Curves of growth in live-weight, from birth to 16 weeks of age, of 362 Suffolk × Welsh lambs were analysed for the effect of sex, birth type, sire and test centre environment and related to variation in age at slaughter.

The relative pre-natal disadvantages of twin lambs resulted in their curves of growth differing from those of single-born animals, particularly in males. Test centre environment exerted a marked effect in such cases. At one centre, male twins showed marked compensatory growth.

Differences in growth existed between the 14 sire progeny groups. As the linear component of the growth curves decreased, the quadratic values became increasingly negative. Deceleration of growth was most marked in slowest growing progeny groups and this was accentuated by a poor test centre environment.

These factors combined to influence age at slaughter, which was also related to birth weight of the lamb. Lambs at the best test centre reached slaughter weight 10 and 16 days earlier than lambs at the two remaining centres. Sires produced differences in age at slaughter of 10 to 14 days, within centres.

Sixty-four British Friesian castrated male cattle (steers) with an average starting weight of 292 kg and an average slaughter weight of 460 kg were used to compare compound diets containing 0, 10, 20 or 30% NaOH-treated straw. A basic diet of 1·8 kg hay, 1·8 kg barley straw and sugar beet pulp, on a scale rising from 1·4 to 2·8 kg according to live weight, was given throughout the trial. Compound diets were individually offered on a scale starting at 3·8 kg rising to 5·8 kg with an average intake of 4·9 kg/day. Treatments did not differ significantly in respect of live-weight gain, which ranged from 0·94 kg/day with the control to 0·97 kg/day with the 30% NaOH-treated straw compound. The grading of the animals, based on the Meat and Livestock Classification scheme, also showed no significant difference.

A second trial with a further 64 British Friesian steers tested inclusion levels of 0, 30,45 and 60% treated straw in a compound diet. At the start of the trial, the cattle averaged 328 kg live weight and were slaughtered from 450 kg live weight. Animals were yarded in store condition and were given a combination of grass silage and compound diets according to a scale, based on live weight and a predicted performance of 1 kg live-weight gain per day. There were no significant differences between treatments in live-weight gain, which ranged from 0·97 kg on the control to 1·02 kg/day on the 45% NaOH-treated straw diet. There was some refusal on the 60% NaOH-treated straw diet in respect of twice daily allocations, with a few cattle on occasions not being able to consume the allowance in the 30 min provided. However, each feed allocation was always consumed before the next meal. There were no significant differences between treatments in respect of fat class, but cattle on the 45% treated-straw diet had statistically superior conformation compared with the control.

The objective of this study was to examine the effect of dietary vitamin A (retinol) on leptin in cattle. The relationship between plasma leptin and insulin was also examined. The experiment studies 16 9-month-old steers over the following 20-month fattening period. Four treatment diets were given to four steers in each of four groups. Cattle in treatment A were given a diet high in vitamin A (9000 to 10500 µg/day) throughout the experiment. Cattle in treatment B were given a diet low in vitamin A (300 to 4500 µg/day) for 0 to 10 months, after that they were given the high vitamin A diet during the period 10 to 20 months. Cattle in treatment C were given the low vitamin A diet for 0 to 14 months, after that they were given the high vitamin A diet for the period 14 to 20 months. Cattle in treatment D were given the low vitamin A diet throughout the experiment. Plasma samples were collected at 2-month intervals during the experiment to determine the plasma leptin, insulin and vitamin A concentrations. Plasma leptin concentration significantly increased over the fattening period (P < 0·001) but did not differ between the treatments (P > 0·05). Plasma leptin concentration was positively correlated with insulin concentration (r = 0·44, P < 0·001), although it was not correlated with plasma vitamin A concentration (r = –0·01, P > 0·05). It was concluded that dietary vitamin A in cattle does not affect plasma leptin concentration.

Breeding data from 1543 artificial inseminations, performed on 763 purebred and crossbred zebu cattle reared on 73 small farms, in the Amazon basin of Peru from 1980 to 1986, were evaluated. Inseminations were performed during morning hours using Holstein or Brown Swiss frozen semen. The calving to first oestrus and calving to conception intervals, number of services per conception, intervals between services and conception rate were evaluated. A total of 64-4% of first services and 61-4% of conceptions occurred between the middle of the dry season and the middle of the rainy season. Farm effect proved to be the most important source of variation for all reproductive traits. Other important factors influencing the interval from parturition to first service were breed of cow, parity and season of service. Parity influenced the interval from parturition to conception while parity, time of oestrous detection and inseminator influenced conception rate. The long post-partum anoestrous interval was found to be the most important factor limiting reproductive efficiency on small farms involved in the artificial insemination programme. The reproductive performance of the crossbred cattle tended to be better than that of the purebred zebu cattle.

