The rationale for a method of computing selection indices for dairy cows is outlined. It uses predicted transmitting abilities of sires from a best linear unbiased prediction or similar method of evaluation together with mean transmitting abilities (cow indices) of dams to estimate herd genetic levels. Indices for individual cows are computed using deviations from those of contemporaries in the herd of her sire's transmitting ability, her dam's index and her own production in each lactation.

The method is being used in the UK, cow indices being expressed as transmitting abilities relative to the same fixed genetic base as for sire evaluation.

The relationship between the composition of the fat-free carcass and carcass fatness was studied by considering the relationship as one between two shape vectors, with the effect of size removed, using an extension of the multivariate linear least squares technique for studying multivariate allometry.

In two sets of data, one of dressed carcasses of cattle and the other of empty carcasses of lambs, the composition of the fat-free carcass (in terms of protein, water and ash) was significantly related to carcass fatness (P < 0·10 and P < 0·05 respectively). The consequences of this relationship to the study of the chemical composition of carcasses are discussed.

Examination of the relationship in more detail showed that the fatter carcasses were those with more protein and less water in their fat-free carcass, in both sets of data, and with more ash in the empty carcasses of lambs.

The maintenance energy requirements of 29 Hereford × Friesian and 27 Blue Grey (White Shorthorn × Galloway) cows each offered one of six levels of feeding supplying between 0·5 and 1·2 likely maintenance requirements for 56 days were estimated, from regressions of daily live-weight change on energy intake, as the energy intake corresponding to zero live-weight change.

There were no effects of level of intake on diet digestibility or of genotype on maintenance requirements.

Maintenance requirements (M, MJ metabolizable energy per day) were shown to be determined by both live weight (LW, kg) and body condition score (C) according to the relationship: M = 0·147LW – 0·016C.LW.

The estimates derived are compared with other published values and the hypothesis is advanced that maintenance requirements are likely to be more closely related to body protein mass than to body weight.

The dietary energy equivalent of 1 kg loss of live weight is calculated to be 26·7 MJ and it is estimated that in non-lactating cows body tissue is used for maintenance with an efficiency of 0·77.

The objective of the studies reported was to examine the potential usefulness of measurements of concentrations of plasma glucose, 3-hydroxybutyrate and non-esterified fatty acids as means of assessing in quantitative terms the adequacy of energy intake of beef cattle.

Relationships between the concentrations of these metabolites and of either energy intake or energy status were examined in three experiments conducted respectively on 56 housed, mature, non-pregnant, non-lactating cows, on 115 housed, mature, pregnant cows, and on groups of 10 to 12 mature, non-pregnant, non-lactating cows grazing five plant communities.

The results indicated that under the conditions pertaining in these studies plasma glucose concentration was not likely to constitute a useful index of energy status in housed or grazing animals.

Plasma 3-hydroxybutyrate concentration was closely related to estimates of energy status in the pregnant cows and was considered to be potentially valuable as an index of energy status in animals in which there is a relatively high glucose demand.

Plasma non-esterified fatty acids concentration was closely related to and a potentially useful index of either energy intake or energy status in all cases, but postulated effects of diurnal variations in circulating concentrations make it imperative that relationships used for predictive purposes are derived under the conditions in which they are to be applied.

Sixteen British Friesian-cross steers of early- or late-maturity types were reared on either a 16- or a 24-month system of production. The steers on the 24-month system were subjected to a reduced nutrient intake during two phases of growth: 1) during early growth when the steers were approximately 9 months old and 2) during a store period when the steers were 13 to 19 months old. Animals on the 16-month system were fed to appetite throughout. Blood sampling was carried out at various periods during growth and serum samples were analysed for growth hormone, insulin, prolactin, glucose and blood urea nitrogen. Serum growth hormone concentrations were elevated during reduced nutrient intake, whilst serum insulin concentrations fell. Serum prolactin followed a seasonal pattern, but was lower in the underfed steers. Serum glucose concentrations also tended to fall during underfeeding, but blood urea nitrogen results were inconclusive. Hormone concentrations were not influenced by the maturity type of the steer, suggesting that the hormones measured are not primarily involved in determining the differential growth patterns in steers of different maturity types.

