sunflower oil

Abstract: Lee, M R F, Tweed, J K S, Moloney, A P, Scollan, N D (2005) The effect of fish oil supplementation on rumen metabolism and the biohydrogenation of unsaturated fatty acids in beef steers given diets containing sunflower oil Animal Science, 80, (3), 361-367

An improved model for the French genetic evaluation of dairy bulls on length of productive life of their daughters

Abstract: Functional longevity of dairy cows has been routinely evaluated in France since 1997 using a survival analysis model. Recently, we proposed a genetic trend validation test that could be used before including national data in an international evaluation of bulls on longevity of their daughters. Its application to the French Holstein data revealed a large overestimation of the genetic trend. It was found that the bias is the result of a change in the baseline hazard rate over time. A new proportional hazards model is proposed which accounts for this change. In the new model, the baseline is described as a stratified, piecewise Weibull hazard function within lactation, i.e. a function of the number of days since the most recent calving. Stratification is within year and parity. Different Weibull hazard functions are used over four periods: 0 to 270 days, 271 to 380 days, 381 days to day when dried, dry period until the next calving. The non-genetic effects included in the model were slightly different from the previous one. In particular the interaction effects between the within herd-year class of production and lactation number × stage of lactation on the one hand and year-season were accounted for. The estimated genetic variance was smaller than with the old model. The new genetic trend is almost flat. An illustration of the efficiency of selection on the estimated breeding values for longevity is presented.

Characteristics of cattle movements in Britain - an analysis of records from the Cattle Tracing System

Abstract: This paper reviews the main temporal and spatial characteristics of cattle movements in Britain, based on an analysis of records in the British Cattle Movement Service’s Cattle Tracing System (CTS) database, focusing on the period 2001 to 2003, during which notifi cation of cattle movements was mandatory. Movements vary weekly and seasonally according to the production cycle, with peaks in late spring (April) and early autumn ( October), and an average 1·63 million farm-to-farm movements per month, equivalent to 19·6 million per annum. The geographical distribution of these movements appears to be relatively stable from year to year, with the great majority of animals moving less than 100 km per journey, although many tens of thousands move over far greater distances of up to 1000 km. The procedures developed to extract, match, geo-reference, analyse and display movement records have greatly enhanced the utility of the CTS database, in that it is now feasible to assess, monitor and map the spatial dynamics and geographical distribution of cattle movements, and provide this information in standardized format on a regular basis.

Impact of grazing management on biodiversity of grasslands

Abstract: This paper reviews recent work carried out by the Institute of Grassland and Environmental Research and collaborating organizations that addresses some of the impacts of grazing management on both species-rich and species-poor lowland neutral grassland. Results indicate that for species-rich grassland, lenient grazing pressure maintained botanical diversity and the abundance of positive indicator species of nature conservation value over a 5-year period and also enhanced faunal diversity and abundance reflecting improvements in spatial, architectural and temporal structure. However, there was no enhancement in positive indicator species and there was also an increase in pernicious weeds suggesting that grazing alone may not suffice to deliver all the biodiversity goals for these grasslands and that additional management interventions may be required. For species-poor grassland, results indicate that distinctive differences in structure can lead to differences in faunal diversity. There is also some tentative evidence that livestock breed may affect invertebrate species assemblages.

Performance of weanling pigs offered low or high lactose diets supplemented with avilamycin or inulin

