Grass silage with a dry-matter content of 19·4% and containing 16·7% crude protein was offered ad libitum to 42 first lactation British Friesian cows during the first 75 days post-calving. In addition the animals received supplementary concentrates containing either 10·3, 13·6, 17·3, 21·1, 25·2 or 30·3% crude protein on a fresh weight basis, with extracted soya bean meal being used as the main protein source. All concentrates were offered at an equal level of 8·0 kg per day. The relationship between milk yield and protein content of the supplement was curvilinear and was described by the following equation:

Y= 8·95+ 1·0×–0·0205×

where Y = milk yield per day in kg, and × = percentage protein in the supplement. This equation indicated that maximum milk yield was obtained with a concentrate containing 24·4 % protein on a fresh weight basis. The protein content of the milk was also curvilinearly affected by the level of protein in the supplement, and it was calculated that maximum milk protein (nitrogen × 6·38) would be obtained with a supplement containing 23·9% protein. Plasma blood urea levels increased linearly with increasing protein intake. The effects on live-weight change and blood components were also recorded.

Twenty-one mature autumn-calving Blue Grey cows were divided into three groups for a 3-year change-over experiment, and each group was allocated to one of three planes of nutrition for the first 150 days of lactation during each year. Milk yields were recorded by machine milking twice daily. The three planes of nutrition corresponded to 1·63, 1·21 and 0·89 of the cow's maintenance allowance 12 h post partum. Increasing the plane of nutrition significantly (P<0·05) increased 150-day cumulative milk yield, but had no significant effect on milk composition. The extent of live-weight loss decreased significantly (P<0·001) as plane of nutrition increased and was reflected in cows maintaining better condition, measured as condition score, through the experimental period.

The small 150-day cumulative milk yield response (32·8 kg per additional 10 MJ metabolizable energy and 62 g digestible crude protein/day) demonstrated the limitation of feeding beef cows for increased milk production in comparison with feeding the calf directly. However, the possible relationship between plane of nutrition, live-weight loss and fertility suggests an important limitation of under-feeding cows during the mating period. Within the constraints imposed, the medium treatment (64 MJ metabolizable energy and 516 g digestible crude protein/day) resulted in levels of cow performance similar to those currently recorded in commercial units. One of the major constraints in the present investigation was the high level of body reserves available in the cows at the start of lactation.

Four groups of 14 3-month-old Israeli Friesian male cattle were each given monensin supplement in their concentrates at the following rates: between 3 and 6 months of age, 0, 0, 25 and 35 p.p.m.; and between 6 months and slaughter, 0, 35, 35 and 35 p.p.m. They were offered hay at approximately 0·3 % of their live weight and concentrates ad libitum.

Daily gain between 3 and 6 months was 1·36, 1·40, 1·50 and 1·57 kg/day, respectively; between 6 months and slaughter it was 1·22, 1·32, 1·33 and 1·24 kg/day, respectively. Differences in intake of concentrates were small. There were no significant differences in slaughter data.

Daily carcass gain throughout the experiment was 0·71, 0·74, 0·77 and 0·76 kg/day, respectively.

Monensin-supplemented animals were approximately 9% more efficient in the conversion of metabolizable energy into live weight or carcass weight than the control animals.

Production of propionate in the rumen was significantly increased in response to monensin supplementation, and the acetate to propionate ratio was significantly reduced.

Three groups of five male pigs (boars) were reared from an early age under various social conditions. The sexual and social behaviour of the boars was studied from 31 to 56 weeks of age. Boars individually reared from 3 to 12 weeks of age in adjacent wire-mesh pens had similar copulatory performance to that of group-reared boars. However, an apparently important component of courting behaviour, ‘nosing activity’, was significantly reduced (P<0·05) amongst those boars individually reared from 3 weeks of age in adjacent wire-mesh pens. Social behaviour appeared to be unaffected by the rearing treatment.

