Changes in the frequency of the poll gene and the effect of polledness on production were measured from 1970 to 1979 in four closed lines of crossbred cattle. The lines were Africander cross (AX), Braham cross (BX) and two Hereford × Shorthorn (HS lines, one selected for production (HSS) and one a control line (HSR).

Calves were classified as horned, polled or scurred. Except in the HSS line, horned males were more common than horned females. Horned HS bulls sired only horned calves when mated to horned cows but corresponding matings of AX and BX breeds produced some polled progeny. The incidence of scurs was highest in the AX line, lowest in the HS lines and higher in males than females. These observations are discussed in relation to existing models of inheritance of horn-type.

Prior to 1970 the frequencies of the poll gene declined from their initial values in the BX and HS lines and increased in the AX line. These changes were ascribed to random genetic drift. After 1970 the frequency of the poll gene remained stable in all lines.

No significant differences were observed between horned and polled cattle in live weight, fertility or mortality rates indicating that polledness had no detrimental effect on production in these lines.

Changes in progesterone levels in milk and in milk fat were measured by radioimmunoassay in nine crossbred cows for 40 days after insemination. On average, progesterone in milk was minimal: 1·10μg/l at the morning milking (M) and 1·63μg/l at the evening milking (E) on the day of oestrus; this increased to 15·72 μg/l at M and 22·8 μg/1 at E on day 13 after insemination, and thereafter declined to 0·99 μg/l at M and 1·12μg/l at E on the day that the next oestrous cycle commenced in non-pregnant cows. In pregnant animals the level was maintained, and fluctuated from 1505 to 19·60μg/l at M and 18·09 to 23·01 μ/1 at E up to 40 days of pregnancy.

The average progesterone concentration in milk fat was 18·9μg/l at M and 24·1 μl at E on the day of oestrus, and rose to a peak of 141·7μ/l at M and 153·8μg/1 at E on day 13 after insemination. It continued to increase and fluctuated between 160·6 and 195·8μg/l at M, and 161·1 and 225·6μg/l at E, in pregnant animals, but dropped to 12·0μg/1 at M and 16·7 μg/l at E on the day of the succeeding oestrus in those animals which failed to conceive. Progesterone concentration in milk and in milk fat was significantly higher in evening samples than in morning samples (P<0·05).

Mean daily milk yield, fat percentage and protein percentage were recorded monthly, from August 1978 to July 1979. for 579 303 British Friesian, 6 608 Shorthorn, 27 374 Ayrshire, 19 529 Jersey, and 19 760 Guernsey cattle and classified by breed, parity and stage of lactation. Parameters of the function y(n) = anb ecn were estimated for each breed/parity group for yield, fat percentage and yield, protein percentage and yield, and energy (MJ) output as milk (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). In the mature cows of each breed (parity 4 or more), the shape constants (b, c) for milk, fat and protein production in kg respectively were:

Generally, cows of all five breeds which calved in the winter produced about 4% more milk, fat and protein than average, and those that calved in the summer produced about 4% less. After allowing for that, and removing the effect of the calving pattern, a seasonal variation in production occurred to produce a peak in June 1979 nearly 12% above average for liquid milk, in July 1979 about 4% for fat and in June 1979 about 12% for protein production (not percentage). Trough month was January 1979 for all three characters: —8%; —4% and — 9% respectively.

A consideration of the theory of metabolizable energy suggested that the peak of energy output which occurred about week 4 of lactation in all breeds and parities, expressed as a fraction of the live weight of the animal, had a critical bearing on the need to mobilize body reserves.

Live weight, milk yield, fat, protein and lactose percentage of 236 cows and heifers of four breeds of dairy cattle were recorded at 2-week intervals, starting within a week after calving, during the winter and spring of 1972/73. Lactation curves of the form X(n) = Xnb ecn were fitted to each animal's records, where X, b, c are constants, e the base of natural logarithms and X(n) the value of the character at the nth 2-week interval. Correlations between the curves, and between deviations from the curves, showed that the production of milk, fat, protein and lactose was negatively correlated with live-weight change in the long term, but that deviations from the curves were not correlated. There were significant positive correlations between milk yield and size, and between potential compositional quality and size (the values of × in the model). Of the four breeds studied, Friesian, Ayrshire, Guernsey and Jersey, adult Friesian cows required less dietary energy per kg of total solids produced than any other group, according to the principles of the metabolizable energy system of calculating energy requirements. During the period of negative energy balance, an average 10% to 15% of energy output in the form of milk was derived from the mobilization of body reserves.

1. Ground forages were digested in vitro in rumen liquor supplemented with four concentrations of magnesium as MgSO4-7H2O (5, 20, 80, 320mg Mg/1) to determine the effects of magnesium on organic matter digestibility. A medium concentration of magnesium (generally 80 mg/1) resulted in optimum digestion although there was a large interaction between forage type and the response to magnesium.

2. Supplements of MgSO4-7H2O (2g Mg/day) increased the apparent digestibility of two types of hay fed to sheep, the difference being significant for poor quality hay (P<0·05).

