1. The reproductive performance of 128 first-lambing ewes born during 1966–71, and of 118 ewes kept on a twice-yearly lambing system during 1968–1972/73, in a commercial flock of Finnish Land-race sheep in Finland, was analysed.

2. The first-lambing ewes were exposed to the ram throughout the year, except in June and July. Out of 95 ewes born between January and May, 92 (97%) lambed at the age of 376·4 ± 29·9 days, and out of 20 born between July and September, 15 (75%) lambed when 323·8 ± 50·4 days old.

3. The average litter sizes at first lambing were 1·6, 1·9 and 2·6 for ewes with average ages of 324, 388 and 534 days, respectively; the 5-mo litter weights averaged 41·7, 45·7 and 70·5 kg per ewe for the three groups.

4. In the twice-yearly lambing system 55% of ewes lambed once within a calendar year and 45% lambed twice. The number of consecutive lambings and the number of lambs born per ewe per year were 1·52 ± 0·29 and 4·03 ± 1·18, respectively. The consecutive lambings of the 118 ewes, over a period of 1½ to 5½ yr, did not indicate any decline in reproductive performance.

5. The estimated lambing-to-conception interval in consecutive lambings was 116·6 ± 64·3 days; February had the lowest conception rate (0·7%) and November the highest (20·8%); April (16·5%) and September (15·5%) were similar.

6. Litter size was not affected by year, age of ewes, or lambing period. The mean lamb mortality up to 14 days of age, based on 1168 lambs born dead or alive, was 12·8% and the annual ewe wastage averaged 21·9%

7. For ewes which lambed twice within a calendar year, the lambing to conception interval was 71·7 ± 24·7 days. Such ewes produced 5·0±1·4 lambs per calendar year and the combined 5-mo weight of both litters was 168·2 ± 43·2 kg per ewe.

Dried grass pellets of high density (1·3 g/ml) were fed ad libitum to British Friesian male calves 5 to 7 mo old (Experiment 1) or 2 to 5 mo old (Experiment 2). All eight animals in Experiment 1 and eight out of 12 in Experiment 2 were fitted with rumen fistulae. In some subperiods of both experiments, pellets were broken down in water and administered as a slurry directly into the rumen at a level equivalent to approximately one-third that of voluntary intake. Intake per os was significantly reduced by this treatment but total intake (per os+per rumen) was not affected.

In Experiment 3 pellets of high (1·24 g/ml) or medium (1·14 g/ml) density were fed ad libitum to 40 9-mo-old Suffolk × Scottish Halfbred wether sheep, either alone or with access limited to 3 hr a day, in which case chopped hay was always available. Pellet density did not affect total intake, but when offered as supplements to hay the consumption of medium-density pellets was higher than that of high-density pellets. In all three experiments animals required 2 or 3 weeks to reach maximum intake of pellets. Over the 42 days of Experiment 3 the proportion of pellets in the feed consumed by animals given pellets as supplements to hay increased from 60 to 80%.

One-hundred-and-seventy British Friesian heifers were individually fed from 6 weeks before to 6 weeks after artificial insemination on a diet of 90% maize silage and 10% decorticated groundnut in the dry matter. Three levels of nutrition were compared: 48, 55 and 62 g/day of digestible organic matter/kg live weight0·73, which gave mean growth rates of 0·34, 0·50 and 0·68 kg/day respectively. Pregnancy rates to first service were not significantly different, averaging 67, 69 and 65%. Heifers were given a body condition score at the time of insemination, and pregnancy rates corrected for level of nutrition were 42,72, 70 and 63% for heifers in poor, moderate, good or very good condition. For heifers in poor/moderate condition increasing the level of nutrition increased pregnancy rates and for those in good/very good condition pregnancy rates declined, but these effects were not significant.

Birth weights, weaning weights (75 days of age) and pre-weaning average daily gains of 291 lambs and post-weaning average daily gains, feed conversions and market weights of 136 ram lambs were studied. The lambs were of three fat-tailed Iranian breeds of sheep, Karakul, Mehraban and Naeini, and their crosses with Corriedale and Targhee rams.

The crossbreds were significantly superior to the purebreds in all the traits studied, by approximately 7% in the pre-weaning traits and up to 18·4% in the post-weaning daily gain. Among the purebreds, Mehraban lambs were superior to the other two breeds in the preweaning traits and final weight.