Abstract: One hundred and eighty piglets (24 days old, 6·0 kg live weight) were used to investigate interactions between lactose, avilamycin and inulin on growth performance and nutrient digestibility in weaned piglets. The piglets were blocked on the basis of live weight and within each block assigned to one of six dietary treatments (six replicates (pens) per treatment). The piglets were offered diets containing either a low (175 g/kg) or high (295 g/kg) lactose levels with one of the following food additives (1) 0 supplementation (2) avilamycin (60 mg/kg) or (3) inulin (15 g/kg) in a 2 × 3 factorial arrangement. The starter diets were offered for 21 days and all diets contained chromium III oxide at 150 p. p. m. There was an interaction (P < 0·05) between lactose level and both avilamycin and inulin on average daily gain (ADG) during the starter period (days 0 to 21). The pigs receiving 295 g/kg lactose level had a higher overall ADG than pigs receiving 175 g/kg lactose level. However, there was no difference between 295 g/kg lactose and 175 g/kg lactose in ADG when the diets were supplemented with avilamycin or inulin. There was an interaction between lactose level and inulin in the apparent digestibility of gross energy (GE) and nitrogen (N) (P < 0·05). The inclusion of inulin with 175 g/kg lactose increased GE digestibility compared with the 175 g/kg lactose only diet. However, the inclusion of inulin with 295 g/kg lactose had no effect on GE digestibility. The inclusion of inulin with 295 g/kg lactose reduced N digestibility compared with the inclusion of inulin at 175 g/kg lactose. However, there was no difference in N digestibility between 175 and 295 g/kg lactose only diets. In conclusion, there was no benefit in terms of pig growth rate to supplementing diets high in lactose with either inulin or avilamycin. However, the inclusion of inulin improved the energy digestibility of diets low in lactose.

The effects of an Aspergillus oryzae extract containing alpha-amylase activity on ruminal fermentation and milk production in lactating Holstein cows

Abstract: The effects of an Aspergillus oryzae extract containing alpha-amylase activity (Amaize™, Alltech Inc., Nicholasville, KY) were examined in vivo and in vitro. A lactating cow study employed 20 intact and four ruminally fistulated Holstein cows in a replicated 4 × 4 Latin-square design to examine the effects of four concentrations of dietary Amaize™ extract on milk production and composition, ruminal fermentation and serum metabolite concentrations. The treatment diets contained 0, 240, 480 or 720 alpha-amylase dextrinizing units (DU) per kg of total mixed ration (TMR) (dry-matter basis). The supplemental alpha-amylase increased the yields of milk (P = 0·02), fat (P = 0·02) and protein (P = 0·06) quadratically. The maximum milk yield was obtained when 240 DU per kg of TMR were offered. Ruminal in situ starch disappearance was not affected by alpha-amylase supplementation in lactating cows or ruminally cannulated steers. Supplemental alpha-amylase extract reduced the molar proportion of propionate in the rumen of steers (P = 0·08) and lactating cows (P = 0·04), and in rumen-simulating cultures (P = 0·04). The supplement also increased the molar proportions of acetate (P = 0·06) and butyrate (P = 0·05), and the serum beta-hydroxybutyrate (P = 0·01) and non-esterified fatty acid (P = 0·03) concentrations in lactating cows. The improvements in milk production appear to be a consequence of the effects of alpha-amylase on ruminal fermentation and the potential changes in nutrient metabolism that result from them. We conclude that supplemental alpha-amylase may be given to modify ruminal fermentation and improve milk and component yield in lactating Holstein cattle.

Effect of ewe feeding system (grass v. concentrate) on intramuscular fatty acids of lambs raised exclusively on maternal milk

