Twin lambs grazing with their dams at herbage allowances of 30 or 60 gdry matter per kg live weight per day (low and high, respectively) were weaned at 6, 8, 10 or 14 weeks of age. After weaning, the lambs were given a herbage allowance of 160 g dry matter per kg live weight per day.

Ewes on the low allowance ate less herbage, produced less milk and lost more weight than those on the high allowance. The lambs on the low allowance were lighter at weaning than those on the high allowance (137 v. 168, 16·2 v. 20·5, 17·9 v. 24·2 and 21·9 v. 30·4 kg at 6, 8, 10 and 14 weeks respectively).

Lambs weaned from ewes on the low allowance grew more slowly than the unweaned lambs when removed at 6 weeks, but not when weaned at 8 and 10 weeks of age. Weaning lambs from ewes on the high allowance reduced their growth rates at all weaning ages, despite the weaned lambs being grazed at an allowance which would not limit their intake of herbage. The intake of herbage per unit live weight by weaned lambs reached its maximum at approximately 8 weeks of age. After weaning, intake was higher for lambs from ewes on the low allowance than for those on the high allowance (38 v. 33 g organic matter per kg live weight per day). Lambs slaughtered at 17 weeks of age were heavier from the high allowance than from the low allowance. However, after 17 weeks of age the remaining lambs from the low allowance grew more rapidly than those from the high allowance, and when slaughtered at 25 weeks of age had similar weights. Treatments had no effect on the weights of the body components or carcass dimensions independent of their effect on empty-body weights at slaughter.

Using a pedigreed population of Drosophila melanogaster, various indices of individual and full-sib family information were compared for predicting progeny performance for bristle score. On average, the indices were 14% more accurate than individual performance or family mean taken separately. Index weights computed a priori from data solely on the parent's generation gave an index almost as accurate as that computed a posteriori by multiple regression of performance of progeny on parents and parent's full sibs. The value of the index was therefore as predicted from theory.

Twenty-five mature Finnish Landrace × Dorset Horn ewes, each suckling two lambs, were used to measure the effects of dietary concentration of crude protein on food intake, milk yield and changes in body composition during the first 6 weeks of lactation. Diets were complete mixes of milled hay and concentrates, and the amounts of barley and fish meal were altered to give crude protein concentrations of 116 and 143g/kg dry matter. Ten ewes were slaughtered at 5 to 7 days of lactation and the remaining ewes were slaughtered at 40 to 43 days of lactation.

The higher concentration of crude protein in the diet did not alter food intake or digestion. Milk yield was not altered in the first 3 weeks of lactation but was increased in weeks 4 and 5 (P<0·05). Production of milk protein was increased by a higher protein concentration in the diet (P<0·01) and this effect was evident from the 2nd week of lactation. Weight of chemically determined fat in the body decreased from 179 to 13-0kg from 6 to 42 days of lactation (P<0·001) for ewes on diets of both concentrations of crude protein.

It was concluded that the higher level of protein intake during early lactation increased yields of milk and milk protein. The data suggest that the energy lost from the body was used more efficiently by ewes given the diet of high, rather than low, protein content.

A new technique was used to analyse data from an experiment involving sequential measurements on the same experimental units. Results may be inconclusive if analysed in several univariate analyses of variance, one for each occasion, because the successive measurements contain the cumulative effect of treatments.

An experiment was carried out in which two pre-weaning herbage allowances and four ages of weaning were applied to 80 lambs and their live weights recorded twice-weekly until 25 weeks of age. The direct and residual treatment contrasts were evaluated over time using a response surface equation. The continuous variation of treatment effects over time was demonstrated simply by plotting the treatment contrasts and fitting the most appropriate equations to them. Treatment effects were tested by analyses of orthogonal regression coefficients over time, evaluated within each sex of each treatment group by multivariate analysis of variance.

