The present study estimates the mean fat and solids-not-fat concentrations, and 305-day yields of fat, solids-not-fat, total solids and milk for three zebu breeds (Tharparkar, Sahiwal and Red Sindhi) and for halfbred F1 and F2 Brown Swiss ♂ × Sahiwal ♀ and ¾ Brown Swiss ♂ × Sahiwal 9 cattle maintained at this Institute during the period 1972–75. Mean fat and solids-not-fat concentrations ranged from 46·4 to 47·8 g/kg and 90·3 to 90·9 g/kg respectively, which were similar for all breeds. The 305-day fat, solids-not-fat, total solids and milk yields differed significantly between different breeds (P < 0–01). These yields were similar for the three zebu breeds (86 to 96 kg fat, 164 to 186 kg solids-not-fat, 250 to 282 kg total solids and 1 814 to 2 054 kg milk), but crossbreds showed significantly higher yields (125 to 171 kg, 242 to 332 kg, 368 to 503 kg and 2 670 to 3 676 kg, respectively), the highest being for F1 halfbreds. Season of calving had no significant effect on mean fat and solids-not-fat concentrations whereas the lactation yield parameters were found to be significantly higher for Tharparkar, Sahiwal and F1 Brown Swiss × Sahiwal cattle calving in the winter, followed in order by those calving in the monsoon and those calving in the summer. Selection of animals based on milk production alone was also found to increase the yield of milk constituents.

The effects of selection for low backfat thickness on tissue deposition in different body sites has been investigated in pigs. Eight castrated male and eight female pigs from each of the selection and control lines maintained at the University of Newcastle upon Tyne were used. One castrated male and one female from each line was killed at 15, 30, 45, 60, 75, 90, 105 and 120 kg live weight following ad libitum food consumption and fully dissected.

There were only small effects of line on carcass composition, selected pigs having 120 g/kg more bone than controls at the mean side weight (P < 0·001) and 40 g/kg more lean (NS). At the same mean weight of subcutaneous fat, selected pigs had thinner backfat than controls (approximately 3 mm) over m. longissimus at the last rib and over the shoulder but not at the mid-rump or mid-back positions. There appears to have been a slight shift in the sites of fat deposition from above m. longissimus in the loin towards the mid-line and rump as a result of selection, even though mid-rump, C and K measurements were all included in the selection index. However, there was no difference between the lines in the weight distribution of subcutaneous fat between six regions and so these shifts must have been very localized. There was no difference between lines in the relationship between P2 fat thickness and proportion of lean in the side.

The effects of selection on the sites of deposition within tissues other than subcutaneous fat were small. In particular there was no evidence that selection has caused relocation of body fat from subcutaneous to the other sites.

Three trials were conducted on commercial premises using sows naturally infested with gastro-intestinal nematodes, primarily Oesophagostomum spp. In two trials the farrowing performance of sows treated approximately 7 days before farrowing with thiophanate (‘Nemafax’) in-feed at a median dosage of 62·5 mg/kg was compared with that of untreated controls. In the third trial a similar comparison was made between sows treated approximately 7 days before expected service and untreated controls. In all cases faecal egg counts indicated thiophanate was highly effective against the nematode burdens present. Administered pre-farrowing, thiophanate resulted in better pre-weaning weight gains and relatively lower creep feed consumptions of the piglets. This effect was most marked in the trial with a higher level of Oesophagostomum spp. infestation in the sows. Under similar circumstances, pre-service medication produced a response in terms of live piglets born and those surviving to weaning.

The lactation model of Wood, y = Anbe−cn was fitted, using a logarithmic transformation, to two sets of lactation data obtained from the Agricultural Research Institute of Northern Ireland. The first set was from animals calving in the autumn and the second set from animals calving in winter and early spring. A categorical variable was added to the transformed model to investigate the effect on the parameters of the animals going out to grass. The technique proved more useful with the autumn-calving herd.