Abstract: Twenty pregnant Comisana ewes were divided into two groups of 10. One group was allowed to graze a vetch pasture (grass). The second group of animals was housed collectively in a pen and was given hay and concentrates (concentrate). After lambing, all the ewes were allowed to stay with the respective lambs between 18:00 h and 07:00 h of the following day in two different pens. Therefore all the lambs were raised exclusively on maternal milk. The lambs were slaughtered at 38 days of age. Milk and lamb meat ( longissimus dorsi muscle) fatty acids were analysed. Ewes on grass produced milk with a lower ( P < 0·001) proportion of saturated fatty acids and with a higher proportion of both monounsaturated ( P < 0·05) and polyunsaturated fatty acids ( P < 0·01) than ewes given concentrates. Trans-vaccenic acid was significantly higher ( P < 0·001) in milk from grass-fed animals compared with ewes given concentrates. Linoleic acid (C18 : 2 n-6) tended to be higher ( P = 0·06) in milk from ewes on concentrates while linolenic acid (C18 : 3 n-3) was significantly higher ( P < 0·001) in milk from animals grazing pasture. Conjugated linoleic acid (cis-9, trans-11 C18 : 2) was almost double in milk from grass-fed ewes compared with animals given concentrates ( P < 0·001). Regarding lamb tissue, trans-vaccenic acid (C18 : 1 trans-11) was higher ( P = 0·01) in the fat from lambs raised by grazing ewes. Linoleic acid (C18 : 2 n-6) was at higher concentration ( P < 0·001) in the fat from lambs raised by ewes given concentrates. Linolenic acid (C18 : 3 n-3) was increased three-fold ( P < 0·001) in the fat of lambs from the grass group compared with lambs suckled by ewes given concentrates. The isomer cis-9, trans-11 of conjugated linoleic acid was present at double concentration ( P < 0·001) in the fat from animals raised by grazing ewes. Eicosapentaenoic (C20 : 5 n-3; EPA) and docosaesaenoic (C22 : 6 n-3; DHA) acids were higher (respectively P < 0·001 and P = 0·01) in the intramuscular fat from lambs from the grass group compared with animals from the concentrate group. The n-6/n-3 ratio was lower ( P < 0·001) in the meat from lambs raised by grazing ewes. Overall this trial showed that ewe feeding system strongly affects intramuscular fatty acids even in lambs raised exclusively on maternal milk.

Biohydrogenation of n-3 polyunsaturated fatty acids in the rumen and their effects on microbial metabolism and plasma fatty acid concentrations in sheep

Abstract: Six cannulated wether sheep weighing 57 (s.d. 4·3) kg were used to investigate the susceptibility of unprotected and protected n-3 polyunsaturated fatty acids from different sources to biohydrogenation in the rumen, their uptake into plasma and effects on ruminal metabolism. The sheep were assigned to one of six dietary treatments formulated to have a similar fatty acid content (60 g/kg DM) and containing: linseed oil (LO), linseed oil absorbed into vermiculite (VLO), formic acid-formaldehyde treated whole linseed (FLS), fish oil (FO), fat encapsulated fish oil (PFO) or a mixture of fish oil and marine algae (1: 1 on an oil basis; AF), in six periods of 28 days duration in a Latin-square design. Biohydrogenation of C20:5 (n-3) and C22:6 (n-3) was high in FO at approximately 870 g/kg, but reduced to 625 and 625 g/kg respectively for PFO, and 769 and 601 g/kg respectively for AF. Ruminal biohydrogenation of C18:3 (n-3) was similar across treatments based on linseed, averaging 860 g/kg, but C18:2 (n-6) was lower (P < 0·05) in animals given VLO or FLS at 792 and 837 g/kg respectively, compared with LO (907 g/kg). Duodenal flow of C18:1 trans in animals given any of the diets containing fish oil averaged 8·4 g/day compared with 2·8 g/day in animals given diets based on linseed (P < 0·001), whilst cis-9, trans-11 conjugated linoleic acid was not significantly different among treatments. Plasma C20:5 (n-3) and C22:6 (n-3) proportions were highest in animals given the AF diet (11·8 and 8·2 g per 100 g of the total fatty acids respectively) and lowest in animals given LO (2·8 and 2·7 g per 100 g of the total fatty acids respectively; P < 0·001). By contrast, plasma C18:3 (n-3) proportions were highest in animals given the LO or VLO diets at approximately 6·9 g per 100 g of the total fatty acids, and lowest in the AF treatment at 0·9 g per 100 g (P < 0·001). Duodenal non-ammonia-N flow was similar among treatments at 21·0 g/day except in animals given FLS which had the highest flow (25·9 g N per day; P < 0·01). Microbial N flow was also similar among treatments whilst microbial efficiency (g N per kg OM truly degraded in the rumen) was higher (P < 0·05) in animals given FLS than LO, FO or AF. By contrast, ruminal fibre digestion was higher (P < 0·05) in animals given LO or FO than those offered VLO, FLS, PFO or AF. In conclusion, compared with linseed oil, absorption of linseed oil into vermiculite improved duodenal flow but not plasma levels of C18:3 (n-3), whilst formic acid-formaldehyde treatment of linseed had little effect on protecting C18:3 (n-3) in the rumen, although duodenal non-ammonia nitrogen flow and microbial efficiency were improved. Compared with fish oil, the provision of marine algae or fat encapsulated fish oil resulted in a lower biohydrogenation of C22:6 (n-3) and C20:5 (n-3), and an increased duodenal flow and plasma concentration and offers the potential to favourably manipulate the n-3 fatty acid composition of sheep meat.

