Showing papers in "The Journal of Agricultural Science in 1975"

Manipulation of rumen fermentation in sheep by increasing the rate of flow of water from the rumen

Abstract: The effects of an altered rumen dilution rate (D) upon the molar proportions of volatile fatty acids (VFA) in rumen liquor, VFA production rate, microbial protein synthesis and carbohydrate digestion within the rumen were studied using adult wether sheep.Dilution rate and VFA proportions were unaltered by the infusion of up to 121 water/day into the rumen of sheep fed dried grass and concentrate (9:1). There was a small but significant (P < 0·05) increase in the rumen volume when the infusion rate was increased from 8 to 12 1/day.The intraruminal infusion of artificial saliva (41/day), or artificial saliva containing 4% or 8% w/v polyethylene glycol (PEG) caused a significant increase in D with an associated decline in the molar proportion of propionate (Pr) in the rumen liquor. A similar effect was obtained with the intraruminal infusion of 2·5% w/v sodium bicarbonate. The overall regression of Pr on D was highly significant: Pr = 32·5–82·1D; r = –0·99, P < 0·001.A diet of flaked maize: dried grass (6:4) was offered to three sheep each fitted with a rumen cannula and with a re-entrant cannula at the proximal duodenum. The intraruminal infusion (4 1/day) of artificial saliva containing 4% w/v PEG caused a significant (P < 0·01) increase in D and a significant (P < 0·01) depression in Pr in two animals. The dilution rate and Pr in the third animal were virtually unaltered by infusion. The regression of Pr on D for the three animals was highly significant: Pr = 34·8–136·8D; r = –0·98, P < 0·001. Each increase in D was associated with an increased flow of α-linked glucose polymer, total amino acids and total microbial amino acids into the small intestine and with an increased efficiency of microbial protein synthesis within the rumen.

Thiomolybdates and the copper–molybdenum–sulphur interaction in ruminant nutrition

Abstract: In 1945 we reported (Dick & Bull, 1945) the first observations on the effects of molybdenum in the diet of ruminants in limiting the accumulation of copper in their tissues.Further observations (Dick, 1952) indicated that there was a third factor which materially altered the control by molybdenum of copper accumulation and this factor, present in lucerne hay, was identified as inorganic sulphate (Dick, 1953a). It was also shown that sulphate regulated molybdenum excretion (Dick, 1953b) in the urine and hence the level of molybdenum in circulating blood (Dick, 1953c).

Genotype-environment interaction – a challenge for plant breeding

Abstract: Much has been written and said about genotype-environment (GE) interactions and the particular problems which they pose for plant breeders It is not the purpose of this article to dwell upon every aspect of this story, but rather to discuss how these problems came to be recognized, to comment upon the various techniques which have been employed in seeking a solution to them and to suggest what developments might lie ahead

The interaction of nutrition and body condition at mating on ovulation rate and early embryo mortality in Scottish Blackface ewes

Abstract: One hundred and fifty-six Scottish Blackface ewes were differentially group-fed over a 2-month period to achieve three distinct levels of body condition (good, moderate and very poor). Over 5 weeks prior to mating, one group of good-condition ewes was maintained in that condition, one group of good- and one of moderate-condition ewes were brought down in condition by restricted feeding and one group of moderate and the very poor condition ewes were raised in condition by a high level of feeding. Ewes were therefore in good, moderately good or poor condition at mating. After mating, ewes were killed either on return to service or at 25 ± 5 days for counts of corpora lutea and viable embryos.Poor body condition, irrespective of feeding level, was associated with a delay or suppression of oestrus and with a high return-to-service rate. Ovulation rate was positively related to body condition at mating but not to the level of pre-mating food intake at the condition levels studied.Embryo mortality decreased as body condition at mating increased and the interaction between condition and the level of pre-mating food intake had a differential effect on mortality of single- and multiple-shed ova. The lowest rate of embryo mortality was found in ewes in moderately good condition which had been well-fed before mating.

Quantitative analysis of the growth, development and distribution of flowers and pods in oil seed rape (Brassica napus L.)

Abstract: The growth and development of single plants of oil seed rape, variety Zollerngold, are described quantitatively and particular attention paid to the sequence and pattern of flower and pod production on the different inflorescences. The period of flower opening over the whole plant spanned an average of 26 days and more than 75% of the pods which were retained to maturity were formed from flowers which opened within 14 days of anthesis. Most of these flowers were found on the terminal raceme and on the basal and middle regions of the axillary inflorescences arising from the uppermost three nodes.

