Five Karan Swiss cows were allowed to calve spontaneously and served as controls (Group A), while another 10 were induced to calve about 1 month prior to expected term using either 25 mg dexamethasone alone (Group B) or 25 mg dexamethasone in combination with 25 mg stilboestrol dipropionate (Group C). Blood samples were collected prior to, and for 50 days following, parturition for subsequent hormone analysis, and observations were made on the occurrence of retained placentae.

Parturition was successfully induced in all treated cows within 72 h of drug administration. Placental membranes were retained for 24 h in all treated animals and were manually removed in the farm veterinary clinic. No incidence of placental retention occurred in control cows.

Mean plasma oestradiol-17β in control cows showed a gradual rise from days 30 to 5 pre partum, followed by a sharp increase to peak value 1 day before calving. The rise in mean oestradiol-17β levels in the 2 days before parturition in controls was significantly greater than that recorded for the treated animals. A precipitous drop in plasma oestradiol-17β level occurred following parturition in all groups, with the levels staying low for the rest of the sampling period. Drug administration to animals in groups B and C resulted in a rapid and significant drop in plasma progesterone concentrations to a level similar to that for control animals at parturition. Subsequently, the plasma progesterone remained low in all treatment groups. Mean plasma cortisol levels showed a significant but transient increase at calving in control cows, but were suppressed for at least 48 h following drug administration in treated cows before exhibiting a rebound phenomenon to reach high values after calving.

It is concluded that for normal placental expulsion, oestradiol-17β levels are more critical than progesterone, and that the rise in oestradiol-17β and fall in progesterone levels pre partum must be gradual.

Haryana and crossbred (Holstein × local Haryana) bullocks were subjected to work under heavy loads in summer. During the work, bullocks exhibited distress symptoms. After work, rectal temperature, respiration rate, heart rate and minute volume increased significantly, the average pO2 content increased, muscle lactic acid increased and creatine phosphate level declined. From the results it was evident that oxygen availability in blood improved during work. Despite the enhanced oxygenation of blood, there was accumulation of lactic acid in muscle. This indicated a certain degree of tissue hypoxia, which probably brought about fatigue earlier.

Compositional and acidity changes in fermented normal or antibiotic milk, and the effects of feeding jch milk on the growth, food conversion efficiency and overall health of dairy calves were studied, Type of milk (normal or antibiotic) did not significantly affect pH, lactose, crude protein, fat and free (H3—N content of milk. Lactose content and pH values decreased with time whereas free NH3—N lcreased. Higher room temperatures were associated with lower pH; values below 5 were obtained after weeks of fermentation in winter, 2 weeks in spring, 1 week in autumn and less than 1 week in jmmer. Overall pH values and lactose content declined until week 4 and remained constant thereafter, calves fed fermented antibiotic milk gained less weight from birth to weaning than those on fresh milk, put post-weaning growth rates were similar. Incidence of scouring was higher among calves fed antibiotic lilk, but no deaths occurred. Milk intake was similar, and consumption of dry food (pre and post eaning) differed slightly.

In a multibreed experiment, 292 heifers from 25 British cattle breeds were fed a standard pelleted diet ad libitum from 12 to 72 weeks of age. Inter-age correlations involving body weight, weight gain, average daily food intake and cumulated food intake were measured across traits at the same age and within and across traits at ages separated by an interval of 12, 24, 36 and 48 weeks. Within-breed correlations were phenotypic but between-breed correlations were genetic.

The between-breed inter-age correlations involving body weight, cumulated intake and average daily intake were all very high (range 104 to 0·94) and declined only gradually as the intervening age interval increased from 12 to 48 weeks. Inter-age correlations involving weight gain were lower but usually above 0·7. The within-breed correlations by contrast were invariably lower and declined much more rapidly as the age interval increased. Although the between-breed and within-breed correlations differed in magnitude there was a similarity in their overall pattern.

For breed samples, body weight at young ages provided very accurate rankings at later ages for body weight, cumulated intake and average daily intake. Body weight was almost as reliable as food intake itself for predicting cumulated intake.

For individuals within breeds predicted rankings at later ages were not very accurate for body weight or cumulated intake and they became worse as the age interval increased. Neither weight gain nor average daily intake could be predicted with any reliability.