Genetic analysis of body condition in the sow during lactation, and its relation to piglet survival and growth

Abstract: A study seeking to estimate phenotypic and genetic parameters for sow body condition around lactation and their relationship with piglet growth and survival is described. It also investigates the genetic relationship between piglet growth and survival, including both direct and maternal effects for both traits. Records were available from 24 549 Swedish Yorkshire piglets born in 2198 litters. Sows had records of weight and backfat depth at farrowing and at weaning. Piglets had individual records for weight at birth and weaning and cause of death for those that failed to survive during lactation. Mixed linear bivariate models were used to estimate correlations between traits. The models for the sow traits took into account the random effects of permanent environment and the genetic effect of the sow, whereas the models for the piglet traits included a litter effect as well as direct and maternal genetic effects. Estimated heritabilities for sow weight and backfat at farrowing and change of weight and backfat during lactation were low to moderate (0·10 to 0·47). We found significant genetic correlations between change of weight and backfat during lactation and piglet survival and growth, indicating that sows with the genetic capacity for rapid early piglet growth and high survival rate may lose more body reserves during lactation. Negative direct-maternal correlations for early piglet growth and survival imply that both the piglet and the sow trait should be included in a genetic evaluation for these traits. Genetic correlations between piglet survival and growth were not clearly favourable. Selection for the direct effect of piglet survival may lead to a decrease in early growth rate. We conclude that in a selection programme aiming at improving piglet survival and growth, attention should be paid to the sow's body condition during lactation. A high enough level of body reserves needs to be maintained in the sow if the incidence of reproductive problems and involuntary culling is not to increase.

Splanchnic metabolism of volatile fatty acids in the dairy cow

Abstract: Volatile fatty acids (VFA) are quantitatively important substrates for dairy cows and other ruminants It has been a central dogma in the nutritional physiology of ruminants that the ruminal epithelium metabolizes a large fraction of VFA during theirabsorption and consequently a relatively small fraction of VFA is available for peripheral tissues including the mammary gland New data on splanchnic metabolism of VFA indicate that the ruminal epithelium metabolizes none or small amounts of acetate and propionate absorbed from the rumen However, the ruminal epithelium has a large fractional uptake of butyrate and valerate during their absorption from the rumen The liver takes up proportionately 0·9 or more of the absorbed propionate, however multiple factors are involved in regulation of hepatic metabolism and propionate does not determine glucose availability to the cow per se In light of the quantitative importance of VFA to the dairy cow it is important that future research attempts to bridge the gap between the biology of food degradation/digestion in the gastro-intestinal tract and availability of specific nutrients to the cow which impact intermediary metabolism and nutrient utilizationin productive tissues

Effects of age and breed of beef bulls on growth parameters, carcass and muscle characteristics