The ‘teat order’ of suckling pigs: I. Relation to birth weight and subsequent growth

Abstract: Teat orders were determined for 76 litters of Large White and Large White × Landrace pigs. Regression analysis within litters revealed a relationship between suckling position and weight both at birth (P<0·01) and at 3 weeks of age (P<0·001), with the heavier piglets tending to occupy the more anterior teats. The correlation coefficients, however, were very small (r = –0·16 and –0·22 respectively). The correlation between birth weight and 3-week weight was much larger (r = +0·47); and a comparison of pairs of litter-mates showed that a difference in birth weight of 0·25 kg or more persisted at 3 weeks in the majority of cases, regardless of which piglet suckled the more anterior teat. Birth weight accounted for much more of the variation in 3-week weight than did teat number, and, when the effect of birth weight had been taken into account, teat number accounted for only an additional 2·3% of the variation. Even so, the anterior teats did appear to confer some advantage which was independent of that of the birth weight of the piglets suckling these teats. From the results of this and other studies it is concluded that there is only a weak relationship between suckling position and weight at birth and 3 weeks. Other unidentified factors are probably of more importance for the within-litter variation in weight gain of suckling pigs.

An analysis of the problem of lodging with particular reference to wheat and barley

Abstract: It has been shown that structural failure in small grain cereals occurs by buckling rather than by loss of anchorage. A theoretical study established the relationship between a lateral force applied to the head, and failure of the straw. Resistance to bending is determined by two factors, Young's modulus and outer diameter of the straw. These were determined in laboratory tests. The value of Young's modulus was affected by stage of maturity of the straw. Wind-tunnel experiments established a relationship between air velocity and deflexion of the head. An attempt was made to calculate the wind speed necessary to cause straw breakage in the field. The kinetic effect of raindrops was not a significant factor in lodging. Attention has been drawn to the possible importance of taper in the straw.

An equation to predict the leaching of surface-applied nitrate

Abstract: The fraction (f) of surface-applied nitrate leached below any depth h cm in a uniform soil profile may be calculated from the equationwhere P is the quantity of water draining through the soil (in cm) and Vm is the percentage volumetric field capacity. The fraction of nitrate retained is then (1—f).This equation has been tested using published data. Values of h corresponding to the mean displacement (f = 0·5) were calculated for a wide range of soil and weather conditions and the results compared with mean displacements measured in the field. Similar comparisons were made with the leaching equation of Rousselle (1913) and Levin (1964). The new equation gives good agreement with the observed data, whereas the Rousselle-Levin equation generally overestimates the mean displacement of nitrate. Methods of applying the equations to field situations are discussed.

Energy values in pig nutrition:I. The relationship between digestible energy, metabolizable energy and total digestible nutrient values of a range of feedstuffs

Abstract: Nineteen feedstuffs were evaluated for total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME) using growing pigs. DE values, on a drymatter basis, ranged from 1570 kcal/kg D.M. (grassmeal) to 4890 kcal/kg D.M. (BP Grangemouth protein). ME averaged 97·4% of DE for cereal feeds and 81·9% of DE for protein feeds, the ratio of DE to ME being significantly affected by the crudeprotein content of the feedstuff:ME/DE × 100 = 99·7–0·18 × crude protein (%): r = –0·94; P < 0·01.TDN was more closely related to ME than DE:DE (kcal/kg D.M.) = 45 TDN + 156: r = 0·92; P < 0·01,ME (kcal/kg D.M.) = 43 TDN + 71: r = 0·98; P < 0·01.ME values were corrected to both 30% and 0% nitrogen retention. Correction to 30% retention caused a maximum change of 3% in ME value while correction to 0% retention had a variable effect related to protein content of the feedstuff:(ME(N0)/ME) × 100 = 98·3–0·113 × crude protein (%): r = –0·80; P < 0·01.

