The diurnal cycle of chromium excretion was estimated over the last 24 h of a 13-day period in which nine single- and nine double-suckled cows were dosed twice daily (10.00 and 16.00 h) with shredded Cr2O3 paper. All faecal passages voided were sampled and analysed for chromium. Rectal samples were also taken at 10.00 and 16.00 h during this period. Sources of variation in the patterns of excretion that could be attributed to cow live weight, daily milk yield or total weight of the calf or calves being reared were also investigated.

Mean faecal Cr concentrations followed a cyclic pattern which was significantly described by a sinusoidal equation.

The estimated fundamental period (0·1334 rad/h) did not differ significantly from the theoretical value (2π/48 = 0·1309 rad/h). Fitting the model for each cow explained from 0·61 to 0·99 of the variation in faecal Cr concentration. Differences between suckling treatments in predicted faecal Cr content at discrete 2-h intervals over the 24-h period were not significant. Equations for heavier cows had lower constant terms, consistent with lower faecal Cr contents expected as a consequence of higher intakes. Differences in cow milk production and total calf live weight being reared were related to the pattern of Cr excretion (P < 0·05) but the reasons for these effects were not readily apparent. Mean Cr concentration in rectal samples was significantly correlated (r = 0·916) with mean 24-h faecal Cr content predicted from the model.

One hundred and sixty Friesian heifers were divided into four groups on the basis of live weight and age. All four groups received a production ration of 15 kg maize silage, 0·5 kg straw and either 1·5 or 0·5 kg concentrates according to their mean live weight. This ration supplied only 38 mg (3-carotene per animal per day.

Two groups of heifers received a daily supplement of 300 mg β-carotene per head. The other two groups acted as controls and received a daily supplement of 60 000 i.u. vitamin A (18 mg retinol). All heifers received an adequate supply of vitamin A.

Supplementation with 300 mg β-carotene per day significantly increased mean plasma concentrations from 3·52 mg/1 at housing to 5·58 mg/1 at first insemination (P < 0·001). Mean plasma concentrations in the control heifers declined from 3·31 mg/1 at housing to 2·42 mg/1 at first insemination and to 2·13 mg/1 50 days later. Of the 40 smaller controls half had concentrations below 1·00 mg/1 50 days after first insemination.

Supplementation with β-carotene did not affect reproductive performance or growth rate in heifers receiving a ration based upon maize silage.

In two experiments cows with access to self-feed grass silage were offered concentrates either twice daily in the milking parlour at a fixed level (controls) or in addition given free-access to a concentrate dispenser sited in the self-feed area (dispenser). A time-lapse mechanism on the dispenser limited successive 1 kg feeds to a minimum of 10 min in experiment 1 and 5 min in experiment 2. The ‘dispenser’ cows had significantly greater total concentrate intakes than had the controls (10·4 v. 7·1 kg/day in experiment 1, 13·4 v. 7·3 kg/day in experiment 2), but there was a large variation in intake between individuals. Access to the dispenser increased milk yields only slightly, reduced milk fat concentration and increased milk protein concentration and live-weight gain. Following turnout to grass in the spring, there was evidence that the cows that had been on the dispenser treatment showed a faster rate of decline in milk yield than did the controls, and this was supported by lower lactation yields in the dispenser group.

Ten crossbred (Karan Swiss) cows were induced to calve about 1 month prior to expected term using either 25 mg dexamethasone alone (Group B) or 25 mg dexamethasone in combination with 25 mg vetoestrol (Group C). Another five animals served as controls (Group A). The average time interval from injection to calving was not significantly influenced by the two treatments used, and was 52·2 ± 4·07 h and 49·0 ± 1·55 h for groups B and C respectively. The mean gestation lengths for animals in groups A, B and C were 283·60 ± 2·77, 255·20 ± 1·93 and 255·20 ± 2·3 days respectively. The calves born from cows induced to calve early were significantly lighter at birth compared to controls (P < 0·05). The average live-weight gain over the first 12 weeks among calves was not significantly influenced by treatment averaging 2·58 ± 0·07, 2·81 ± 0·16 and 2·20 ± 0·16 kg/week for groups A, B and C respectively. Foetal membranes had not been voided by 24 h in the animals induced to calve early and hence required manual intervention. The length of the service period, number of services per conception and the milk yield of the cows induced to calve was not significantly different from their previous records (P > 0·05).