Abstract: The effects of age and breed on growth parameters, carcass and muscle characteristics of bulls, slaughtered at 15, 19 and 24 months of age, were analysed in four French breeds: Aubrac (AU), Charolais (CH), Limousin (LI), and Salers (SA). Muscle characteristics were determined in three muscles: longissimus thoracis (LT), semitendinosus (ST) and triceps brachii (TB). They included: (1) the % frequency, cross-sectional area and % area of fibre types, which were classified according to the contractile nature of the fibres and their metabolic properties (SO slow oxidative, FOG fast oxidative glycolytic and FG fast glycolytic); (2) the isocitrate dehydrogenase (ICDH) and lactate dehydrogenase (LDH) activities, representative of oxidative and glycolytic metabolism respectively; and (3) the total and insoluble collagen contents.In the four breeds, the average daily gain and the food efficiency decreased with age (P < 0·001). The carcass characteristics (muscle, fat and bone weights) increased with age (P < 0·001). The increase of muscle carcass weight with slaughter age was in parallel with the increase in cross-sectional area of individual muscle fibres. Oxidative fibre (SO and FOG) areas increased more between 15 and 24 months than glycolytic fibre (FG) area. Differences between muscles in increases in areas of muscle fibres were consistent: the increase was greater for TB than ST and LT. The muscles studied became more slow and more oxidative above 19 months of age, as evidenced by the fact that the SO % frequency (P < 0·001) and % area (P < 0·001) and ICDH activity (P < 0·05) increased, and LDH activity decreased (P < 0·01). Insoluble collagen content decreased between 15 and 19 months (P < 0·001), and both total (P < 0·01) and insoluble (P < 0·001) collagen contents increased from 19 months.So carcass characteristics were modified between 15 and 24 months, and muscle characteristics were especially modified from 19 months of age. In addition, differences in slaughter data between breeds were clear and consistent, whereas those of muscle characteristics were few and not consistent.

Genetic relationships between indicator traits and nematode parasite infection levels in 6-month-old lambs

Abstract: This study investigated traits that could be used to aid selective breeding for increased nematode resistance in sheep. Data were collected on approximately 1000 Scottish Blackface lambs over a 5-year period (1992–6). The animals were continually exposed to mixed nematode infection by grazing. Anthelmintic treatment was administered and blood samples were collected every 28 days from 4 to 24 weeks of age. Approximately 500 of the lambs were necropsied at 6 to 7 months of age and their worm burdens were recorded. The traits measured were the number of adult males, adult females, fifth-stage larvae and fourth-stage larvae for all species present. In addition, the mean length of adult females and the number of eggs in utero were estimated for Teladorsagia circumcincta. Several indicator traits were also measured on some of the animals, including : faecal egg counts, immunoglobulin A activity and eosinophil count as markers of the local immune response, and plasma pepsinogen activity and fructosamine concentration as indicators of the pathological consequence of infection. The heritabilities for worm length, eggs in utero and worm burden were 0.53±0.17, 0.50±0.16 and 0.13±0.10 respectively. At a mean age of 22 weeks the heritabilities for fructosamine concentration, IgA activity, eosinophil count and pepsinogen activity were 0.39±0.16, 0.57±0.15, 0.35±0.15 and 0.56±0.16 respectively. Strong negative genetic correlations (< −0.6) were often observed between necropsy traits and eosinophil count, IgA activity and pepsinogen activity. Substantial genetic correlations were also observed between fructosamine concentration and worm length (0.67) and number of fourth-stage larvae (−0.80). The genetic and environmental correlations between indicators and necropsy traits were often opposite in sign. The indicator traits studied could aid selection for increased resistance to gastrointestinal nematodes in sheep.

Reproductive rhythm and litter weaning age as they affect rabbit doe performance and body energy balance

