1. Eighteen New Zealand White × Califomian young female rabbits (does) were paired by weight and age and, at 800 g live weight, placed on a restricted intake based on the mean body weight of each pair. On attaining 1 kg one of each pair was then given 10 mg trenbolone acetate by injection on days 1, 3 and 5 of each week. This continued until the animals reached 2·3 to 2·4 kg (5 to 6 weeks).

2. There were no differences in digestible or metabolizable energy intakes between treated and untreated rabbits. However, the treated animals showed small but significant increases in rates of gain for live and empty body weight compared with control does. Treated animals also had significantly more nitrogen (P < 0·001) and less energy (P < 0·05) per unit empty body weight than controls. Although the proportion of total nitrogen retention was 0·19 greater (P < 0·001) in treated does, total energy retention was only slightly less. Treated animals had approximately 40 g (200 g/kg) less fat and 50 g more protein (N × 6·25) than control does at the end of the trial.

3. Increases in liver weight and clitoral size were observed in treated animals.

The study was based on 1156 lactation records of 545 Murrah buffaloes. Initial milk yield, peak yield, ascending phase milk yield and days to attain peak daily production, the means of which were 26·7 kg, 10·3 kg, 407 kg and 58·9 days respectively, were all affected by period, season and parity of calving. Heifers recorded the least initial milk yield and peak yield and took the longest time to reach peak production. Peak yield was the most important single factor (R2 = 0·41) in causing variation in 43-week milk yield. The heritability estimates for initial, peak and ascending phase milk yields and days to attain peak yield were 0·35, 0·51, 0·27 and 0·13 respectively, whilst that for 43-week milk yield was 0·18. Peak yield had the highest phenotypic (rP = 0·64) and genetic correlations (ra = 0·68 ± 0·19) with the 43-week milk yield. Other genetic correlations with the 43-week milk yield were low and non-significant. The results indicated that indirect selection for peak yield would be more effective than direct selection for improving the 43-week milk yield in buffaloes.

Dairy Shorthorn (DS), Red Friesian (RF), Red Holstein (RH), Danish Red (DR), Meuse-Rhine-Yssel (MR), Simmental (SM), British beef breeds (BB) and hybrid (HY, RF♂ × DS9 and RH♀ × DS?) bulls were progeny tested on DS, RF and HY cows as part of a breed improvement project. Live-weight records for 4 450 animals in 17 herds by 350 sires were used to calculate adjusted hundred-day weights from 100 to 700 days of age. Genotype × environment interactions were significant (P < 0·001) and data for two production systems (cereals and grass) were analysed separately. RF, RH, DR and MR progeny were, proportionally, 0·10 to 012 heavier than DS (P < 0·001). On cereals the SM were significantly heavier than these crosses (0·095, P < 0·001 at 400 days) but not on grass. BB and HY were generally not significantly different from DS. Only DS dams were represented on cereal systems. On grass, breed differences were similar for different dam breeds but estimates of hybrid vigour averaged 0·051 in RF♂ × DS♀, 0·061 in RF♂ × (RF♂ × DS♀)♀ and were not significantly different from zero in DS♂ × (RF♂ × DS♀)♀. Apparent heritability averaged 0·50 ± 0·12 but was lower during a period of feed restriction. The within-breed genetic correlation for live weight on the two systems of production was unity.

Genetic relationships among leg and performance traits were estimated for 23 975 Large White and Landrace boars fed twice daily to appetite from 27 to 91 kg live weight at Meat and Livestock Commission testing stations between 1966 and 1972. For each boar, an overall leg score was derived as the sum of scores for 19 individual leg traits categorized as ‘absent’ (0), ‘slight’ (1) or ‘severe’ (2) at 91 kg. Heritabilities of leg score were 017 ± 0·03 in Large White and 0·19 ± 0·04 in Landrace. Genetic correlations with a visual ‘leg action’ score on a scale from 1 to 5 averaged 0·93 ± 0·02 over breeds. Genetic and phenotypic correlations between leg scores on the same boars at 27 and 91 kg averaged 0·50 ± 0·17 and 0·15 ± 0·01 respectively.

Both breeds showed significant adverse genetic correlations ranging from 0·20 ± 0·10 to 0·40 ± 0·08 between leg score and boar ultrasonic backfat. From slaughtered littermates, leg scores showed favourable genetic correlations with eye-muscle area (0·30 ± 0·10) and killing-out proportion (0·35 ± 011) in Large White and unfavourable correlations with carcass length (0·31 ± 0·10), lean content (0·30 ± 0·14) and backfat (0·33 ± 0·11) in Landrace. There were no associations with growth rate, feed efficiency or the performance index on which boars are selected. The study indicates that leg condition and fatness are adversely genetically related, but that selection on the present national performance index would not be expected to cause a rapid decline in leg condition. Culling on leg score would be expected to reduce the frequency of leg weakness.

