Twenty-four Hereford × Friesian cows (HF) and 24 Blue-Grey (Whitebred Shorthorn × Galloway) cows (BG) were housed in individual stalls. For the last 12 weeks of pregnancy they were fed hay to supply 75% of estimated maternal maintenance energy requirements. From calving (11 February to 9 April) until turning out to graze on 15 May they were given hay for maintenance, and a concentrate sufficient for either 2·25 kg (L) or 9·0 kg (H) milk per day, balanced within genotype. From 15 May until the end of the experiment on 7 September the cows and calves grazed as a single herd in a paddock grazing system, at a controlled daily herbage allowance of 50 g dry matter, measured to ground level, per kg total weight of cows and calves.

Cows on Treatment L lost more weight between calving and turnout than those on Treatment H, gave less milk, and their calves grew more slowly and were lighter at turn-out. Milk yields increased substantially after turn-out. Subsequently, milk yields and calf growth rates, and herbage intakes by the cows, did not differ significantly, although all were marginally higher for animals previously on Treatment L. Final calf weights, cow weights and cow body condition scores did not differ significantly.

Calves from HF cows were heavier at all stages than calves from BG cows. HF cows were heavier at calving than BG cows, gave more milk (though the difference was not significant) and lost more weight in early lactation. Final live weights and condition scores did not differ significantly.

The limited evidence suggested that conception to artificial insemination following oestrus synchronization was not affected by plane of nutrition in early lactation.

The use of variation in metabolism to predict genetic merit for milk production was studied using 42 Friesian calves: 11 ♀♀, 10 ♂♂ were the offspring of four bulls with high (H), and 11 ♀♀, 10 ♂♂ of four with low (L) improved contemporary comparison (ICC) values (mean = + 402 kg and − 276 kg respectively). The animals were 14 or 15 weeks of age at the start of the study and treated similarly throughout.

Blood samples were collected: I—in relation to feeding; II—at set intervals; III—during a 44-h fast; and IV—following the sudden introduction of an energy metabolite (sodium propionate), and then refeeding. Plasma concentrations of β-hydroxybutyrate, glucose, urea, free fatty acids, total proteins and albumin were measured in all samples.

Blood characteristics apparently differed among animals, particularly protein and urea (repeatability 0·74 and 0·62 respectively).

The progeny of high ICC bulls had lower levels of urea during fasting (H = 4·70, L = 5·62 P < 0·05) but higher levels of free fatty acids (H = 578, L = 492 μ equivalents/l; P < 0·05). There was a small difference in total protein (H = 69·7, L = 66·8 g/l, P < 0·05) but the other metabolites showed no significant ICC group difference.

In general, sex of the animal did not influence the metabolites.

Results suggest that calves with different potentials for milk production vary in aspects of energy and nitrogen metabolism; the possibility of using these as criteria for genetic selection for milk production is discussed.

A 3 × 2 factorial design experiment using 84 British Friesian cows was conducted to assess the effect of offering three types of grass silage and two levels of concentrate supplementation during early lactation on the total lactation performance of cows which calve during January and February. The three types of silage were early-cut wilted (ECW), early-cut unwilted (ECU) and late-cut unwilted (LCU), and the two levels of concentrate supplementation were 538 kg (LC) and 738 kg (HC) during a mean post-calving period of 71 days. The animals had a mean calving date of 29 January and were blocked according to calving date, and allocated at random to the treatments within each block on day 7 of lactation. The treatments were applied from day 7 of lactation until the animals were turned out to pasture on 18 April. Mean milk yields for the indoor period were: HC treatments 1963 (ECW), 1979 (ECU) and 1830 (LCU); LC treatments 1938 (ECW), 1942 (ECU) and 1731 (LCU) ± 41·3 kg; and for the total lactation were: HC treatments 5375 (ECW), 5438 (ECU) and 5284 (LCU); LC treatments 5509 (ECW), 5529 (ECU) and 5316 (LCU) ± 184·1 kg. There was no significant interaction between silage type and level of concentrate supplementation.

Milk composition, animal live weight and body condition were not significantly affected by either silage type or level of concentrate supplementation.

Forty British Friesian calves aged approximately 90 days, mean initial live weight 107 kg, were divided into five groups and the animals in each group offered, ad libitum for 84 days, one of five diets based on maize silage. The basal diet of maize silage and 20 g urea/kg dry matter (diet 1) was supplemented with fish meal at 47 g/kg dry matter (diet 2) or with legume silage supplements at 310 g silage dry matter/kg dry matter. The silage supplements were red clover ensiled with formic acid (diet 3), red clover ensiled with formic acid plus formaldehyde at 30 g/kg crude protein (diet 4), or sainfoin ensiled with formic acid (diet 5). Diets 1 to 5 contained 23·7, 28·8, 28·3, 28·3, and 27·1 g total nitrogen/kg dry matter respectively.