Growth performance and body composition differences between Large White control (C) and 10th generation index-selected (S) pigs were evaluated on a fixed food, fixed time trial. This avoided the complicated interpretation associated with interacting variations in food intake, days on test and body composition. Thirty-nine C and 40 S boars were slaughtered, their carcasses dissected and whole empty bodies minced and chemically analysed after an 84-day trial starting at 26·6 ± 0·27 kg live weight. S boars were older at the start of test (95·2 v. 89·0 days, P < 0·001), were heavier at the end of test (96·2 v. 93·8 kg, P < 001) and converted food more efficiently (0·392 v. 0·378 kg gain per kg food, P < 0·01) than C boars. Bodies of S boars contained more water (48·3 v. 45·9 kg, P < 0·001), less lipid (17·4 v. 18·8 kg, P < 0·001) less gross energy (1 004 v. 1 045 MJ, P < 0·05), but similar amounts of protein (13·8 v. 13·4 kg, NS) compared with C boars. S carcasses contained more lean (34·1 v. 31·8 kg, P < 0·001), less subcutaneous fat (12·5 v. 13·7 kg, P < 0·001), and had lower P2 backfat depths (15·8 v. 18·3 mm, P < 0·001) than C carcasses. Although carcass leanness had been increased, 10 generations of index selection had also reduced the overall energetic efficiency of the selection line, apparently by increasing non-productive heat loss.

Four silages were prepared from perennial ryegrass. Half the crop was picked up soon after mowing and the remainder left to wilt for 24 h. Half the unwilted and half the wilted grass was chopped by a forage harvester with its normal complement of knives; the remainder was chopped by a forage harvester with all but two of its knives removed. The ensiled material was offered ad libitum for 80 days as the sole food to 32 British Friesian male castrates initially 14 weeks of age and 111 kg live weight.

Wilting raised silage dry-matter content by 31 g/kg fresh weight and gave lower concentrations of acetic acid whilst short chopping gave lower butyric acid. Concentrations of acetic acid, butyric acid and ammonia nitrogen were high on all treatments. Organic matter digestibility was significantly increased by wilting (P < 0·001) and significantly depressed by chopping (P < 0·001). There was no response in dry-matter intake to short chopping, but wilting raised daily intake from 18·4 to 19·9 g silage dry matter per kg live weight (P < 0·001). Live-weight gain was increased from 0·42 to 0·46 kg/day by short chopping (P < 0·05) and from 0·40 to 0·48 kg/day by wilting (P < 0·01)

Ultrastructural parameters of muscle growth were measured in lines of mice which had undergone 15 generations of selection for high and low body weight. Previous light microscopic studies of these lines had shown that selection for altered body weight evokes correlated responses in the weight of skeletal muscles as a result of changes in both the number and the longitudinal and transverse dimensions of the fibres.

The length of the myosin filaments and of the actin filaments (including the Z disc) did not differ significantly from the controls in the mm. sternomastoideus, biceps brachii and tibialis anterior of mature male mice from the two selection lines. The mean cross-sectional area of the myofibrils of the mm. sternomastoideus and biceps brachii were also unaltered by selection for high and low body weight. Changes in the area of the fibres were brought about by increases and decreases in the number of their constituent myofibrils and corresponding changes in the non-contractile elements.

Selection for high and low body weight did not affect the dimensions of the contractile elements of the muscle fibres. The genetically determined alterations in the length and cross-sectional area of the fibres were due to changes in the number of their constituent sarcomeres and myofibrils. These changes are similar to those which occur during growth.

Two separate experiments were conducted with 12 lactating and four non-lactating Ayrshire cows to compare three frequencies of feeding concentrates per day. Milk production was measured in a 16-week experiment in which the lactating cows were given either a low- or a high-protein concentrate 2, 4 or 22 times (×) per day. Eating behaviour was measured in a 15-week experiment in which the non-lactating cows were also given the low- and high-protein concentrates 2 and 22 × per day. The low- and high-protein concentrates had concentrations of 128 and 202 g crude protein/kg dry matter respectively. Grass silage with a digestibility of organic matter in the dry matter of 0·655 was offered ad libitum to all the cows. Frequency of feeding had no significant effects on silage intake, total nutrient intake, milk yield and live weight. The milk fat concentration increased as the frequency of feeding increased but none of the differences in this and the other milk constituents was significant. Total eating time per day and eating and ruminating time per kg dry matter were not significantly different on the 2 × and the 22 × feeding treatments. There were no interactions between the feeding-frequency treatments and the two types of concentrates. It is concluded that there were no advantages in offering concentrates in more than two separate feeds per day when the daily amount averaged about 7 kg per cow and good-quality silage was available ad libitum