Eighty multiparous Camborough hybrid female pigs (sows) and their litters, on average 15 days post partum, were housed in groups of five in multi-accommodation pens. The sows were fed ad libitum on a proprietary diet containing 160 g crude protein per kg from grouping to 30 days post partum, when they were fed to scale twice daily in individual feeders until weaning at 42 days post partum. One of four Large White male pigs (boars) was introduced to each group on the day following grouping, each boar being run with four groups.

Oestrus occurred in 62 sows, on average 10·2 ± 3·3 days after grouping. The differences between groups in the interval from grouping and boar introduction to the onset of oestrus were statistically significant (P < 0·01). Neither the incidence nor the timing of oestrus could be related to the identity of the boar.

Regression analysis revealed relationships between a number of independent variables and the incidence and timing of lactational oestrus. Sows which gained more live weight from farrowing to weaning and whose litters consumed more creep food were more likely to show lactational oestrus. Sows were slower to show lactational oestrus when they gained little weight from farrowing to weaning, had lower live weights at weaning and gained less weight from the previous weaning, despite eating comparatively more food during grouping. The sows which took longer to show lactational oestrus also had heavier piglets at grouping and more piglets in their litters at weaning. The difficulties arising in the interpretation of these results are discussed.

Maturing patterns are established for 26 body organs using data from 35 rams of two strains of Merinos of different mature size (97 and 120 kg).

The proportion of shorn full live weight represented by each structure at maturity was very similar for all organs except the head, hide and distal limbs which were relatively heavier in the small strain. and small intestine and blood which were relatively heavier in the large strain.

All organs were early maturing relative to shorn full live weight except the hide and the penis plus bladder, which matured at the same rate as live weight. The maturity coefficients differed between strains only for the head, thyroid and omasum.

Differences in the proportion of live weight comprised by each organ in the two strains were compared at the same shorn full live weight and at the same proportion of mature shorn full live weight. Differences in the various portions of the alimentary tract and other internal organs, with the exception of the kidneys, which were evident in comparisons at the same weight, were reduced when compared at the same proportion of maturity. The difference between strains for head, hide and distal limbs was greater at equal maturity than at equal weight suggesting a functional relationship to body weight rather than to ultimate mature body size.

It was concluded in genetic comparisons of animals of different mature size, the most appropriate basis of comparison of relative organ weight will be at the same proportion of mature live weight.

Three experiments employing 40, 39 and 15 Large White × (Landrace × Large White) gilts respectively were carried out to investigate possible primer pheromone activity (i.e. regulating endocrine systems) for those 16-androstene steroids with known signalling pheromone activity (i.e. immediate behavioural effects) in the pig. Experiment 1 consisted of groups of prepubertal gilts exposed to one of the following odour sources (a) 5α-androstenone (5α-androst-16-en-3-one), (b) 3α-androstenol (5α-androst-16-en-3α-ol), (c) a mixture of both steroids, and (d) a diethyl ether extract of boar submaxillary salivary gland. Age at the onset of puberty in these gilts was compared with that in an unstimulated control group. Experiment 2 was similar to Experiment 1 except that the steroids were used at a higher concentration (100 fold), and a fifth group of gilts was exposed to an intact boar. In the third experiment, age at the onset of puberty was noted following exposure of groups of gilts to one of the following (a) a castrated boar which had received long term injections of testosterone, (b) urine from an intact boar, (c) an intact boar.

The results confirmed that the intact boar accelerates puberty in gilts. Although there was no conclusive evidence indicating that isolated boar odours had an effect on the onset of puberty, it is noteworthy that of those gilts exposed to 3α-androstenol, more reached puberty earlier than control gilts. However there is the possibility that transportation may have enhanced the earlier puberty found in some of the gilts taken to a source of 3α-androstenol. Prolonged treatment of a castrated boar with testosterone did not maintain its ability to accelerate puberty in gilts.

Carcass characteristics of 246 bulls and steers by Dairy Shorthorn (DS), Red Friesian (RF), Red Holstein (RH), Danish Red (DR), Meuse-Rhine-Yssel (MR), Simmental (SM) and North Devon (BB) bulls were recorded as part of a breed improvement programme. Carcasses of animals on grass-feeding systems were older, had lower fat and conformation scores and higher estimated lean yield than on intensive cereal systems, BB were fatter, and MR and SM leaner, than the remaining breed groups which were similar to DS and SM progeny had high conformation scores. Estimated lean in the live weight (g/kg) relative to DS was RF +5, RH −3, DR +5, MR +16, SM +16 and BB +6 with an average standard error of 3.

