Twenty-eight lactating cows were used in an experiment of changeover design with four periods to evaluate concentrates containing 0, 16, 32, 49, 65, 81 and 97% dried grass. The dry matter of the dried grass was 63% digestible. The concentrates also contained barley, together with groundnut meal to equalize their protein content at approximately 16-5% of dry matter. All animals had grass silage ad libitum and all concentrates were given at the rate of 0·4 kg/kg milk. Milk yield, milk composition and liveweight change were not affected by including dried grass in the concentrate. No significant effect of concentrate on silage intake was obtained. Ration digestibility and nitrogen utilization were measured with four animals per treatment. The digestibility of dry matter, organic matter and nitrogen was not reduced by increasing the proportion of dried grass in the concentrate. The efficiency of utilization of apparently digested nitrogen for total productive purposes (body retention and milk nitrogen) was also not affected by the proportion of dried grass.

The intake of drinking water of lactating British Friesian cows in 14 herds with a total of 840 animals was measured monthly from November to April inclusive. The intake of food, the air temperature and relative humidity were also recorded. The herds which mainly contained autumn-calved cows were managed under controlled commercial conditions.

The average daily intake of drinking water was 49·9 (range 20·1 to 87·1) kg/cow for animals yielding an average of 16·8 kg milk/day in an environment with a mean temperature of 8·2°C and a relative humidity of 84·8%. The amount of water drunk daily was positively and significantly related to the mean daily milk yield and the drymatter content of the ration, but not significantly related to either the mean air temperature or the relative humidity. The average intake of water was 3·70 kg per kg of dry matter consumed after subtracting the amount of water in the milk. On average, 40·0% of the total daily intake of water was drunk between 15·00 and 21·00 hr.

Behaviour studies of 24 hr duration on five herds showed that drinking time ranged from 2·0 to 7·8 min/cow per day, and the rate of drinking varied from 4·5 to 14·9 kg/min.

Recommendations are made for the provision of drinking water for dairy cows being offered a wide range of forages under modern conditions of housing.

Five measures of persistency of milk yield were compared by means of apparent heritabilities and repeatabilities using 598 first lactation records from the Danish progeny testing stations and 354 records of all parities from Red Danish cows at a state experimental farm. Unbiased estimates of heritabilities could not be obtained because of common environmental effects. Results indicate that measures of persistency giving equal weight to single milk records are superior to measures giving different weight to single records.

Correlations between persistency, expressed as the absolute decrease of yield, and maximum daily yield were —0·46 to —0·52 (phenotypic) and —0·22 (genetic). Correlations between persistency and 305-day yield were —0·06 to —0·10 (phenotypic) and 0·02 (genetic).Correlations between persistency, expressed as the decrease of yield relative to level of yield in early lactation, and maximum daily yield were —0·06 to —0·13 (phenotypic) and 0·17 to 0·42 (genetic). Correlations between the measure of persistency and 305-day yield were 0·12 to 0·45 (phenotypic) and 0·45 to 0·69 (genetic).

The effects of roughage level (15 and 35% of the ration) and of slaughter weight (400,450 and 500 kg) were studied in an experiment of 2 x 3 factorial design. Daily live-weight gains and carcass gains were significantly higher on the lower roughage levels, but there was no difference in degree of fatness of the carcass. Dry-matter intake expressed as a percentage of body weight was 2·91 on 35% roughage compared with 2·53 and 15% roughage, i.e. 15% higher on the highroughage diet. This compensated the animals on the high-roughage diet for the lower energy content of their feed. Rate of gain increased with an increase in slaughter weight. The percentage of fat trim and of saleable meat increased, while that of bone decreased significantly with an increase in slaughter weight. The animals on the lowroughage diet were approximately 11% more efficient than the others in converting metabolizable energy into live weight.