An effect of soil ingestion on the utilization of dietary copper by sheep

Abstract: To test the hypothesis that the ingestion of Mo-rich soils by ruminants might adversely affect Cu metabolism, four groups of initially hypocupraemic ewes were repleted with a Cu-supplemented diet either soil-free or containing 10% of one of three soils of low, medium and high Mo content. The three soils were equally effective in inhibiting the response in plasma Cu and probably reduced the availability of Cu by more than 50%. The ingestion of certain soils produced increases in urinary Mo and Zn concentrations, indicating that the Mo and Zn ingested in soil can be biologically available: however, these Cu antagonists were probably released in insufficient quantities to have contributed greatly to the observed interference with Cu metabolism. Soil ingestion may be involved in the aetiology of hypocuprosis in cattle and swayback in sheep, since it commonly constitutes 10% of the D.M. intake of animals grazing winter pasture.

Some observations on metabolite production and utilization in vivo by the gut and liver of adult dairy cows

Abstract: Metabolite production rates were determined in the portal vein and hepatic veins of catheterized adult dairy cows maintained under normal conditions of husbandry. The production rates were calculated from the metabolite concentrations in arterial, portal and hepatic-venous blood, and from the rates of blood flow in the portal vein and the hepatic veins. In general, qualitatively similar metabolite production was observed in three non-lactating and two lactating cows, but production rates tended to be higher in the lactating cows due to higher blood flow rates. About half the lactate utilized by the liver was absorbed from the gut, while the other half was derived from endogenous sources. Lactate absorbed from the gut was quantitatively of less significance than propionate as a substrate for hepatic metabolism. Even in cows that were well fed, there was a net production of ketone bodies from the liver that was almost as great as the net production from the gut. However, while the liver produced D-3-hydroxybutyrate it took up acetoacetate. In the lactating cows, acetate, propionate and butyrate were absorbed from the gut in the proportions of 9·5:2·5:1, respectively. About 90% and 80% of the absorbed propionate and butyrate, respectively, were taken up by the liver. On the routine hay/concentrate diet there was little net uptake or output of glucose by the gut. However, there was consistent production of glucose by the liver, amounting to a maximum, in this study, of about 11 mol/24 h, assuming constant glucose production throughout the 24 h day. The rate of carbon dioxide appearance in the portal vein was about twice that of oxygen uptake by the gut. The liver used oxygen, and produced carbon dioxide, at nearly equal rates. The uptake of glucogenic substrates by the liver accounted adequately for the observed rates of hepatic gluconeogenesis. In one of the lactating cows it was observed that there was a net production of acetate by the liver that amounted to half the net absorption of acetate from the gut (ethyl alcohol was not the precursor of this acetate) and that (glutamine + asparagine) and serine had the highest rates of appearance in the portal vein and the highest rates of uptake by the liver.

Effect of diets low in calcium and phosphorus on the development of growing lambs

Abstract: Five groups of four 8-week-old Blackface lambs were used to compare the effects of dietary deficiencies of calcium and/or phosphorus: four were given for 16 weeks a semi-purified diet low in Ca (0·07 %) and P (0·13 %), either unsupplemented (LCaLP) or supplemented with 0·3 % Ca (NCaLP), 0·3 % P (LCaNP) or both (NCaNP), and the remaining group was slaughtered initially.The only clinical abnormality observed was twisting of the forelegs in group LCaLP. Food intake was depressed by 26 % in LCaNP group, by 41·5 % in NCaLP group but was largely unaffected in group LCaLP. Apparent D.M. digestibility was lower for group NCaLP (57·7 %) than for other groups (61·2 %). Differences in live weight and body fat reflected the differences in food intake between treatments but the weights of fat-free body components were lowest in the groups given low P diets.The LCaNP diet decreased plasma Ca and increased plasma P but the NCaLP diet had the opposite effects. The LCaLP diet had no effect on plasma Ca and decreased plasma P less than the NCaLP diot.The three mineral deficient diets caused equally marked decreases in Ca and P retention but did not induce negative balances; they also impaired the quality of bone in the tibia and lumbar vertebra, by reducing both the amount of bone matrix and the degree to which it was mineralized, and produced histological lesions of rickets and osteoporosis. Diets low in P caused a marked fall in Mg content of the skeleton.Urolithiasis was common in lambs given diets adequate in P.