Grass silage was offered ad libitum to twelve 4-month-old British Friesian steers in an incomplete Latin-square experiment. The silage was given either alone or supplemented isonitrogenously with 50 g fish meal or 63 g groundnut meal per kg silage dry matter.

Both protein supplements significantly increased the intakes of dry matter and organic matter by an amount about equivalent to the (calculated) contribution of the supplement (P < 0·05); they also increased the intakes of digestible organic matter and nitrogen (P < 0·001) but with no significant difference between supplements. Protein supplementation had no effect on the intake of indigestible organic matter.

The digestibility coefficients of dry matter and of organic matter were significantly increased by supplementation (P < 0·05) as were the digestibility coefficients of gross energy and of nitrogen (P < 0·001). Nitrogen retention was also increased from 1·4 to 8·2 g/day (P < 0·001), with no significant difference between supplements.

Eating qualities of beef from entire and castrate male animals were compared using taste panel, objective texture and chemical measurements and a consumer panel. The eating quality of roast m. longissimus dorsi, casseroled m. supraspinatus, minced m. gastrocnemius and grilled m. psoas major from bull beef, slaughtered at 400 days was different (by triangular tests) from that of twin steer beef. The differences (attributed to flavour, texture and juiciness) were not substantiated using descriptive scaling tests when the only significant difference was that roast m. longissimus dorsi from bulls was slightly drier than that from steers. Tenderness, juiciness and flavour of roast m. longissimus dorsi from 71 bulls and 84 steers raised semi-intensively to 390 to 510 kg and slaughtered commercially were assessed using descriptive category scales and the instrumental toughness values. There was no significant difference in organoleptic qualities and the distributions of tenderness and juiciness within these populations were similar. Bull beef contained more connective tissue and had less intramuscular fat. Fatness was poorly related to tenderness (r = 0·3) and unrelated to juiciness or flavour. A consumer panel of 606 assessors showed that bull beef was not as pale as steer beef and found no difference in fatness of the cuts, flavour or juiciness. Fore-rib roasts of bull beef were marginally less tender than steer fore rib.

The calving dates of spring-calving cows in New Zealand Angus and Hereford herds, taken from 350 and 240 herd-years respectively, and the intercalving intervals (CI) of cows in 95 Angus and 73 Hereford herds have been summarized. The relationships of each CI with the calving date which initiated it were also analysed. Results for each breed were analysed taking account of district, herd, year and cow age (in years), a total of 35 890 Angus and 22 397 Hereford records being used. The first-calving date (FCD) was identified for each herd-year, and 0·82 of Angus and 0·75 of Hereford cows were recorded as calving within 60 days of the FCD. On a herd basis, proportionately only 0·27 of Angus and 0·15 of Hereford herds had calving spreads of 80 days or less (defined as the time from the FCD to the last calving date). With barren years ignored, the CIs of cows averaged 370 days (Angus) and 368 days (Hereford). Two-year-old cows had on average a CI of 12 (Angus) or 7 days (Hereford) longer in 1974-75 than older cows, and the differences were both 12 days in 1975-76. Regression analyses showed that, on average, the later the calving date within a herd-year and age group, the shorter the subsequent CI. For cows calving early in the first year, the CI increased by 7 days for Angus and 5·4 days for Herefords for each 10 days before the mean calving date for the breed. There were significant effects of district and cow age on the regression estimates. The overall regressions were not consistent with those derived from British beef industry data.

Data records from 556 beef heifers which included age at first oestrus (AFE) were used to test the null hypotheses: 1) daylength at birth is not a determinant of AFE in beef females; and 2) there is not an association between the day on which first oestrus occurred and the lunar phase.

The effect of daylength at birth was measured by forming a variable, X1 where X1 = sine (X1′ 360/365·25)°, and including it among the set of variables in a multiple linear regression equation with AFE as the dependent variable. The resultant estimated coefficient on X1 was -3·617 with a standard error of 21·32, and led to the conclusion that daylength at birth was not a factor which affected AFE in this group of beef heifers.

The lunar phase hypothesis was tested by forming the frequency distribution of the 556 observations of first oestrus over the 30-day lunar cycie. The chi-square test was applied with the theoretical (hypothesized) distribution being the uniform distribution. The value of the test statistic was such that the null hypothesis would not be rejected even with an a value approaching 0·50. Additionally, coefficients of autocorrelation calculated for lag phases of 7, 14 and 21 days were quite small. Thus it was concluded that the occurrence of first oestrus was uniformly distributed over the lunar cycle.

