Estimates were obtained of the variability among herds of dairy cattle of the standard deviation (s.d.) and coefficient of variation (CV) of milk, fat and protein yield. For fat yield, for example, the mean s.d. within herds for heifers was about 30 kg, the s.d. among herds was 5·2 kg and the mean and s.d. of CV were 0·15 and 0·026, respectively. Correlations of both s.d. and CV were high between both heifers and cows in the same herd and year and between heifers or cows in the same herd in successive years, showing that variability was consistent over time and over age groups.

Ways of correcting for the heterogeneity of variance for use in cow index calculations are suggested; because CVs are heterogeneous, simple log transformation is not sufficient.

In each of 2 years, 20 Friesian cows were given either a low-energy or a high-energy complete diet to appetite during weeks 3 to 20 of lactation. The diets for trial 1 contained concentrates, lucerne silage and chopped grass hay in the proportions 33:47:20 or 58:29:13. In trial 2, concentrates and lucerne silage were mixed in the proportions 38:62 or 75:25. These mixtures had energy concentrations of 10·2 or 11·2 and 10·3 or 11·9 MJ metabolizable energy per kg dry matter (DM) and crude protein concentrations of 144 or 160 and 140 or 157 g/kg DM in the low- and high-energy diets of trials 1 and 2 respectively.

Cows offered the low-energy diet consumed less DM daily (14·5 v. 17·4 (P < 0·001) and 15·2 v. 18·2 (P < 0·001) kg DM per day in trials 1 and 2). Daily milk yields were lower with low-energy diets (19·2 v. 22·3 (P < 0·001) and 18·7 v. 24·2 (P < 0·001) kg/day in trials 1 and 2), and there were significant differences between treatments in milk composition and live-weight changes.

The correlation between food intake and milk yield during weeks 3 to 20 was moderately strong (r2 = 0·58). Variation in food utilization efficiency between diets and parity groups was small in comparison to variation within parity groups.

During weeks 21 to 44 of lactation the cows were at grass. In trial 2, but not in trial 1, cows previously given the low-energy diet gave less milk (1999 v. 2644 (P < 0·001) kg) but gained more live weight. There were also differences in the composition of milk produced in this period.

Primary growths of perennial ryegrass (Lolium perenne) were cut on 22 May and 12 June and wilted for 24 h prior to ensiling. A 40: 60 mixture of the two silages was offered ad libitum with two pelleted supplements. Supplement Ba was a mixture of (dry matter (DM) basis) 932 g rolled barley and 68 g fish meal per kg. Supplement SBP/FF consisted of 555 g unmolassed beet pulp, 314 g extracted rice bran, 56 g fat prills and 75 g soya-bean meal per kg. The factorial combination of the two supplements (Ba and SBP/FF) given at two levels, 6 kg DM (L) or 12 kg DM (H), provided the four treatments imposed over weeks 3 to 10 of lactation on 40 British Friesian cows. During weeks 12 to 20 of lactation (post-experiment period) the cows were given an equal mixture of the two concentrates at 9 kg DM per day.

Supplement Ba contained less ash (31 v. 94 g/kg), acid-detergent fibre (68 v. 218 g/kg) and fat (29 v. 77 g/kg) but more starch (558 v. 89 g/kg) and digestible organic matter in the dry matter in vitro (DOMD) (781 v. 627 g/kg) than SBP/FF. The concentration of total nitrogen (N) was similar at 25·6 g/kg. Silage had a DOMD of 643 g/kg, a pH of 3·8 and proportionately 0·82 of fermentation acids as lactic acid.

Apparent digestibility of gross energy was higher for Ba diets (0·748) than for SBP/FF (0·704). Cows given SBP/FF ate 0·9 kg more silage DM than those given Ba (P < 0·01) but there was no difference in digestible energy intake or in substitution rate (−0·37 kg silage DM per kg additional supplement DM). Increasing the amount of supplement increased milk yield by 3·9 kg/day (P < 0·001). Cows given SBP/FF yielded on average 1·6 kg more milk than those given Ba (P < 0·05). However, this increased output consisted almost entirely of lactose and water as a result of a high concentration of fat in the milk of cows given Ba at the low level (46·3 g/kg). Further, the concentration of protein was less with SBP/FF (28·0 g/kg) than with Ba (29·2 g/kg).

The effects of SBP/FF in early lactation were translated into a positive residual effect in mid lactation equivalent to the immediate effect. In contrast, raising yield by increasing the amount of supplement did not result in increased output subsequently. The results show that a supplement of fibre and fat despite having a lower digestibility than barley can produce more milk but a similar yield of fat and protein provided silage is offered ad libitum.