Two field trials were conducted with 138 and 123 bacon-weight pigs respectively from one farm to determine the effect on bacon yield of feeding the animals sugar solutions prior to slaughter. Three treatments were tested: immediate slaughter on arrival at the abattoir; lairage overnight with access to water only (15 h); and overnight lairage with access to a sugar solution (6 h) followed by water only (9 h) prior to slaughter. A glucose syrup solution was used in one trial and a sucrose solution of similar hexose-equivalent concentration (550 g/kg) in the other. Access to either of the sugar solutions, relative to water only or immediate slaughter, increased bacon yield. This was entirely due to glucose-fed pigs having a higher carcass yield (2·3 % and 1·5 % respectively) and a trend in this direction for the sucrose-fed animals (0·9% and 1·0% respectively). Carcasses of glucose-fed pigs actually gained less weight than those of their counterparts during the curing process, but this did not occur with the sucrose solution. Access to sucrose relative to water only and immediate slaughter increased liver weights by 32% and 42% respectively. Lower hepatic responses were obtained with glucose syrup (18% and 12%). Both sugar solutions reduced muscle ultimate pH (0·1 to 0·2 unit) relative to water only in overnight lairage.

Ten sows were each infected with 300 000 larvae of Oesophagostomum dentatum after weaning their second litter, and subsequent per formance over one parity was compared with that of 10 ‘worm free’ controls. Mean worm burden in the sows when slaughtered immediately after weaning, was 13 480 ±2377. From service to weaning of the litter the mean body weight of worm-free sows increased (+11·3 kg) whereas that of infected sows declined (—13·1 kg) and at slaughter the carcasses of infected sows had lower depths of backfat. Worm-free sows averaged 12·8 pigs born of which 11·3 were born alive, corresponding values for infected sows being 12·4 and 9·5. Worm infection reduced birth weights by 15% but differences were not significant. Litters were equalized at eight pigs shortly after birth, and subsequent weaning weights were 10·5 % lower in those of infected sows despite a 29 % higher consumption of creep feed. Clinical disease was never observed in the infected sows, and no parasitic infection was found in the piglets. It is concluded that sub-clinical infections of O. dentatum in sows may be of economic significance.

Sixty-four growing pigs, with equal numbers of females and castrated males, were fed diets containing from 10 to 17·6% crude protein but in which lysine was maintained at 0·95%. Over the 25 kg to 55 kg live-weight range studied, growth performance was unaffected by a reduction in crude protein level from 17·6 to 14·5%. Below 14·5% crude protein, daily live-weight gain and feed conversion ratio deteriorated linearly. Percentages of lean meat and fat in the middle joint showed similar trends. Significant sex effects were confined to carcass characteristics which indicated that the females produced leaner carcasses. It was concluded that below 14·5% crude protein a deficiency of the next limiting amino acid to lysine, or possibly non-essential nitrogen, depressed growth performance.

A computer program is described which allows the calculation throughout pregnancy of the energy requirements of a ewe of any weight carrying any number of foetuses. The calculations rely on a prediction of potential lamb birth weight, from which a foetal growth curve of weight against time from conception is generated. Tied to the foetal growth curve are the growths of the placenta and fluids, while growth of the uterus is related to the ewe's weight at mating. Weights are converted to energy through energy density curves applicable through pregnancy for each component. An efficiency factor converts this energy requirement into a metabolizable energy requirement. With assumptions on the maintenance requirements for the ewe-foetus system, the total requirement for energy during pregnancy is calculated.

Predictions from the model are compared with other estimates of energy requirements available in the literature. The sensitivity of the predictions of energy requirements for the pregnant ewe to variations in the assumptions made in the construction of the model is discussed. The most important assumptions are those on the maintenance requirements for the ewe-foetus system. Effects on the predicted energy requirements of varying either the efficiency for foetal growth or the gestation length are also discussed.

A computer-based model of the response of the ewe to energy nutrition during pregnancy is described, based on a previous analysis of energy requirements. A ewe of specified weight and body condition 30 days from conception, carrying a known number of lambs, is predicted to grow them to an optimal weight if the nutritional regime allows. Daily energy requirements of the ewe-foetus system are calculated as the sum of requirements for maintenance and for growth and are compared with the daily energy supplied.If the feed provides energy surplus to requirements, the ewe herself gains weight; otherwise, the ewe mobilizes her own reserves, within limits, to protect the foetus. If this does not produce the energy required for optimal growth, foetal growth is reduced.

Published experimental results are compared with predictions of the model when run under similar conditions; in general, predictions of total maternal weight at the end of pregnancy are within 5 % of those observed in the experiments. Model predictions of the effects of some particular nutritional regimes during pregnancy are presented and the sensitivity of the predictions of the model to certain of the assumptions made in its construction are discussed.