The progeny of the Targhee and Corriedale rams were similar in performance except for feed conversion, in which the lambs sired by Targhee rams were more efficient. Breed of dam had a significant effect on the pre-weaning traits and feed conversion. Mehraban ewes produced lambs with the highest pre-weaning average daily gain and weaning weight among the crossbreds, but they were the least efficient lambs after weaning.

Age of dam significantly influenced the pre-weaning but not the post-weaning traits. Lambs born to 4-yr-old ewes were the heaviest and those born to 2-yr-old ewes were the lightest at birth. The lambs reared by 2-yr-old ewes had significantly lower rates of growth and were the lightest at weaning. Sex had a highly significant effect on the pre-weaning traits in favour of the male lambs.

The nutritive value of four silages was compared using eight rumenfistulated wethers. Wilted ryegrass was ensiled without additive (A); with formic acid (13·9 kg/t dry matter) (B); with formic acid (10·3 kg/t dry matter) plus formalin (formaldehyde at 4·8 kg/t dry matter) (C); with formic acid (4·9 kg/t dry matter) plus formalin (formaldehyde at 2·3 kg/t dry matter) plus propionic acid (5·6 kg/t dry matter) (D).

Dry-matter intakes were 13·8, 15·1, 14·3 and 14·3 g/kg live weight for A, B, C and D respectively. Digestibilities of organic matter and dry matter were not affected by the additives. Digestibility of nitrogen and peak ruminal ammonia concentration were significantly (P<0·05) reduced by the addition of formaldehyde.

The effect on rumen fermentation characteristics, of chemically restricting in-silo fermentation, is illustrated. Differences in the rumen volatile fatty acids and in the efficiency of utilization of the energy for growth, fattening and lactation are discussed.

Data were available from 11 474 gilts performance-tested on 137 farms. The data were analysed to provide pooled within-farm sire component estimates of h2 and genetic correlations.

Estimates of h2 of 0·43 ± 0·10, 0·44 + 0·09 and 0·49 ±009 were obtained for weight for age, C + K and shoulder fat depths respectively in 3583 gilts in 49 Large White herds. Comparable Landrace values derived from 2810 gilts in 43 herds were 0·44 + 0·11, 0·40 ±0·10 and 0·51 ±0·12 respectively. Estimates were consistent from herd to herd.

Estimates of h2 made on data from 5081 crossbred pigs, of mainly Large White and Landrace parentage, varied with herd from 0·10 to 0·40 for weight for age and from 0·08 to 0·96 for shoulder fat depth. Significant differences between breeds were found for the genetic correlations between weight for age and the fat depths, and between shoulder and mid-backfat depths. The variance was partitioned into various components. For index score, the within-herd variance averaged 73% of the total variance.

Food intake, eating rate, weight change and fasting metabolic rate were measured on 12 animals of each of the following breed-types: Hereford × Shorthorn (HS), Brahman × HS (BX) and Africander × HS (AX). Measurements were made on ad libitum and fixed levels of lucerne and ad libitum and fixed levels of low-quality tropical pasture hay (approx. 1·2% N) during feeding periods of about 100 days' duration.

The BX and AX were heavier and either gained more weight or lost less weight than the HS on all diets. At feeding levels close to maintenance, which included the ad libitum pasture hay diet, adjustment for differences in either live weight or intake did not alter the unadjusted ranking of the breeds. On ad libitum lucerne, however, adjustment for either weight or intake showed higher gain in the HS than in the BX. The voluntary food intake per kg live weight was consistently and significantly highest for the HS and lowest for the BX. Rates of eating were not significantly different for the different breed-types but they were higher for high-quality lucerne and for the lower level of feeding. Fasting metabolic rate per kg live weight was highest for the HS and lowest for the BX; the difference between the breeds varied with the previous dietary treatment. The ratio of voluntary food intake to fasting metabolism was practically constant between breeds and animals within breeds, though different between diets.

Correlations for animals within breeds and years between the various parameters within diets and between diets are presented.

Data from 14 074 gilts, performance-tested on 66 farms, were matched with those from 3835 station-tested boar sibs, the whole comprising progeny test results on 456 sires. Both groups of data were adjusted independently for effect of month of test and the farm data further adjusted to a constant weight of 91 kg. Analysis of variance and covariance was carried out within herds using weighted sire progeny means. Phenotypic correlations between the same traits recorded ‘on-farm’ and in station, ranged from 0·12* (weight/age) to 0·25** (‘C’ + ‘K’ fat depth) while genetic correlations, computed using the estimated accuracy of each test, ranged from 0·23* (weight/age) to 0·49** (simple performance test index). Correlations were generally higher in Large White than in Landrace pigs.