The effects of level of supplemental carbohydrate from turnips and level of rumen degradable nitrogen on bacterial cellulolysis, food intake, live-weight gain and diet digestibility were examined with 36 300-kg Friesian steers allocated, in a randomized-block design, to one of six dietary treatments: (i) sodium hydroxide treated straw plus a supplement of urea (30 g urea per kg straw dry matter (DM)) (uO); (ii) uO plus turnips (23·5 g DM per kg M0·75); (Hi) uO plus a high level of turnips (47 g DM per kg M0·75); (iv) (v) and (vi), the same three diets, but with additional urea (60 g urea per kg straw DM). In two separate experiments each lasting for 56 days, the turnip allowance was given in either two feeds, or one feed per day and the straw was given to appetite. Rumen fluid was obtained by stomach tube from all steers before feeding (07·30 h) and after feeding (11.00 h) on days 10 and 24 of each experiment.

Weight gains for all groups given straw plus turnips were high (> 0·90 kg/day). Increasing the quantity of turnips gave significantly increased DM intakes and weight gains but then turnips substituted for straw, and the proportion of straw consumed decreased from 0·8 to 0·6 of the dietary DM (P < 0·01) There were no significant interactions between frequency of feeding of turnips and level of urea on the variables food intake and weight gain. Fibre digestibility was not depressed by the addition of turnips to the diet. Rumen fluid pH decreased after the steers ate turnips but tended to remain above 6·7. There were no large changes in the total number of viable cellulolytic bacteria as a result of either addition of urea or turnips to the diet; counts remained in the order of 107 per ml. Steers consumed large quantities of sodium hydroxide treated straw; turnips were therefore only a small proportion of the overall DM intake with relatively little effect on bacterial cellulolysis.

Barley straw constitutes up to half of the dry-matter intake of Awassi sheep in areas of Syria where the rainfall is 200 to 350 mm. The genotype of barley planted could therefore, through the nutritive value of its straw, significantly affect flock production levels. Selection of suitable barley genotypes may have greater economic potential as a means of improving roughage feeding quality in these areas than chemical or physical processing.

The voluntary intake and digestibility of the unsupplemented straw of three genotypes of barley was evaluated with Awassi castrated male sheep. The voluntary organic-matter (OM) intakes of handharvested Beecher, Arabic Abied and ER/Apam straw were 22·2, 34·7 and 27·0 g/kg M0·75 per day and OM digestibility coefficients were 0·39, 0·44 and 0·42. The factors affecting voluntary intake and digestibility appeared to be the proportions of leaf and stem. Beecher straw had less leaf and more stem than the other two genotypes. The chemical composition and in vitro cellulase digestibility of the leaf indicated that it had a higher potential feeding value than stem.

ER/Apam appears to be an example of a genotype which under dry environmental conditions combines higher barley grain yields with more acceptable straw feeding value than several other genotypes evaluated.

The carcasses of 15 ram and 15 ewe lambs of the Dorset Down breed, weight range 12 to 23 kg, were separated into individual muscles, bones and fat depots.

At the same carcass weight (16-8 kg) the ram lambs contained 41 g more muscle per kg, but there were few important differences between sexes in individual muscle weights; 65 of the 72 muscles differed in weight by less than 10 g.

The distribution of total muscle weight between eight anatomical groupings differed significantly between the sexes; ewes had proportionately more muscle in the proximal pelvic limb (8 g/kg) and less in the neck (7 g/kg) and distal thoracic limb (1 g/kg). Despite these small differences in muscle-weight distribution in higher-valued joints in favour of the ewe lambs, each of their joints contained less muscle than those of ram lambs.

In these lambs, reared under commercial conditions in the United Kingdom, there were no signs of gross morphological differences which could result in their disqualification for the Variable Premium of the European Economic Community Sheepmeat Regime. In particular the m. splenius cervicus was a very small proportion of total muscle in both sexes (1·5 and 2·5 g/kg for ewe and ram respectively).

Seventy-eight lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given a barley-fish meal diet containing 1-6 g magnesium and 5·9 g phosphorus per kg dry matter for 13 weeks. Urinary excretion of Mg and P was estimated from the ratio of Mg or P to creatinine in spot samples of urine. A relationship between creatinine excretion and live weight was obtained using total urine excretion from a sample of 20 lambs, two of each sex from each sire breed group. Good agreement was found between the actual and predicted urinary excretion of minerals by the 20 lambs on three occasions.

The effect of sire breed on urinary excretion of P was significant (P < 0·05) and the breed types ranked, in descending order of excretion rate, Texel, Blackface, East Friesland, Finnish Landrace and Suffolk, with a four-fold difference in excretion rate between Texel and Suffolk. This difference in urinary excretion of P was taken as evidence of breed differences in efficiency of absorption of dietary P.

Urinary excretion of Mg was correlated with the intake of Mg. The mean estimated efficiency of absorption of dietary Mg varied, over the three occasions, from 0·42 to 0·50 and from 0·39 to 0·45 for total collections and for spot samples of urine respectively. Individual variation in the estimated efficiency of absorption within sires was not significant whereas that between sires was significant (P < 0·05). Heritability was estimated to be 0·62 (s.e. 0·30).