Twenty-four British Friesian dairy cows in early lactation were used in a change-over design experiment with three periods, each of 4 weeks duration. The aim of the experiment was to assess the effects of both the type of concentrate and the level of concentrate supplementation on the utilization of grass silage for milk production. Four treatments consisted of offering 10 kg/day of either a barley (10B) or a sugar beet pulp-based concentrate (10S), each concentrate being offered at two crude protein concentrations of 175 (low) and 245 (high) g/kg dry matter. In a further two treatments the barley-based concentrates containing the low and high protein concentrations were offered at 7 kg/day (7B). All concentrates were offered in addition to the cows having ad libitum access to grass silage containing a dry-matter concentration of 213 g/kg and a digestible organic matter concentration of 668 g/kg dry matter.

Silage dry-matter intakes (kg/day) for cows given the low- and high-protein concentrates respectively were: 9·06 and 9·28 for the 7B treatments; 8·21 and 8·33 for the 10B treatments; and 8·04 and 7·97 for the 10S treatments (pooled s.e. 0·11). Fat-corrected milk yields for cows given the low- and high-protein concentrates respectively were: 24·0 and 24·1 for the 7B treatments; 25·9 and 27·0 for the 10B treatments; and 25·7 and 26·2 for the 10S treatments (pooled s.e. 0·57).

The higher level of concentrate feeding significantly increased milk yield (P < 0·001) whereas neither energy source nor protein concentration in the concentrates had a significant effect on milk yield (P > 0·05). There was a trend towards a greater response to increased protein concentration at the higher level of feeding.

An experiment was conducted to study the possibility of using marker concentration in faeces to estimate rumen outflow of Cr-treated protein supplements and the liquid phase (PEG). There were no significant differences in the outflow of each marker from the rumen when determined directly from rumen or indirectly from faeces, suggesting that faeces could be used to measure the outflow from the rumen without the need for surgical preparation of the animals. The outflow rate of the liquid phase was considerably faster than Cr-treated protein supplements.

The performance of predominantly Suffolk-sired lambs from Border Leicester (BL), Bluefaced Leicester (BFL) and ABRO Damline (DL) crossbred ewes was compared on 18 commercial and college farms throughout England and Wales. The comparison took place over the 5-year period 1977 to 1981 and was the second stage in a comparative study on the productivity of the crossbred ewes. A total of 1277 crossbred ewes were involved with data on up to 3 years lambings per ewe, giving a total of 3522 mating records and 4864 lamb records.

The BFL lambs were heaviest and the DL lambs were lightest. The DL lambs had the lowest survival rates, and the BFL lambs the highest. The BFL lambs were slaughtered earlier (12 days) and at heavier weights (1·4 kg) than the DL and BL lambs, and had slightly heavier carcasses. The DL and BFL carcasses had better MLC carcass classifications than the BL, resulting in an advantage of 4 p/kg of carcass.

In productivity per ewe, the BFL litters had the highest slaughter and carcass weights and the highest income per litter, with the DL litters intermediate. An attempt was made to express productivity per unit of sheep weight maintained, taking account of ewe weight, litter size and the lamb slaughter date. On this index, the DL were marginally superior to the BFL, and both were superior to the BL.

In two experiments, ewes carrying two, three or four foetuses were offered restricted amounts of concentrates in the range 0 to 1050 g fresh weight per day and hay ad libitum from day 105 of pregnancy until lambing. The replacement rates of concentrates for forage were similar for both Teeswater × Dalesbred and Finnish Landrace × Dorset Horn ewes in experiment 1 (mean −0·63) when the ewes were offered hay which had an organic matter digestibility (OMD) in vitro of 0·56. There was no significant effect of number of foetuses carried on hay intake. As pregnancy progressed, hay intake increased slightly when hay alone was given and decreased at the higher levels of concentrates.

In experiment 2, hay intake by Finnish Landrace × Dorset Horn ewes was significantly higher when hay of higher digestibility was offered (0·52, 0·69 and 0·84 OMD) and decreased when higher levels of concentrates were given. Ewes carrying two foetuses ate more than ewes with three or four foetuses particularly when hay was offered as the sole food. Generally, hay intake decreased as pregnancy progressed and this was more evident when concentrates were offered.