Abstract: One hundred and twenty multiparous does were synchronized to give birth the same day (initial kindling). The trial lasted until the successive (final) kindling. Immediately following initial kindling, 22 does were selected for comparative slaughter. The remaining does were assigned to three reproductive rhythms and mated 2 (R2), 11 (R11) or 26 (R26) days post partum. Within each rhythm, the does were further divided into two groups with litters weaned at 21 (W21) or 25 (W25) days of age. A total of 54 does were pregnant and were slaughtered soon after final kindling. By increasing the kindling-to-mating interval from 2 to 26 days, total milk production was increased (5590 to 6065 g for R2 and R26, respectively; P < 0·05); voluntary food intake during lactation was not affected (356 g/day on average), but during the dry period was reduced (182 to 169 g/day; P < 0·05) in this way accounting for a decrease during the experimental period on the whole (299 to 249 g/day; P < 0·01). At the final kindling, the number of kits born per litter was lower in does submitted to the R11 than to the R26 rhythm (P < 0·01). By increasing the kindling-to-mating interval, doe body water concentration decreased, while fat and energy increased (P < 0·01) and higher empty body gain was recorded (from −123 to −4, and to +97 g, in R2, R11 and R26 does, respectively; P < 0·001). As a result, body protein, fat and energy balances changed from negative values to approach equilibrium as reproductive rhythm became extensive (energy balance: −0·14, −0·02 and +0·01 of the initial body content in R2, R11 and R26 does, respectively; P < 0·001). At 28 days after kindling, blood leptin concentration was higher (P < 0·01) and IGF-1 lower (P < 0·05) in R26 does. Daily food intake throughout the experiment was lower (P < 0·05) in W21 does due to the longer dry period. Increasing weaning age from 21 to 25 days increased both number of kits born alive per litter (from 7·4 to 9·6; P < 0·05) and doe body water concentration, while body energy tended to decrease (P < 0·1). At 28 days after kindling lower blood leptin concentration was recorded in W21 than W25 does (1·87 v. 2·76 μg/l, P < 0·05).

Effect of variety and preservation method of cassava leaves on diet digestibility by indigenous and improved pigs

Abstract: Digestibility and nitrogen (N) balance studies were carried out on the leaves of short-term (ST) and long-term (LT) varieties of cassava, preserved by sun-drying and grinding into a meal or by ensiling. The cassava leaf meal and ensiled leaves (471 and 373 g/kg total diet dry matter, respectively) were mixed with palm syrup and palm oil, to give the experimental diets CLM and CLS, respectively. Four Mong Cai (MC) (17·2 (s.e. 2·61) kg) and four Landrace × Yorkshire (L×Y) (41·5 (s.e. 2·12) kg) male castrate pigs were used. The experiment was designed as a 2 × 2 × 2 factorial, with breed, cassava variety and processing method as factors. The hydrogen cyanide (HCN) levels of the fresh cassava leaves of ST (545 mg/kg dry matter (DM)) and LT (408 mg/kg DM) varieties were reduced by proportionately 0·63 and 0·33, respectively, after sun-drying and by 0·78 and 0·77, respectively, after ensiling. Intake was higher for DM, crude protein (CP) and organic matter (OM) ( P P P P P P P P > 0·05) in the digestibility of other nutrients or DM. There was a breed by cassava variety interaction for ADF digestibility and breed by processing method for CF digestibility ( P P P P P P

Effect of a high fibre intake on the resistance of the growing rabbit to an experimental inoculation with an enteropathogenic strain of Escherichia coli

Abstract: Response to an experimental infection with an enteropathogenic E. coli O103 strain (EPEC) was assessed in growing rabbits given a high or a low dietary fibre diet (200 and 120 g acid-detergent fibre per kg respectively for high ‘HF’ or low ‘LF’ fibre diet). The two experimental diets, differing in fibre level but not fibre quality, were given ad libitum from 21 days of age to two groups of 12 litters of nine pups, weaned at 28 days (trial 1) and caged collectively. At 42 days of age, the two groups were divided in two subgroups (i.e. four groups of 18 animals), inoculated or not with an EPEC O103 strain. Two further groups of 48 rabbits (trial 2) were given LF and HF diets from 28 days (weaning) to 70 days, and were individually housed to control precisely the food intake. Reducing the fibre level led to a lower post-weaning food intake (64 v. 85 g/days in the period from 28 to 42 days of age, P 105 CFU per g) was found in LF than in HF rabbits (respectively 65 v. 26·7%, P = 0·04). The caecal pectinolytic flora reached 108 CFU per g at 42 and 65 days of age, and was not affected by diet or EPEC challenge. In 42-day-old rabbits the caecal volatile fatty acid concentration was higher in HF than in LF groups (respectively 79 v. 60 mmol/l, P < 0·05), while the caecal pH was slightly lower (respectively 5·93 v. 6·09, P < 0·01). At 65 days of age, rabbits resistant to the inoculation showed a similar fermentation pattern and fibrolytic flora level to non-inoculated animals. Caecal ammonia level was not affected either by age, diet or E. coli challenge (mean = 12·1 mmol/l). From these results, we conclude that a high fibre intake improved the resistance of the growing rabbit to a specific enteropathy, in association with a higher caecal fermentative activity and lower caecal pH.