The effect of Oesophagostomum dentatum on the performance of growing pigs over the live-weight range 20 to 80 kg was investigated. Fourteen individually-penned pigs in Experiment 1 and 16 group-penned but individually fed pigs in Experiment 2 were orally dosed once with 80 000 or 20 000 larvae respectively at about 18 kg live weight. Worm-free but otherwise similar pigs served as controls. Three energy and nitrogen balance studies were undertaken in two open-circuit calorimeters on four infected gilts and their paired worm-free counterparts on two levels of feeding at 7, 21 and 49 days after infection. Worm burdens averaging 4 255 and 4 722 in Experiments 1 and 2 respectively were recorded post mortem but performance and carcass measurements were not affected, neither were there any clinical symptoms. No significant differences between infected and worm-free pigs were recorded for either apparent digestibility of nitrogen and gross energy or for nitrogen retention. Possible reasons for the lack of measurable effects on pig performance are discussed.

Forty purchased male Hereford ♂ × Friesian ♀ calves (about 14 days old) were offered concentrate diets containing 0, 170, 230 or 320 g chopped (20 mm) straw per kg. Food intake and live-weight gains of calves were increased by the inclusion of straw, but the 320 g straw treatment tended to depress intake and gain. The optimum concentration of fibre for maximizing live-weight gains was 150 g trichloracetic acid fibre per kg of diet (220 g chopped straw per kg).

The pattern of food intake as a function of age, and live weight as a function of food consumed was examined from soon after weaning to maturity in groups of fine and strong wool Merino rams and Dorset Horn rams and wethers. Each group, which initially comprised 20 sheep and from which individuals were removed for slaughter at approximately 6-kg increments in live weight, was fed a pelleted ration ad libitum for 98 and 77 weeks for the Merino and Dorset Horn groups respectively.

The pattern of food intake was similar for all groups of sheep, in that food intake increased to a maximum at approximately 50 weeks of age and then declined with age with a regular oscillation superimposed on this curve. In all three groups of rams, but not in the Dorset Horn wethers, the oscillations in food intake were on an approximate annual cycle with a decrease in food intake in summer and an increase in winter.

Estimated mature live weights for the strong and fine wool Merino rams were 120·5 and 97·6 kg, and for the Dorset Horn rams and wethers 108·6 and 101·4 kg. Variation between breeds in the level of food intake, food efficiency and consequently the pattern of growth, was largely a function of mature size. The Dorset Horn rams were slightly more efficient at converting food to live weight than the wethers.

The influence of the level of dry-matter intake and the dry-matter concentration in the diet on the water consumption of dairy cows in early lactation was investigated for a 2-month period from early August to early October. The importance of the various components of weather on voluntary water intake was also examined. The cows used in the experiment either grazed pasture alone, or were offered pasture and pasture hay supplements. Mean voluntary water intake increased by 2·30 kg per cow per day for every additional kg dry matter consumed and also increased by 0·053 kg per cow per day for each g/kg increase in dry matter concentration. Of the climatic factors, rainfall had the greatest single influence on the daily fluctuations in voluntary water intake and this was negative. Intake was also negatively related to minimum temperature, relative humidity and wind, and positively related to sunshine and evaporation. Although maximum temperature per se had no apparent influence on intake, it showed a positive relationship after the removal of the effects of rainfall. A model for the prediction of total water consumption is:

Total water consumption (kg per cow per day) = 11·34 + 4·63 dry-matter intake (kg per cow per day) –0·036 dry-matter concentration (g/kg) + 0·84 mean temperature (°C).

This can only be used to predict the water requirements of lactating dairy cows in different environments.

One hundred tonnes of spring-sown barley harvested as whole crop were treated on a commercial farm with pearl sodium hydroxide at 46 g/kg dry matter.

The treated material was stored in a silage clamp beneath grass and lucerne silage. A thin layer of grass, cut and wilted to hay-making dry matter, was placed immediately on top of the barley to absorb any silage effluent.

Monthly samples were taken for microbiological examination and chemical analysis throughout winter storage, while the material was fed to British Friesian dairy cows. There was no evidence of fermentation by clostridia in the whole-crop barley or wilted grass and there was no spoilage of the exposed feeding face. The treatment increased the in vitro organic matter digestibility and the in vitro digestible organic matter in the dry matter of the whole-crop barley. No excessive urination or other ill effects were observed in the stock.

The method proved practical for the satisfactory storage and feeding of sodium hydroxide-treated whole-crop barley.

1. Two experiments were conducted to determine the feeding value of high moisture wheat straw treated with ammonia. The straw was chopped, water added to attain 350 g dry matter per kg treated straw, then treated with 84 or 90 g anhydrous ammonia per kg wheat straw dry matter and stored in a large plastic bag.

2. In Experiment 1, the treated straw was provided ad libitum to lambs in individual pens with either a control supplement (molasses and minerals), or 200 or 400 g of a soya bean meal- or maize gluten meal-based supplement.