The ‘teat order’ of suckling pigs: II. Fighting during suckling and the effects of clipping the eye teeth

Abstract: The development of stable suckling order, the incidence of fighting when suckling, weight gain during the suckling period, and the severity of facial wounding were studied with litters of piglets in which the canine and lateral incisor teeth were either clipped at birth or left intact. Facial wounding was largely confined to litters with unclipped teeth. Severity of wounding correlated with the observed incidence of fighting on the udder (P<0·01); and both wounding and fighting were more common among litters comprising a large number of piglets (P<0·05). When the effect of litter size was taken into account, there were no substantial differences in weight gain to 3 weeks between piglets with high and low scores for facial wounding, nor between clipped and unclipped litters. Piglets which habitually occupied the most anterior or most posterior teats had less facial wounding than middle-suckling piglets, and showed greater consistency in teat choice. No gross differences between clipped and unclipped litters were observed in the development of stable suckling order during the first week of life. It is concluded that the ‘eye’ teeth, although used in disputes over teat choice, have little influence on the frequency of such disputes or on the original development of stable suckling order.

Quantitative digestion of fresh herbage by sheep: IV. Protein synthesis in the stomach

Abstract: The proportions of bacterial and dietary protein entering the duodenum of sheep fed fresh herbage were assessed using 2,6-diaminopimelic acid as a marker. The herbages fed were Lolium perenne L., ‘Grasslands Ruanui’ perennial ryegrass; L. (perenne × multiflorum), ‘Grasslands Manawa’ short-rotation ryegrass; Trifolium repens L., ‘Grasslands 4700’ white clover.The dietary protein degraded in the stomach was approximately 70% for all herbages. The bacterial contribution to protein entering the duodenum was 43·1, 57·1 and 52·9% for Ruanui, Manawa and white clover respectively. Protein entering the duodenum contained only a small amount of protozoal protein.Bacterial protein synthesis in the stomach was different for all three herbages, averaging 16·2, 30·7 and 19·8 g/100 g organic matter apparently digested for Ruanui, Manawa and white clover respectively. It is suggested that the micro-organisms digesting Manawa synthesized protein more efficiently.

The limiting effect of plant size at inflorescence initiation on subsequent growth and yield of oilseed rape (Brassica napus)

Abstract: A substantial loss in yield usually occurs when oilseed rape is sown later than mid-September. Field experiments in 1972–3 tested whether this is because all plants, irrespective of size, initiate inflorescences during the winter, thus restricting the eventual size of the leaf canopy and the yield potential of late-sown plants, which are still very small when the change to the reproductive phase occurs.Sowing a standard winter variety, Victor, from mid-August to mid-October resulted in initiation occurring from late October to February. When sown after mid-September yields were proportional to plant size at initiation. The winter was mild, and in colder conditions earlier sowing may be required to enable plants to reach a critical size before initiation takes place. When sown in August plants were very large but yield was not improved. A study of the development of the pod canopy showed that the extra yield potential was not realized because heavy losses of pods and seeds occurred, particularly in the more shaded positions.When a range of winter varieties, chosen to contrast the timing of phasic development, was sown on two dates yield was proportional to the interval between sowing and initiation, particularly when late sown, presumably because late initiators were able to lay the foundation of a more substantial root and shoot system. This has implications for plant breeding programmes because the low erucic acid varieties currently being grown initiate inflorescences early. When spring types were sown in mid-October they formed floral initials very early, and gave particularly small and weak plants, with a low yield. Winter types sown in March did initiate flowers and produce large plants, but yields were no better than spring types as flowering and ripening were irregular and late, the cold requirement for initiation being only marginally fulfilled.

A study of feeding types and certain rumen functions in six species of South African wild ruminants

Abstract: In order to characterize the rumen digestive physiology of South African wild ruminants investigations were made on a total of 35 individuals of six species killed in various regions during the dry season.In buffalo, blue wildebeest and gemsbok grasses constituted 85–100% and in impala, springbok and kuduless than 10% of the diet. In the case of the latter three species effects of the habitat and of predilection for certain plant materials were apparent.Compared with the grazers, the species feeding mainly on plant material other than grass were characterized by a smaller physiological capacity of the rumen reticulum, higher counts of ciliate protozoa and ‘large bacteria’, higher levels of rumen ammonia and higher molar proportions of rumen propionate and valerate. Within these feeding types differences between species were indicated.

