Mean daily milk yield, fat concentration and protein concentration in the milk of 579 303 British Friesian, 6 608 Shorthorn, 27 374 Ayrshire, 19 529 Jersey and 19 760 Guernsey cattle were recorded monthly from August 1978 to July 1979 inclusive, and classified by breed, parity, stage of lactation, and five geographical areas according to the location of the herd. Parameters of the function Y(n) = anbecn were estimated for each breed/parity/area group for yield, fat concentration and protein concentration (b and c describe the shape of the curve, a is a scalar, n the week of lactation and e the base of natural logarithms). Systematic deviations from the function were associated with the season of production, reflecting the spring and summer flush of milk yield. Fat and protein concentrations also exhibited seasonal variations from the underlying curve. After correction for the seasonal fluctuation in production, there was no variation in total yield, fat concentration or protein concentration associated with the month of calving.

To assess the variability of hormone values obtained from calves at an early age, plasma concentrations of prolactin, growth hormone, insulin and thyroxine were measured in blood samples taken twice-weekly from seven heifers maintained under commercial conditions during their first 110 days of life. With the possible exception of thyroxine, there was considerable variation in the concentration of each hormone in each animal throughout the period of sampling, thus indicating that twice-weekly sampling was inadequate for investigating differences in hormonal concentrations between cattle of different production potential. Although there were trends in the pattern of plasma hormone concentrations as the calves progressed from the pre-ruminant to ruminant states, few of the changes during the pre-weaning, weaning and post-weaning periods were consistent between animals.

Five groups of six Hereford × Friesian steers, approximately 1 year old and weighing 363 kg at implantation, were individually fed according to body weight and slaughtered 100 days after implantation. Group 1 was sham-implanted subcutaneously in the ear. Group 2 was implanted with 20 mg of the steroid oestradiol-17β group 3 with 140mg of the steroid trenbolone acetate; group 4 with oestradiol-17β in one ear and trenbolone acetate in the other; and group 5 with oestradiol-17β and trenbolone acetate as a single implant in one ear.

Groups 1 to 5 had mean overall live-weight gains (±s.e.) of 0·79, 0·88, 0·89, 0·98 and 1 15±0·067kg/day; mean feed conversion ratios of 9·30, 8·78, 8·45, 8·13 and 6·92 + 0·61; and mean cold carcass weights of 236, 246, 250, 252 and 257 ± 6.4kg, respectively. Oestradiol-17/? reduced omental (P <0·05) and kidney (P <001) fat. The two steroids appeared to produce independent and additive effects except when used together as a single combined implant (group 5), when the effect on live-weight gain was more prolonged. The mean concentrations of oestradiol-17/i in plasma in groups 2, 4 and 5 were greater than in the control group at 28, 28 and 91 days after implantation respectively (P < 0·001). Trenbolone acetate was present in the plasma in groups 3, 4 and 5 throughout the experimental period.

A single intra-muscular injection of either 6mg or 12 mg Dexamethasone on day 142 of gestation resulted in a high degree of synchrony in the time of lambing compared with untreated controls, with no increase in lambing difficulty or perinatal mortality. Birth weight and growth rate of lambs born to treated ewes were not significantly different from those of untreated control ewes.

A single intra-muscular injection of 12 mg Dexamethasone on day 125 of gestation resulted in abortion in nearly half of the ewes, and their lambs were either stillborn or died soon after birth.

These data demonstrate the need to know precise mating dates if parturition is to be induced in this way.

Three groups of winter-housed Friesian cows were fed according to maintenance and production requirements on dairy cake and poor quality hay for 5 weeks (5 cows), 4 weeks (4 cows) or 2 weeks (3 cows). They were then treated as one group with two injections of 500 μg cloprostenol 11 days apart to synchronize oestrus, followed by insemination 72 and 96 h after the second treatment.

Blood samples were taken for β-carotene estimation 1 day before the first cloprostenol injection, 3 days before the second injection, and the day after the second insemination. Conception was confirmed by rectal examination. Haematological parameters and metabolic profiles for all 12 cows were in the normal range and condition scores showed no correlation with time of conception. However, plasma β-carotene levels declined rapidly and uniformly between the three sample points for all cows. The individual animal means were directly correlated with length of time on the described diet and with time of conception (P<005). A theory of β-carotene involvement in ovarian function is advanced.

Forty-five crossbred cattle were scanned by ultrasonics at three sites on the body and were ‘condition scored’ before slaughter and subsequent dissection of a sample rib joint.

Ultrasonic measurements gave a better indicator of fat content than did ‘condition score’. The third lumbar vertebra site on the body gave a better prediction of sample joint composition than did the 10th or 13th rib.

The mean ultrasonic measurement of fat depth at the three sites did not improve the prediction of composition as compared with the value obtained at the third lumbar vertebra. The overall standard deviation for total fat concentration was 42·1 g/kg and for lean concentration was 35·4 g/kg. Area of fat at the third lumbar vertebra was the best single indicator of fat concentration and lean concentration in the sample joint, with residual standard deviations of 25·1 and 23·1 g/kg respectively. A combination of fat measurements at the 3rd lumbar position was the best overall predictor (residual standard deviation: 23·8g fat and 23·0g lean per kg).