An experiment was designed to establish the growth response of young housed steers to the feeding of stack-ammoniated low-quality hay, and to a range of different supplements for 16 weeks, and any carry-over effects during the following 24 weeks at pasture. Ammoniated hay was offered alone (TA), or with daily supplements of either 0·75 kg barley (TLB), 1·50 kg barley (THB), 0·1125 kg fish meal (TF), 0·75 kg or 1·50 kg of a barley-based concentrate (TLC and THC, respectively). Untreated hay was offered with either urea (UU) or with a daily supplement of 0·75 or 1·50 kg concentrates (ULC and UHC respectively).

Ammoniation increased the total nitrogen concentration of the hay from 13·4 to 24·2 g/kg dry matter, and resulted in a small increase in the organic matter digestibility measured in vivo (0·597 to 0·653), compared with that measured in vitro (0·572 to 0·667). Digestibilities of the fibre fractions, measured in vivo, were also increased by ammoniation (0·626 to 0·734, 0·637 to 0·761, 0·678 to 0·771 for acid-detergent fibre, neutral-detergent fibre and cellulose, respectively). Intakes of hay were reduced by supplementation, with the exception of TF, although total intakes were increased. During the housed period, live-weight gains of steers given ammoniated hay were 0·58, 0·71, 0·81, 0·69, 0·80, 0·86 kg/day for treatments TA, TLB, THB, TF, TLC, THC, respectively. The live-weight gains of steers offered the untreated hay were 0·49, 0·66, 0·87 kg/day for treatments UU, ULC, UHC, respectively. There was no carry-over effect of treatments on live-weight gains over the grazing season (mean 0·66 kg/day). It is concluded that when high levels of supplementation are available, no benefit is to be gained by ammonia treatment of ihe hay. However, without supplementation stack ammoniation of hay produces a marked improvememt in performance, compared with the addition of urea at feeding.

The objective was to evaluate different oestrous synchronization schemes in beef cattle under range conditions. In experiment 1, 202 heifers averaging 26 months of age were assigned randomly to three treatments: (a) GnRH-PG. (no. = 44) day 0 (D0): injection of GnRH; D7: injection of PGF2α; D0 to D25 oestrous detection (OD) and artificial insemination (AI); (b) OD-PG. (no. = 45) D0 to D4; OD + AI; D5: injection of PGF2α; D5 to D25 OD + AI; and (c)Ovsynch. (no. = 113) D0: injection of GnRH; D7: injection of PGF2α; D9: injection of GnRH and 16 h later AI at fixed time. In experiment 2, 318 non-suckling cows were assigned randomly to three treatments: (a) GnRH-PG. (no. = 106) D0: injection of GnRH; D7: injection of PGF2α; D0 to D25 OD + AI; (b) GnRH-MAP-PG. (no. = 106) D0: injection of a GnRH analogue and insertion of an intravaginal sponge impregnated with 250 mg of medroxyprogesterone acetate; D7: injection of PGF2α and sponge withdrawal; D0 to D25 OD + AI; (c) controls. (no. = 106) OD and AI. The experimental period lasted 25 days and, with exception of the Ovsynch treatment, oestrous detection was carried out twice a day (a.m./p.m.) and inseminations performed 12 h later. The pregnancy rates assessed by ultrasonography 30 days after AI were: experiment 1: (a) 30·0%; (b) 28·6% and (c) 62·3% (P < 0·05); experiment 2: (a) 60·2%; (b) 57·8% and (c) 45·5% (P < 0·05). It is concluded that in heifers and non-suckling cows, oestrous synchronization treatments result in higher pregnancy rates. In non-suckling cows, the addition of a progestagen did not improve the response.

Fifty-six young female Suffolk × (Cadzow Improver × Scottish Blackface) sheep were used in a 2 × 2 × 2 factorial experiment investigating: (i) change in daylength (constant C v. reduced R), (ii) level of feeding (to appetite, H, v. 75% of that allowance, L), and (iii) age at hormone treatment (20 v. 28 weeks). At the appropriate age, the sheep were treated with a progestagen (MAP) and 750 i.u. PMS, inseminated, and slaughtered 26 days later. In a second experiment, change in daylength and level of feeding only were investigated. Hormone treatment took place at 20 weeks of age. In both years, all sheep showed oestrous behaviour and ovulated. A greater number of sheep yielded embryos on C than on R treatments (P<0·05 in Year 2), but no effect of feed level or age was found. Of those sheep not yielding embryos, a greater number on R than on C treatments showed a second ovulation at 20 weeks but not at 28 weeks.