Experiments on the nutrition of the dairy heifer:IX. Food utilization in lactation

Abstract: Food utilization by lactating dairy cows was studied in a randomized experiment covering the first 24 weeks of lactation, with further observations on performance over the remainder of the lactation under farm conditions. Over a 3-year period 90 firstcalf cows each took part in the experiment for one lactation, making six groups of 14–16 animals.For the experimental period a fixed basal diet was given of hay, concentrates, and wet brewer's grains. One group received only the basal ration. Four groups received in addition a fixed concentrates supplement for 4, 8, 12, 16 weeks from calving onwards respectively. The sixth group also had supplementary concentrates for 16 weeks but for weeks 5–12 inclusive the amount was doubled so that this group's diet simulated broadly ad libitum feeding in early lactation.Milk yield was increased by extra concentrates. The greater part of the effect was apparent in the first 2 weeks of different levels of intake, with a further build-up over the next 6–8 weeks. The size of the response fell as time from calving to initiation of different intakes increased. Additional food increased and delayed peak yield level. Persistency of milk yield was not affected by fixed differences in intake. Rate of liveweight change was improved by extra concentrates, less so in the third compared with the first month on treatment.A higher level of feeding in early lactation led to a greater partition of nutrients in mid-lactation to milk at the expense of gains in body reserves. This advantage to milk production extended to the end of lactation. In it the greatest response per unit concentrates was obtained from supplementation in the first 4 weeks of lactation but the total effect was increased by giving a double allowance of concentrates, and by extending the period of extra feeding to 8 weeks after calving.Solids-not-fat content and yield, and fat yield but not fat content, showed a similar response pattern to milk yield.Animal-to-animal variation in output on constant diets was characterized by negative regressions of live-weight change on milk yield. The regression coefficients were greater in early than in mid-lactation but they were constant in size at any one time for the various groups. A change in ration induced a change in output of the individual in which that production pathway favoured naturally by the animal was the more affected.

A quantitative comparison of the growth, development and yield of different varieties of oilseed rape

Abstract: A field experiment to compare the growth, development and yields of four varieties of oilseed rape, Cresus, Guile, Rigo and Nilla, is described and the results discussed. Cressus was the highest-yielding variety largely because it produced more pods and more seeds per pod. The numbers of pods and seeds per pod were positively correlated with the leaf area index at the onset of flowering. This suggests that the rate of supply of carbon assimilates to the inflorescences around the time of anthesis is an important yield-determining character. The mean weight of the individual seeds was greater in Cresus than Guile and this difference, which developed late on in pod growth, also contributed to the higher yields in Cresus.

Competition between maize and Rottboellia exaltata

Abstract: One pot and five field experiments were made to study different aspects of the competition between R. exaltata and maize.The growth of young maize plants was not inhibited by being grown together in pots with young R. exaltata plants. In the field the soil tended to be somewhat wetter when the two species were grown together than when maize was grown alone, and was wettest with R. exaltata grown alone. Maize grain and total yield decreased and shoot yield of R. exaltata increased with R. exaltata plant density on both irrigated and unirrigated blocks of land, but yields were not much affected on either block by increase in plant density of maize or in nitrogen supply; maize yield was increased by irrigation but that of R. exaltata was not. Maize plant arrangement did not greatly affect maize grain and total yield or R. exaltata shoot yield, nor did arrangement of R. exaltata plants have much influence on their depression of maize yield, but R. exaltata caused a greater decrease in the grain yield of a short than of a tall maize cultivar.R. exaltata plants germinating at the same time as the crop plants did not have much effect on maize grain yield if they were removed by 8 weeks after the seedlings emerged, but decreased it considerably if allowed to remain for 12 weeks or more; weeds sown 2 or more weeks after the maize emerged hardly grew and had little effect on maize yield. When maize and R. exaltata were grown together leaf area of the maize was little affected up to the time of flowering, but was decreased after flowering, while leaf area of the weed was greatly depressed. Up to 7–8 weeks after seedling emergence more of the ground area was covered by foliage when maize was grown with R. exaltata than when it was grown alone, but later the ground was completely covered by foliage in both cases. Dry weight of grain and shoot of maize increased and that of shoot of R. exaltata decreased when the weed plants were shortened with growth regulators.

Effect of soil water stress on water economy and oil composition in sunflower (Helianthus annuus L.)

