Two progeny tests for beef, one using 452 calves brought centrally to a test centre, the other using 768 calves commercially fattened on 81 farms, were compared to isolate environmental sources of variation. It was concluded that appreciable reduction of error variance ensued from the use of a growth curve, the maintenance of pen identity, and the removal of variation due to pens and months of birth. The fixed effects model underlying the experimental design on the centre yielded relatively robust estimates of variance components.

1. The voluntary dry-matter intake, water intake and rate of live-weight gain of indigenous, exotic and crossbred cattle on low- and medium-roughage diets have been compared under similar conditions of management.

2. At similar live weights and on similar diets exotic cattle usually have a higher food intake than indigenous animals.

3. When roughage was freely available the voluntary dry-matter intake of both types of cattle increased.

4. Water intake was closely related to dry-matter intake and varied with the nature of the diet. The ratio of water to dry-matter intake was not affected by live weight and varied only slightly between the different types of cattle.

5. Exotic cattle were generally more efficient than indigenous cattle of comparable live weight in converting food into live-weight gain; crossbred animals were intermediate. It is suggested that this largely reflects their higher intake of food relative to their maintenance requirement.

6. One group of indigenous animals that were initially mature but under weight gained weight as quickly, and converted their food as efficiently, as did exotic animals.

One hundred and forty-four weanling Duroc barrows were individually fed to study effects of season (summer and winter), energy concentration of the diet (high and low), protein concentration (high and low), and orally administered hormones (none, diethylstilboestrol, and mefhyltestosterone) on performance and carcass characteristics of growing-finishing swine.

In summer the rate of gain of pigs was 6% slower and yielded carcasses with 19% smaller loin-eye areas but 3% more lean cuts than in winter.

Pigs fed on high-energy diets gained 13% faster, consumed 8% less feed daily and required 18% less feed per unit of weight gain than pigs fed on low-energy diets. Pigs fed on high-energy diets also had a dressing percentage 2·5 units higher and yielded carcasses 2% shorter, with 15% more backfat, than those fed on low-energy diets.

Pigs fed on low-protein diets had a dressing percentage 1·6% higher and yielded carcasses with about 7% thicker backfat than pigs fed on high-protein diets. Dietary energy and protein concentrations interacted significantly in their effect on rate of gain. Pigs fed on low-energy, low-protein diets gained weight about 7% faster than pigs fed on low-energy, high-protein diets; however, pigs fed on high-energy, high-protein diets gained weight about 3% faster than pigs fed on high-energy, low-protein diets.

The only significant effect of giving each pig about 2 mg of diethylstilboestrol (DES) per day was a 2% increase in weight of lean cuts. An average daily consumption of 20 mg methyltestosterone (MT) per pig decreased rate of gain, daily feed intake, dressing percentage and backfat thickness, but increased carcass length, area of the loin-eye and weight of lean cuts. Hormones and dietary energy levels interacted in their effects on rate of gain and feed efficiency. Pigs fed on low-energy diets with or without hormones gained weight at about the same rate, but high-energy diets increased rate of gain in pigs receiving no hormone or DES by about 17% and 21%, respectively, while having no effect in pigs receiving MT. Pigs fed on low-energy diets with MT required about 7% and 6% less feed per unit of gain than pigs fed on low-energy diets without hormone or with DES, respectively; whereas pigs fed on high-energy diets containing MT required about 10% and 14% more feed per unit of gain than did pigs fed on high-energy diets without hormone or with DES, respectively.

A sample of 6846 Friesian heifers recorded in 672 herds during the year ending 30 September 1968, taken from two areas of England and Wales, has been used to estimate the effect of the calving month on total lactation yield. In both areas, the North and the South-West, a variation amounting to nearly 12% of the mean yield was estab-lished, with lactations resulting from October-December calvings the highest and those from May-June calvings the lowest. There was no evidence of association with particular levels of management, or management systems, as exemplified by a seasonal calving pattern.