Intake, growth and meat quality of steers given diets based on varying proportions of maize silage and grass silage

Abstract: Simmental × Holstein-Friesian steers were offered four forage diets. These comprised grass silage (G); proportionately 0·67 grass silage, proportionately 0·33 maize silage (GGM); 0·33 grass silage, 0·67 maize silage ( MMG); maize silage ( M) from 424 (s.d. = 11·5) kg to slaughter at a minimum weight of 560 kg. Forages were mixed and offered ad libitum. Steers were offered 2 kg of a concentrate daily, the concentrate being formulated such that all steers had similar crude protein intakes across dietary treatments. A sample of steers was slaughtered at the beginning of the experimental period to allow the calculation of the rate of gain of the carcass and its components. Carcass dissection of a sample of steers allowed the development of a prediction equation of carcass composition based on thoracic limb dissection of all carcasses. Forage dry matter intake and live-weight gain increased linearly as maize silage replaced grass silage in the forage mixture, resulting in improvements in food conversion ratio (all P = 0·001). Killing-out proportion increased with maize silage inclusion ( P < 0·001) but fat and conformation scores did not differ significantly between diets. However, increasing maize inclusion in the diet resulted in a greater weight ( P = 0·05) and proportion ( P = 0·008) of fat in the carcass, and significant increases in internal fat deposition. The inclusion of maize led to a progressive increase in the daily gains of carcass ( P < 0·001), and significant increases in the daily gains of both fat ( P < 0·001) and lean tissue ( P < 0·001). Fat colour was more yellow in cattle given diets G and GGM than diets MMG and M ( P < 0·001) and colour intensity was lower on diet M than the other three diets ( P < 0·001). There were no significant differences in any aspects of eating quality between diets. Therefore, maize silage has the potential to reduce the time taken for finishing beef animals to achieve slaughter weight with no apparent detrimental effects on subsequent meat quality.

Mapping of multiple quantitative trait loci for growth and carcass traits in a complex commercial sheep pedigree

Abstract: The confirmation of the segregation of experimentally discovered quantitative trait loci (QTL) in a variety of commercial populations is required before their commercial significance can be fully realized. The use of complex pedigrees in the design of such confirmation experiments has the potential to increase the probability of the QTL segregating within the pedigree while maintaining the power to detect this segregation. Here a QTL analysis is applied across candidate chromosomes of a complex pedigree of 570 Charollais sheep from commercial flocks in the UK. This pedigree also contained a moderately sized half-sib family which was analysed separately. Two QTL significant at the 5% chromosome- wide level were detected in the half-sib analysis and seven were detected in a maximum likelihood variance component analysis of the complex pedigree using identity-by-descent values estimated by Markov chain Monte Carlo methods. The estimation of QTL effects was achieved by fitting all QTL for a specific trait simultaneously, reducing the large upward bias observed in the single QTL models. Both methods of analysis detected QTL for live weight, although these mapped to different regions, and the variance components method detected QTL for ultrasonically measured fat depth. This analysis demonstrates the viability of applying a variance component analysis to large pedigrees with the presence of considerable inbreeding.