3. Lambs fed the control supplement consumed 24·8 g of treated straw dry matter per kg live weight and lost 32 g live weight per day during the 28-day study. Source of supplemental protein did not affect live-weight gain or treated straw consumption. Level of supplement increased live-weight gains (P < 0·01) but did not affect treated straw consumption.

4. In Experiment 2, the lambs were fed one of three levels of supplement that each supplied 58 or 116 g of crude protein per day. Supplemental protein level increased cellulose digestibility (P < 0·01) with no effect on hemicellulose digestibility. Protein level did not affect treated straw consumption or live-weight gain.

5. Supplement level decreased cellulose digestibility (P < 0·01), hemicellulose digestibility (P < 0·01), and treated straw intake (P < 0·01) but increased live-weight gain.

6. The results are discussed in relation to the effects of amount and type of supplemental protein and level of supplementation on utilization of the treated straw.

The relations between the gross energy concentration of milk and its concentration of fat and protein were calculated for samples of Jersey and Friesian milk. Stage of lactation and level of feeding had no consistent effects on the relations.

The calculated equations can be used to predict the energy concentrations of milk from Jersey or Friesian cows fed on pasture, from the concentrations of fat alone or from the concentrations of fat and protein. The predicted values agree with those predicted by earlier published equations.

A discrete-time population model is presented which is specific to the characteristics of a breeding colony. It is intended to be a rigorous yet an easily applied model. The model is based on a female-dominated demographic system with constraints on colony size. Fecundity and survival probabilities are incorporated into a net reproductive rate which is age-specific and time and population size invariant. The model is applied to solve an optimization problem for a breeding colony of African Green monkeys and to examine a set of external constraints imposed on the colony.

Results are presented from six trials dealing with aspects of management on the cold ad libitum system of calf rearing using an acidified milk replacer containing over 600 g skim milk powder per kg.

Thirty-six calves were housed in pens of six for each trial and were fed through a teat and pipeline from a storage barrel. Acidified milk replacer, pH 5·6, was mixed cold at 125 g/1 and made available ad libitum to 3 weeks. A rationed allowance was given daily, on a reducing scale, over the following 2 weeks with weaning completed at 35 days. A pelleted dry food containing 180 g crude protein per kg, together with water in buckets and barley straw in racks, was available ad libitum throughout. Each trial lasted 8 weeks. Results for the mean of the six cold ad libitum trials involving 216 calves were compared with the mean results of 10 conventional bucket-fed trials carried out separately at the same unit, involving 912 calves. All calves were purchased British Friesian male (bull) calves.

Calves on the ad libitum system showed improved live-weight gains of 9·4 kg at 3 weeks, 8·8 kg at 5 weeks and 7·5 kg at 8 weeks, compared with the conventional system. The consumption of milk replacer powder was higher in ad libitum trials at 29·4 kg cf. 12·5 kg by bucket but intake of pelleted dry feed was lower on the ad libitum system at 50·7 kg cf. 71·3 kg to 8 weeks. Calf appearance scores were significantly improved on the ad libitum system which gave the main improvement in performance in the first 3 weeks.

A urfia-formaldehyde-molasses complex appeared to be a promising slow ammonia-releasing urea derivative in in vitro studies. It was compared with urea-molasses mixtures as a non-protein nitrogen supplement to an ad libitum wheat chaff ration for steers. The significantly lower (P < 0·01) crude protein digestibility and intake of digestible crude protein, and the non-significantly lower nitrogen retention on the urea-formaldehyde-molasses complex ration revealed the superiority of simple urea-molasses mixtures as a non-protein nitrogen supplement.

A simple criterion is described for selecting which of a number of sample joints estimates most precisely for a given cost (T) the mean lean percentage of a population of carcasses, using double sampling. It is shown that the best joint is the one giving the largest value of:

where ρ is the correlation between the lean content of the sample joint and the lean content of a carcass side (y), and k is the cost of the sample joint dissection as a proportion of the cost of side dissection. The optimum proportion of carcasses to side dissect is:

and the standard error of the estimated mean is then:

where σyis the standard deviation of y and C is the cost of measuring y.

A metabolism trial was carried out to examine the influence of an antibiotic food additive (Avoparcin) on the apparent digestibility of nutrients and nitrogen retention in the growing pig. Two groups of pigs, comprising 12 castrates per group, were fed a barley-based diet (190g crude protein per kg dry matter) with or without the inclusion of the antibiotic (at a dietary concentration of 20 mg/kg). Addition of Avoparcin had no significant effect on the apparent digestibility of dry matter or gross energy but resulted in a small increase in the apparent digestibility of nitrogen (0·012; P < 0·05). There was a corresponding improvement in nitrogen retention (0·051) but the difference was not statistically significant.