To investigate possible pre-test environmental effects on testing station performance, pigs from a total of 107 litters from two breed types were weaned on one of three treatments: weaning at 3, 5 or 8 weeks of age, with a different creep-feeding regime on each. At 8 to 10 weeks of age, litter groups (usually consisting of two boars, one male castrate and one gilt) were sent to a Meat and Livestock Commission testing station and performance-tested from 27 to 85 kg live weight on twice daily to-appetite feeding.

Weaning treatment significantly affected live weight at 50 days and boar growth rate and feed efficiency on test, but carcass traits were largely unaffected. Boars weaned on the 8-week treatment showed a significant advantage in index score of two-thirds of a standard deviation over those weaned at 3 weeks. A smaller number on the 5-week treatment were intermediate but did not differ significantly from those on the other two. It is concluded that wide variation in the weaning methods of herds sending pigs to a testing station could affect selection decisions. Ways of removing any bias by standardizing weaning methods or by statistical adjustment are discussed.

The performance of two flocks of crossbred Masham ewes (Tees-water × Dales Bred) was measured for 6 and 4 years respectively. The ewes in Flock 1 were mated with Dorset Down rams and the ewes in Flock 2 with Suffolk rams.

The overall mean mating weight of each flock was 68-0 kg with no consistent year-to-year variation. The mating weight repeatability values for ewes entering the flocks as 2-year-olds were 0·532 (±0·0681) and 0·524 (±0·1118) for Flocks 1 and 2 respectively.

Mean litter size increased with age, but repeatability was low. Over- all litter weights for singles, twins and triplets were 5·89, 9·88 and 12·43 kg respectively. Two-year-old ewes had lighter litters than mature ewes. Repeatability for litter weight in Flock 1 was 0·337 (±0·0755).

Lamb growth rate to 4 weeks of age was lower for 2-year-old ewes in both flocks and the repeatability was 0·322 (±0·0947) in Flock 1. For ewes having twin lambs, significant correlations (P < 0·01) were found between mating weight and birth weight and between birth weight and lamb growth rate to 4 weeks of age.

Perinatal mortality was higher for lambs with a birth weight below 3·9 kg, but overall lamb mortality was only 8%: this low figure was probably due to the relatively high birth weight of the twin and triplet lambs.

Three experiments, involving a total of 84 pigs of approximately 90 kg live weight, were undertaken to determine the effects of feeding sugar solutions immediately prior to slaughter on carcass yield, liver weights, ultimate pH of the musculature and some chemical characteristics of muscle and liver. In the first, where water-only (14 h) prior to slaughter, or access to a solution of either glucose syrup (12 h) or sucrose (12 h) followed by water-only (2 h) were the treatments, sugar feeding did not influence carcass yield. Liver weight was increased with glucose (39%) and markedly so with sucrose (77%). Livers from sugar-fed pigs had higher glycogen and lower protein concentrations. Glucose reduced muscle ultimate pH (0·2 to 0·4 units) but sucrose had little effect. In the second study various sugars were tested (pure glucose, glucose syrup, sucrose and fructose) and pigs had access to solutions of them for 4 h and water-only thereafter for 10 h prior to slaughter. All sugar treatments increased liver weight and reduced muscle ultimate pH relative to water-only before slaughter. The final experiment involved access to varying amounts of a glucose syrup solution for 4 h followed by water-only (10 h). In comparison with ‘water-only’ prior to slaughter, an intake of some 250 g hexose equivalent reduced muscle ultimate pH (0·2 to 0·3 units) and increased liver weight but a response in carcass yield required in excess of 1000 g hexose equivalent.

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.