Twenty-five Californian does were mated and given pelleted diets of either 8(LE) or 10(HE) MJ/kg dry matter (ruminant metabolizable energy values) throughout gestation and lactation. Litter sizes were adjusted to six offspring per doe. Milk yield was estimated from the weight differences of the litters before and after suckling, when the opportunity for nursing was confined to once daily. The young rabbits were allowed access to either the LE or HE diets from 18 days of age. Weaning took place at 32 days of age when four rabbits from each doe grouP × pre-weaning diet were slaughtered. Diet had no effect on litter size or birth weight, but does on the LE diet had lower live weights post partum (P < 0·05). Dry-matter consumption by the does on the LE diet was greater than for the HE diet (P < 0·05) both during gestation and lactation, but calculated metabolizable energy intakes were lower during lactation. There were no statistically significant differences between treatments for milk yield or live-weight gain to weaning and dry-matter intakes of the young at weaning, but daily live-weight gain from fostering to 18 days of age was greater for litters of does fed the HE rather than the LE diet (P < 0·05). There were no statistically significant differences between diets for carcass traits at weaning.

After weaning, 32 rabbits were given either the LE or HE diet until 2 kg live weight when they were slaughtered. A post-weaning × pre-weaning diet interaction (P < 0·05) occurred for live weights of the rabbits at the start of the post-weaning trial (i.e. after a 10-day adaptation period) with LE: LE rabbits being lighter than other rabbits as a results of poor live-weight gains during the adaptation period. Live-weight gains to slaughter were greater for the pre-weaning LE diet (P < 0·05) and the post-weaning HE diet (P < 0·01), although dry-matter intakes of the HE diet were less (P < 0·05). Rabbits on the LE diet had greater empty gut weights (P < 0·05) and lighter livers (P < 0·05) at slaughter.

Food intake was individually measured for Large White control (C) and 10th generation index-selected (S) pigs fed twice daily to appetite on a fixed time trial. Thirty-nine C and 38 S boars were slaughtered, their carcasses dissected and whole empty bodies minced and chemically analysed after an 84-day trial starting at 28·6 ± 0·30 kg live weight. S boars ate proportionately 0·08 less than C boars in the first 42 days of the trial (79 v. 86 kg, P < 0·01), but S and C boars ate similar amounts (114 v. 117 kg, NS) in the last 42 days. S boars grew 0-04 faster than C boars (918 v. 886 g per day, NS), and had 0·09 better food conversion efficiency (0·404 v. 0·369 gain per kg food, P < 0·001). S boars contained more water than C boars (53·5 v. 48·9 kg, P < 0·001), more protein (15-4 v. 14-2 kg, P < 0·01), less lipid (20·8 v. 25·1 kg, P < 0·001), less gross energy (1 199 v. 1 357 MJ, P < 0·01) but a similar amount of ash. S carcasses had 3 kg more lean (36·5 v. 33·5 kg, P < 0·001) and more bone than C carcasses (7·14 v. 6·71 kg, P < 0·05), but contained 3 kg less total fat (19·6 v. 22·6 kg, P < 0·01). The lean tissue growth rate of S boars was 327 g per day which was 31 g per day faster than for C boars (P < 0·001). Appetite reduction in S boars enhanced fatness differences between the lines.

Forty-five piglets were used to study the effects of feeding diets containing 153, 239 or 321 g crude protein per kg dry matter between 1·8 and 6·5 kg live weight, and low and high protein diets subsequent to 6·5 kg live weight on growth performance, body composition and the cellularity of skeletal muscle to 45 kg live weight.

Reducing dietary crude protein between 1·8 and 6·5 kg live weight depressed growth performance and at 6·5 kg live weight increased body fat content but reduced body protein, body water and the weight and DNA content of the adductor muscle. The effects of dietary protein content before 6·5 kg live weight on body composition at the latter weight were still evident in pigs killed at 11·5 kg live weight whilst the differences in muscle DNA persisted to 45 kg live weight.

On the lower protein treatment subsequent to 6·5 kg live weight there was a tendency for pigs given the lowest protein diet before 6-5 kg live weight to exhibit better growth performance and deposit protein at a faster rate than those given the higher protein diets. However, these responses were reversed on the higher protein treatment subsequent to 6·5 kg live weight.