Hereford ♂ × British Friesian ♀ cows that had calved in September/October and were suckling mainly Charolais ♂ × calves were offered individually one of three planes of nutrition based on their estimated maintenance requirement during their first 150 days of lactation.

The mean daily intakes of metabolizable energy were 95·8, 71·5 and 52·1 MJ for the high, medium and low planes of nutrition respectively. Data were collected from 122 lactations. The mean 150-day cumulative milk yields of the cows were 1 355, 1 258 and 1 187 kg for the high, medium and low planes of nutrition respectively (P < 0·001). A i-kg increase in calf birth weight was associated with an increase in 150-day cumulative milk yield of 14·7 ± 2·17 kg (P < 0·001). Losses in live weight and condition score were significantly greater for cows given the low plane of nutrition during lactation (P < 0001).

Although there was a significant (P < 0·01) positive correlation between the growth rate of the calves and their dams' nutritional level during the winter there was evidence of compensatory growth at grass, since by the time of weaning in August, the plane of nutrition of the dam during the winter had no significant effect on the weight of the calves.

The experiment demonstrates that energy-deficient beef cows will attempt to maintain milk production at the expense of body reserves and that when supplementary solid food is made available to the suckled calves, their weaning weights are unaffected by the plane of nutrition of the dam during the winter.

Data were obtained from 233 heifers and 246 steers born in the autumn (September) or spring (March) seasons. The calves were sired by Polled Hereford (British) and Charolais, Chianina, Limousin. Maine- Anjou and Simmental (Continental European) bulls, from Aberdeen Angus (♂ × Holstein ♀ cows. Autumn-born calves weighed more at birth than did spring-born calves ( P < 0·01 ). Season of birth did not affect 205-. 305-. 365-day or slaughter weights. Incidence of dystocia was greater for Maine-Anjousired calves than for Polled Hereford calves (P < 0·05) with the other breeds intermediate. Significant sex differences were observed in practically all live and carcass traits with the exception of Warner- Bratzler tenderness and taste panel evaluations.

There were significant breed effects in which Continental European-sired calves gained weight more rapidly than did Polled Hereford-sired calves (P < 0·01) within each 90-day period, with the exception of 180 to 270 days. Slaughter weight and carcass weight per day of age followed the same trend. At slaughter at a mean age of 416 days, mean live weight of calves from Continental European breeds of sire was 1·075 of that of the Polled Hereford-sired calves. Proportion, weight and gain per day of edible meat in the carcass were greater for calves sired by Continental European bulls (P < 0·01). Although fat thickness and marbling score means were greater for Polled Hereford-sired cattle (P < 0·01), there were no significant differences in taste panel evaluations. There were no important two-way interactions between the main effects (sex, season of birth or sire breed).

An experiment was conducted to show the effectiveness of selection for improved food conversion ratio on ad libitum group feeding. Selection (32 ♀♀ and 8 ♂♂) and unselected control (32 ♀♀ and 16 ♂♂ lines were maintained for seven generations at the rate of one per year. Progeny were fed ad libitum from 27 to 82 kg live weight: boars singly or in pairs, and gilts in litter groups. Selection was on pen average food conversion ratio (food/live-weight gain), recalculated as each pig reached 82 kg.

In spite of selection differentials averaging 0·61 s.d. per generation, there was no response (selection minus control) in food conversion at Generation 6 (−0·03, s.e. 0·08). However, there were correlated increases in daily live-weight gain (56, s.e. 18 g), daily food intake (145, s.e. 59 g) and ultrasonic backfat (2·4, s.e. 0·4 mm). In Generation 7, 146 full-sib pairs (male castrate and gilt) were tested on ad libitum or scale (0·77 g/g ad libitum daily food intake) feeding. Line by feeding regime interactions were absent for all traits except killing-out proportion and belly thickness.