Fitted equations of treatment contrasts were used to demonstrate the continuous variation of effects of pre-weaning herbage allowance on live weights of unweaned lambs, the residual effect of pre-weaning allowance on the weights of weaned lambs, and, separately, the effects of weaning and weaning age on live weights of the lambs.

All the live-weight data recorded in the experiment were used in the analyses. The assumptions made for the application of the method were satisfied and the results were much more informative than those of several univariate analyses of variance.

1. The primary growth of perennial ryegrass (Lolium perenne cultivar Endura) was cut on 23 May (high digestibility) and 23 June (low digestibility) and ensiled with an additive consisting of equal volumes of formic acid and formalin to supply 30 g formaldehyde per kg crude protein. The silages were given ad libitum, together with 6·3 kg dry matter per day of a barley/soya bean supplement, to 24 British Friesian cows over weeks 4 to 18 of lactation.

2. The delay in cutting the primary growth led to an increase in grass yield from 3·78 to 6·94t dry matter per ha but a depression in the content of digestible organic matter in the silage dry matter from 748 to 639 g/kg. However, the effect of the digestibility of the silage on the digestibility of the total diet by the cows was small. The silages contained low levels of fermentation acids and ammonia-nitrogen.

3. The digestibility of silage did not influence silage dry-matter intake in early lactation but in mid lactation the intake of the low-digestibility silage declined whilst that of the high-digestibility silage increased slightly.

4. Cows given silage of high rather than low digestibility produced significantly more milk (high, 28·0 v. low, 24·7kg/day, P < 0·01 ) of lower fat content (high, 36·1 v. low, 41·0 g/kg, P < 0·01 ) but higher protein content (high, 31·5 v. low, 29·4g/kg, P < 0·05). Cows given silage of low digestibility lost more live weight than cows given silage of high digestibility but the effect was not significant.

The intake of silage, concentrates and grazed herbage, and the performance of 16 Masham ewes carrying and suckling either single or twin lambs, was measured during the last 7 weeks of pregnancy, during lactation and after weaning.

There was no difference in intake between ewes with singles or twins in pregnancy, lactation or after weaning. The metabolizable energy intakes, from silage and concentrates, of the ewes with singles and twins were 101 and 100 MJ per head per day in weeks 7 and 6 pre partum, 21·4 and 19·9 MJ in weeks 3 and 2 pre partum, and 24·4 and 23·8MJ in the 1st week of lactation. The intakes from grass and concentrates were 32·3 and 338MJ in weeks 5 and 6 of lactation for the ewes with singles and twins respectively, and 13·8 and 15 2M J from grass alone after weaning. There was no effect of ewe live weight on intake and, although the ewes with singles were producing less milk than those with twins, their intakes were similar.

The same ewes consistently ate the most feed. The overall coefficient of concordance was 05 6 and the coefficients for mid- and late-pregnancy, late pregnancy and early lactation, and early- and mid-lactation were 0·57, 0·62 and 0·66 respectively. The ewes with twins that consistently ate the most lost less weight in pregnancy, produced similar litter weights and suckled lambs that grew faster. Their levels of intake and production were high: the growth rate from 0 to 6 weeks of age of the twin lambs suckling the large-eaters was 721 g/day compared with 631 g/day for those suckling the small-eaters. During lactation the ewes with singles appeared t o consume more metabolizable energy than their maintenance, milk yield and live-weight gain requirements justified, whereas the group of smaller-eating ewes with twins put on more weight than expected from their intakes.

Scottish Blackface ewes in uniform, good, body condition at mating were differentially fed during pregnancy, such that two groups lost 0·15 to 0·20 (groups A and B) and one group gained 0·05 (group C) of maternal live weight by lambing time. The treatments had little effect on the number of lambs born per ewe lambing (1·39, 1·46 and 148 respectively).