1. Homologous antibodies to Salmonella pullorum were produced by immunising pigs between 100 and 200 lb. live-weight.

2. Standardised doses of antibody, extracted from whole serum after these pigs were slaughtered, were administered to 245 piglets by stomach tube during the first 24 hr. after birth.

3. The marked variation in uptake of the marker antibody, determined by direct agglutination tests on the blood serum of the dosed pigs, was chiefly due to variation between litters. This variation was attributed to maternal effects, associated with agents secreted in varying quantities into colostrum. Concentration of antibody in the dose administered to piglets, time elapsing between birth and dosage and differences between sire families, were subsidiary causes of variation. Possible mechanisms influencing efficiency of antibody absorption were examined and discussed.

Since the year 1900 the number of Border Leicesters has been fairly stable, between 3,000 and 5,000 females being registered each year. The number of flocks, however, has shown a fairly steady increase from 200 to over 600. There has been a decline in the number of ewes registered per flock from 16 to about 6 to 8. The important flocks would seem to number 15 to 20; only a few flocks persist for any appreciable length of time. Generation intervals are short, being only about 2 years on the sire side and 3½ years on the female side.

As with other breeds, relatively few rams have an importance out of proportion to their numbers—14 rams and 2 ewes with direct coefficients of relationship greater than 5% were found. Inbreeding per generation was only 0·32%, and there was no evidence of strain effects.

This study investigated the effect of forage type (grass or red clover) and harvesting time (primary growth or regrowth) of silage on energy and N utilisation by sheep fed at maintenance level. Specifically, the assumption of constant loss of energy of digestible organic matter from energy losses in urine and CH4 applied in evaluation of silage metabolisable energy (ME) was investigated. Urinary excretion of high-energy phenolic compounds related to solubilisation of lignin was assumed to affect urinary energy (UE) losses from sheep fed highly digestible grass silage (GS). A total of 25 primary growth and regrowth silages of timothy (Phleum pratense) and meadow fescue (Festuca pratensis) grass mixtures and red clover (Trifolium pratense) samples collected in digestibility trials with sheep, including faecal and urine samples, were used for energy and N determinations. Urinary concentration of monophenolic compounds and CH4 emissions in vitro were also analysed. Daily faecal N output, CH4 yield (MJ/kg DM intake), proportion of CH4 energy in digestible energy (DE) and proportion of UE in DE were greater (P ≤ 0.03) in sheep fed red clover silage (RCS) than GS. Furthermore, less (P = 0.01) energy was lost as UE of DE in sheep fed primary growth GS compared with the other treatments. The relationship between UE and silage N intake or urinary N output for both silage types (i.e. grass v. red clover) was strong, but the fit of the regressions was better for GS than RCS. The CH4/DE ratio decreased (P < 0.05) and the UE/DE ratio increased (P < 0.05) with increasing organic matter digestibility in RCS. These relationships were not significant (P < 0.05) for the GS diets. The regression coefficient was higher (P < 0.05) for GS than RCS when regressing ME concentration on digestible organic matter. The results of this study imply that ME/DE ratio is not constant across first-cut GS of different maturities. The ME production response may be smaller from highly digestible first-cut GS but could not be clearly related to urinary excretion of monophenols derived from solubilisation of lignin. Furthermore, energy lost in urine was not clearly defined for RCS and was much more predictable for GS from silage N concentration.