The paper describes the results of the analysis of over 3000 records of Cambridge sheep kept on 11 farms over a 12-year period. The heritability of the number of lambs born per ewe increased from a low value for the 1-year-old ewes to a high value for the 3-year-old ewes; the multiple age value for 2-, 3- and 4-year-old ewes was 0·33 (s.e. 0-121). Heritability estimates for number of lambs surviving were lower, but showed the same trend of increasing values with increasing ewe age. This trend in heritability was also evident for the mean 50-day lamb weight, as a trait of the ewe, which had a multiple age value of 0·20 (s.e. 0·151). The estimates of heritability of various measures of early lamb mortality were relatively low. Date of first oestrus showed a variable heritability although the multiple age value was 0·42 (s.e. 0·149).

Prolificacy was strongly correlated with various measures of early lamb mortality although the correlation with the final number of lambs weaned was positive. Prolificacy was positively correlated with the ewe's mature weight and the ewe's date of first oestrus and the genetic correlation with mean 50-day lamb weight was slightly positive.

The effect of increases in prolificacy on numbers of lambs weaned was markedly curvilinear with maximum numbers of lambs weaned at an intermediate level of prolificacy.

Twenty-four indigenous goats suckling either single (male or female) or twin kids were traditionally reared during a 32-week lactation period. During the suckling period of 12 weeks, milk production was estimated at 7-day intervals. During the milking period the goats were hand-milked twice daily and their milk production was measured at 4-week intervals. Milk samples were analysed for fat, protein, lactose, ash and dry matter concentration and solids-not-fat and energy concentration were calculated. During lactation, the goats were weighed at regular intervals and their body-condition score assessed at each weighing.

Goats with twins produced more milk than did those with singles during the suckling period but not after weaning. Peak yield occurred between the 10th and 11th week of lactation. Yield declined rapidly after weaning at 12 weeks and then decreased gradually from 16 to 32 weeks. The sex of the single kids had no effect on lactation yield. Milk composition was not affected by the number or sex of the kids suckled. Fat, protein and ash concentration fell during the 1st month of lactation and thereafter showed a gradual rise. Lactose concentration fell gradually after the 2nd month. Both live weight and body condition of the goats increased continuously throughout lactation.

Data are provided from four Kenya ranches relating to seasonality of breeding, age at first parturition, parturition interval, sex ratio, gestation period and the early survival of young in one-humped camels. A total of 799 births was recorded. Births occurred throughout the year with no marked peak, there being no significant correlation of conception with rainfall. Age at first parturition (no. = 37) was 54·3 months. Parturition interval (no. = 460) was 20·2 months and was significantly affected by the random effects of the dam as well as by the fixed effects of the herd and the survival of the previous young. The sex ratio at birth was 1·06 males to 1·00 female. Gestation period was 377·1 days, and was not significantly affected by any of herd, month of conception, sex of young or age of animal. Abortions amounted to 11·6% of all births with the total of pre-weaning losses (including abortions) being 25·7%. Improving familiarity of the owners with the animals and better management could lead to considerable increases in performance.

The adhesion of Escherichia (E.) coli K88ac to epithelial cells of the small intestine was studied after slaughter in 564 crossbred pigs (Swedish Landrace x Swedish Yorkshire). E.coli K88ac adhered to epithelial cells obtained from different parts of the small intestine in 40·8% of the pigs studied. Performance data indicated that presence of the receptor resulted in poorer daily gain during the 1st weeks of life, but that it had a beneficial influence on daily lean growth during the fattening period (24 to 100 kg live weight).

Four diets were formulated from cereals, animal and vegetable protein supplements and tallow, to contain digestible energy (DE) concentrations of 14·1 or 17·1 MJ/kg and crude protein concentrations of 12·7 or 17·0 g/MJ DE in a 2 X 2 factorial design. In each of two experiments, pigs were weaned and allocated to dietary treatments when 21 days old and were fed twice daily to appetite. In experiment 1, six replicates of four male littermates were used. They were individually fed in metabolism cages and continuous energy and nitrogen (N) balances were made from 28 to 63 days of age. In experiment 2, three male and three female pigs were slaughtered at weaning to determine initial body composition, and three replicates of four littermates of each sex were allocated to the dietary treatments. The latter were fed in treatment groups in flat-deck pens and slaughtered at 63 days of age.

In experiment 1, increased energy concentration reduced food intake only slightly and improved liveweight gain and food: gain ratio; higher protein concentration increased gains only at lower energy concentration. Daily N balance improved with increased energy and protein concentration but the response to protein was greater with the low energy diet. Dietary energy was efficiently utilized even with 163 g tallow per kg diet. From 63 days of age until slaughter at 60 kg all pigs were given the same grower diet to appetite. Performance was not affected by previous treatments.