The increased fatness of the selection line on ad libitum feeding was retained on the scale (2·2 v. 2·4, s.e. 10 mm), suggesting a primary difference in partition of nutrients rather than intake. The selection procedure adopted was not successful in improving food conversion, but no clear conclusions could be drawn from the experiment. Uncertainty remains as to the value of group food consumption measurements in selection programmes.

An analysis was performed on data from three breeds recorded at the Pig Testing Station in Antrim in order to estimate and apportion variation in the measure of efficiency considered here, namely the daily food consumption after allowance had been made for maintenance and production requirements and other fixed effects. Results suggest that a considerable proportion of the variation in residual consumption is due to genetic causes (h2 = 0·3) and that selection to exploit this variation would result in an appreciable reduction in food costs. There were indications of considerable litter effects upon the trait.

The effects of source of protein on performance and nitrogen metabolism were studied in pigs weaned at 21 days of age. All diets contained 190 g crude protein and 14·6 MJ digestible energy per kg, and had a similar essential amino acid composition. Sources of protein were a combination of soya bean meal, fish meal and dried skim milk which was compared with soya bean meal alone, or in combination with either fish meal or dried skim milk. Seven groups of pigs (four pigs per group) received each diet ad libitum until 56 days of age. Performance was similar with the combinations of sources of protein, but with soya bean meal alone, food intake and growth rate were reduced (P < 0·05), but food conversion efficiency was not affected. Nitrogen metabolism was studied in seven pigs per diet given a restricted intake. Under these conditions, protein source had no effect on performance or retention and apparent digestibility of nitrogen. Nitrogen retention increased (P < 0·05) between 35 and 49 days of age, and was affected by the duration of the balance period (P < 0·01). In a second experiment, imparting a fish-like odour to the diet with soya bean meal as the sole source of protein by the addition of a fish oil did not affect food intake or performance.

These results indicate that a mixture of protein supplements in the diet of pigs weaned at 21 days of age may be unnecessary.

Thirty-three crossbred boars, 47 to 58 days of age, were randomly allocated to receive maize-soya bean meal diets containing 0·05, 0·15 or 0·30 mg selenium per kg. Body weights, testicular widths, and blood samples from vena cava puncture were taken at regular intervals. Libido was subjectively scored upon exposure to ovariectomized-oestrogenized gilts. Seven animals from each group were slaughtered at 9 months of age and selected reproductive structures were retrieved. Analysis of the relationships among body weight, libido and plasma testosterone levels indicated that differences (P < 0·01) existed between treatments, as analyzed over time, but that the overall treatment effect was not significant. Testicular widths were also found to be different (P < 0·05) over time. Values for all four criteria as measured over time were greater for boars fed 0·05 mg selenium per kg than for those fed 0·15 which were in turn greater than those fed 0·30. Post-mortem examination showed no treatment differences (1) in testis weights; (2) spermatozoan concentrations within the capita, corporea or caudae segments of the epididymis and (3) spermatozoan morphology examined within the caudae epididymis. Also testis lengths, weights, circumferences and spermatozoan concentrations were not significantly different between treatments. These results suggest that boars fed selenium at 0·15 or 0·30 mg/kg may exhibit some signs of retarded sexual development for a short period preceding the onset of sexual maturity

In the first experiment there were significant correlations between the average product of the length and width of the boar's testicles and the sperm output of the boar under a high collection frequency over two 6-h periods and over a 6-week period (r = +0·80, d.f. = 4, P < 0·05 and r = +0·77, d.f. = 7, P < 0·05, respectively). In the second experiment there were no significant differences in the fertility or fecundity of mature boars that had either two or six copulations per week over a 25-week period. However, there was a significant correlation between the average width of the boar's testicles and the fertility of the boar under the high mating frequency (r = +0·74, d.f. = 8, P < 0·05). There were also significant correlations between the number of copulations achieved in two mating tests and the number of copulations achieved and the refusal rate to mate under the high mating frequency (r = +0·86, and r = –0·89, respectively, d.f. = 6, P < 0·01). The implication of these results to the development of tests to predict mating performance of boars is discussed