1. In a comparative slaughter experiment, 12 female pigs (six at 80 kg and six at 100 kg) were allocated at first oestrus to each of five treatments: Treatment 1, initial slaughter, or Treatments 2, 3 and 4, mated and given 19·5, 25·8 or 32·1 MJ ME/day for the last 100 days of pregnancy, or Treatment 5, not mated (virgin) and given 25·8 MJ ME/day over a similar period. Pigs on Treatments 2, 3, 4 and 5 were given the same amount of protein and were killed about 123 days after first oestrus. Piglets were removed at birth.

2. There was no evidence of any special effect of pregnancy in the stimulation of permanent maternal growth. The average live weight, ingesta-free body and carcass gains of the pair-fed, mated and virgin gilts (±SE of difference) were, respectively, 32·3 and 36·9 + 2·8, 27·5 and 27·6 ± 3·4, and 26·0 and 26·7 + 2·1 kg. There were no statistically significant differences between these two treatments in carcass composition, specific gravity or backfat thickness. The mated pigs had lighter livers (P < 0·01) and heavier reproductive tracts (P < 0·05), and lost about 9 kg within a week of parturition.

3. Increasing energy intake increased piglet birth weights (P<005) but had no effect on the number of piglets born. The pigs that were initially heavier (100 kg v. 80 kg) had 1·5 more piglets, though this was not statistically significant (P<0·1).

4. Although there was no special effect of pregnancy on permanent maternal growth, the conversion of food by the once-mated pig was very efficient if an allowance was made for the food cost of producing the piglets.

The milk production of three groups of cows grazing on veld and receiving different amounts of concentrates during winter and the first 8 weeks of lactation was studied over four successive calving seasons. Calves were weaned at either 150 or 240 days.

Cows offered most concentrates and those whose calves had been weaned early in the previous year produced more milk per lactation (P < 0·01) than other cows but weaning age did not affect yield/cow per year. Data for each treatment in each year were considered as a separate class. Regression analyses showed that milk yield increased with cow weight at calving and with calf birth weight. Changes in cow weight during early lactation, after adjusting for initial weight, were directly related to milk yield.

In a concurrent experiment, three groups of heifers were confined in pens and given sufficient amounts of a complete diet to promote either gain, maintenance or loss of weight during lactation. Heifers that gained or maintained weight produced significantly (P<0·01) more milk of a higher solids-not-fat and protein content than those which lost weight. Food intake had a significant (P < 0·01) positive effect on milk yield but the effects of weight and weight change on milk yield were negative after adjusting for food consumption.

Twenty-eight Landrace × (Landrace × Large White) young female pigs (gilts) were allocated to one of four treatment groups at about 75 kg live weight. The gilts were mated at second oestrus and suckled their piglets for 35 days. Gilts were slaughtered 14, 21, 28 or 35 days after weaning. The ‘effective’ food conversion ratios (i.e. total gilt plus litter feed intake (kg) divided by total gilt weight gain plus litter weaning weight) of the four groups were 5·22; 4·70; 4·62; and 4·56 respectively. The differences were not statistically significant.

Neither carcass weights nor individual joint weights were significantly affected by treatment. Samples of 11 middle sections from the 14-, 21- and 28-day slaughter groups were boned and cured. Bacon produced from the streak blocks had poor colour, texture and moisture-holding capacity. It was concluded that streak blocks from gilts that had farrowed were unsuitable for curing as streaky bacon.