Herbage from the same timothy/meadow fescue/white clover sward was ensiled at four different dry matter contents. The resulting silages had dry matter contents of 19·0, 27·3, 32·3 and 43·2%, the dry matter content increasing with the length of the wilting period. An experiment was carried out to determine the voluntary intake of the silages. Each silage was given to 7 animals individually, the mean live weight of these being 334 kg.

Although the silages made from wilted herbage were lower in digestibility than that made from unwilted herbage, wilting increased dry matter intake and metabolizable energy (ME) intake. The mean daily intakes of digestible organic matter were 53·0, 58·1, 59·6 and 59·6 g/kg W0·73, for silages of increasing dry matter content. The corresponding ME intakes, expressed as a multiple of the ME requirement for maintenance, were 1·17, 1·29, 1·30 and 1·28. The percentage of acetic acid in the silage dry matter was significantly (r = −0·56) and linearly related to voluntary intake. The relationship between lactic acid concentration and voluntary intake was significantly curvilinear (r = 0·48).

1. Two growth trials and a digestibility trial were carried out with 48 Friesian steers given diets containing approximately 5, 20, 35 and 50% chopped barley straw and concentrates up to 100%.

2. Rates of live-weight gain between 130 and 400 kg declined from 1·18 to 0·65 kg/day and carcass gain declined from 0·62 to 0·30 kg/day as the straw content of the diet increased from 5 to 50%.

3. Alimentary tract ‘fill’ increased from 10·5% of live weight with 5% straw to 21% of live weight with 50% straw, and killing-out percentage dropped from 55·5% to 48·3%.

4. Both dry-matter digestibility and apparent nitrogen digestibility were lowest for the diet with 50% straw.

1. Two experiments are described in which groups of 12 autumn-born calves were strip-grazed at different intensities. In Experiment 1 (1966), ‘standard’ and ‘high’ grazing intensities were compared. In Experiment 2 (1967), ‘standard’ and ‘low’ intensities were compared. In both experiments the same meadow fescue—ryegrass ley provided 0·24 ha per head for grazing and conservation; herbage surplus to grazing requirements was conserved as silage.

2. The grazing season was divided into three parts according to the type of grazing, and estimates were made of daily herbage allowances, herbage quality, efficiency of herbage utilization and the live-weight gain of the cattle.

3. Grazing intensity was regulated by controlling daily herbage allowances by strip-grazing. Within grazing seasons, differences in grazing intensity had little effect on the digestibility of the herbage dry matter on offer. Dead herbage accumulation was low (10%) in the early and late parts of the season, but rose to 25% in mid-season.

4. The efficiency of herbage utilization was estimated in three ways: from sample cuts of herbage on offer and refused; from measurements of herbage intake; and from feeding standards for maintenance and gain. Efficiency was highest for the ‘high’ group of Experiment 1 and lowest for the ‘low’ group of Experiment 2. The validity of efficiency estimates is discussed in relation to measurements of pasture yield, herbage intake and the assessment of the nutrient requirements of growing cattle.

5. Live-weight gain over the whole season was 0·59 and 0·89 kg/head per day for the ‘high’ and ‘standard’ groups of Experiment 1, respectively. In Experiment 2, the ‘low’ and ‘standard’ groups gained weight at 0·95 and 0·84 kg/head per day, respectively.

An estimate of the frequency of twin calvings was obtained from the analysis of over 38 000 calvings of Friesian cows in M.M.B. milk-recorded herds. The incidence of twinning increased from 0·54 % in the first parity to 3·37% in the fifth parity. A significant excess of cows above expected produced either more than one set of twins or no twins at all. Repeatability ranged from 0·0 for cows with three calvings to 0·063 for cows with five calvings.

Data on lactation yield and duration, butterfat percentage and calving interval showed no significant effect of twinning. However, consistent trends were noted showing that dams which calve twins have longer subsequent lactations, higher whole lactation yields and lower fat percentages than contemporary dams with single calves. The possible causes for these trends are discussed and are considered to be the lower breeding efficiency and longer calving intervals of dams of twins.

1. Two experiments are described in which the consequences of variation in grazing intensity were studied during the subsequent period of winter feeding from 12 months of age to slaughter at 18 months. The cattle were loose-housed and fed on silage ad libitum, together with allowances of rolled barley. Individual organic-matter intake was measured periodically, chromic oxide being used to estimate faecal output. The digestibility of the diet was estimated with stall-fed steers.