Inter-age correlations while dependant on age interval did not depend on age itself in the case of body weight and cumulated intake, although they were age-dependant for weight gain and to a lesser extent for average daily intake. Reciprocal correlations between body weight and cumulated intake were very symmetrical whereas those involving weight gain and daily intake were asymmetrical.

The Milk Marketing Board beef shape (BS) score for a sire is derived from the beef conformation assessments made during the routine inspection of his first lactation daughters in the Dairy Progeny Testing Scheme. The trial compared the scores for seven Friesian/Holstein sires with the beef characteristics of their steer progeny. Two groups of cattle, 189 in total, all out of Friesian dams, were used in the trial. The dams were assessed for BS. The cattle were reared on a standard grass/cereal system designed to achieve an overall target live-weight gain of 0·85 kg/day and slaughtered at 530 kg live weight. An assessment of BS was made at seven points during the lifetime of each animal. Carcass classification and assessment together with dissection of the shin joint was undertaken by the Meat and Livestock Commission. In addition to this, 40 carcasses representing high and low BS scores were taken for full dissection of the left side.

The BS score of the dam had no significant effect on the score of the calf at any point during its life. The relationship between the sire BS score and the calf score did not become significant until the calf was 12 months old (P < 0·01) and was still significant immediately prior to the slaughter of the calf (P < 0·05). Carcass conformation scores showed highly significant progeny group differences (P < 0·001). The regression of the sire progeny group means, corrected for estimated proportion of subcutaneous fat, on the sire BS scores was significant (P < 0·001). The carcasses in the high BS score group had a significantly greater weight of lean than those in the low BS score group.

Thirty-six individually-penned ewes (mean live weight 69 kg), each suckling two lambs, were given one of three diets containing either 128 (low), 155 (medium) or 186 (high) g crude protein (CP) per kg dry matter. All diets contained (g/kg), milled hay, 570; molasses, 95; and a barley/fish meal concentrate, 330. The three protein concentrations were achieved by adjusting the proportions of barley and fish meal in the concentrate. Each diet was given at daily metabolizable energy (ME) intakes of 19, 23 and 27 MJ. Mean daily yields of milk in weeks 3 to 8 of lactation for ewes given the diet with the low concentration of crude protein increased from 2·32 kg at 19 MJ ME to 2·53 kg at 27 MJ. Corresponding values for the medium concentration of CP were 2·49 and 2·67 kg and for the high concentration 2·52 and 3·09 kg (P < 0·05 for differences between ME intakes and differences between dietary protein concentrations). For milk composition, interactions between the concentration of dietary protein and level of ME intake were not statistically significant but the main treatment effects were significant, with the protein concentration in milk increasing from 49·6 g/kg for ewes given the low concentration of dietary protein to 54·1 g/kg for those given the high (P < 0·001). Corresponding values for protein concentration in milk for the lowest and highest energy intake were 51·2 and 53·4 g/kg (P < 0·05). Losses of tissue protein were variable but decreased from 26 g/day for ewes given the low-protein diet to 8 g/day for those given the high. In discussing the responses in milk yield to dietary protein and ME intake attention is drawn to the modifying influence of the energy contributed from body tissue.

Two experiments were conducted in successive years with, respectively, 112 and 194 mature Scottish Blackface ewes to study the effects of shearing during pregnancy on lamb birth weight and subsequent growth. In each year half the ewes were shorn approx. 10 weeks before lambing. Shorn and unshorn ewes were offered and consumed equal quantities of food.

In both years the shorn ewes lost approx. 2 kg of live weight shortly after shearing (making allowance for the weight of wool removed); thereafter live-weight differences remained relatively constant. Plasma 3-hydroxybutyrate concentrations indicated that the initial live-weight loss was probably attributable to short-term increases in heat production and energy expenditure.

Respiration rates and rectal temperatures of unshorn ewes were always higher than in shorn ewes, but were not elevated to an extent indicative of heat stress.

Shearing had no effect on the birth weights of single or twin lambs, nor was there any effect on lamb growth rate to 14 weeks of age.

It is postulated that the effects of shearing on lamb birth weight reported by others working with sheep fed ad libitum are most likely to be due to the increased voluntary food intakes of shorn ewes.