Two experiments were conducted on the fattening of 8- to 10-month-old lambs weighing about 40 to 55 kg live weight, using diets based on whole barley sprayed with a solution of urea and minerals or supplemented with a pelleted fish-protein concentrate.

In one experiment the lambs had been adapted to indoor conditions but had been subjected to low levels of nutrition. In the other experiment the lambs were not previously adapted to indoor conditions. The lambs in the first experiment suffered no growth check while the lambs taken inside did not gain in weight for 2 to 3 weeks. In both experiments the lambs showed a short term or compensatory growth response to protein after which there were no differences between lambs receiving fish-protein supplements or urea-fortified grain.

The results are discussed in relation to response to protein and urea and the method of incorporating urea and minerals as solubles in whole grain is discussed.

Testis diameter and body weight were recorded for 37 Finn-Dorset ram lambs born in winter and 38 born in summer 1977 from 8 to 24 weeks of age. Testis growth in summer-born ram lambs reared during a period of decreasing daylength was more rapid than that of winter-born lambs reared during a period of increasing daylength. Hemicastration at 12 weeks of age (19 of the winter-born and 18 of the summer-born lambs) increased the rate of growth of the remaining testis. Season of birth did not affect the response to hemicastration. It was deduced that the feed-back of gonadal hormones on gonadotrophin release was similar in both seasons.

Production in 210 mature Corriedale ewes first mated between 7 and 11 or at 18 months of age was studied at Paysandu, Uruguay. Ewes were classified into one of the following five classes according to their oestrous and lambing performance in 1968: (1) reared a lamb; (2) lambed but lamb died; (3) mated but did not lamb; (4) oestrus detected by vasectomized ram, true mating deferred for 12 months; and (4) no oestrus, mating deferred for 12 months. Records on flock performance and mortality were kept from all ewes from 1969 to 1973, when the dental status of all ewes present was assessed.

There were no significant differences between classes in number of ewes lambing per ewe exposed to the ram, number of lambs born per ewe exposed to the ram, number of lambs weaned per ewe exposed to the ram, weight of lamb weaned per ewe exposed to the ram, and pre-mating body weight.

Greasy fleece weight varied significantly (P < 0·01) with class of ewe. The least squares means for ewe classes 1 to 5 were 3·93, 3·99, 4·06,4·12 and 3·92 kg respectively. Class 4 ewes differed significantly (P < 0·01) from class 1 ewes and from class, 3 and 5 ewes (P < 0·05). Class 3 ewes differed significantly (P < 0·05) from class 1 ewes. Other differences were not significant.

Ewe mortality between 1969 and 1973 was independent of class of ewe. The dental status of ewes appeared to vary with class of ewe. Early mating of Corriedale ewes apparently had no adverse effects on mature reproductive performance, but somewhat reduced wool production. If mating is to take place for the first time at 18 months of age, ewes that have shown oestrus previously are likely to exhibit greater overall productivity (wool plus lambs).

One hundred and thirty-nine Scottish Half bred ewes were studied during the last 8 weeks of pregnancy, through parturition and early lactation. They were divided, on the basis of their metabolizable energy intake during this period, into low (483 MJ/ewe; L), medium (742 MJ/ewe; M) or high (974 MJ/ewe; H) feeding groups.

Ewe weight change (from mating to 12 h post lambing) was directly related to nutritional level and the number of lambs born, e.g. L ewes with triplets lost a mean 13·8 kg, while H ewes with single lambs gained 14·3 kg.

Lamb birth weight and perinatal lamb mortality levels were affected by ewe nutrition and litter size. L twins weighed 19% less at birth than H twins; L triplets weighed 26% less than H triplets. The mortality rate of L twins was 23% greater than M twins; L triplets exceeded the H triplet mortality rate by 87%.

Ewe energy feeding during late pregnancy affected the mean daily weight gain of lambs for at least 3 weeks after birth. H single, twin and triplet lambs grew 12%, 15% and 16% faster than M lambs and 19%, 31 % and 31 % faster than L lambs respectively.

The H group produced 33 % more lamb live weight at 3 weeks of age for every lamb born than did the L group.

Lamb serum immunoglobulin levels were related to litter size but did not reflect the differences in ewe feeding during late pregnancy.

Some factors affecting perinatal lamb mortality were studied with 63 Finn × Dorset Horn ewes and 85 Scottish Half bred and Greyface ewes, having an average litter size of 2·26. Total perinatal lamb mortality averaged 29 % of which 44% were stillborn, 1 % attributed to dystocia, 35 % died between birth and 48 h of age, 14 % from 48 h to 10 days, and 5 % after 10 days.