2. Groups of 12 steers were grazed at different intensities over five-month periods, so that those grazed at the higher intensity were 38 and 16 kg lighter at the start of the 1966 and 1967 winter feeding periods respectively. They did not make significant compensatory growth over the subsequent winter feeding periods, although they had a significantly higher intake of feed organic matter per 100 kg live weight than the control steers.

3. With supplements of 3·63 and 1·81 kg/head per day of barley, live-weight gains were 0·77 and 0·50 kg/head per dayin the first half of the winter, but in the second half, when barley allowances were raised to 4.54 and 2·72 kg/head per day, both groups gained weight at the same rate (0·94 kg/head per day).

4. The higher level of barley feeding reduced silage intake by 0·4 kg OM/kg barley OM at all stages of the winter, and the additional 306 kg of barley was associated with the production of 21 kg more carcass weight at slaughter. This higher yield of carcass was reflected in a higher weight of fat in a three-rib sample joint.

1. Three groups, each of eight steers, were fed on pelleted diets containing 30, 50 or 70% ground barley straw, maize and soya bean meal. On an air-dry basis the diets contained 12% crude protein.

2. Daily live-weight gain was 1·29, 1·19 and 1·02 kg/day for the 30, 50 and 70% straw diets respectively, and was negatively related to the percentage of crude fibre in the dry matter (r = −0·61, P < 0·05).

3. The apparent digestibility of dry matter, determined in sheep at the maintenance level of feeding was negatively related to percentage crude fibre in the dry matter (r = −0·91, P < 0·001).

4. All animals were killed at approximately the same live weight, which was reached on average in 140,153 and 163 days by the 30, 50 and 70% groups, respectively.

5. The differences in mean carcass weight between treatments were significant (P < 0·05). Killing-out percentage was significantly reduced (P < 0·05) as the proportion of ground barley straw in the diet was increased from 30 to 70%.

6. The proportion of straw in the diet had no direct effect on the composition of carcass gain.

7. The results are discussed in relation to the intake of digestible energy.

The ruminal activity, daily live-weight gain and feed conversion efficiency of zebu calves inoculated with whole rumen contents from a mature cow were compared with those of calves maintained under the same conditions except that they were ciliate-free and isolated from other ruminants.

A thriving mixed population of ciliate protozoa became established in the rumen of calves two weeks after inoculation. Entodinium was the first genus to appear and was followed by Isotricha, Polyplastron, Ophryoscolex, Diplodinium and Dasytricha.

The ruminal volatile fatty acid and ammonia concentrations in the inoculated calves showed a pronounced rise above the values found in the uninoculated controls.

The inoculated calves grew faster and had a higher feed conversion efficiency than the uninoculated controls.

A total of 64 Border Leicester × Greyface ewes were offered eight diets comprising four levels of digestible crude protein and two levels of metabolizable energy (ME) intake during gestation. After parturition the ewes on each gestation treatment were offered a high or low level of ME intake at a constant level of crude protein intake. Nitrogen balances were carried out on all ewes during weeks three and four of lactation.

Digestibility coefficients and output of nitrogen in the milk measured during the lactation balance periods were not significantly affected by the gestation treatments. Body nitrogen balance during lactation was significantly affected by the level of protein offered during gestation.

Empirical equations relating digestible crude protein intake and ME intake to milk nitrogen production and body nitrogen balance indicated that a digestible crude protein intake of 7·9 g/kg W0·75 per day and a ME intake of 220 kcals/kg W0·75 per day resulted in the production of 0·70 g milk nitrogen per kg W0·75 or approximately 100 g of milk per kg W0·75. The corresponding level of body nitrogen retention was 0·162 g/kg W0·75 per day and showed no consistent trend due to level of protein intake during gestation.