The effects of dietary protein content subsequent to 6·5 kg live weight on growth performance, body composition and the cellularity of muscle tissue were qualitatively the same as those for the live-weight phase 1·8 to 6·5 kg.

Twenty-four bull calves, eight Hereford × Friesian, eight Aberdeen Angus × Friesian and eight Friesian, were reared from birth to slaughter at 13 weeks of age solely on a milk substitute diet given ad libitum.

Samples of jugular blood were taken at weekly intervals from 5 days to 89 days of age for determination of concentrations of prolactin, growth hormone (GH), insulin and total thyroxine (T4) in plasma, tri-iodothyronine (T3) uptake, and thus free T4 index (FTI).

The Friesian calves had a higher mean body temperature and lower mean T3 uptake than did either of the beef crosses.

The Aberdeen Angus cross had a higher mean dry-matter intake per unit of metabolic body size (DMI/W0·73), heart rate and plasma insulin concentration than did the Hereford cross, and a higher insulin concentration but not a higher heart rate than did the Friesian. Live-weight gain and DMI/W0·73 for the Friesian was intermediate between that of the Aberdeen Augus cross and the Hereford cross.

DMI/W0·73 was positively correlated with insulin: GH ratio, prolactin: GH ratio and T4: GH ratio.

The increase in heart rate per unit DMI/W073, a measure of the heat increment of feeding, was negatively correlated with the plasma insulin concentration, insulin: T4 and insulin: GH ratios.

Prolactin concentration, GH concentration and T3 uptake declined with age, whereas insulin concentration, T4 concentration and FTI increased with age. The relationship was linear for prolactin and insulin concentrations, but curvilinear for the other variables. The Friesian breed had a higher GH concentration than did the beef crosses during the first 12 days of life. The large increase in insulin concentration for the Aberdeen Angus × Friesian occurred from about 47 days of age. The peak T4 concentration and the lowest T3 uptake of the breeds occurred between 33 and 42 days of age.

Possible mechanisms for the control of dry-matter intake by preruminant calves and the difficulties associated with prediction of performance from plasma metabolic hormone concentrations obtained at a young age are discussed.

Thirty Hereford × Friesian steers initially weighing 320 kg were used in two experiments, to compare the effects of mechanical processing of barley straw and the amount of rolled barley offered on intake and live-weight gain. The straw was offered ad libitum either in the long form or shredded through a 40 mm screen and supplemented with 20, 35 and 50 g barley DM per kgW"75 per day (L, M and H respectively). A solution providing 12 g urea per kg straw dry matter (DM) was sprayed onto the straw and all the animals were offered daily 480 g of soya bean meal with minerals and vitamins. In the first experiment, which had a change-over design, the animals were weighed at the beginning and the end of each period. The daily consumption of shredded straw (kg DM) was L 3·38, M 3·29 and H 3·00 and of long straw L 3·94, M 4·02 and H 3·56 (s.e. of difference, 0·29). There were significant differences in straw intake between steers offered the long and the shredded straw (P < 0·001) but no differences in intake when different amounts of barley were offered within the same physical form of straw. The mean daily live-weight gains for treatments L, M and H respectively were 0·25, 0·66 and 0·80 kg for steers given shredded straw and 0·32, 0·62 and 0·87 kg (s.e. of difference, 0·1) for those offered long straw. At the end of the first experiment the same animals were kept for a further 10 weeks on the same straw treatment but only treatments L and H were continued, the steers from treatment M being distributed between L and H. The straw intakes and live-weight gains were in agreement with those observed in the first experiment