For the Finn × Dorset ewes, the 41 viable twin lambs weighed at birth 3·47 kg and 12 twin lambs which did not survive weighed 2·51 kg. Triplet weights were: viable 2·98 kg (34 lambs) and nonsurviving 2·00 kg (14). Quadruplet weights were: viable 2·79 kg (12) and non-surviving 1·90 kg (16). Quintuplet and sextuplet weights were: viable 2·45 kg (2) and non-surviving 1·35 kg (14).

In the aggregated Halfbred and Greyface breeds, viable twin lambs weighed 4·5 kg at birth (91) and non-surviving 3·64 kg (11). Viable triplets weighed 3·77 kg (23) and non-surviving 2·68 kg (16).

Serum gamma-globulin and total serum protein values were lower in the lambs which failed to survive, and this was particularly marked with triplets. Fractionating the gamma-globulins (IgG) indicated that IgGi was particularly low in non-viable lambs.

Litter size, lamb birth weight, and colostrum intake by the lamb had important effects on perinatal lamb mortality.

Twin Scottish Half bred × Suffolk lambs born to well-nourished ewes suffered no ill effects, in terms of growth rate or serum immunoglobulin levels, when deprived of colostrum for periods of up to 9 h after birth provided they received adequate colostrum after the deprivation period was completed.

Poor ewe nutrition during the last 8 weeks of pregnancy, when combined with 9-h periods of colostrum deprivation, adversely affected serum immunoglobulin levels and appeared to increase mortality.

Live weights at weaning, and 10, 15 and 20 weeks of age, and postweaning gains of 738 lambs (390 males and 348 females) obtained from purebred and crossbred lambs were studied. The main breeds involved were the Cyprus fat-tailed, Chios and Awassi. Male lambswere heavier (P< 0·01) and grew faster (P< 0·01) than female lambs. Singles were heavier (P< 0·01) than other multiples at all ages, which probably reflects differences in initial weight, since no differences were found in growth rate. Crossbred lambs were heavier at 20 weeks of age and had a faster growth rate than purebred lambs. Ewe lactation number significantly affected lamb weaning weights, the heaviest lambs being those from 3- to 5-year-old dams (third and fourth lactation).

In a consumer test involving 108 households, liver from pigs fed a sucrose solution in lairage overnight prior to slaughter was preferred on its appearance to that from pigs which had received water only during the resting period. Highly significant preferences were shown for fried and casseroled sugar-fed liver in relation to tenderness and juiciness but not flavour. When all eating characteristics were taken into consideration participants were equally divided in their preferences for ‘sugar-fed’ and normal liver.

Two temperature regimes were compared in relation to the growth and feed conversion ratio of groups of cage-reared pigs between 10 and 38 days of age. The treatments were: 27°C at 10 days reducing by 1°C every 4 days to 20°C at 38 days; and 27°C at 10 days reducing by 1°C daily to 20°C at 17 days and then remaining constant. Twelve replicates using 244 pigs were completed, the group size varying between 9 and 12 pigs. The mean growth rates on the two temperature regimes were respectively 234 and 243 g/day, and in both cases feed conversion ratio (kg DM/kg gain) averaged 1·03. It is concluded that temperatures lower than those currently recommended for pigs weaned at 14 to 16 days into controlled-environment houses would support satisfactory performance with direct savings in heating costs under winter conditions.

The effects of the inclusion of increasing quantities of cereal straw treated with sodium hydroxide in the diet of rabbits weie studied on 68 animals, both males and females, of the Spanish Giant and New Zealand × Spanish Giant breeds, weaned at different weights. The nitrogen and fibre digestibilities, the overall growth rate (from weaning to 2·25 kg) and the partial growth rate (from weaning to 2 weeks after weaning) increased linearly, while the feed conversion rate decreased when the content of treated straw in the feed was raised. The overall growth rate for males was significantly higher (P < 0·001) and feed conversion rate lower (P < 0·01) than for females. The crossbred animals had a significantly higher overall (P < 0·001) and partial (P < 0·05) growth rate. As weaning weight increased, overall (P < 0·001) and partial (P < 0·05) growth rate also increased, whereas the dressing percentage of the carcass decreased significantly (P < 0·01).