Changes in the pattern of food intake, food conversion efficiency and growth from weaning to maturity, were examined in 35 rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. The sheep were individually fed a pelleted ration ad libitum for at least 72 weeks and up to 90 weeks post weaning. Weekly food intake was described as an increasing exponential function of age with a linearly declining asymptote, about which a regular oscillation occurred, and weekly body-weight gain was described as an increasing exponential function of weekly food intake, about which a regular oscillation also occurred.

The oscillations in weekly food intake had a period of about 52 weeks and appeared to be largely associated with seasonal variations in temperature, with an increased food intake during winter and a decreased food intake during summer. The oscillations in both the food-intake and body-weight functions were of similar phase and period and it was suggested that the body-weight oscillations were due to variation in gut-fill, a result of the seasonal oscillations in food intake.

Selection for weaning weight changed the shape and magnitude of the food-intake curve, with the weight-plus having a greater rate of food intake (i.e. appetite) in the early stages of growth and a greater asymptote than the weight-minus animals. Selection for high and low weaning weight also resulted in an increase and a decrease in mature weight. Both strains had a similar growth efficiency, although when calculated as gross food conversion efficiency the weight-plus were higher than the weight-minus animals at the same body weight, whereas there was no difference between strains at the same age.

The rams had both a higher asymptote and a slower rate of decline in food intake than the ewes. Rams had a higher mature weight than the ewes, although ewes had a slightly greater growth efficiency. However, when calculated as gross food conversion efficiency, ewes tended to be lower than rams, when compared either at the same age, or at the same body weight.

When the food-intake curves were standardized for differences in mature size, strain differences in the magnitude of the food-intake curves were reduced, although differences in the shape were still apparent. Shape differences in the food-intake curves were reflected in the shape of the standardized growth curves, with the weight-plus maturing at a faster rate than the weight-minus animals. There was little difference between the sexes in the initial shape of the food-intake curve, although at later ages ewes had a lower food intake than rams. There was little difference between the sexes in the shape of the standardized growth curves.

The changes in chemical and dissectible body composition from birth to maturity were examined in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. Body composition was examined in 34 mature animals and the maturing patterns for body components calculated using mean values from the mature animals and individual data from 106 immature animals.

In the 34 mature animals, strain had no effect on the proportions of chemical and dissected fat, protein and muscle in the body. The weight-plus had greater proportions of ash and carcass bone in the body than the weight-minus animals. Mature rams had lower proportions of chemical and dissected fat and greater proportions of protein, muscle, ash and carcass bone in the body than mature ewes.

The weight-minus animals had later maturing patterns for both chemical and dissected fat than the weight-plus animals. Strain had no effect on the maturing patterns for protein and muscle, although both ash and carcass bone were later maturing in the weight-plus, than in the weight-minus animals. Chemical and dissected fat were later maturing in the ewes than in the rams, whereas protein, muscle, ash and carcass bone were earlier maturing in the ewes than in the rams.

The weight-minus animals were fatter at the heavier body weights, although there was a trend for the weight-plus animals to be slightly fatter at the lighter body weights. When compared at the same stage of maturity of body weight, strain differences in the proportion of fat in the body declined as the animals matured. Compositional differences between the rams and ewes varied according to the body weight or stage of maturity of body weight at which they were compared.

Using a simplified energy balance equation, changes in energetic efficiency and energy expenditure were examined as a function of stage of maturity in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock.

Specific combustion energy of the body (i.e. MJ/kg of body weight) was an increasing linear function of stage of maturity, which increased at a slightly faster rate in the weight-minus than in the weight-plus animals (15·1 v. 13·1 MJ/kg per unit of maturity), and at a faster rate in ewes than in rams (17·2 v. 11·3 MJ/kg per unit of maturity). At maturity, all strains had a similar mean specific combustion energy (18·3 MJ/kg), whereas the ewes were greater than the rams (20·1 v. 16·6 MJ/kg).