Prior to parturition, group A was transferred to a poor hill pasture, and groups B and C to an improved upland reseeded pasture. Herbage intake by six single- and six twin-suckling ewes from each group was estimated in the 3rd, 6th and 8th week after parturition, and mean daily milk production was estimated on 1 day following each intake measurement period. Herbage intake by six dry ewes in each of groups A and B was also estimated.

There were significant differences amongst groups A, B and C, respectively, in mean organic matter digestibility of the herbage consumed (0·701, 0·771 and 0·773), mean daily digestible organic-matter intake (1·06, 1·46 and 1·46kg), mean live-weight change over the period ( –2·9, +5·4 and +l·3kg) and mean daily milk yield (0·64, 1·93 and 1·95 kg).

By the following mating time, after grazing the same pasture from weaning, there was still a difference in body condition score according to pasture type during lactation (2·08, 2·36 and 2·29, respectively). Ovulation rate measured after mating was consistent with the direct effect of body condition (1·34, 1·56 and 1·52, respectively).

An experiment was conducted with 84 suckling Scottish Blackface twin lambs on an improved hill pasture with a history of cobalt deficiency and molybdenum/sulphur-induced copper deficiency. The dams of 13 pairs of twins were treated with 90 mg copper at parturition (Cue) and one member of each pair was given a cobalt bullet (Co + ). One member of each of a further 29 pairs was treated periodically with 5 to 15mg copper to maintain plasma copper concentrations >0·6mg/l (Cu+) while their siblings received no supplementary copper (Cu). Fourteen of these pairs also received a cobalt bullet (Co + ). Lambs not treated with cobalt are designated Co−.

The Cue treatment increased milk copper concentrations, but only for a short time, and resulted in transitory increases in lamb plasma copper concentrations and rate of live-weight gain. At the end of the grazing phase, at approximately 20 weeks of age, Cu+ lambs had gained 0-28 kg more weight than Cue lambs and 158 kg more than Cue lambs, and had higher liver copper concentrations. Cu+ and Cue lambs had heavier and fatter empty bodies and carcasses than Cu− lambs. The cobalt treatment produced no effects at this stage.

Fifty-four of the lambs were housed and given dried grass pellets ad libitum. After 83 days liver copper concentrations were higher in Co− than Co+ lambs, and in Cu+ than in Cu− and Cue lambs. The copper treatments had no effect on rate or efficiency of live-weight gain, but Co− lambs gained weight more quickly and more efficiently than Co+ lambs.

Sixteen Hereford-cross cattle (mean live weight 263 kg) in groups of four were individually given 1·5 kg cubed barley per day with ad libitum access to oat straw. In a 4 × 4 Latin square design (21-day feeding periods) they were additionally given either no supplement (diet A) or 100g/day of a fully soluble liquid supplement containing urea (equivalent to 1090 g crude protein per kg), calcium, phosphorus, sodium, trace elements and vitamins, presented either in the cubed barley (diet B), in the drinking water (diet C) or in a molasses lick (3 parts molasses:2 parts liquid supplement:1 part water) (diet D). Each method of supplementation significantly increased the mean voluntary straw dry-matter intake from approximately 2·9 to approximately 3·25 kg. Mean blood urea concentrations were significantly increased from approximately 1·0 to approximately 1·9 mmol/1 by all three treatments. The coefficients of variation for the individual blood-urea values of the cattle when given each of the three treatments were very comparable, indicating that there was a reasonable individual uniformity of intake of liquid supplement irrespective of method of presentation.

A study was made of some aspects of reproduction in the Nungua Black Head and the Ghanian variety of the West African Dwarf sheep. The gestation period of the two breeds was similar: 150 and 148 days respectively. Ewes mated in August and September tended to have slightly longer gestation periods than those mated in March. The mean birth weights were 2·2 kg in the Nungua Black Head and 13 kg in the West African Dwarf. Type of birth affected the weight of lambs at birth. The Nungua Black Head had no triplets, 0·132 twins and 0·868 singles. The West African Dwarf was more prolific: 0·402 singles, 0·557 twins and 0·041 triplets. The weight advantage of the Nungua Black Head lambs at birth was maintained to weaning and they also had better survival rates. The adjusted 12-week weaning weights averaged 9·8 and 5·8 kg respectively for the Nungua Black Head and West African Dwarf. What the West African Dwarf lost in individual weight it appeared to make up in numbers so that, when the breeds were compared in terms of kg of lamb weaned per ewe mated, there was no significant difference between them.