Regression of litter weight of newborn lambs on the live weight of ewes at mating has been estimated from data on 15 breeds after conversion of group means of ewes and lambs to natural logarithms. Regression coefficients were estimated to be 0·721 for single lambs, 0·741 for twins and 0·773 for triplets. These values are not signi-ficantly different from each other. Data from ewes with single lambs and from ewes with twins are consistent with the hypothesis that litter weight at birth as a proportion of ewe weight at mating tends to dechne as ewe weight rises from small to large breeds. In a breed with ewes averaging 25 kg the expected birth weight of singles is 9·6% and of twins 15·2%, of ewe weight. For a breed with ewes of 100 kg the corresponding weights would be 6·5% and 10·6% of ewe weight. Since the estimated regression coefficient and the coefficient in the expression for metabolic weight (0·730) are alike, the regression equations can be interpreted as showing that single lambs were 22·6% and twin pairs 36·1% of ewes' metabolic weight.

1. Three experiments are reported in which chromic oxide, administered as a component of shredded paper at 09·00 and 16·30 hr daily, was used in the estimation of the faecal output of steers fed on silage and barley.

2. Four Friesian steers of 160 kg live weight were used in experiment 1. They were fed on grass silage ad libitum with controlled allowances of concentrate supplement. ‘Absolute’ recovery of Cr2O3 in total collections was 85–91%, though it was apparent that some faeces may have been lost from the total collections. ‘Relative’ recovery in grab samples was 97%.

3. Diurnal variation in Cr2O3 excretion was investigated in experiment 2 with four yearling Friesian steers. Faeces were sampled in three 24-hr periods at each natural defaecation. A significant and consistent diurnal variation was observed, with the lowest concentration of Cr2O3 occurring during the night. Concurrent grab samples taken at 09.15 and 17.00 hr over four days gave estimates of cr2O3 in the faeces which were 16·27% higher than the mean concentration for the three 24-hr sampling periods.

4. Day-to-day variation in the Cr2O3 content of grab samples was examined in experiment 3 with eight yearling Friesian steers. Four steers received 3·63 kg/head per day of barley supplement and four received 1·81 kg. Both groups were offered silage of 25% dry matter ad libitum. Faeces were sampled per rectum twice daily at 09.15 and 17.00 hr over four-day sampling periods. The degree of day-to-day variation was small and tended to be random.

1. Experiments carried out in two herds to examine the effects of a treatment designed to induce oestrus and ovulation during the lactational anoestrus of the sow and to allow the establishment of pregnancy during lactation are described. Two aspects are examined: (a) the effects on the reproductive performance of the sow of repetition of the treatment in successive lactations and (b) the effects of the treatment on the suckled young.

2. The treatment involved the separation of each sow and litter for 12 hr on days 21, 22 and 23 of lactation followed by an injection of 1500 IU pregnant mare serum gonadotrophin (PMSG) at the end of the third period of separation.

3. It is concluded that oestrus and ovulation can be induced with some consistency in the fourth week of lactation, that lactation is not incompatible with the first two to three weeks of pregnancy, and that the establishment of pregnancy during the fourth week of lactation is not detrimental to the growth of the suckled young when supplementary food is provided.

1. Performance tests were made on 221 bulls of eight breeds or crosses from 90 days of age (weaning) up to 400 kg live weight. Feeding was in individual pens on a high-energy complete diet.

2. Pre-weaning gain was not significantly related to gain on test (r = 0·11) nor was 90-day weight to gain on test (r = 0·26) or feed conversion (r = −0·15). Weight for age at 200 and 300 kg was highly correlated with final weight for age (r = 0·72 and 0·89 respectively) while gain on test and final weight for age had a pooled correlation (across breeds) of r = 0·95. The correlation of feed conversion with gain on test was highly significant in all breeds. The range of values (−0·72 to −0·86) is higher than any previously reported estimates possibly due to an absence of initial weight effects, a reduction in the proportion of feed used for maintainenance and the use of complete diets.

3. It is suggested that with this testing system at least 50% of bulls could be culled at 300 kg without affecting selection of the best 20% of all bulls starting the test.

Eight hundred and ninety-eight records of the interval between calving and conception (service period) of 349 Hariana cows, the progeny of 79 sires, were analysed by fitting constants for the effects of year, month of calving, calving sequence, sex of the calf, weight of the cow at calving and weight of the calf at birth. The average service period was 272·7 days with a coefficient of variability of 50·7%.