Three field trials were undertaken to determine the influence of feeding sugar solutions to pigs immediately prior to slaughter on carcass yield, liver weight and muscle quality. In the first, which involved 168 pigs of 85 to 95 kg live weight, provision of a glucose syrup solution in lairage (4 h) followed by water (12 h), compared with water-only (16 h) increased carcass yield (3%) and liver weight (27%) and reduced muscle ultimate pH (0·1 to 0·4 unit). When water was not made available after consumption of the sugar there was no response in carcass yield. In the second trial conducted with 169 pigs of 110 to 125 kg live weight, and involving the same treatments as in Trial I, except that sugar was provided for a longer period (6 h), corresponding responses in carcass yield, liver weight and muscle ultimate pH were +2·7%, +24% and a decrease of 0·2 to 0·3 units. In both trials responses to sugar feeding were less when compared with pigs slaughtered shortly after arrival at the abattoir. In the final trial, which also involved heavy pigs (88), access to a glucose syrup solution (9 h), but not a sucrose one, followed by water (8 h), relative to water-only in lairage, improved carcass yield (1·1%). Liver weight was increased with glucose (34·2%) and markedly so with sucrose (49·7%) and both sugars reduced muscle ultimate pH (0·1 to 0·6 units).

Changes in body composition during lactation were measured in 12 Border Leicester × Scottish Blackface ewes by serial slaughter at 12, 41 and 111 days of lactation. Ewes suckled twin lambs and were given daily 1·6 kg dry matter of a complete diet containing 151 g crude protein and 10·2 MJ metabolizable energy/kg dry matter.

Live weights of ewes averaged 60·2, 58·9 and 55·8 kg at 12, 41 and 111 days of lactation respectively. There were no significant changes in weights of stomach, small and large intestine and liver.

The weight of body fat averaged 9·19, 2·28 and 1·19 kg at 12, 41 and 111 days respectively (P < 0·001) and weight of ash increased from 1·72 kg at 12 days to 2·30 kg at 111 days (P < 0·001). Water to protein ratios at the three stages of lactation were 2·94, 3·36 and 3·18 (P < 0·10). The energy value of weight loss varied from 68 to 17 MJ/kg, depending on the relative changes in total body water and fat. Live-weight change was therefore a poor indicator of change in body energy during early lactation.

Body fat could be predicted from its combined relationships with live weight and total body water (residual s.d. ±0·70 kg), but when deuterium oxide space was used to estimate body water separate equations were necessary for early and later stages of lactation. This was apparently due to differences between stages of lactation in the time required for deuterium oxide to equilibrate with water in the reticulo-rumen.

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.

1. Seven experiments involving 191 calves and 40 cows were under- taken over a 2-year period into the effect of copper treatment of hypocupraemic calves on their subsequent performance.

2. Significant increases in mean live-weight gain of copper-treated calves ranging from 19·9 to 34·3 kg/head relative to untreated control groups were obtained in three cases.

3. The frequency of copper injection required to maintain plasma copper levels above 0·60 mg/1 varied from 6 to 12 weeks.

4. The live-weight gain and plasma copper concentration responses are discussed in relation to the pasture herbage concentrations of copper, molybdenum and sulphate.

Thirty-six Large White × (Large White × Landrace) young female pigs (gilts) were allocated to one of nine treatments. These were 30 min daily boar contact from 125, 132, 139, 146, 153, 160, 167, 174 or 181 days of age. Gilts were fed so as to maintain them on a pre-determined growth curve, gaining 0·45 kg per day. Once puberty had been detected, gilts were mated at the next (second) oestrous period and subsequently slaughtered 20 days post coitum.

The interval from first boar contact to puberty was significantly longer (P<0·05) amongst gilts first exposed to a boar at ages below 139 days. Amongst gilts older than this the interval was similar. Though the 174- and 181-day groups were significantly older at puberty (P<0·05) no significant differences were observed amongst the younger age groups. Synchronization of pubertal oestrus appeared to be better for the 160- and 167-day groups, with three out of four gilts reaching puberty within an 8-day period. There was no indication that weight at puberty, ovulation rate, percentage embryo survivval, or number of viable embryos at 20 days post coitum were affected by treatment.

From the results it appears that the optimal gilt age at which to commence boar contact, in terms of age at puberty, interval from first boar contact to puberty and synchronization of the pubertal oestrus, is in the age range 160 to 170 days.

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.