In this study, we used two different grain-rich feeding models (continuous or transient) to determine their effects on in situ fiber degradation and abundances of important rumen fibrolytic microbes in the rumen. The role of the magnitude of ruminal pH drop during grain feeding in the fiber degradation was also determined. The study was performed in eight rumen-fistulated dry cows. They were fed forage-only diet (baseline), and then challenged with a 60% concentrate diet for 4 weeks, either continuously (n=4 cows) or transiently (n=4 cows). The cows of transient feeding had 1 week off concentrate in between. Ruminal degradation of grass silage and fiber-rich hay was determined by the in situ technique, and microbial abundances attached to incubated samples were analyzed by quantitative PCR. The in situ trials were performed at the baseline and in the 1st and the last week of concentrate feeding in the continuous model. The in situ trials were done in cows of the transient model at the baseline and in the 1st week of the re-challenge with concentrate. In situ degradation of NDF and ADF of the forage samples, and microbial abundances were determined at 0, 4, 8, 24 and 48 h of the incubation. Ruminal pH and temperature during the incubation were recorded using indwelling pH sensors. Compared with the respective baseline, both grain-rich feeding models lowered ruminal pH and increased the duration of pH below 5.5 and 5.8. Results of the grass silage incubation showed that in the continuous model the extent of NDF and ADF degradation was lower in the 1st, but not in the last week compared with the baseline. For the transient model, degradation of NDF of the silage was lower during the re-challenge compared with the baseline. Degradation of NDF and ADF of the hay was suppressed by both feeding models compared with the respective baseline. Changes in fiber degradation of either grass silage or hay were not related to the magnitude of ruminal pH depression during grain-rich feeding. In both feeding models total fungal numbers and relative abundance of Butyrivibrio fibrisolvens attached to the incubated forages were decreased by the challenge. Overall, Fibrobacter succinogenes was more sensitive to the grain challenge compared with Ruminococcus albus and Ruminococcus flavefaciens. The study provided evidence for a restored ruminal fiber degradation after prolonged time of grain-rich feeding, however depending on physical and chemical characteristics of forages.

Genetic evaluation of Piétrain sires in Flanders occurs under standardized conditions, on test stations with fixed dam breeds, standardized diets and uniform management practices. As environmental conditions vary on commercial farms and differ from the test stations, this study aimed at understanding to what extent the sire, the dam breed and the interaction between both affects the translation of breeding values to practice. Dams of two commercial breeds were inseminated with semen from one of five different sires selected for contrasting breeding values (daily gain, feed conversion ratio and carcass quality). For each sire by dam breed combination, six pen replicates (with three gilts and three barrows per pen) were evaluated for growth performance from 9 weeks of age (20 kg) to slaughter (110 kg), and for carcass and meat quality. In our experimental setup, both sire and dam breed affected growth, carcass and meat quality traits. No significant sire×dam breed interactions on performance could be detected. Though a tendency for interaction on average daily feed intake between 20 and 110 kg (P=0.087), and on pork colour (lightness) (P=0.093) was present. In general, offspring of all tested sires behaved similarly in both dam breeds, indicating that estimated breeding values for Piétrain sires determined in one dam breed are representative in other dam breeds as well.

Forty-eight pregnant Manchega dairy ewes bearing twins or singles penned in groups of six during the last 11 weeks of gestation were used to study the effects offorage type (Italian ryegrass hay or alfalfa hay) and number of foetuses (one or two) on voluntary dry-matter (DM) intake and digesta kinetics. Hays were supplemented with 0·6 kg/day of concentrate. When measured directly for group-fed ewes, forage DM intake was affected byforage type (P < 0·01), whereas litter size had no significant effect. An internal (rumen-undegradable DM) and an external (chromium III oxide) marker were also used to determine intake of individual ewes to account for errors in diagnosing litter size. Estimated DM intake confirmed the effect offorage type on DM intake and revealed the effect of litter size on food intake (F < 0·05). Forage type also affected chromium III oxide fractional outflow rate and flow of undegradable DM, whereas litter size only had an effect at the end of pregnancy by reducing hay intake, rate of passage and digesta flow mainly with alfalfa diets. In conclusion, DM intake, rate of passage and digesta flow was higher with alfalfa hay than with ryegrass hay, in spite of the similar DM apparent digestibilities of both hays. Furthermore, litter size affected DM intake at the end of pregnancy causing an intake decline, which was greater with alfalfa hay than with ryegrass hay.

An abrupt fall in live weight of grazing cattle occurs at the beginning of the growing season in the seasonally dry tropics. In an experiment with grazing crossbred bulls in central Tanzania designed to monitor changes in gut fill, 16 were slaughtered in the dry season and 14 in the early wet season. Bulls were measured and weighed before, and weighed after, a 20-h fast and then slaughtered. Gut fill was measured and empty body weight (EBW) calculated.

During fasting, the ratio gut fill/EBW fell from 0·291 to 0·217 in the dry season and from 0·207 to 0·119 in the wet season. Heart girth/EBW1/3 was 0·2577 and 0·2567 m/kg1/3 in the dry and wet seasons respectively.

It was concluded that live weight before or after fasting is seriously affected by season and can give biased predictions of EBW change. On the other hand, heart girth is little affected by season and can be used to monitor relative increases or decreases of EBW within animals.