Mortality to one year of age was studied in artificially-reared calves of Tharparkar, Sahiwal and Red Sindhi breeds together with Murrah buffaloes and Brown Swiss x Sahiwal and Brown Swiss x Red Sindhi. Data covered 6267 animals over the period 1952–71. There were significant breed differences with the Brown Swiss crosses and buffaloes suffering higher losses than the Zebu breeds. Age effects (0 to 1, 1 to 3, 3 to 6 and 6 to 12 months) showed that losses were greatest in the first month of life and declined thereafter. There were significant year effects but seasons (summer, monsoon and winter) showed no significant effects although a tendency to higher losses in winter did exist. Sex effects showed no differences. Pneumonia was the major cause of loss to 6 months accounting for 30 to 40% of deaths with scours and enteritis being the second most serious factor (15 to 35% of losses).

One hundred and four Damascus goats with their kids were used study the effects of early weaning on the lactation of the goats and the growth rate of the kids. The treatments studied were: 2-day suckling (S2) where the kids were suckled by their dams for 2 days a d then reared artificially on milk replacer; 35-day suckling (S35) where the dams suckled their kids for 35 days; 70-day suckling (S70) where the dams suckled their kids for 70 days.

The differences among treatments in 150-day and total milk yield and lactation length were not significant. Conversely, the differences in the yield of milk available for marketing were highly significant. The goats on S2 produced more marketable milk than those on S35 and S70, and the goats on S35 produced more than those on S70. The growth rate of the kids weaned at 35 days of age was significantly lower than that of those weaned at 70 days. The differences between kids reared artificially and those suckled by their dams to 70 days of age were not significant. It was concluded that early weaning does not materially affect lactation performance and that it can increase the milk available for marketing.

An intensive sheep production system using flocks of 100 Scottish Halfbred (SHB), 100 Welsh Speckleface (WSF) and 100 Finn Blackface (FBF) ewes maintained by 8, 4 and 6 ha grassland respectively for a 5-year period, was investigated to establish the consequences of high flock prolificacy and the measures taken to achieve it, including PMS administration. Mating occurred in late October/November at ewe: ram ratios of 25 or 33: 1. Ewes were housed in winter and fed silage, with supplementary cereals in late pregnancy. Lambs in excess of 2 (SHB) and 1 (WSF and FBF) per ewe were artificially reared and fattened indoors; ewes and lambs at grass were rotationally grazed (with forward creep grazing by the lambs). Prolificacy in the SHB breed was 225 lambs born per 100 ewes mated for untreated ewes and 237 for hormone-treated ewes; 119 and 155 respectively for WSF ewes; and 255 for FBF ewes (all untreated). Lambs sold per 100 ewes mated were: for SHB, 200 and 177; WSF, 102 and 107; FBF, 201.

Good ewe condition and heavy live weights at mating were associated with appetite problems on silage in late pregnancy; PMS injection with a failure to secure conception rates above 80% at the critical oestrus and a markedly lower prolificacy for ewes conceiving at later oestruses; mating in the middle of the breeding season and March/April lambing with slow lamb growth rates on grass in July and August. Hormone-induced high prolificacy was associated with a greater proportion of large multiple litters than natural high prolificacy, and consequent smaller lamb birth weights and more perinatal mortality. There was a significant negative regression relating fleece weight with litter size. The results suggest the existence of an optimal level of prolificacy for the system employed.

The value of E, defined as the weight of carcass produced per 100 units of digestible organic matter (DOM) consumed, was used to assess the biological efficiency of meat production in housed sheep. The effect on E of weaning lambs at 4, 6, 8, 10, 12, 14 and 16 weeks post partum was studied for a number of different breed crosses. The age at which lambs were weaned was found to have little effect on the growth rate of lambs and no significant effect on the biological efficiency with which sheep produce meat.

By fitting a range of numerical values to a model, genetic responses from performance testing male pigs (boars) were examined in a population in which pig farms either conduct their own tests or send boars to a central station for testing. Where selection intensities are the same for station and farm tests the former almost always has an advantage over the latter. Factors which lead to this advantage are genetic differences between farms, genetic sampling within farms and limitations on the accuracy of performance measurement in farm tests. In a large station test response in a trait of 50% heritability is expected to be 15% greater than in tests comprising boars from 10 effective parents on farms whose average genotype contributes 5% of the total genetic variation and whose environmental variation is 25% greater than in the station. In populations with limited station testing space available, farm tests should be able to compensate for their lower efficiency by increasing selection intensities.