In the first phase of the Meat and Livestock Commission's beef breed evaluation programme, cattle were slaughtered at a fixed subcutaneous fat percentage in carcass. Slaughter point was determined from fat areas measured over the m. longissimus at the 10th and 13th ribs by the Scanogram ultrasonic machine.

The accuracy of the slaughter procedure was examined using data for 1367 cattle from the first 3 years of the programme. Subcutaneous fat percentage predicted from the ultrasonic measurements was compared with the percentage estimated by visual assessment of carcass fat cover. The s.d. of the difference between the two was 1·65.

Data for a subset of 313 cattle were used to examine the relationships between the ultrasonically measured fat areas and actual subcutaneous fat percentage obtained by dissection. The residual s.d. for the prediction of subcutaneous fat within breed and production system was 1-18.

The level of accuracy achieved was considered to be satisfactory within the context of the beef breed evaluation programme.

Field data were analysed in an attempt to identify factors contributing to differences between haemoglobin types n i the proportion of ewes lambing per ewe exposed to the ram in flocks grazing oestrogenic pastures. The number of ewes mated and the proportion of ewes failing to conceive to first service per ewe exposed to the ram were analysed. Neither was found to significantly differ between matings of different haemoglobin type. It is concluded that differences in reproductive performance between haemoglobin types could possibly result from differences in embryo survival.

An alternative form, y = Anmce−cn, of the lactation model of Wood, y = Anbe−cn, is suggested. The new parameter, m, is the time required to achieve maximum milk yield. The correlations between non-linear parameters are reduced.

Sixteen pork carcasses were purchased from those exhibited in Class 146 at the Royal Smithfield Show 1978 (i.e. pork carcasses of 48 to 61kg dead weight, age <5 months). Eight had thinner backfat than the average for the class (‘very lean’ group with 6 mm fat over m. longissimus at the last rib and estimated lean content in side of 63%), while eight had thicker backfat than the average (‘lean’ group with 12 mm fat over m. longissimus at the last rib and estimated lean content in side of 57%). Both groups were leaner than the national average. The carcasses were returned to the Meat Research Institute for eating quality assessments. Muscle quality was similar in both groups. Toughness (assessed instrumentally), tenderness and flavour (assessed by taste panellists) were also similar. Juiciness was lower in the ‘very lean’ group but was not matched by higher cooking losses and the difference was considered to be relatively unimportant. In conclusion, the eating quality of pork is maintained at very low values of carcass fatness.

The rate of heat transfer from a model animal, covered with one of three animal pelts, was measured when the pelts were dry and when they were exposed to a fine spray of water. Wetting of the pelts increased heat transfer by 192, 114 and 15W/m2 respectively for the hairless skin, the skin with calf's hair coat (5 to 10 mm) and the skin with the lamb's fleece (60 mm). These results demonstrate the considerable protection against the thermal effects of wetting which is provided by animal coats, particularly if these are relatively deep.

The twinning rate of Finn × Awassi ewes in a breeding management system which included three breeding periods a year, namely, June, September and December-January, was studied in animals mated at their natural or induced oestrus.

A similar number of lambs per ewe lambing was obtained from the ewes mated either at the induced oestrus in June or September, or at their natural oestrus in December. A significant decrease was found in the twinning rate of the ewes mated in January after hormone treatment. The conception rate was highest in the ewes mated in December-January.

The elements of prolificacy have been analysed for the D'man sheep, a prolific Moroccan breed, by laparotomy on 38 animals. The average ovulation rate was 2·50 (s.e.0·45); a slight difference was observed between nulliparous and multiparous ewes due to high simultaneous activity by both ovaries in the latter group. Embryonic survival (42% overall) was 94% (87 to 100%) for multiparous and 44% (36 to 52%) for the nulliparous ewes at one ovulation, decreasing with increasing numbers of corpora lutea. The average litter size showed an optimum at four ovulations.

Whole, moist barley treated with ammonia (A), whole, untreated barley (WU) and ground barley (G) were fed with hay and a little high protein, mixed concentrate. Digestibilities of dry matter, organic matter and crude fibre, assessed with young adult female sheep, were highest in diet A and lowest in diet G. The digestibilities of dry matter and crude fibre were also higher in diet WU than in diet G. Digestibility coefficients for dry matter and organic matter in barley, calculated by difference, appeared higher in A and in WU than in G. Young female sheep fed on the above diets from the age of 7 to 11 months ate more hay and gained more weight on A than on G; again diet WU was intermediate. Differences also occurred between the three groups as regards volatile fatty acids in the rumen fluid. Sheep on A or WU had a higher pH in the rumen fluid than those on G. Finally, sheep on A gave birth to more offspring than those on WU or G. All these differences were significant.

ANIMAL PRODUCTION, Volume 31, Part 2, pp. 191-199

PIG COURTSHIP BEHAVIOUR: PHEROMONAL PROPERTY OF ANDROSTENE STEROIDS IN MALE SUBMAXILLARY SECRETION

G. C. Perry, R. L. S. Patterson, H. J. H. MacFie AND C. G. Stinson

On page 193, Fig. 2, the legends on the figure have been reversed:

upper legend should read 'Gilt receptive to boar';

lower legend should read 'Gilt non-receptive to boar