The performance of crossbred ewes sired by Border Leicester (BL), Bluefaced Leicester (BFL) and ABRO Damline (DL) crossing sires was compared. The dams of the crossbred ewes were of three hill breeds (Scottish Blackface, Swaledale and Welsh Mountain). Contemporary comparisons were made on 18 commercial and college farms throughout England and Wales from 1977 to 1981. A total of 1 277 crossbred ewes were involved with data on up to three years' lambings per ewe, giving a total of 3 522 mating records. The analyses were by least squares, fitting constants for terminal ram breed × farm × year of birth of ewe groups, sire breed, dam breed, age of crossbred ewe and all two-way interactions.

The DL crossbred ewes were lighter at mating than the other crossbreds at each age. The proportion of 1-year-old crossbred ewes lambing was highest for the DL (0·78), compared to BFL (0·73) and BL (0·62), indicating earlier sexual maturity. Over all ages, the DL crossbreds were more prolific with 1·79 lambs per ewe lambing compared to BFL (1·63) and BL (1·53) and more lambs were weaned (1·33, 1·29 and 1·19 respectively). The total litter weight at both birth and weaning of the DL crossbreds was greater than the BL crossbreds but less than the BFL crossbreds at each age. For prolificacy and early sexual maturity, the DL cross is superior to both breeds. In overall production, the DL cross had no advantage over the BFL cross, as the litters of the DL crossbred ewes were lighter than the BFL litters at both birth and 10 weeks of age

Maturing patterns are established for the weight of bones relative to the weight of total bone and for the weight of fat depots relative to the weight of total body fat in two strains of Merino rams of different mature size. The maturing coefficients for all bone and fat depots are tabulated.

In the mature animals the partitioning of fat in each strain was similar, except for scrotal fat which was more abundant in the smaller strain. The maturity patterns of the depots were not different for the strains and also not different from the pattern of total fat, except in the case of scrotal fat. Accordingly, comparisons of the partitioning of fat were similar at equal maturity to the comparisons made at equal weight.

The distribution of weight among the bones was similar at maturity for both strains. However, unlike the fat depots, the individual bones had maturity coefficients which were mostly different from that of total bone. The limb bones, with the exception of the scapula, were early maturing relative to total bone. Accordingly, when compared at equal weight, limb bones, except the scapula, were a higher proportion of total bone weight in the larger strain and the differences between the strains were reduced when compared at equal maturity.

A summary of conclusions from this series of papers shows that tissues and organs had similar maturity coefficients in both strains of rams, and that stage of maturity was important in comparisons of proportions of tissues which have maturity coefficients which differed greatly from 1·0, but of little consequence where the maturity coefficient was close to 1·0

Six ewes with twin lambs were allocated to each of six restricted feeding treatments with 10, 0·8, 0·6, 0·4, 0·2 or 0 of the diet as perennial ryegrass and the remainder as white clover, and to two treatments with either perennial ryegrass or white clover offered alone ad libitum. Fresh herbage was offered and measurements were made over 8 weeks, with the exception of the ad libitum clover treatment which was terminated after 5 weeks. All lambs were allowed access to clover from 14 days of age. Digestibilities of the herbages were measured during four periods in the experiment.

Increasing the proportion of clover in the diet significantly increased the intake of nitrogen by the ewes and the growth rate of their lambs, but had no effect on the live-weight changes of ewes on the restricted treatments. When there was no restriction of intake, ewes ate slightly more clover than ryegrass and lost less weight, but mean daily live-weight gains of their lambs over the first 5 weeks did not differ significantly (0·30 and 0·34 kg for ryegrass and clover, respectively).