Data from 726 male and 765 female pigs (364 litters) from 28 threebreed crosses obtained from mating Poland China boars to gilts and sows from different two-breed-crosses were analysed. The 28 two-breed-crosses were obtained from mating Yorkshire (Y), Landrace (Ld), Lacombe (Lc), Hampshire (H), Duroc (D), Berkshire (B) and Large Black (LB) sows to Ld, Lc, H, D, B, LB and Tamworth (T) boars in an incomplete diallel mating design. The traits studied were age at slaughter (72 kg carcass weight), carcass backfat measurement and an index combining both traits.

The youngest pigs to reach slaughter weight were those from LB x D sows (191·3 days) while the oldest were from T x D sows (211·6 days). The pigs with the least depth of backfat were those involving the Hampshire breed (mean 7·28 cm) while those involving the Large Black had the thickest backfat (mean 7·81 cm). In descending order, the five highest ranking crosses based on the index were those from H x Ld, H x Lc, LB x D, Lc x Ld and H x Y sows.

The live-weight changes of 48 sows were recorded over three reproductive cycles. All sows were given standard amounts of feed in gestation and one of four energy allowances during lactation. The daily intakes of digestible energy during lactation ranged from 12·2 to 182·2 Meal in the first, 122·9 to 192·6 Meal in the second and 132·2 to 202·2 Meal in the third lactation. Weight change in lactation responded to energy intake; sows on the lowest energy intake lost weight whilst those on the highest intake gained. At weaning of their third litters, sows on the highest energy allowance weighed 44 kg more than those on the lowest level and this was equivalent to a carcass difference of 372·3 kg at slaughter.

All the sows were slaughtered after the third litters had been weaned and the carcasses were dissected into lean, subcutaneous fat+skin, and bone. Sows from all treatments had less subcutaneous fat+skin and more muscle and bone than non-pregnant gilts killed at a mean weight of 129 kg, a weight equivalent to that of the experimental animals at their first mating.

The reduction in fat reserves was linearly correlated with dietary energy intake of the sows. Sows receiving the lowest energy intake in lactation possessed fat reserves which were estimated to be only 25% as great as in gilts comparable to those used to initiate the experiment. This reduction in body reserves has implications with regard to the long-term effects of feeding lactating sows low intakes of energy during 6-week lactations.

1. Large White x Landrace pigs were used to study the effects of supplementation with limiting amino acids of diets based on wheat containing 13% crude protein. Measurements were made of growth rate, feed conversion, carcass composition, plasma-free amino acid concentrations, digestibility of dry matter, nitrogen and gross energy, nitrogen retention and metabolizable energy.

2. A wheat diet supplemented with lysine and threonine, the firstand the second-limiting amino acids respectively, produced almost the same growth rate and feed conversion ratio as one supplemented with fish meal and meat meal. Methionine was probably the thirdlimiting amino acid, and additional supplementation with methionine produced a further small improvement in growth rate and feed conversion ratio to the point where they were equal to those on the diet supplemented with fish meal and meat meal.

3. Supplementation of the wheat diet with lysine only produced the same growth rate and feed conversion ratio as a least-cost commercial diet; performance was, however, inferior to that on a wheat diet supplemented with fish meal and meat meal. The commercial diet had a lower dry-matter digestibility.

4. Eye-muscle area of pigs on the wheat diet supplemented with lysine was similar to that of pigs on a wheat diet supplemented with fish meal and meat meal; however, backfat thickness was significantly lower on the latter diet.

5. Except for threonine, plasma-free amino acid concentrations reflected with reasonable accuracy amino acid deficiencies in the diets.

1. The effects of supplementing diets containing 10% or 17% crude protein wheat, vitamins and minerals with the limiting amino acids were studied with growing Large White x Landrace pigs. Performance was measured in terms of growth rate, feed conversion, carcass measurements, plasma-free amino acid concentrations, digestibility of dry matter, nitrogen and gross energy, nitrogen retention and metabolizable energy.