A predictive equation is given to enable hay intake to be derived from hay digestibility, concentrate level, ewe live weight, number of foetuses carried and week of pregnancy.

One hundred and sixty-four Scottish Blackface ewes from two different farm sources were brought into a uniform moderately-poor level of body condition by early November. Five groups of approximately 33 ewes were then fed different amounts of pelleted dried grass and hay on pasture to achieve either high (H) or live-weight maintenance (M) levels of intake for different durations and at different times in the 36 days prior to mating at a synchronized oestrus. One group of ewes was fed the M level throughout, two groups were fed the H level for 18 days either preceded or followed by 18 days of the M level and two groups were fed the H level for 27 days either preceded or followed by 9 days of the M level. After mating, all ewes were fed the M level until slaughtered on return to service or at 28 (± 8) days after mating for counts of corpora lutea and viable embryos relating to first mating.

The gain in body condition and live weight after 18 days of H feeding was about half that achieved after 27 days. Time of H feeding had no differential effect on gain in condition or live weight. H feeding increased ovulation rate only if fed immediately prior to mating. When a period of M feeding preceded mating, most of the advantage was lost, particularly with 18 days of M feeding after 18 days of H feeding. Embryo mortality measured as ova loss was not significantly affected by either the duration or time of H feeding, although there was a trend for loss to decrease with increasing duration. Potential lambing rate to first mating was therefore significantly increased by H feeding for 27 days even when followed by 9 days of M feeding prior to mating but was not significantly increased by H feeding for only 18 days even when fed immediately prior to mating.

Differences in response were obtained from the ewes from the two sources. H feeding only produced a significant improvement in reproductive performance when potential was high and this was partly related to greater size. In populations with low potential, the provision of H feeding in the pre-mating period is therefore of doubtful economic advantage.

Carcass composition and quality and eating quality of the m. longissimus dorsi (LD) were compared in 15 entire male (ram) and 15 female (ewe) pure bred Dorset Down lambs (carcass weight range 12 to 23 kg).

Rams grew 28 g/day faster than ewes, taking on average 2 weeks less to achieve 35 kg live weight. At the mean carcass weight of 16-8 kg, ram carcasses contained more lean (42 g/kg carcass weight) and bone (19 g/kg) and less fat (subcutaneous, 33 g/kg; intermuscular, 28 g/kg; perirenal-retroperitoneal, 14 g/kg) than ewe carcasses.

At the same level of fat cover in the commercially prepared side, ewe carcasses required more trimming of subcutaneous fat than rams. However, there was more intermuscular fat (which is not removed by conventional cutting) in the ewes; consequently their saleable meat contained 51 g/kg more fat and 37 g/kg less lean than that from rams.

The roast LD was invariably tender and the eating quality of LD from rams was as desirable as that from ewes, while overall eating quality compared favourably with that of animals studied previously. There was no evidence of an undesirable sexual odour or flavour in ram meat.

With early maturing breeds, which can be finished off grass, non-castration of entire males offers the opportunity of improving the efficiency of lean meat production whilst retaining good carcass and eating quality.

Five experiments, involving the hand milking of 53 farrowing sows, examined aspects of colostrum yield during and soon after farrowing. The initial and abundant yield of colostrum from a teat (averaging 6 to 10 g/min) declined after several minutes of continuous milking. Thereafter, most colostrum was released in discrete ejections, possibly caused by discrete releases of oxytocin. Colostrum ejections varied greatly in their yield and duration, and were sometimes associated with the birth of a piglet, sounds of other sows nursing, or other factors.

Teats varied greatly in their yield. During the initial minutes of milking, the most anterior teats gave, on average, 3 to 5 times more colostrum than the most posterior teats, with a nearly monotonic decline from front to rear. However, the difference between anterior and posterior teats disappeared after several minutes of continuous milking. Stimulation of the anterior teats appeared to cause the release of more colostrum than did either the stimulation of the posterior teats or no stimulation of the udder at all. A strong sucking stimulus, applied to several teats by a milking machine, elicited a large, prolonged release of colostrum.

The results suggest that (1) much of the colostrum received by newborn piglets is obtained in discrete ejections rather than in a continuous manner; (2) appropriate stimulation of the udder by the piglets may be important to elicit maximum colostrum yield; and (3) a high initial yield from anterior teats, coupled with a higher yield when anterior teats are stimulated, may help to explain the piglets' preference for anterior positions on the udder.