When ryegrass and clover were eaten alone or together their organic matter digestibilities (OMD) did not change, although OMD declined with increasing level of intake.

Initial body condition of the ewes had a significant effect on the decline of ewe live weight and body condition during lactation, and on lamb live-weight gain

The paper reports an experiment conducted with 50 Scottish Blackface and 10 South Country Cheviot ewes all suckling twin lambs and grazing, from parturition for some 18 weeks, pasture previously shown to cause a molybdenum-sulphur induced copper deficiency. The objectives were to examine the efficacy of various means of prophylaxis and the susceptibility of the two genotypes to copper deficiency.

The treatment of ewes at parturition with copper, either as an injection of 90 mg copper as copper methionate or orally with cupric oxide needles (3·2 g copper), delayed the onset of signs of copper deficiency in their lambs but did not prevent completely the development of hypocupraemia or hypocuprosis.

The treatment of lambs with a single injection of 15 mg copper as copper calcium edetate at about 6 or 10 weeks of age was not effective in preventing the development of hypocupraemia. Four injections (1 × 5 mg and 3 × 15 mg) at approximately equal intervals maintained normocupraemic values in lambs, but the most effective treatment, as judged by plasma and liver copper concentrations and by live-weight gain, was the administration of cupric oxide needles (1.6 g copper) to lambs at about 6 weeks of age.

The between-genotype comparison indicated that the Cheviot ewes and their lambs were as severely affected by the induced copper deficiency as were the Blackfaces.

Medium-wool Australian Merino rams were sampled in 1978 and 1979 to estimate the relationships between the follicle curvature score, fleece and body characteristics.

As a high correlation coefficient between two independent observers was found in both years, only one observer was used to correlate follicle curvature score with wool production.

Repeatability of the follicle score between lambs at weaning and 14- to 15-month-old rams was 0·61*** and 0·65***.

Clean fleece weight was significantly correlated with greasy fleece weight (0·8***, 0·9***), clean scoured yield (0·6***, 0·7***), staple length (0·4*, 0·5**) and crimps per cm (-0·3, -0·4*), but the correlation was very low with fibre diameter (0·01, 0·06).

The correlation of clean fleece weight with body weight at 14 to 15 months varied between 0·2 and 0·5 (P < 0·001).

Follicle curvature score was significantly correlated with clean fleece weight (-0·5**), clean scoured yield (0·6***, 0·7***), staple length (-0·4*, -0·7***), fibre diameter (0·3, 0·6***) and crimps per cm (0·4*. 0·6***). Non-significant correlations of follicle curvature score with greasy fleece weight (–0·2) and body weight at 14 to 15 months (–0·04, –0·1) were found.

Depending on whether the proportion of superior 14- to 15-month-old rams which are to be retained for breeding is 0·10 or 0·05, then, according to our data, the proportion of lambs that can be culled at weaning (with an accuracy of P < 0·05) is 0·31 or 0·42, respectively.

Seventy-nine Scottish Blackface and 79 North × South Country Cheviot ewes were fed to increase their mean condition score by 0·5 over periods of either 4 (M/H group) or 8 (I group) weeks prior to mating. Thereafter, they were fed a live-weight maintenance ration until they were slaughtered at 50 to 65 days after mating. Reproductive tracts were recovered, corpora lutea counted and embryos counted and examined. Plasma progesterone levels were monitored at selected times after mating. The proportion of ewes in each treatment group that were pregnant at the time of slaughter was similar (0·75 to 0·83) but there was evidence of differences in the pattern of reproductive failure with treatment. The proportion of non-pregnant ewes which had apparently been pregnant initially was 0·55 in the M/H group compared with only 0·27 in the I group. Circulating progesterone levels were not affected by premating nutritional treatments but differed with breed.

Two rations were prepared for sheep in which whole oat grain was mixed with molasses, urea, minerals and vitamins. Chemical analysis showed that the minerals had adhered to the grain and that there was little loss of minerals after one year of storage. The diets were readily consumed by sheep.