Thermochemical efficiency (TCE, defined as the gain in body energy per unit of metabolizable energy intake) was a quadratic function of stage of maturity. In the early post-weaning period, the weight-plus had a greater TCE than the weight-minus animals and the maximum TCE occurred at an earlier stage of maturity in the weight-plus than in the weight-minus animals (0·40 v. 0·45 maturity). The ewes had a higher TCE than the rams at all stages of maturity, although the differences decreased as the animals matured. The maximum TCE occurred at a later stage of maturity in the ewes than in the rams (0·46 v. 0·38 maturity).

After scaling for differences in mature size there was little difference between the strains in the rate of energy expenditure, with the exception that at the later stages of maturity the weight-minus animals had a slightly greater rate of energy expenditure. After scaling for differences in mature size, the rams had a greater rate of energy expenditure than the ewes from weaning to maturity.

A model is described, which maximizes hay intake in the formulation of rations for pregnant ewes in the last 6 weeks of pregnancy. A regression of hay intake upon hay digestibility, concentrate level, ewe live weight, number of foetuses carried and week of pregnancy, derived from an experiment on individually-recorded ewes, is used as the intake constraint in a linear programme. This is solved in an interactive program which can be implemented on several makes of microcomputer. The intakes of hay predicted by the model are lower than those reported elsewhere, reflecting the more accurately recorded intakes of the original experiment compared with most other published data. The rations formulated by the model show that in weeks 16 to 18 of pregnancy hay could provide most of the ewes' requirements and especially when hays of high metabolizable energy concentration are used. The ease of changing the values of the inputs and the speed of the ration formation enable any number of rations to be formulated quickly for a range of hays and individual conditions.

Finnish Landrace × Dorset Horn ewes were offered 300, 600 or 900 g fresh weight per day of concentrates and forage ad libitum from day 105 of pregnancy until lambing. Spring barley straw (S) or hay (H) was offered either untreated (U) or following treatment with anhydrous ammonia in an oven (T). Organic matter digestibilities (in vitro) were 0·42, 0·58, 0·42 and 0·60 and nitrogen contents were 7·2, 18·6, 12·0 and 25·0 g/kg dry matter for US, TS, UH and TH respectively. Forage intake did not differ between ewes carrying two or more foetuses but the small number of ewes carrying one foetus ate more straw (6·8 v. 4·5 g organic matter (OM) per kg live weight) than ewes carrying two or more foetuses. Ammonia treatment increased intake; the increase was larger on straw (4·6 v. 100 g OM per kg live weight) than on hay (9·0 v. 10·7 g OM per kg live weight). Replacement rates of forage by concentrates were -0·21, +0·06, -0·48 and +0·08 kg forage per kg concentrates for treatments US, TS, UH and TH respectively; only the value for treatment UH differed significantly from zero. On most treatments forage intake decreased as pregnancy progressed and the declines were greater when treated forages were offered. Concentrate level had a large effect on most aspects of ewe performance. Ewes offered treated forage gained slightly more weight in pregnancy (138 v. 104 g/day), had a slightly smaller decrease in body condition score (-0·54 v. -0·68) between day 105 and lambing but did not have greater lamb birth weights than ewes on untreated forage.

Two experiments are described in which individually-penned Suffolk × (Blue-faced Leicester × Swaledale) lambs were given complete diets based on grass silage, and voluntary intake, live-weight gain and nitrogen (N) retention were measured.

Experiment 1 investigated the effects of supplements of fish meal (0, 60 and 120 g/kg diet dry matter (DM)) and barley (0, 150 and 300 g/kg diet DM) in a 3 × 3 design using 72 lambs. The lambs averaged 35 kg live weight at the start of the 47-day experiment. Fish-meal supplements increased daily intakes of diet DM, silage DM and metabolizable energy (ME), and improved daily gains, carcass weights and N retention. Barley supplements increased daily intakes of diet DM and ME, but reduced silage DM intake; live-weight gain, carcass weight and N retention were all improved.

Experiment 2 investigated the effects of supplements of rapeseed meal (0 and 120 g/kg diet DM) in two forms (untreated and formaldehyde-treated) and barley (0 and 150 g/kg diet DM) in a 2 × 2 × 2 design with two missing treatments and using 48 lambs. The lambs averaged 39 kg live weight at the start of the 42-day experiment. Rapeseed meal supplements increased daily intakes of diet DM, silage DM and ME, and improved daily gains, carcass weights and N retention. Form of rapeseed meal had no effect. Barley increased diet DM and ME intakes and improved daily gains and carcass weights.