To study their relationship to milk yield, the concentrations, in jugular venous blood, of thyroxine iodine (T4I), thyroxine (T4), 3,5,3'-tri-iodothyronine (T3), glucose, non-esterified fatty acids (NEFA), triglycerides, phospholipids, cholesterol, total protein, albumin, urea, haemoglobin and packed cell volume (PCV) have been measured in 36 cows (Simmental, Swiss Brown, Holstein and Simmental × Holstein) of different ages during a full lactation, pregnancy, dry period, parturition and 150 days of the ensuing lactation. Thyroid hormones and triglycerides were negatively, and total protein, globulin, cholesterol and phospholipids were positively, correlated with uncorrected or corrected milk yield during several periods of lactation, whereas glucose, NEFA, albumin, urea, haemoglobin and packed cell volume were not correlated with milk yield. The 10 animals with the highest milk yield (18·9 to 23·5 kg/day) exhibited significantly lower values of T4I, T4, T3 and glucose, significantly higher levels of total protein and globulin and tended to have higher levels of NEFA than the 10 cows with the lowest milk yield (10·9 to 14·3 kg/day) throughout or during certain periods of lactation, whereas concentrations of triglycerides, phospholipids, cholesterol, albumin, haemoglobin and PCV did not differ. Changes in T4I, T4, T3, glucose and total protein during lactation were also influenced by age, presumably associated with an increase in milk production with age. T3 was consistently lowest and cholesterol and phospholipids, during later stages of lactation, were highest in Holsteins, which had the highest milk yields of all breeds. Changes of blood parameters were mainly caused by shifts in energy and protein metabolism in association with level of milk production

Twenty-two pairs of female Friesian twin calvxs, fed a standard pelleted diet with an ME value of 9·3 MJ 'kg, were split between the following nutritional treatments: (a)ad libitum (b) a weekly amount equal to 24% of body weight or (c) equal to 20% of body weight. Each proportionally-fed animal eventually reached a break-point when the amount of food it was offered exceeded its intake capacity.

For the ‘24%’ and ‘20%’ regimes respectively, break-points occurred at a mean age of 40 and 48 weeks and at a mean body weight of 222 and 258 kg. Surprisingly, the mean body weights at these ages on the ad libitum regime were virtually the same (223 and 265 kg). Thus growth up to break-point was, on average, just as fast for proportional feeding as for ad libitum.

In general, growth up to break-point was significantly slower than the exponential rate expected from a simple linear model. Nevertheless, animals fed at the 20% level grew almost exponentially beyond 6 months of age, and the normally expected decline in the food efficiency ratio was delayed.

The hypothesis being tested was that a proportional feeding system, while in operation, would ensure highly efficient growth and that the break-point could be used as a self-determined optimal slaughter point for each individual. On the evidence obtained, further investigation would be worthwhile, especially at proportional feeding levels giving break-points beyond 1 year of age.

1. Fifty-seven piglets were used to study the effects of rearing pigs on the sow or artificially on a low or high level of feeding between 1·8 and 6·5 kg live weight and either a low or high level of feeding between 6·5 and 20 kg live weight on growth and development to 75 kg live weight.

2. The artificially reared pigs fed at the higher level grew more rapidly (P < 0·05) and were fatter (P < 0·05) at 6·5 kg live weight than their more restrictedly fed counterparts. The pigs reared on the sow grew at the same rate as the artificially reared pigs fed at the low level but at 6·5 kg live weight were as fat as the artificially reared pigs fed at the higher level.

3. Between 6·5 and 20 kg live weight the artificially reared pigs previously fed at the lower level grew more rapidly (P < 0·05) than their more liberally fed counterparts which in turn, grew at a faster rate (P < 0·05) than pigs previously reared on the sow. However, nutrition prior to 6·5 kg live weight had no influence on performance or body composition subsequent to 20 kg live weight.

4. Raising the level of feeding between 6·5 and 20 kg live weight increased growth rate (P < 0·05) and body fat content at the latter weight (P < 0·05). However, subsequent to 20 kg live weight, the pigs previously fed at the lower level exhibited more rapid and efficient growth (P < 0·05) and at 75 kg live weight were leaner (P < 0·05) than those fed more generously between 6·5 and 20 kg.

5. At 6·5 kg live weight the pigs reared on the sow contained less deoxyribonucleic acid (P < 0·05) in the m. adductor than pigs from either of the two artificially reared groups. Muscle deoxyribonucleic acid at 20 and 75 kg live weight was unaffected by nutrition before 6·5 kg live weight or level of feeding between 6·5 and 20 kg live weight.