Abstract: In a field experiment sunflower plants were subjected to soil water stress (SWS) at — 15 bar during stages of slow elongation, rapid elongation, flowering and ripening.Significant decreases in yield, 100-seed weight and oil content were found as a result of SWS. The treatment resulted too in less evapotranspiration and a better water economy for production of seeds and oil.The iodine value but not the acid or saponification values of the oil was affected by SWS. No qualitative differences in oil composition occurred at different treatments. However, percentage of oleic acid was higher than that of linoleic acid; SWS resulted in a clear tendency for an increase in the ratio of oleic/linoleic acids especially for plants subjected to SWS during elongation stage.Sunflower plants were more sensitive to SWS during the elongation and flowering stages than during ripening stage

Fatty acid composition of adipose tissue of Jersey cattle during growth and development

Abstract: The effect of age on the fatty acid composition of depot fat of Jersey cattle has been investigated. Serial samples of subcutaneous fat were obtained by biopsy of the same animals from 3 months to 2 years of age. Samples of depot fat were also obtained from various anatomical locations of animals slaughtered between birth and 11 years of age.In subcutaneous fat at biopsy the percentage stearic acid remained constant to 1 year of age and then declined from 20% to 5% during the period 1–2 years post partum.In perinephric fat the stearic acid content increased from 10–15% at birth to 40% at 1 year of age, and then declined during the period 1–2 years post partum.Changes in the percentage stearic acid above the 10% level were accompanied by inverse change in octadecenoic (C18:1) acid, and below 10% mainly by change in hexadecenoic (C16:l) acid.There was a gradient of unsaturation between subcutaneous and internal body fats, and also within the subcutaneous fat itself.Evidence is presented to suggest that the decrease in the unsaturation of depot fat during the period 1–2 years post partum is associated with the deposition of more unsaturated fatty acids during the fattening phase of development.

A study of relationships of breed, time of mating, level of nutrition, live weight, body condition, and face cover to embryo survival in ewes

Abstract: Embryo survival was studied in flocks of 500 Saxon Merino and 500 Border Leicester × Merino ewes introduced to rams in either summer or autumn. The ewes were fed 200, 100 or 25% of a maintenance diet from day 2 to day 16 after mating. Embryo survival was greatest in ewes fed the maintenance diet. There was no suggestion that live weight, face cover or condition score were important factors affecting embryo survival. Embryo survival in the twin ovulating cross-breds was higher than in the twin ovulating Merinos, but there was no significant difference in embryo survival in ewes with single ovulations. Embryo survival in ewes with twin ovulations was significantly higher at the autumn mating than in summer.

Effect of variations in dietary protein and of supplements of cod-liver oil on energy digestion and microbial synthesis in the rumen of sheep fed hay and concentrates

Abstract: Estimates have been made of the amount of energy fermented and the amounts of microbial protein and total fatty acids synthesized in the rumen of sheep given various rations of hay and concentrates. The sheep had re-entrant cannulas in the proximal duodenum. The amount of protein synthesized was calculated from the flow of RNA-N at the duodenum. The change in the amount of total fatty acids between the food and the proximal duodenum was also measured.In Expt 1, six sheep were given a low-protein basal diet and the same diet supplemented with a vegetable protein concentrate with or without tannin treatment. Some 72% of the digestible energy was apparently digested in the rumen and an estimated 150–170 g microbial protein were synthesized per kg organic matter apparently digested in the rumen. Differences due to the dietary treatments in the amount of energy digested and the amount of microbial protein synthesized were small and non-significant.In Expt 2, the effect of a supplement of 20 g/day of cod-liver oil (CLO) on digestion of a mixed diet of hay and concentrates was examined in five sheep. Despite a marked fall in the ratio of acetic acid to propionic acid in the rumen volatile fatty acids when CLO was added, there were no clear differences in the amount of energy fermented in the rumen, which averaged 64% of the digestible energy, or in the efficiency of microbial protein synthesis, which averaged 200 g/kg organic matter apparently digested in the rumen. On the basal diet an increase of 6·7 g total fatty acid/day occurred in the stomach. This was presumably synthesized in the rumen. However when CLO was added to the diet, a decrease of 4·1 g total fatty acid/day was measured.

The utilization of maize silage for intensive beef production: 3. Nitrogen and acidity as factors affecting the nutritive value of ensiled maize