Single and twin purebred Scottish Blackface lambs born to Blackface ewes, and Suffolk cross lambs born to East Friesland × Blackface ewes, were removed from their dams at birth and cross-fostered to give all combinations of breed of ewe, breed of lamb and number of lambs suckled, with no ewe rearing her own lamb.

Milk production was measured on 1 day/week for 14 weeks. The effect of ewe breed was significant in all weeks, with the East Friesland cross ewes having a higher peak and a more sustained level of production than the Blackface ewes. Ewes suckling twins produced more milk than those suckling singles. Breed-of-lamb effect was significant during the first 5 to 6 weeks of lactation, with crossbred lambs inducing a higher milk output than Blackface lambs, irrespective of the breed of ewe suckled. Beyond this stage, lactation potential of the ewe replaced demand by the lamb as the first limiting factor.

Food intake by ewes during the first 6 weeks differed slightly with both ewe and lamb breed but there were larger differences associated with number of lambs suckled.

The data suggest that lambs on higher milk intake consume a smaller proportion of solid feed but that, in all groups, live weight at 14 weeks of age was closely related to milk intake.

Cassava is increasingly available in the United Kingdom for use in compound feeds. The trial reported here was a 2 × 4 factorial and compared dairy cow compound feeds containing nil or 400 g of cassava per kg, and crude protein levels of 100, 120, 140 and 160 g/kg, given in conjunction with grass silage.

Forty-eight Friesian cows were used in a change-over design with four periods each of 4 weeks. The trial, therefore, compared six blocks of four cows on each of the non-cassava and cassava treatments, with each cow in a block receiving a different protein level. Compound feeds without cassava had a mean barley content of 600g/kg whereas feeds with cassava had a mean barley content of 103g/kg.

There were no significant differences in milk yield (21 14 and 22·27 kg/day) or milk fat level (41·4 and 40·4g/kg milk) on the non-cassava and cassava treatments respectively (P ≤ 0·05). Differences in solids-not-fat concentration were also not significant.

Average intakes of silage were similar on each type of diet. Daily intakes of the compound feed per cow varied from 6·95kg on the non-cassava treatment to 7·08kg on the cassava treatment. This difference in compound intake was not significant. The results indicated that compound feed containing 400 g of cassava per kg perform as well as cereal-based feeds and, therefore, cassava can be considered as a satisfactory replacement for cereals up to a level of 400 g/kg in compound feeds for dairy cows.

The development of sexual activity, sperm production, semen characteristics, testis growth and body size was studies in 10 male sheep (ram lambs) of the Romanov breed and 11 of the Finnish Landrace breed between the ages of 4 and 15 months.

The sexual responses, observed daily for 40 days from the age of 4 months, developed earlier and more intensively in the Romanov than in the Finnish ram lambs, being fully developed in the former breed after 4 days as compared with 14 days in the latter breed. All lambs of both breeds, however, were considered capable of impregnating females by 5 months of age.

In both breeds there was a considerable delay between the onset of sexual maturity and the time at which it became possible to collect semen by means of an artificial vagina. Successful collection was not achieved until the age of 11 months, there being no difference between breeds in this respect.