Data from 265 female goats (does) from seven herds in Year 1 and 130 does from four herds in Year 2 were analysed using a general linear interactive model for factors affecting gestation period (GP), litter size (LS) and birth weight (BW) of offspring (kids). Gestation period could be described by the regression equation GP = α – 0·890LS –1·072S where S is the proportion of male kids in the litter and the constant (a) depends on breed and herd and was 154·240 (s.e., 0·843) days for British Saanen does in Herd 1. The model established for LS was a quadratic regressional relationship LS = a – 0·000103 (MW - 60))2 + 0-0172 (MW -60) where MW was live weight of the doe at mating and a at MW = 60 kg depends on herd and period of kidding. For early-kidding does in Herd 1 a was 2·277 (s.e., 0·090) kids. The expression BW —α 0·363LS + 0·057P is a simplified multiple regressional form involving BW, LS and parity (P) where a varies according to breed, herd and age of the doe. The estimate of a for kids from British Saanen, 1-year-old does in Herd 1 was 3·879 (s.e., 0·632) kg.

In experiment 1, nine Hereford × Friesian steers weighing 325 kg were used in a changeover design and offered long barley straw that had been treated with 30 g anhydrous ammonia per kg for 8 weeks, a solution providing 25 g urea per kg straw dry matter or a solution providing 23 g urea and 3 g ammonium sulphate per kg straw dry matter. In addition they were offered 3 kg/day of mineralized rolled barley. In experiment 2, 30 Hereford × Friesian steers weighing 380 kg were used in a continuous growth trial of 10 weeks duration. They were allocated to one of the following barley straw treatments, straw that had been exposed to 30 g anhydrous ammonia per kg for 4 weeks, untreated straw with a urea supplement in the barley or untreated straw. The straw was fed ad libitum with either 2·8 or 4·4 kg rolled barley daily.

The barley straw contained 43 and 27 g crude protein per kg dry matter in experiment 1 and 2 respectively. In both experiments, ammonia treatment increased the crude protein content of the straw and resulted in improved straw intakes and higher live-weight gains. The results of experiment 2 cast doubt on the practice of providing supplementary nitrogen with food based on long barley straw and barley when steers weighing about 400 kg are used.

1. Forty-two piglets were used to study the effects of a low, medium or high level of energy intake (1·0, 1·4 and 1·9 MJ gross energy per kg W0·75 per day respectively) from 1·8 to 10 kg live weight and a low or high level of energy intake (1·4 and 1·8 MJ digestible energy per kg W075 per day respectively) subsequent to 10 kg live weight on growth performance, body composition and the cellularity of muscle and subcutaneous adipose tissue to 30 kg live weight. During both live-weight periods all pigs received the same daily intake of crude protein.

2. Raising energy intake in the period prior to 10 kg live weight increased (P < 0·-05) growth rate, body fat content and fat cell size but reduced food conversion efficiency, body protein and water (P < 0·05) and muscle deoxyribonucleic acid. These effects on body composition and muscle deoxyribonucleic acid at 10 kg live weight were still evident at 30 kg live weight.

3. Subsequent to 10 kg live weight, pigs previously given the lowest energy intake deposited protein and fat at a faster rate and exhibited more rapid and efficient growth (P < 0·05) than pigs previously given the high energy intake.

4. At 30 kg live weight pigs given the two higher levels of energy intake before 10 kg live weight contained less deoxyribonucleic acid (P < 0·05) in subcutaneous adipose tissue and had larger (P < 0·05) fat cells than those given the lowest energy intake before 10 kg live weight.

5. The effects of energy intake subsequent to 10 kg live weight on growth performance, body composition and the cellularity of muscle and adipose tissue were qualitatively the same as those for the period 1·8 to 10 kg live weight.

Nursing frequency, suckling duration and teat order were recorded in 12 ‘hybrid’ sows and their litters from parturition to weaning at day 42 post partum. Sows and their litters were moved from the farrowing quarters at day 20; half were housed as a group (G) and fed ad libitum with a boar present and the other half were housed individually (S) with no boar present and ration-fed to scale.

Some differences occurred in behaviour from day 20. A significantly greater number of false nursing periods, significant synchronization of nursing periods, and a tendency for more long and short nursing intervals occurred in G than S sows and litters. The duration of the preliminary nosing phase and the total nursing period were significantly longer in S than G litters. Teat order scores, indicating consistency of piglet suckling position on the sow, tended to be greater in S than G litters, and there was a fall in the score for G litters in the weeks following grouping. This was associated with a check in live-weight gain.

All G sows showed oestrus during lactation, on average 15 days after grouping. There was no incidence of lactational oestrus in the S sows which showed oestrus 5 days after weaning.