The proportion of the total nitrogen insoluble in water, an indicator of the protein in the diet that was likely to escape degradation in the rumen, was 273, 356, 377, 413 and 339 g/kg for diets 1 to 5 respectively. Increasing the proportion of insoluble nitrogen in the diet by including fish meal or formaldehyde-treated red clover silage improved rates of live-weight gain and efficiency of feed conversion. Mean daily intakes of 15·2, 16·2, 16·2, 15·4 and 15·8 g digestible organic matter/kg live weight produced daily live-weight gains of 0·79, 1·05, 0·88, 0·93 and 0·83 kg/head by calves on diets 1 to 5 respectively. Diet 2 produced live-weight gains and gains per kg of digestible organic matter intake that were greater than those for diets 1, 3 or 5 (P<0·05), but not significantly greater than those for diet 4 (P<0·05). Calf live-weight gains were similar and satisfactory on the basal diet (maize silage and urea) and the diets with formic acid-preserved silage of red clover or sainfoin, but poorer than on the diet with 47 g fish meal/kg diet dry matter (P<0·05).

The milk production of 14 Hereford × British Friesian females in their second lactation (cows) and 36 in their first lactation (heifers) was measured at three levels of nutrition either by machine-milking twice a day, without the use of exogenous oxytocin, or by a calf-suckling technique. Machine-milking significantly increased the number of cows drying-off within 150 days of parturition (i><0·05) and significantly reduced milk yields compared with the calf-suckling technique (P< 0·01).

The 150-day cumulative milk yields of the heifers were not significantly affected by method of milking, but the coefficient of variation of milk yield was significantly greater in the machine-milked group(P< 0·05). One machine-milked heifer dried-off within the first 150 days of lactation.

There was no evidence of an interaction between method of milking and plane of nutrition in either the cows or the heifers.

It was concluded that measuring the milk production of beef cows by machine-milking, without the use of exogenous oxytocin, may be unreliable. Factors influencing the usefulness and reliability of the calf-suckling technique are discussed.

1. An experiment was undertaken with 44 finishing steers (initially of more than 400 kg live weight) into the effects of copper and cobalt treatments.

2. Significant responses to copper treatment of up to 0·41 kg per head per day of live-weight gain were obtained.

3. A different response to copper treatment between Friesian and beef-type (Hereford or Devon) steers reflected not a true breed effect but a difference in initial copper status.

4. Cobalt bullet therapy proved to be ineffective in maintaining normal plasma vitamin B12 concentrations over the course of the experiment although liver cobalt levels were generally adequate.

The sweating rate of N'Dama cattle was found to show a significant stepwise increase from 10.00 h to 14.00 h (P ><0·01).

Among breeds, the sweating rates (mg/10 cm2 per 5 min) in White Fulani and N'Dama cattle were similar (100·8 to 118·3), but were significantly higher than for N'Dama × German Brown (74·4), German Brown (62·6) and Friesian (56·7) cattle (P<0·10).

Sweating rate was significantly higher for the neck and midside (90·0 to 93·3) than for other sites (75·1 to 80·0) (P<0·05).

Four animals from a group of eight Hereford × Friesian heifers weighing approximately 365 kg were implanted with 300 mg trenbolone acetate at the beginning of a 60-day trial period. Treated heifers grew more quickly (P<0·05) and converted food to liveweight gain more efficiently (P < 0·01) than untreated cdntrols. They had lower overall concentrations for serum albumin and plasma urea (P<0·01), the differences being maintained throughout the diurnal periods studied. No significant differences were recorded in the mean values for serum total protein, plasma glucose or free fatty acids. Similarly, the absence of significant differences in the mean values for serum growth hormone, insulin and prolactin suggested that these hormones did not mediate the response to trenbolone acetate. Implanted heifers had a significantly greater retention of nitrogen (P<0·01) which was mainly due to a reduction in the excretory products associated with total urinary nitrogen.

1. Gestation diets formulated to contain A, 9 or B, 11 % protein, and lactation diets with C, 13; D, 15; E, 17 and F, 19 % protein provided eight treatment combinations. They were given at 2 kg/day in gestation and approximately 5·7 kg/day in lactation to sows at eight centres, which remained on experiment for 3 to 5 parities and produced in total 529 litters. Mean results for parities 1 to 3 are given in this summary.

2. Sows given more protein during gestation (i.e. diet A v. B) gained more weight in gestation (18·3 v. 22·5 kg net gain) but lost more in lactation (—1·7 v. —5·2 kg). Their offspring were significantly heavier at birth (1·31 v. 1·36 kg) and at 3 weeks old (5·28 v. 5·49 kg), but not at 6 weeks old (weaning).

3. Giving more protein in lactation caused linear increases in piglet weights at 3 and 6 weeks, and a linear reduction in creep feed consumption. From a sample of sows whose milk yields were recorded, extra protein appeared to increase milk yield and its protein content. Extra protein for lactating sows also reduced their live-weight loss in lactation, but this effect was partially counterbalanced by smaller gains in gestation.