1. Forty entire male pigs between 7 and 28 days of age and forty entire male pigs between 28 and 56 days of age were fed ad libitum basal diets of wheat and lupins containing 2·4 and 1·9 g of methionine per kg respectively. These were supplemented with 0, 0·3, 0·6, 0·9 and 1·2 g of synthetic methionine per kg of diet.

2. The methionine required for maximum performance and nitrogen retention was 3·0 g/kg of dry matter between 7 and 28 days of age and 2·5 g/kg between 28 and 56 days of age. These values were equivalent to 1·14 and 1·19g/100g of dietary crude protein at the two ages. The cystine contents of the diets were 3·7 and 3·1 g/kg respectively.

3. The concentration of methionine in the blood plasma did not give a clear indication of methionine requirement.

Forty multiparous Large White × Landrace sows were randomly allocated to five treatment groups: (1) control (C) — no partial weaning, movement or boar contact, (2) partial weaning (PW) only — sow and litter separated for 12 h/day, (3) PW + boar contact (B) in the sow's pen (1 h/day), (4) PW + sow moved (M) to empty pen (1 h/day), (5) PW + sow moved to occupied boar pen (1 h/day). Treatments were imposed from day 10 post partum until weaning at day 35 (s.e. 1). All sows were generously fed throughout lactation (7 kg/day) and in the post-weaning period (3 kg/day). One sow (treatment 5) exhibited lactational oestrus and was mated on day 33 of lactation, while the remaining sows on treatments 2 to 5 had significantly reduced (P < 0·05) weaning to remating intervals relative to control sows (4·84 v. 6·63 days, respectively). Litter creep food intakes tended to be higher in PW litters than controls (512 v. 376 g/day; P > 0·05), whereas sow live-weight gains during lactation were significantly increased when PW was employed (+0·43 kg/day v. −0·13 kg/day for control sows; P < 0·001). Partial weaning significantly (P < 0·001) reduced litter weaning weights (74·8 v. 87·0 kg for controls). However, there were no significant treatment effects on individual piglet weaning weights, subsequent growth performance of the weaned litters, or the size of litter subsequently produced by the sows.

In heifers, plasma progesterone levels were low (<0·3μg/l) from the 59th to about the 15th day before puberty (defined as the day when oestrus was first detectable by the fern pattern of dried cervical mucus). Plasma oestradiol-17β levels varied randomly within the range 1 to 4 ng/l over the same period, but then showed three peaks of about 6, 9 and 4 ng/l, respectively 8 days before puberty, on the day of puberty and 4 days later. The pre-pubertal oestradiol-17p peak was followed by a short period of elevated progesterone levels. Whether this oestradiol-17β peak induced ovulation is uncertain; it is however clear that a corpus luteum of normal life-span was not formed. The oestradiol-17β peaks on the day of puberty and 4 days later, when progesterone levels were rising rapidly, were typical both in magnitude and duration of those occurring before and after ovulation in post-pubertal oestrous cycles.

The proportion of Holstein blood for each of 725 bulls progeny tested by the Milk Marketing Board, was obtained from a three generation pedigree. The bulls were grouped according to the proportion of Holstein blood and the means and standard deviations for their progeny tests for Beef Shape Score calculated. Only bulls with Beef Shape Scores based on an effective number of daughters of at least 20 were included. The mean Beef Shape Score decreased from 99·6 in pure Friesian bulls to 88·5 in pure Holsteins. Only four bulls within the pure or three-quarter (0·75) Holstein groups had a Beef Shape Score above the overall mean of 98·6 with the maximum being 102. The range of Beef Shape Scores for all bulls was 76 to 116.

The product moment correlations between Beef Shape Score and milk, fat and protein yields were −0·36, −0·35 and −0·32 respectively. These values were significantly different from zero (P < 0·01).

Sixty-three Large White ♂ × (Landrace ♂ × Large White ♀) ♀ gilts were allocated to one of three treatments as follows: (i) boar contact for 20 h/day; (ii) boar influence through a mesh pen division for 20 h/day; and (iii) control, which had no boar exposure.

The experiment started when gilts averaged 156 days of age, and continued until either puberty was detected or the age of 210 days was reached. Analysis revealed significant differences between groups for proportion of gilts reaching puberty (0·76, 0·38 and 0·19), the interval from stimulation to-puberty (10·4, 34·1 and 36·7 days) and age at puberty (167·9, 192·2 and 191·2 days) respectively.