A randomized block experiment was conducted using 27 British Friesian cows to assess the effects of three levels of concentrate input (589 (H), 456 (M) and 316 (L)±19·2 kg/cow) on performance. The animals, mean calving date of 6 January, were blocked according to calving date and allocated at random to treatments. All concentrates were given during the post-partum indoor feeding period (mean of 86 days) in addition to access ad libitum to grass silage. All animals received equal concentrate inputs/kg milk produced for 29 days after calving, following which the concentrate inputs were reduced, the reduction depending upon treatment. The milk outputs during the treatment period were 2147, 2075 and 1850 ± 75·8 kg and live weights at the end of the period were 504·1, 500·0 and 468·8 ± 4·96 kg for the H, M and L levels of concentrate supplementation respectively. Six animals per treatment were rotationally grazed at pasture at a stocking rate of 6·0 cows/ha for 11 weeks following the indoor feeding period. Performance at pasture was not affected significantly by previous treatment, with the milk outputs for the pasture period being 1647, 1673 and 1738 ± 53·0 kg, for the H, M and L treatments respectively. The milk outputs during the total indoor feeding plus grazing period at 3887, 3852 and 3636 ± 103·5 kg for the H, M and L treatments respectively did not differ significantly. Milk composition data are also presented.

1. Two experiments were conducted, one with pigs fed individually on a restricted scale of feeding, and one with pigs fed ad libitum in groups, to test Probioticum as a feed additive with and without nitrovin and zinc bacitracin.

2. Growth rate, feed conversion, killing-out percentage and carcass quality were measured.

3. No significant difference was shown in any of the characteristics measured between diets containing any of the additives, singly or in combination.

In an analysis of data from 211 litters in a Pietrain herd, litter size at birth and at weaning was lower than is generally found in indigenous breeds. Mortality in growing and breeding pigs was high with circulatory failure accounting for 23% and 95% of deaths respectively. Pietrains, fed ad libitum over the live-weight range 27 to 87 kg, grew more slowly by 130 g/day than contemporary Large Whites on the same feeding regime, had higher killing-out percentages (by 3 to 4 units) and larger eye muscles in cross-section (by 9·9 cm2) but tended to have higher feed conversion ratios. There was no breed difference in backfat measurements but Pietrain carcasses were shorter by 83 mm and their muscle quality was markedly inferior to that of the Large Whites.

Equations relating biomass to cumulative food ingested ad libitum were defined in rats from weaning to 200 days of age. Two inbred lines of the IIM strain: α, of medium adult weight, and b, of low adult weight, were fed on two different diets, × and Z. The following groups were formed: αX, αZ, bX and bZ. Body weight and food intake were recorded over a 1-day period every second day. For each of the four groups, body weight, W, could be described as a function of cumulative food intake (F) by the equation:

Each exponential term was assumed to measure the behaviour of a portion of the biomass. The first exponential term implied an intense growth and a high initial efficiency, which became effectively zero by about 100 days of age. The second exponential term implied a weak growth and a low but significant efficiency of food utilization. Type of diet influenced level of intake and was important at early ages (<100 days). At 46 days of age, animals of both lines were heavier and more efficient when fed on diet Z. The genetic influence determining final adult weight becomes evident after 46 days of age.

Body weights were recorded at birth, 45 and 90 days on 199 Merino lambs. Serum samples were obtained and analysed with horizontal starch gel electrophoresis to identify the transferrin types. Sixteen transferrin phenotypes, TfAA, TfAB, TfAM, TfAD, TfAE, TfBB, TfBM, TfBD, TfBE, TfMM, TfMD, TfMS, TfME, TfDD, TfDE and TfEE were detected in this study. The phenotypes were confirmed on the basis of international nomenclatures. Lambs were grouped according to their transferrin types. The average weight of different groups at birth and the weight gains in the first and second 45-day periods were estimated. TfDE was the poorest weight gainer but the differential value was significant only in the second 45-day period.

Data from a large field trial comparing the performance of contemporary crossbred ewes from traditional and experimental prolific rams were used to study two factors, (1) the influence of lambing at 1 yr of age on subsequent ewe performance and (2) the effect of level of farm performance on the difference between the traditional and the prolific types. Neither effect was found to be important.

The in vitro dry-matter digestibilities (IVDMD) of three rations containing different proportions of hay and a mixed concentrate (pellets) were each determined by fermenting the feeds with inocula obtained from rumen contents of sheep fed on either the hay, hay and pellets, or pellets. These inocula had no significant effect on the IVDMD which averaged 60·9, 68·8 and 77·8% for the hay, hay and pellets, and pellets respectively.

Measurements were made of the heat production of cattle while standing at rest or walking on a treadmill at different speeds, both on the level and at a gradient of 6°. The energy cost of horizontal locomotion was about 2 J/kg per m at speeds of 40 to 85 m/min, irrespective of body weight or plane of nutrition. The energy cost of vertical locomotion was about 26 J/kg per vertical m.