2. With diets based on wheat containing 17% crude protein, a lysine supplement gave a slightly higher growth rate and a slightly lower feed conversion ratio than when fish meal and meat meal was the supplement.

3. With diets based on wheat containing 10% crude protein, performance was significantly poorer when the diet was supplemented with the four most limiting amino acids (lysine, threonine, valine, methionine) than with fish meal and meat meal. Meat meal and soya bean meal appeared to be a good source of the limiting amino acids, other than lysine, when added to a diet based on wheat containing 10% crude protein.

4. Eye-muscle area was lower and backfat thickness greater when diets based on wheat containing 10% crude protein were unsupplemented or supplemented with lysine than when they were supplemented with protein or with the four most limiting amino acids. However, no significant differences in backfat thickness were obtained between similar comparisons when the wheat contained 17% crude protein.

In trials with 64 pigs growing from 37 to 60 kg or from 65 to 88 kg growth rate and food conversion were not affected by either a 10°C or a 20°C range in diurnal air temperature cycle compared with a constant temperature equal to the mean of the cycle when the mean temperatures were optimal. However, with a constant temperature and cycle mean at 6°C above optimum, performance declined with a 20°C range cycle.

1. An experiment involving 64 individually-penned pigs (32 females (gilts) and 32 castrated males (barrows)) was conducted over the live weight range 50 to 83 kg, to study the effects of a parenterally administered anabolic steroid upon the performance and carcass measurements of gilts and barrows given either a 15·0% or an 18·8% crude protein (CP) diet at two different levels.

2. The steroid significantly improved both daily weight gain (+5·2%) and food conversion ratio (+4·8%) of gilts and barrows.

3. There were no significant treatment interactions for either daily weight gain or food conversion ratio, but the data suggest that gilts responded to the hormone to a greater extent than barrows at the particular dose level of the steroid administered.

4. The steroid significantly improved the carcass, as assessed by linear backfat measurements, of pigs given the higher CP diet but had no effect upon carcass measurements of pigs given the lower CP diet.

Female pigs (sows) which had lactated for about 10 days were allocated at random either to a control group or to a group given 75 mg methallibure per day for 5 consecutive days, followed by an intramuscular injection of 1000 IU PMSG. All sows were mated as soon as they came into oestrus and again 24 hr later. Nineteen out of 21 treated sows exhibited a controlled oestrus 9·4 + 0·25 days after weaning, compared with 21 out of 23 control sows in 8·2 + 0·64 days. Fourteen treated and 17 control sows conceived at that oestrus resulting in total pigs born per litter of 9·4 and 9·9 respectively. None of these differences was statistically significant.

An experiment was undertaken to examine the effects of the micronization process followed by grinding on the chemical composition of barley and on digestibility and nitrogen (N) retention in the growing pig. Micronization relative to normal grinding increased the dry matter (DM) content and starch availability in vitro and decreased the protein content of the cereal. Retention of N was not affected by the process but apparent digestibility of the DM, N and gross energy was improved. The improvement in digestible energy content of micronized barley over the ground grain was 3·8%. In a subsequent trial 24 pigs were individually and scale-fed a diet containing 75% of barley in ground or micronized and ground form over the liveweight range 33 to 80 kg. Processing treatment did not influence growth rate, DM food conversion ratio, killing-out percentage, deposition of backfat or area of ‘eye muscle’ in cross-section.

The inclusion of 60 p.p.m. of 2,4-dichlorophenoxy acetic acid (2,4-D) or of M15† in the diet of lambs had no effect on the concentrations of volatile fatty acids and ammonia in rumen liquor, on the contents of haemoglobin, protein and non-protein nitrogen in blood or on the composition of the blood serum proteins. Over weeks 1 to 6 of experiment, there was a significant increase in live-weight gain in lambs receiving a diet containing M1S but the effect had disappeared at the end of 12 weeks. Inclusion of 2,4-D in the diet had no effect on live-weight gain.