Comparison of growth curves of three strains of female dairy cattle

Abstract: The objective of the present study was to compare growth curves for live weight (LW) and body size of three strains of female dairy cattle reared under common environments in Ireland. One strain (HP) was selected from a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production. The second strain (HD) represented a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production but with greater selection emphasis on functional non-production traits. The third strain (NZ) consisted of New Zealand Holstein-Friesian females of high genetic merit for profitability in New Zealand. The data consisted of 99 animals (33 animals in each strain) with records on LW, length, girth and height from birth to a minimum of 594 days of age. The von Bertalanffy growth function was fitted to each animal’s records separately and least-squares analyses were used to investigate the effect of strain on birth LW/body size, parameters of the growth function and average daily gains. Average mature live weight of the HD animals (591 kg) was significantly larger than that of the HP (566 kg) or NZ (543 kg) strain; the HD strain matured more slowly. The HD (134 cm) and HP (135 cm) strains were significantly taller than the NZ (128 cm) strain. Although the data set was relatively small there are indications that dairy females of North-American genetic origin were heavier at birth, grew faster, and were heavier and taller at maturity than dairy females of New Zealand origin.

Quantitative aspects of ruminant predicting animal performance

Abstract: Rations for dairy cattle are currently balanced to meet needs for energy, protein, vitamins, and minerals. While individual vitamins and minerals are considered, energy and protein are generally treated in aggregate even though entities within those aggregates can affect milk yield and composition. Significant efforts have been undertaken to describe ruminal metabolism in detail, but descriptions of post-absorptive metabolism assume constant fractional conversions of energy and protein to milk. A quantitative understanding of nutrient metabolism by the post-absorptive tissues is required, and the splanchnic tissues are critical components of the post-absorptive system as they mediate absorption of nutrients and play a role in regulation of metabolite availability.Glucogenic precursor supply can significantly affect endocrine status as well as splanchnic release of glucose, acetate, lactate, ketones, and the non-essential amino acids. Although the relative affinities of the splanchnic tissues for the essential amino acids (AA) are low as compared with the udder, net clearance on a daily basis represents approximately 2/3 of the net supply to the animal due largely to recycling of AA back to the tissue bed. This could be significantly reduced by stimulating removal and use by the udder as splanchnic affinities are much lower than mammary affinities. Additionally, the essential AA composition of absorbed protein is significantly modified by these tissues due to differing affinities for each of the AA. The extent of that modification is not a fixed constant but rather a function of several factors including milk yield. The accuracy of our current feeding systems could be improved if such variable rates of substrate removal replaced current static estimates.

In vitro microbial growth and rumen fermentation of different substrates as affected by the addition of disodium malate

Abstract: The effects of two concentrations of disodium malate on the in vitro fermentation of three substrates differing in their forage: concentrate ratio (0·8: 0·2, 0·5: 0·5 and 0·2: 0·8; g/g dry matter; low-, medium- and high-concentrate substrates, respectively) by rumen micro-organisms were studied using batch cultures. Rumen contents were collected from four Merino sheep offered lucerne hay ad libitum and supplemented daily with 400 g concentrate. Disodium malate was added to the incubation bottles to achieve final concentrations of 0, 4 and 8 mmol/l malate and 15N was used as a microbial marker. Gas production was measured at regular intervals from 0 to 120 h of incubation to study fermentation kinetics. When gas production values were corrected for gas released from added malate, no effects (P > 0·05) of malate were detected for any of the estimated gas production parameters. In 17-h incubations, the final pH and total volatile fatty acid (VFA) production were increased (P 0·05) were detected in the final amounts of ammonia-N and lactate. When net VFA productions were corrected for the amount of VFA produced from malate fermentation itself, adding malate did not affect (P > 0·05) the production of acetate, propionate and total VFA. Malate reduced methane (CH4) production by proportionately 0·058, 0·013 and 0·054 for the low-, medium- and high-concentrate substrates, respectively. Adding malate to batch cultures increased (P 0·05) its efficiency of growth (55·5, 56·7 and 54·3 mg of microbial N per g of organic matter apparently fermented for malate at 0, 4 and 8 mmol/l, respectively). There were no interactions (P > 0·05) malate × substrate for any of the measured variables, and no differences (P > 0·05) in pH, CH4 production and microbial growth were found between malate at 4 and 8 mmol/l. The results indicate that malate had a beneficial effect on in vitro rumen fermentation of substrates by increasing VFA production and microbial growth, and that only subtle differences in the effects of malate were observed between substrates. Most of the observed effects, however, seem to be due to fermentation of malate itself.