Linear y = a′ + b′x and gamma type y = ea−cx xb models for the lactation curve (y = daily production on day x of lactation) were adjusted to daily production records of 870 lactations. Within- lactations pooled R2 = 0·71 and R2 = 0·74 were respectively obtained for the linear and gamma type models, the latter being preferred for further analyses on account of its general validity under varied circumstances.

The parameters a, b, c of individual gamma type lactation curves were analysed by least squares within a subset of 634 lactations from Holstein-Friesian (HPB), 1/2 HPB: 1/2 Gir (F1) and 3/4 HPB: 1/4 Gir (B1) cows. Crossbreds had both higher initial production and higher persistency of lactation than purebred cows. F1's had higher initial production than B1's, both groups having similar persistency of lactation. Cows calving during the rainy season had higher initial production than cows calving in the dry season, which, however, had more persistent lactations. Parity affected only the initial production a parameter, which was lower for first calvers, while the other parity classes had similar a values.

The effect of fermentation on cassava meal diets supplemented with 0, 2, 4 and 6% levels of palm oil on the performance, carcass characteristics and economic value of broiler chickens was studied. During the growing phase, fermentation had no influence on growth rate, but resulted in reduced mortality and improved efficiency of feed utilization in the chickens. However, there were greater intakes of fermented cassava meal diets, higher efficiency of feed utilization, better growth rate and reduced mortality during the finishing phase. Abdominal fat was lower during both phases in chickens given the fermented cassava meal diets than those given the cassava meal diets. There was evidence of economic benefits in reduced feed cost, increased gross revenue and higher revenue less feed cost values in fermented cassava meal than in cassava meal diets. There were non-significant reductions in feed intake, mortality rate, daily rate of gain, final body weight and carcass quality, but significant economic benefits during both growing and finishing phases as the level of supplementary palm oil increased in the diets. The results suggest that while about 2% palm oil might be required in fermented cassava meal diets, 2 to 4% would be needed in cassava meal diets by broiler chickens for comparable performance.

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.

The effects of days-open on milk yields in current lactations and in following lactations were estimated from 71 911 current and 68 693 following lactation records. Yields were expressed as 305-day, total and annual records, where annual record = 365 × (total yield/days between calvings).

The data were grouped according to current days-open, corrected for initial yield differences and analysed separately for heifers and cows in Moshav (moderate-yielding) and Kibbutz (high-yielding) herds. Current 305-day records increased by 15 to 18 kg milk/day-open up to 90 days-open, and 2 to 3 kg/day-open thereafter. In contrast, the effects of increasing days-open on annual yields were generally small and negative, being positive only for heifers up to 90 days-open. Thus 305-day records heavily under-rated annual yields of fertile cows. For current lactations, 70 to 100 days-open for heifers and 30 to 50 days-open for cows resulted in the highest annual production. Yields in following lactations were positively associated with days-open in the previous lactation. The effect was highest in high-yielding herds, suggesting that high-yielding cows respond positively to some rest between calvings.

Combining the effects of days-open on current and following lactation yields and on the calf crop: in high-yielding herds heifers had the highest productivity when mated not earlier than 70 days post partum, while in moderately-yielding herds days-open did not affect productivity. Cows in high-yielding herds achieved highest productivity at 41 to 90 days-open, while cows in moderately-yielding herds were most productive when mated as early as possible.

A comparison of the economic value of sire fertility and sire transmitting ability for milk production showed that fertility may often be over-rated.

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).

A primary growth crop of perennial ryegrass (cv. S24), containing 17% crude protein and 9·9 MJ metabolizable energy/kg dry matter, was artificially dried, ground through a 3·0 mm screen and pelleted either without further treatment (C), or after the application of formaldehyde (T) at a rate of 1 g/100 g crude protein. The C and T diets were each fed to 20 lambs for 77 days. Diets C and T were given ad libitum and at three lower planes of nutrition. Similar amounts of dry matter, nitrogen and digestible energy were consumed at each of the four planes of nutrition by lambs fed diets C and T. Carcass energy, fat and protein retention, and total body energy retention were measured by the comparative slaughter technique and did not differ between the diets (P> 0·05). Metabolizable energy intake was calculated from digestible energy intake using the factor 0·81. The efficiency of utilization of the metabolizable energy for growth and fattening (kf) and the net energy value were calculated by linear regression analysis from the total body energy retention, the calculated metabolizable energy intake and dry-matter intake data scaled to M0·75. They did not differ between the diets (P > 0·05), and were 0·370 (C) and 0·431 (T) for kf, and 2·09 (C) and 1·97 MJ/kg dry matter (T) for net energy.