An attempt was made to use anal skinfold thickness as a quantitative measurement to estimate body fatness in Boran cattle (Bos indicus). Using the normal single-operator technique the relationship between skinfold thickness and the other measurements was poor but was greatly improved by using two operators. It nevertheless remained inferior to body condition score, which was very highly correlated with estimated body fat proportion, It was concluded that condition scoringprovides a valuable index of the nutritional status of Bos indicus cattle, and that measurements of anal fold thickness are not applicable to such animals.

Three experiments were conducted to investigate the effect of genotype on the morphological characteristics, chemical composition and feeding value of nine chopped barley straws, and responses of the feeding value to a supplement of soya-bean meal (SBM). In experiment 1, the straws were offered ad libitum to 12 wethers and measurements were made of straw intake and dry (DMD) and organic (OMD) matter digestibility using a balanced lattice design with three periods. Experiment 2 used the same experimental design but the straws were offered ad libitum with 200 g SBM. Experiment 3 measured the dry matter losses (DML) of ground straws from nylon bags placed in the rumen of three wethers. The extent (b) and rate (c) of DML were estimated using the equation DML = a + b(l – ect).

There were significant differences in the stem height (P < 0·001), leaf proportion (P < 0·001), and protein (P < 0·001) and modified acid detergent fibre (P < 0·01) concentrations between the straws. Significant (P < 0·05) effects of genotype on intake were seen but the variation in intake between them decreased when the protein supplement was added. Effects of genotype on DMD (P < 0·05) and OMD (P < 0·05) were seen in unsupplemented straws and differences of OMD (P < 0·05) were still apparent when SBM was given with straw. Although there were significant (P < 0·05) differences in DML after 48 h incubation, the constants b and c were similar (P > 0·05) across the genotypes. Protein concentration in the straw, although closely correlated with intake, appears to have less value as a predictor of feeding value than previously thought.

Twenty-four Friesian steers, initially 5 months of age, were involved in a 2 × 2 factorial experiment which spanned grazing and silage feeding periods of 22 weeks' duration. In the first period, cattle were stocked at a uniformly high density, with half of the group being fed 1·25 kg/head per day of supplementary barley. In the second period, the cattle were subdivided into four groups and fed varying levels of barley with silage. Finally all the animals received 3·65 kg/head per day of barley. Replicates of the four treatments were slaughtered at random after 5 to 11 weeks on this treatment. Whilst supplementary cereal feeding significantly increased the live-weight gains of steers at grass by 11%, this live-weight advantage was offset by their slower gains in the final weeks before slaughter. Feeding cereals to grazing cattle had little effect on carcass composition or the proportions of carcass joints, but their beef was considered, by a tasting panel, to be more tender than the meat from the control steers.

Increasing the level of barley fed with silage only increased live-weight gains by 2%, and had little effect on carcass or meat quality.

Ways of conducting a progeny test for growth of carcass characters are discussed with reference to statistical efficiency. An intensive system (375 kg slaughter weight) is compared with a semi-intensive system (475 kg slaughter weight) and the use of intermediate results as predictors of the final outcome is discussed.

The crossbred progeny of 32 Hereford bulls (1043 calves) were admitted to a Progeny Testing Centre at 2-month intervals at 2 weeks of age over a period of 2 years, and divided between the two feeding regimes. Growth and carcass characters were measured, including taste panel assessments.

The semi-intensive system was found to have a higher power of discrimination between progeny groups, and tended to rank the bulls i n a different order from the intensive system. Truncation of the test at various intervals introduced an element of risk into the formation of the final judgement and showed little advantage as a predictor.

1. Attributes desired in the gammons of bacon pigs are discussed, together with the methods whereby they are measured.

2. An experiment is described in which 16 judges made visual assessments of the qualities of the gammons of 10 carcasses of bacon weight from photographs, both of the fresh carcasses and of the cured bacon sides.

3. The judges did not show a high level of agreement in their rankings of the gammons. Although the overall rankings by the panel of the gammons on the fresh carcasses and on the bacon sides were similar, neither ranking was related to the composition or yield of the gammons.

4. The judges showed better agreement in their rankings of photographs of the cut surfaces of these 10 gammons and the cross-sections of the cooked gammons produced from them; in this case their preferences were related to the lean content of the gammons.

5. A second trial in which 25 judges scored 12 actual bacon sides for the quality of their gammons showed an even lower level of agreement between the judges' rankings, and again there was little agreement between the overall rankings of the panel and the results of dissections.