Ewe's colostrum, dried milk, ewe's blood, cow's blood and cow's serum, given to a total of 56 newborn lambs, had various effects on serum immunoglobulin concentrations, the gut closure process and early growth rate.

Cow's colostrum and serum proved to be good alternative sources of immunoglobulin for rearing lambs. Cow's and ewe's blood had adverse effects on immunoglobulin absorption, speeding up the closure process. This process was only slightly affected when lambs were fed immunoglobulin-free powdered milk.

Lambs survived with concentrations of serum immunoglobulin as low as 5 zinc sulphate turbidity units. Similar and satisfactory mean early growth rates were observed for lambs given ovine and bovine colostrum and bovine serum, whilst those given ovine and bovine whole blood had relatively low early weight gains. Those receiving powdered milk substitute followed by ewe colostrum at 8 h post partumshowed intermediate rates of growth.

The effect of castration on fat partitioning in mature animals and on the maturing patterns for fat depots relative to total body fat was examined using slaughter and dissection data from 20 Dorset Horn rams and 20 Dorset Horn wethers. Animals were slaughtered at 6 kg intervals from 18 kg live weight to maturity. Five rams and eight wethers were classified as mature.

In the mature animals the partitioning of fat differed for the rams and wethers in that the rams had a lower proportion of subcutaneous fat, and higher proportion of intermuscular and mesenteric fat than the wethers. However, the proportions of total carcass dissectible fat (i.e. subcutaneous plus intermuscular fat) and of the total non-carcass depots (i.e. kidney plus channel fat, omental, scrotal and thoracic fat) did not significantly differ between rams and wethers.

The maturity coefficients of individual fat depots of rams and wethers were not significantly different and six of the nine depots were average maturing relative to total body fat. The intermuscular and thoracic fat depots were early maturing (maturity coeffient q= 1·19, 2·26 respectively), and the omental depot was late maturing (q= 0·52).

Comparison of the partitioning of fat in rams and wethers reflected the differences in the mature animals when made at either the mean weight or at the mean stage of maturity, as the maturing patterns of most depots were not greatly different from that of total fat.

Housed male (stags) and female (hinds) red deer, initial live weight 43·2 and 38·3 kg respectively, were given ad libitum (1) ammonia-treated straw, (2) a barley and fish meal concentrate, and hay, or (3) potatoes and hay, from 7 to 11 months of age. Dry matter (DM) intakes were low for all deer and some live-weight loss was experienced for the first 6 weeks in January/February. Thereafter DM intakes increased, and deer given the concentrate diet showed higher live-weight gain (P < 0·001) than those given potatoes and hay (273 and 162 g/day, respectively) whereas deer receiving the treated straw continued to lose weight (-18 g/day) (P < 0·001).

From 11 to 16 months of age at grass, deer previously given treated straw grew significantly faster (P < 0·001) than those previously overwintered on concentrate or potato diets (215, 156 and 170 g/day, respectively). Final live weights for animals given straw, concentrates and potatoes in the preceding winter were, respectively, 71·6, 92·6 and 80·8 kg (stags) and 63·0, 71·9 and 68·5 kg (hinds).

The dietary treatments imposed in the previous winter had no lasting effects on the carcass composition of stags slaughtered at 16 months, and the practical implications of the different growth patterns are discussed.

Commercial crossbred pigs weighing about 80 kg and comprising equal numbers of females (gilts) and castrated males (castrates) were killed at a bacon factory 4 h (controls), 24 h or 48 h after food withdrawal. The carcasses from pigs fasted 24 h were on average 1·4 kg lighter, and those from pigs fasted 48 h, 2·9 kg lighter, than those of the control group. Fasting also reduced liver weight by about 0·3 kg but had no significant effect on backfat thickness or mean initial or ultimate pH in the muscles. Carcasses were cured into bacon by the Wiltshire process. Those from pigs fasted longer gained less weight after pumping with brine but also lost less weight during brine immersion and maturation. The overall yield of bacon, in relation to carcass weight, was therefore not affected by fasting. Consequently, the reduced carcass weight in the fasted pigs was carried through almost unchanged to the final yield of matured bacon. This was proportionately reduced by 0·019 in the pigs fasted 24 h and 0·043 in those fasted 48 h when compared with the control group.