Hays varying from 58 to 75% organic matter digestibility (OMD) were offered ad libitum to steers weighing approximately 400 kg, together with concentrates at rates varying from 0·0 to 8·5 g organic matter (OM)/kg live weight per day. Total digestible OM intake (DOMI) increased linearly by 0·75 g/g concentrate OM intake (OMI) for a hay of 58% OMD, but by only 0·26 to 0·36 g/g concentrate OMI for hays above 70% OMD. With hays above 70% OMD, supplementary feeding had little effect on the overall OMD of the diet but significantly depressed the cellulose digestibility of the diet. With the hays of lower digestibility, supplementary feeding increased the OMD of the diet by an average of 0·90% units/unit concentrate OMI, and had no significant effect on the cellulose digestibility of the diet. Live-weight gain increased with increasing digestibility of the hay and with increasing level of supplement.

In multiple regression equations, variations in hay digestibility and concentrate intake accounted for from 77 to 91% of the variation in hay intake, diet digestibility and total DOM intake.

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.

Four experiments were made during early lactation on individually penned Finnish Landrace × Dorset Horn ewes, each suckling two lambs. In Experiment 1, 14 ewes of mean body weight 74 ± 2·4 kg received daily, 1·9 kg dry matter, 20 MJ of metabolizable energy and 300 g of crude protein from a diet (H) containing hay, barley and fish meal. Reduction of the daily crude protein intake of half the ewes to 225 g by replacing fish meal with barley (diet L) in week 2 of lactation resulted in a decrease (P< 0·01) in daily milk yield of 0·53 kg (17%) compared with no change for ewes remaining on diet H. The effect was reversed by returning the ewes to diet H at the end of week 3. In Experiment 2 the use of four ewes fitted with abomasal cannulae showed that the additional non-ammonia nitrogen reaching the abomasum when fish meal was given was used with an efficiency of 0·51 for the production of milk nitrogen. In Experiment 3, involving 20 ewes, a restriction in protein intake for more than 10 days in early lactation by replacing the fish meal with barley depressed subsequent milk yield. In Experiment 4, 24 ewes were given either fish meal, soya bean meal or groundnut meal as protein supplements. In early lactation fish meal was superior by 0·40 and 0·43 kg of milk per day to soya bean meal and groundnut meal respectively, and this was attributed to the greater quantity of non-ammonia nitrogen reaching the abomasum in the fish meal compared with the soya bean meal and groundnut meal supplements. The commercial significance of the results is discussed.

The effect of haemoglobin types A and B on reproductive performance of ewes grazing oestrogenic pastures was studied in four commercial flocks in 1973 and in an additional five in 1974 (a total of nine flocks). The number of ewes lambing per ewe mated differed significantly (P< 0·05) between mating types (male AA × female AA, male AA × female AB, male BB × female AB and male BB × female BB). Differences between mating types in the number of lambs born per ewe exposed to the ram and in the number of lambs weaned per ewe exposed to the ram bordered on significance (0·05<P<0·1). Matings involving BB sires were superior to matings involving AA sires. This finding differs from previously published evidence on this topic. There were no significant differences in lamb mortality or in the number of lambs born per parturition. Reproductive performance did not differ amongst ewe genotypes. Age of dam, farm and year had significant effects on most of the reproductive characteristics studied. Three significant interactions (P<0·05) involving mating type were found: mating type × age on number of ewes lambing per ewe exposed to the ram, mating type × farm on number of lambs born per parturition and mating type × year on lamb mortality. Due to the relatively small differences observed in reproductive performance between mating types it is concluded that selection for haemoglobin type is unlikely to overcome the problem of low reproductive performance in sheep grazing oestrogenic pastures.