In experiment 2, food intakes were higher than in experiment 1 and tended to be reduced to a greater extent with the higher energy concentration; live-weight gains were similar for all treatments and food: gain ratio tended to improve in response to higher energy and protein concentrations. Dietary energy level had no effect on carcass fat content but the higher protein level reduced fat deposition. N retention tended to be lower for the low energy, low protein diet compared with the other three diets. Dietary effects on the amino-acid composition of the carcass were small. Carcass amino-acid ratios at 3 and 9 weeks were similar to published values and there was a tendency for higher amino-acid concentrations (g/16 g N) at 9 weeks than at 3 weeks.

Female reproductive performance over four parities was studied for lines of mice selected for one three criteria: appetite (A), total lean mass (P), or proportion of fat (F). Female mice were first bred 8 weeks of age, and thereafter at intervals of about 7 weeks until fourth parity when they were dissected in late pregnancy to measure components of litter size.

The high A lines had higher litter sizes at the first three parities and higher ovulation rates, numbers of implantation sites and live foetuses at the fourth parity than the low A lines. The high P lines were also higher than the low P lines for each of these traits. In contrast, litter sizes and ovulation rates differed little between the high and low F lines. Fitting body weight as a covariate removed the high-low differences in ovulation rate and litter size between the P lines, but not all the differences between the A lines.

Pre-implantation survival at the fourth parity was slightly lower in the high than in low A and in high than in low P lines. Differences in post-implantation survival were very small. No component of prenatal survival differed substantially at fourth parity between the high and low F lines.

Differences in fertility at each parity and the percentages of females surviving to the end of the study were small. At each litter, dams of the high A lines produced heavier total weights of litters at 12 and 21 days than dams of the low A lines and the corresponding high-low differences in the P lines were larger. There were only small differences in these traits between the F lines. When litter size, fertility and survival were summed over parities, the average total number of young produced per female was substantially higher in the high than in the low A lines (5·0 young born alive or dead) and the P lines (7·2), but the high-low difference was small in the F lines (2-0). For all lines, litter size at first parity gave a reliable indication of reproductive rate during a major portion of the reproductive lifespan.

It is shown that a commonly used method of calculating cumulative selection differentials in experiments where generations overlap is biased, and consequently leads to biased estimates of realized heritability. In one example, the heritability was underestimated by about one-fifth. Since genetic variation in a given progeny crop may be increased by genetic differences between parental age groups, realized heritability estimated by regression may not agree with base population estimates. An alternative form of analysis is proposed to allow for this effect.

Dried molassed sugar-beet pulp in Great Britain has for many years contained about 400 g molasses per kg dry matter (DM). Whilst this high concentration of molasses might help to maximize palatability, in many places outside Great Britain considerably lower amounts of molasses (100 to 300 g/kg) are normally added to sugar beet. The relative costs depend on year-to-year fluctuations.

Zeranol is an anabolic agent with oestrogenic actions commonly used in fattening beef cattle. This experiment was designed to determine the effects of zeranol administration on oestrous cycle lengths, plasma progesterone concentrations and the exhibition of oestrus in mature cows. Administration of 36-mg zeranol implants during the early, middle or later portion of the oestrous cycle did not alter the length or persistence of oestrous cycles, nor were progesterone profiles different from those observed in untreated cows. Some cows that received zeranol exhibited a prolonged oestrus. The regularity of oestrous cycles in cows treated with zeranol indicates that it may be possible to utilize zeranol as an anabolic and lactopoetic agent in post-partum beef cows.

Progesterone (6 mg) was injected intravenously into cows with mild (no. = 6) and severe (no. = 5) fatty infiltration of the liver. Clearance rates of progesterone from blood were similar in both groups of cows.

Thirty-six piglets were used to investigate the effect of six concentrations of dietary protein ranging from 155 to 235 g/kg, and corresponding dietary lysine concentrations from 10·1 to 15·4 g/kg, on the performance of pigs weaned at 28 days of age and growing between 7·5 and 20 kg live weight. Voluntary food intake was not significantly affected by dietary protein, and growth rate increased with increase in dietary protein and lysine up to 167 and 10·9 g/kg respectively (0·75 g lysine per MJ digestible energy (DE)). Food: gain ratio improved significantly with each increase in dietary protein and lysine up to 177 and 11·6 g/kg (0·79 g lysine per MJ DE) respectively.

Dhanoa and Le Du (Animal Production 1982, 34: 243–247) proposed a model in which the milk yield in a particular week is described by a weighted average of a straight-line target yield and the yield in the preceding week. It is demonstrated that the weight parameter × in this model is partially determined by the time from calving to peak yield and hence does not represent correlation between successive yields satisfactorily.