Abstract: Twelve rumen-fistulated British Friesian castrated male calves, initially three months of age and 77 kg live weight (LW) were fed, both ad libitum and at a restricted level of 21 g organic matter (OM)/kg LW, on either maize silage (26% dry matter, 8.6% crude protein in D.M.) alone or with 2% of urea in the silage D.M., added at the time of feeding. At each level of urea (0 or 2%) silage pH was either increased to pH 5·45 by the addition of sodium bicarbonate, or left unchanged (pH 3·95) in a change-over design within each urea level. Addition of urea increased voluntary silage D.M. intake by 8% (P < 0·05) and partial neutralization increased consumption by 12% (P < 0·01). However, the response to urea only occurred when the silage was partially neutralized. At restricted intake, addition of urea increased rumen ammonia nitrogen from 3·17 to 13·41 mg/100 ml (P < 0·001) and blood urea nitrogen from 2·20 to 10·06 mg/100 ml (P < 0·001). There was no significant effect of addition of urea or of bicarbonate on rumen pH, VFA concentration or energy digestibility. However, the addition of urea significantly increased N retention (P < 0·01). Partial neutralization of silage was associated with an increase in venous blood pH from 7·366 to 7·396 (P < 0·001), and urine pH from 7·43 to 8·42 (P < 0·001). It is suggested that both low nitrogen content and acidity limit the nutritive value of ensiled maize, and that the effects of addition of urea and of partial neutralization may be metabolic rather than ruminal.

The growth responses to weather of simulated vegetative swards of a single genotype of Lolium perenne

Abstract: The influence of ambient weather conditions on the regrowth and morphology of a perennial ryegrass sward, over the period May–October 1972, was assessed by following the performance in the field of a succession of vegetative, single genotype, simulated swards previously grown under standard conditions. Crop growth rates estimated from largely non-destructive measurements of growth components (leaf extension, leaf weight/length ratio, tillering rate and tiller density) agreed with, and were more precise than, rates determined from harvests; the components having the greatest influence on growth rate were leaf extension and leaf weight/length ratio. Leaf extension and appearance were closely dependent on temperature; leaf weight/length was only slightly affected by the weather. The growth rates of total above ground parts, especially of herbage above the cutting height, were largely determined by temperature and initial leaf-area index, and insensitive to insolation. At higher temperatures, a greater proportion of assimilates was partitioned into herbage growth.

Body weight and wool production in grazing sheep given access to a supplement of urea and molasses: intake of supplement/response relationships

Abstract: A technique for estimating the intake of liquid supplements by individual, grazing animals was used in a trial with 200 sheep grazing poor quality pasture and given access to a urea-molasses supplement (19%, w/v).A mathematical procedure was developed to estimate intake of supplement based on measurements of the accumulation of tritiated water (TOH) and its rate of turnover in the body of each animal after a TOH-labelled mixture had been available for a period of 7 days.In calculating the level of intake of labelled supplement, it was assumed that each animal ingested the mixture once daily over the 7-day period, since animals were observed to take the supplement daily and the daily loss of supplement from the dispenser was noarly constant. It was estimated that the combined intakes of the animals accounted for 87% of the known total loss of labelled supplement from the dispenser.Of the 200 sheep, 97 did not consume any supplement and among the other 103 animals, estimated intake varied from 5 to 550 ml/day.All sheep lost body weight during the trial, but those consuming the supplement lost significantly less weight, and grew significantly more wool during the period of supplementation, than did the sheep that did not consume the supplement.A small but significant amount of the variance (13%) in body-weight change and wool growth during supplementation was removed by multiple regression analysis, by including the intake of the supplement, faecal egg count (as an indication of parasite burden) and body weight at the start of the trial, as independent variables. Other factors not studied (e.g., dry matter intake) apparently accounted for a large proportion of the variance.The relationship between body-weight change and intake of the urea-molasses mixture was compatible with the hypothesis that the supplement was used largely as a concentrate feed, and not solely as a nitrogen supplement.

Compensatory growth in immature sheep: I. The effects of weight loss and realimentation on the whole body composition*

Abstract: Forty-eight cross-bred wether lambs were used to measure the effects of severe feed restriction and realimentation on the body and carcass composition of immature sheep. Ten of the total number of sheep were used as an initial slaughter group, 12 were continuously fed (six at the ad libitum level of intake and six at 70% ad libitum), 26 were progressively underfed and 18 of them were realimented after a mean loss of about 25% empty body weight (EBW).Shrunk body weight (SBW = weight after an 18-h fast with access to water) was a good predictor of empty body weight (EBW = SBW minus gastro-intestinal contents) and the EBW of continuously growing sheep was a good predictor of body water, protein, fat, energy and ash, but it was not precise after realimentation, particularly in the early stages of refeeding. Restricted continuous supermaintenance feeding did not alter the body composition of the sheep from that of the sheep on the ad libitum intake at any given EBW except slightly to increase the carcass protein content.Although underfeeding to produce an EBW loss of 25% generally produced changes in the chemical body components which were similar to a reversal of normal growth, body fat did not decrease during the first half of the submaintenance feeding and did not increase during the first 2 weeks of realimentation. Under all circumstances percentage body fat was very closely related to percentage body water.Sheep realimented at 26 kg (after losing 25% EBW) contained, at 45 kg EBW, more bodywater and protein and less fat and energy than continuously-fed animals of the same EBW. The treatment effects were greater in the carcass and had little effect on the non-carcass EBW, with th e result that the refed sheep had 1800 g more water × protein in a carcass that weighed 700 g more than one from a normally grown sheep of the same EBW. The regression of calorific value of th e ash-free dry matter on body fat as a percentage of ash-free dry matter gave calorific values of body protein and fat as 5·652 and 9·342 kcal/g of ash-free dry matter, respectively.