The service period was longest after the first calving. Animals calving in the months of February to August had a longer service period than those calving during the months of September to January. Heavier cows tended to have a shorter service period. Sex of the calf, calving sequence and birth weight of the calf did not affect this trait significantly.

Heritability of service period estimated from the paternal half-sib correlation using repeated records was 0·06 ± 0·018 and repeatability was 0·250 ± 0·039. It seems likely therefore that a shortening of the service period may not be possible through direct selection.

On a fattening diet in which final molasses supplied from 68 to 76% of the metabolizable energy and napier grass some 10%, the treatments in a 2 × 2 × 3 factorial design were breed (Brahman or Brown Swiss × Brahman), source of supplementary protein (fish meal or poultry waste) and protein level (low, medium or high—replacing urea). Mean daily gains to 404 kg live weight were better for the crossbreds (0·89 compared with 0·77 kg), as was conversion rate in terms of Meal ME per kg gain (25·6 compared with 29·5); fish meal improved gains by 44% and conversion rate by 39% as compared with poultry waste when the two supplements were fed at levels designed to equate N intakes from this source. The superiority of the crossbreds was only apparent on the fish meal diets where they averaged 1·19 compared with 0·94 kg/day for the Brahmans. Daily N × 6·25 intakes decreased from 3·8 g/kg live weight on the low level of poultry waste to 2·9 on the high level due to low palatability of this material. On this treatment (poultry waste), daily gain (kg) was significantly related (b = 0·119±0·031; P<0·01) to N×6·25 intake (g) per unit live weight (kg). Commercial half carcass dissection showed the crossbreds to have significantly more edible meat, more bone and less e×cess fat than Brahmans. Protein source had no effect on carcass composition.

The experimental animals consisted of 71 heifers or cows of the Black and White Danish breed (SDM), 61 heifers or cows of the Red Danish breed (RDM), and 8 heifers or cows of the Jersey breed. Highly significant differences between breeds were found in yield of colostrum at first milking after calving and in the concentration of immunoglobulin (Ig) in colostrum. The RDM animals had the highest colostrum yield but the lowest Ig %. The total yield of Ig was not significantly different between RDM and SDM. The individual variation in colostrum yield, Ig %, and Ig yield was very marked.

Heifers had a lower colostrum yield and Ig yield than cows in second and later lactations. For SDM the Ig % was not dependent on the lactation number. In contrast the older RDM cows had a significantly higher Ig % in colostrum than the younger cows. No effect of season of the year was found on colostrum yield, Ig %, and Ig yield. An increase of the interval between calving and the first milking caused a very significant drop in colostrum Ig %. Loss of colostrum from the udder before milking increased the probability of getting colostrum with low Ig %. The repeatability in Ig % at successive calvings was found to be high.

In order to obtain a wide range of live weights, two Oxford Down, two Southdown, and two Soay rams of recent feral origin, were used to sire lambs from 169 crossbred ewes. These ewes had been bred from Blackface ewes mated to Border Leicester, Dorset Hora, Clun Forest, Finnish Landrace and Tasmanian Merino rams. Of the 282 lambs weaned by the crossbred ewes, 61 were singles, 166 twins, 51 triplets and 4 quadruplets. Carcass data were obtained from all but three of them.

Oxford Down cross lambs were, in terms of fitted values, 10 kg heavier and 4 days younger than Soay cross lambs and 6 kg heavier and 2 days younger than Southdown cross lambs when slaughtered. Twins and triplets were 1·4 and 2·1 kg, respectively, lighter than singles and were 37 and 58 days older than singles. Ewes of the heaviest groups produced heavier lambs in a shorter time than ewes of the lightest groups.

The Soay cross lambs showed a higher killing-out percentage, less tail fat, and more kidney fat, than the Southdown and Oxford Down cross lambs.

Carcass characters made little if any difference to the price paid for the lambs which depended mainly on weight. Receipts from lambs were highest when the most fertile ewes were mated to the largest rams.