Subsequent semen production increased to the 14th month of age, with little difference between breeds. Respectively for Romanov and Finnish rams at this age (±s.e.), the mean ejaculate volume was 0·85 + 0·062 and 0·77±0·052ml; motility 64·6 ± 1·62 and 59·7±l·66%; sperm concentration 4·75±0·198 and 4·7 ± 0·197 ×1012perl; number of sperm per ejaculate 4 09±0·338 and 3·63 ±0·259 × 109; and fructose concentration 6·84 × 0·2606 and 4·87 ± 0·2707g/1. In the 15th month there was a tendency for these values to decline except in the case of sperm concentration and, hence, total sperm number.

Mean live weight and size increased until the 14th month and there was no difference between breeds, but testis length and diameter were greater in the Romanov rams at this age.

Male crossbred lambs weighing 10 kg were given, by continuous abomasal infusion, one of a series of diets, equal in energy and nitrogen contents, which provided from 0·887 to 14·863 g lysine per 16 g nitrogen. Gross energy intake was l·38MJ/kg0·75 per day. Oxygen consumption and carbon dioxide production were measured using an open-circuit respirometer when the lambs weighed 12·5 kg. Neither heat production, as calculated from respiratory gas exchange and urinary nitrogen excretion, nor the gross efficiency of utilization of metabolizable energy were affected by the lysine content of the diets.

A trial compared the voluntary water intake of 72 purchased British Friesian bull calves fed at different nutrient intake levels by varying the type and strength of the milk replacer given to 5 weeks of age. There was no control group without water on offer. Water was offered from the 1st day the animals entered the unit. All calves received 4 1/day of either cows' milk (12 calves), milk replacer with 100 g fat per kg (24 calves), milk replacer with 170 g fat per kg (24 calves) or milk replacer with 200 g fat per kg (12 calves). Standard early-weaning pellets containing 190 g crude protein per kg and hay ad libitum were on offer from the 2nd day on the unit. Results indicated that voluntary intakes of water were highest with calves fed on cows' milk and lowest on the milk replacer with 100 g fat per kg given at the lowest mixing strength, although differences were only significant in week 5 (P ≤ 0·05). By covariance analysis, the effects of water intakes on live-weight gain and on pellet intake were examined. The regression coefficient of live-weight gain (weeks 0 to 5) (kg) on water intake (weeks 1 to 5) (1) was b= 0·056 (s.e. 0·021, P ≤ 0·01). The regression coefficient of pellet intake (weeks 0 to 5) (kg) on water consumption was: b= 0·082 (s.e. 0·031, P ≤ 0·01). There was thus a significant correlation of both live-weight gain and pellet intake with water intake. For each extra litre of water consumed per day, there was an extra pellet intake of 0·082 kg and an increase in live-weight gain of 0·056 kg. There was a significant difference in total water intake according to the initial live weight of the calf.

The contribution of fat mobilization to the regulation of fat deposition was investigated in intensively fed, rapidly growing pigs of the breeds Large White and Pietrain. The results indicate that no quantitative differences in fat mobilization parameters existed between the breeds. In both breeds the concentration of non-esterified fatty acids i n blood serum, measured 8h after a meal, was very low, and the fatty acid composition of the non-esterified fatty acids did not reflect the variation in fatty acid composition of the body fat that existed between groups of pigs within each breed. Additionally, the fraction of body fat that was mobilized per day was calculated to be zero for both breeds. It is concluded from these results that the observed differences in fat deposition between Large White (195g/day) and Pietrain (130g/day) were definitely not the consequence of fat mobilization.

1. An anatomical explanation of the observed differences between double-muscled and phenotypically normal cattle was sought by detailed dissection of the sides of six double-muscled Santa Gertrudis steers and six Brangus steers.

2. Relative to carcass weight the double-muscled steers had a significantly greater proportion of muscle and a significantly lower proportion of bone and fat than the Brangus steers. Relative to muscle plus bone weight the muscle proportion was greater and the bone proportion lower in the double-muscled steers.

3. The musculature of the double-muscled steers exhibited a gradient of hypertrophy: 12 muscles (234g/kg of total muscle weight) were grossly hypertrophied, 56 muscles (565g/kg) were hypertrophied to a lesser degree and 28 muscles (195g/kg) showed either a minor degree of hypertrophy or no hypertrophy.