4. No treatment had consistent significant effects on litter size or on the interval from weaning to conception. There were no significant interactions between gestation and lactation protein concentrations.

5. The generally large differences between centres were in a few cases associated with centre × treatment interactions, but these were not such as to cast doubt on the general applicability of the main findings of the experiment.

6. From this and an earlier experiment the minimum protein level for diets based on barley was concluded to be 11 % during gestation and 15% during lactation. For lactation diets, however, the economic optimum level may be > 15 %.

Forty-eight 1-day-old pigs were used to compare lactose and glucose as the carbohydrate source for piglets from 1 to 22 days of age. Average daily gains, gain over feed ratios and the apparent digestion coefficients for crude protein, ether extract, nitrogen-free extract, ash, energy and dry matter were similar for the two groups. Apparent net protein utilization was greater with the glucose diet than with the lactose diet (P<0·05), although their apparent biological values and metabolizable energy values were similar. The serum levels of total glucose, total protein and urea nitrogen were also similar for both groups. Serum levels of total protein and urea nitrogen declined with age while the trend for total glucose was inconsistent. Subsequent nursery performance from 22 to 64 days of age when all pigs were fed the same diet was not influenced by the previous neonatal dietary treatment.

Breed and crossbreeding significantly affected variation in 10 fleece, follicle density and fibre diameter traits in 12-week-old lambs. The breeds involved were the Scottish Blackface, South Country Cheviot, Welsh Mountain, Lincoln Longwool, Southdown and Tasmanian Merino, but the last only by rams.

The Southdown came closest to the Merino in affecting density and diameter traits although the Merino crosses remained clearly distinguishable by their high follicle density. The Lincoln and Blackface crosses were notable for their long fibres and the Blackface crosses also had the least dense follicle and coarsest primary fibres. The coarsest secondary fibres were from Lincoln and Cheviot crosses. Heterosis estimates were obtained for crosses involving the Blackface, Cheviot, Welsh and Lincoln breeds. Significant heterosis was present in a wide range of traits but was not apparent in all crosses. Maternal differences were evident for many of the traits but with density these differences were apparently related to maternal effects on live weight of the lamb. The sex of the lamb, its birth type and rearing and its 12-week live weight significantly affected many of the traits.

Among breeds and crosses a strong relationship was found between fibre density and average fibre diameter. The relationship suggested that breed variation in total fibre area per unit area of skin was small compared with the breed variation in its components. Fleece weight per unit area was most closely related to mean fibre length.

The lactation curves of 21 single- (SR) and 28 twin-rearing (TR)ewes were fitted and milk production was estimated by the model Y = axb e−cx, developed in England for dairy cattle. In addition, persistency of lactation of SR and TR ewes was compared using five procedures reported in the literature. Results indicated that the coefficients that characterize the shape of the lactation curve (b and c values) were of similar magnitude to those reported in dairy cattle, thus denning a curve of similar shape. Lactation curves of SR and TR ewes were essentially parallel throughout lactation, with more milk production from TR ewes. The correlation between total milk production estimated by this model and that based on the sum of partial lactations was 0·98, but variability of milk production as estimated by the latter method was slightly less. Lactations of SR ewes had similar persistency to those of TR ewes.

Whole, dry barley treated with ammonia (A), whole, untreated barley (WU) or ground barley (G) were fed with hay and a little high protein concentrate to 7 to 11-month-old lambs. Most apparent digestibility coefficients were found to be 3 to 5 units higher in the diet with barley A than in diets with barley WU or G, the differences being significant. Calculation of the digestibility of barley by difference showed that the coefficients were 8 to 10 units higher in barley A than in barley WU or G as regards dry matter and organic matter. Digestion of crude fibre was better in both A and WU than in G. These differences were also significant.

The effects of feeding monensin and amicloral at 33 and 1500 mg/kg of diet, respectively, were investigated in two experiments using 330-kg steers. Monensin and amicloral, either alone or in combination, increased the digestibility of organic matter and crude fibre compared with a control diet (P < 0·001). Crude protein digestibility was increased by monensin (P < 0·001). Use of monensin and amicloral, alone or in combination, increased molar proportions of propionic acid by 22% on average (P > 0·05), and monensin decreased butyric acid by 37% (P < 0·05).

Ruminal ammonia concentrations were lower in steers fed monensin (P < 0·05). Steers fed monensin consumed 6 % less feed, gained 9 % more weight (P < 0·05) and utilized feed 14% more efficiently (P < 0·05) than control animals. Amicloral, either alone or with monensin, lowered feed intake by 11 % (P < 0·05), had no effect on average daily gain and improved feed efficiency by about 12% (P < 0·05). There were no treatment effects on any of the carcass parameters.