When sows and their litters were grouped 21 days after farrowing, the introduction of a boar 4 days later stimulated lactational oestrus in only 2 of the 21 sows (seven groups of three sows and litters) exposed to the boar, while none of the sows in the control groups showed lactational oestrus. The boar presence in lactation affected the subsequent weaning to first service interval. This interval was 228 days for the sows exposed to a boar and 10·0 days for the control groups, the difference approaching significance (0·05<P<0·10). None of the sows in the boar treatment groups had a weaning to oestrus interval exceeding 9 days.

Forty Large White × (Landrace × Large White) gilts were allocated by litter to one of four treatments, such that one gilt from each of 10 litters was on each treatment. The treatments were: (i) 30-min daily boar exposure; (ii) 30-min daily pen change; (iii) 30-min daily pen change, plus exposure to boar urinary pheromone; and (iv) a control, subject to no stimulation.

The treatments commenced at a gilt age of 165 days and continued either until puberty was detected or a cutoff age of 250 days was reached. Analysis revealed no significant differences between any groups for age at puberty or ovulation rate (determined at slaughter following the second oestrus).

Fifty-one cattle were allocated into five groups varying in time of starvation (0, 17, 24, 41 and 48 h). Most of the loss in fasted live weight, stomach and intestinal contents occurred within 24 h. Weights of water, dry matter and potassium present in the stomach showed a significant decrease in the first 24 h, although the percentage of water in the stomach contents rose slowly over a 48-h period. It is suggested that cattle from pasture need be starved for no more than 24 h to minimize the effect of gut fill for body composition studies.

Growth and carcass traits were measured in pigs grown from 25 to 90 kg live weight on barley stored and prepared in different ways. Some of the barley was prepared in the conventional manner by drying to a moisture concentration of 140g/kg before hammer-milling. The remainder of the barley was rolled after treating batches, containing 140, 180 and 240 g moisture per kg, with propionic acid. A total of 128 pigs was used at three centres.

There were no differences between the centres and no differences in the performance and carcass measurements of pigs given acid-treated and rolled, or untreated and milled barley, despite differences in physical form between the rolled and milled samples. When the intake of dry matter was equalized there was no apparent effect on the pigs of acid treatment of barley containing different amounts of moisture.

Backfat from each of 25 littermate boars, barrows and gilts, which were crosses of the Large White and British Landrace breeds slaughtered at approximately 90 kg live weight, was analysed for fatty acid composition. Fat from boars had a significantly higher proportion of total unsaturated fatty acids (61·6%) compared with barrows (60·2%), This sex difference was due to a lower palmitic acid (16:0) content and higher linoleic (18:2) and linolenic (18:3) fatty acid levels in backfat of boars. Gilts were intermediate to boars and barrows in the degree of unsaturation of backfat.

A procedure has recently been developed for estimating economic values which employs a profit function implying that animals with mean values for variates in the profit function give the most profit. However, the proposed index selects extreme animals, a paradox which is explained by showing that the index is appropriate for only part of the profit function. More appropriate selection indices are developed and illustrated graphically.

The incidence of oestrus in 603 Hereford heifers with a mean age of 545 days (range 515 to 575) was related to live weight (range 130 to 376 kg). Observations were ranked in order of ascending live weight and the percentage of heifers showing oestrus was calculated for consecutive 10 kg increments in live weight from 130 to 380 kg. The percentage showing oestrus was subjected to the probit transformation (Y, probit units) and was then related to live weight (X, kg):

It was predicted that 50% of the heifers showed oestrus at 231 ± 1 kg, and that 5% and 95% showed oestrus at 187 and 280 kg respectively.

ANIMAL PRODUCTION, Volume 30, Part 3, pp. 389-394

THE EFFECT OF TRENBOLONE ON ACETATE GROWTH, BLOOD HORMONES AND METABOLITES, AND NITROGEN BALANCE OF BEEF HEIFERS

H. Galbraith

On page 389, title of paper should read:

THE EFFECT OF TRENBOLONE ACETATE ON GROWTH, BLOOD HORMONES AND METABOLITES, AND NITROGEN BALANCE