4. The grossly hypertrophied muscles were generally the larger, superficial muscles of the proximal pelvic limb and shoulder area. The muscles showing least hypertrophy were mostly small muscles located in the deeper areas of the carcass, particularly around the spine and in the proximal hindlimb, and in the proximal and distal forelimb.

5. Abnormalities of shape in double-muscled cattle may be attributed largely to altered proportions of total muscle and total fat, and to changes in weight distribution within the musculature.

The linear growth rate of wool on three sites on each of six Wenslcydale × Blackface lambs was measured by wool fibre autoradiography following 11 injections of 35S-cystine. The first injection was given at 09.00 h, so that alternate 36h intervals between injections represented predominantly day (09.00 to 21.00h) or night (21.00 to 09.00 h). The overall mean growth rates on shoulder, mid-side and breech were 0·83, 0·96 and 0·95 mm/day. Differences between day and night growth rates were very small (proportionally<0·05) and inconsistent in 16 of the 18 samples; although breech samples from two sheep showed up to 0·14 faster growth in daytime, a circadian rhythm of wool growth seems unlikely on this evidence. Both linear wool growth rate and food intake increased steadily throughout the experiment.

Mid-side wool growth rates in a second group of three crossbred longwool lambs averaged 0·79, 100 and 1·14 mm/day and were relatively stable over a period of several months.

Carcass evaluation data from two breed-comparison trials were used to examine the value of conformation as an indicator of carcass composition when used in addition to carcass weight and different measures of fatness. One trial involved 1478 crossbred lambs out of three ewe types by Border Leicester, Dorset Down, Ile-de-France, North Country Cheviot, Oxford Down, Southdown, Suffolk, Texel and Wensleydale sires. The other trial involved 920 crossbred lambs out of two dam types by Dorset Down, Ile-de-France, Oldenburg, Oxford Down, Suffolk and Texel sires. Each trial extended over 3 years.

Conformation contributed little to the prediction of carcass lean percentage or proportion of lean in the higher-priced joints, although the additional precision was often significant at P<0·01. When conformation was used in association with dissected subcutaneous fat percentage, it was positively associated with carcass lean content; used with a visual assessment of external fat cover on a five-point scale, which provided a less effective control of fatness variation, it tended to be negatively related to carcass lean content.

Conformation was slightly more valuable for the prediction of lean to bone ratio and m. longissimus depth. The addition of sire-breed effect to weight and fat class provided an important increase in the precision of prediction of percentage lean in carcass and lean to bone ratio. Texel progeny had higher lean to bone ratios and more lean in the carcass than progeny of other sire breeds, but they did not have sufficiently high conformation scores to clearly identify this advantage.

Eighty-nine crossbred gilts were used in an experiment to assess the effects of age at puberty on growth and their carcass characteristics at market weight. From 100 days of age each gilt was exposed daily to a boar and observed for standing heat. The gilts were slaughtered in a commercial abattoir as they reached market weight (approximately 109 kg live weight). Thirty-two gilts (36%) reached puberty before slaughter. These 32 earlier-maturing gilts grew more slowly than the other 57 (P<0·001) yet, paradoxically, within the group of 32 which had reached puberty, there was a significant negative correlation between age at puberty and average daily gain (r=−0·565; P<0·001). Of the 32, the date at first oestrus was known in 30 cases. Among these 30, 10 had ovulated more than once (early-maturing) and 20 had ovulated once (intermediate maturing). Consistent with the paradox there was a significant negative correlation between age at puberty and rate of gain within each group but the regression line for the early-maturing gilts had a significantly lower intercept, on the gain axis, than that for the intermediate group (P<0·01). There were no significant differences between sexual maturity groups for any of the large number of physical and chemical carcass characteristics studied.