There was thus no evidence of any material reduction of yield differences during curing which could be caused by equilibriation of water in the carcass tissues with that in the curing brine. The implication is that losses in carcass weight in fasted pigs cannot be attributed simply to dehydration. Cured sides from fasted pigs tended to have proportionately slightly less weight in the ham and middle and more in the shoulder, and bacon from the pigs fasted 48 h was marginally less salty.

The response of the growing female pig (25 to 55 kg live weight) to increasing dietary isoleucine supplies at two levels of dietary leucine was assessed by measurement of growth rate, food utilization, tissue deposition as indicated by ham dissection and changes in plasma urea concentration. A range of isoleucine concentrations from 3·7 g/kg to 5T g/kg of the diet was derived from a basal diet and seven increments of L-isoleucine. Synthetic L-leucine was added to the basal diet to increase the concentration from 12 g/kg to 15 g/kg to achieve the two levels. The basal diet was formulated using barley, maize, blood meal, yeast protein, fat and tapioca with synthetic amino acids included to maintain at least 9·5 g/kg lysine and adequate concentrations of other essential amino acids and non-essential nitrogen. The 16 diets were replicated four times and fed to 64 female growing pigs once daily according to a restricted feeding scale. Blood samples were taken from each pig at 40 kg live weight for the determination of plasma urea nitrogen.

The addition of synthetic leucine to the basal diet had no consistent effect on growth performance or carcass quality, although it did result in elevated levels of plasma urea nitrogen. The response of growth performance and the composition of the ham joint to increasing dietary isoleucine concentration was interpreted by broken line functions which indicated an isoleucine requirement of 4·4 to 4·5 g/kg of the diet.

To examine the influence of boar exposure environment and daily movement on the efficacy of boar-induced precocious puberty in the gilt, 60 Large White × (Large White × Landrace) prepubertal gilts from 12 litters were randomly allocated within litter to five treatment groups of six, in two replicates, at 145 days of age. Treatments were (1) control (no movement or boar exposure), (2) gilts moved to a boar pen and exposed to a mature boar, (3) gilts moved to a different pen and exposed to a boar, (4) gilts moved to a different pen only, (5) gilts moved to a vacated boar pen. Treatments occurred for 30 min/day for 75 days, or until pubertal oestrus was observed. Gilts showing pubertal oestrus were removed and slaughtered. Ovaries were examined to confirm reproductive status. Gilts failing to exhibit oestrus by 240 days of age were slaughtered and nominally ascribed a pubertal age of 245 days. Age at puberty was significantly earlier (P < 0·001) in treatments 2 and 3 involving boar exposure than in treatments 1, 4 and 5 not involving boar exposure. No significant difference was observed in the median gilt age at puberty between the two forms of boar exposure used in this experiment. Thus the efficacy of the boar effect does not appear to be significantly affected by the environment in which exposure to the boar takes place. Additionally, it is suggested that the stress of a daily pen change is insufficient to stimulate precocious puberty in gilts in the absence of boar contact.

A total of 56 individually-penned pigs, with equal numbers of boars and gilts, were fed ad libitum in an investigation of the effects of nutrient density in growing (17 to 35 kg) and finishing (35 to 82 kg) periods.

Diets of high (H) and medium (M) nutrient density, with 13·8 or 12·6 MJ digestible energy (DE) per kg and 10·0 or 9·1 g lysine per kg, were used.

In the growing period, diet H proportionately increased the rates of DE intake and live-weight gain by 0·17 (P < 0·001) and 0·24 (P < 0·001) respectively. While the nutrient density of the diets given in the growing period did not significantly affect the mean performance over the finishing period, carry-over effects were observed for about 4 weeks following the change with evidence of compensation in energy intake.

In the finishing period, diet H proportionately increased the rates of consumption of DE and live-weight gain by 0·06 (P < 0·05) and 0·04 (P = 0·18) respectively. The consumption of energy was virtually identical for the two sexes.

It is concluded that the change in nutrient density had only transitory effects on energy intake and growth rate and did not affect overall performance in the finishing period.