Effect of protein concentration in the diet on blood composition and productivity of lactating Holstein cows under thermal stress

Abstract: An experiment was designed to assess the effect of thermal stress and protein value of the diet on the productivity and some of the blood organic constituents of lactating Holstein cows. Two groups of eight animals each were used in 2 × 2 Latin-square designs with two experimental diets. The percentage of crude protein in the diets was 14.3 and 20.8 %.Rectal temperature and respiration rate were recorded twice weekly and jugular blood samples were collected at weekly intervals for analysis. Daily feed intake, refusals and milk production per cow were recorded. Representative samples of morning and afternoon milk were taken three times a week for chemical analysis.Data on respiration rate and rectal temperature suggested that both groups of animals were under thermal stress. However, significantly lower values were found by increasing the protein level of the diet. The higher level of protein significantly increased total milk production, 4 % fat-corrected milk (4 % FCM), total solids, solidsnot-fat, protein percentage and yield, casein and non-protein-nitrogen in milk. The increase in milk production and 4 % FCM was found to be associated with the increase in total feed and total-digestible-nutrients intake but not with crude-protein intake. Protein levels in the diet had no effect on fat percentage and yield nor on whey protein.The correlation coefficients between respiration rate and rectal temperature with some of the blood organic constituents suggested an inverse relation between thermal stress and the blood organic constituents. The higher level of protein in the diet significantly increased haemoglobin levels but had no effect on oxyhaemoglobin, haemoglobin:oxyhaemoglobin ratio and haematocrit value. Total serum protein was not affected by thermal stress or by the protein value of the diet. Increasing protein levels in the diet increased albumin but decreased the globulin fraction of serum protein. Plasma glucose and non-protein nitrogen were increased by increasing the protein in the diet.

Changes in the biochemical composition of herbage upon freezing and thawing

Abstract: Six herbage samples (ranging from poor quality hill herbages to high quality ryegrass and clover) were analysed for soluble carbohydrate, total and soluble nitrogen (N), cell-wall carbohydrates and in vitro digestibility. Changes during freezing and thawing processes were measured. Invertase activity occurred in all frozen and thawed samples. Although the total N content of all samples remained constant throughout, the soluble-N contents of the four better quality herbages were considerably reduced on freezing and thawing. Cell-wall carbohydrates and in vitro digestibility measurements were unaffected by freezing and thawing.

Response of cotton to water and nitrogen in a tropical environment: I. Frequency of watering and method of application of nitrogen

Abstract: Two experiments were made in successive years in which three frequencies of watering were combined factorially with several rates and methods of applying nitrogen. Soil water content and leaf water potential were measured. The least frequent watering treatment decreased yield and nitrogen applications increased yield. All of the effect of water and most of the effect of nitrogen were associated with changes in the number rather than the weight of bolls. Although the combination of heavy nitrogen with frequent watering caused the crop initially to set fruit more slowly than did heavy nitrogen with infrequent watering, it prolonged flowering and increased the number of fruit ultimately set. Thus yield and the potential duration and cost of insect control were also increased. There were no differences in yield nor rate of setting between the following methods of application of the nitrogen: all applied to the seed bed; split application between the seed bed and side dressing 2 months later; and split application between the seed bed, side dressing, and irrigation water. However, when application was split so that most was applied in the water, the response was not as great. Application of nitrogen combined with frequent watering decreased the weight of the early bolls by decreasing fibre per seed. Nitrogen increased the weight of later bolls by increasing the number and weight of seeds. The practical and physiological implications of these results are discussed and a crop nutritional hypothesis for cotton developed further.