3. The milk production of hypomagnesaemic cows given supplementary magnesium either orally, by rectal infusion, or by subcutaneous injection was compared. Plasma magnesium concentrations were increased to a similar and significant extent (P<0·01 ) but a significant increase in milk and fat production occurred only in the orally treated cows (P<0·05).

It was concluded that a dietary magnesium deficiency results in reduced rumen fermentation and hence poor production, as well as hypomagnesaemia. It was suggested that the effects on performance of other mineral deficiencies may also be mediated in part through depressions in rumen digestion.

Monensin increases propionic acid production in the rumen and improves the efficiency of feed conversion in fattening cattle. Trials carried out in the USA showed that 200 mg monensin/head per day was the optimum dose for increasing the rate of live-weight gain in beef cattle at pasture.

Twelve pasture trials, involving a total of 434 beef cattle, were carried out during 1976 and 1977 to assess the efficacy of monensin for grazing cattle under European conditions. Each trial compared a group given 200 mg monensin/head per day in 0·5 to 10 kg of carrier supplement with a negative control group, fed blank supplement. The average initial live-weight was 260 kg and the average trial duration was 119 days. Daily live-weight gains of the control and monensin-treated cattle averaged 0·786 and 0·893 kg/head per day respectively, an advantage of 107g/head per day or 13·7 % in favour of the monensin treatment (P<0·001). The growth-promoting effect of monensin showed no tendency to diminish with time.

Six production cycles, each of 212 days' duration, were completed with Rambouillet and Suffolk ewes. One group of each breed was maintained under natural light conditions (control) and three groups of each breed were under the influence of various light treatments applied regularly in a rhythmic fashion within each production cycle. Comparison of conception rates between production cycles, breeds, and treatments showed that only in production cycle 2 (mating in June) were the conceptions in control ewes of both breeds significantly lower than those in ewes on altered light treatments. The most meaningful result was the effect of light treatments on prolificacy. Treatment 3 (106 days with 16-h light per day and 106 days with 8-h light per day) gave significantly higher prolificacy than control and treatments 1 (106 days with 8-h light per day starting 65 days before mating) and 2 (42 days with 16-h light per day, then light reduction at 21 min/week for 160 days). Rambouillet and Suffolk control ewes produced annually 179 and 174 lambs per 100 ewes exposed to rams. Corresponding productions were 200 and 197 for treatment 1, 193 and 226 for treatment 2, and 223 and 242 for treatment 3.

The effects of different husbandry systems on production characters of 616 purebred and crossbred sheep are reported. The Cyprus Fat-tailed (L), Chios (C) and Awassi (A) breeds were evaluated under intensive, semi-intensive and extensive production systems. The performance of crossbred (C × L, A × L and A × C) Cyprus Fat-tailed and Awassi sheep was compared under extensive husbandry conditions. Ewes on the intensive systems produced more milk, fat and protein (P<0·01), but with somewhat lower fat and protein content than those on the extensive or semi-intensive systems. Chios and Awassi ewes were superior to Cyprus Fat-tailed ewes in nearly all traits (P<0·1), but inferior in terms of fat and protein content (P<0·1). Awassi × Chios crossbreds outyielded both purebred and crossbred sheep in terms of milk, fat and protein yield (P<0·1). Lactation number had a significant effect on milk traits. Maximum milk production was obtained at fourth lactation.

Sixty crossbred female and male castrate pigs were randomly allocated to five treatments in which 0, 20, 40, 60 and 80% of the ground maize in grower and finisher diets was replaced by triticale on an equal weight basis.

Pigs receiving the basal maize growing diet (0% tritcale) gained less than pigs fed the triticale diets (P<0·05). Pigs given the diets in which 20% of the maize was replaced by triticale gained significantly more than those given the other diets (P<0·05). Increasing replacement in the grower diets beyond 20% resulted in a linear decrease in consumption and weight gains (P<0·05). Feed conversion was similar for all diets which contained triticale.

The basal finisher diet, and the diet with 20% of the maize replaced, promoted better feed consumption and weight gain than the diets in which 40, 60 and 80% of the maize was replaced by triticale during the finishing phase and for the entire 109-day growing-finishing period. Carcass quality grade was higher for pigs fed the basal diet and the diet in which 20% of the maize was replaced by triticale (P<0·05 ) but there were no differences in the other parameters of carcass quality, nor in the composition, cooking quality and organoleptics,. of the longissimus muscle. Fatty acid profiles of the longissimus muscle indicated that palmitic and oleic acids were significantly higher (P<0·05 ) and linoleic and palmitoleic significantly lower (P<;0·05) in pigs given the basal and 20% replacement diets than in pigs given the other diets. The results show that triticale could replace maize partially (up to 20%) in diets for pigs.

One hundred and eight crossbred sows from nine different commercial sources were monitored over two parities for changes in live weight and fatness. All sows were given a common nutritional regime. Thirty sows were slaughtered and physically dissected. After weaning the second litter, mean carcass measurements ( ± s.d.) were: live weight, 139±9·5kg; lean mass, 26·6 ± 2·8kg; subcutaneous fat mass, 4·l ± l·7kg; ultrasonic P2 backfat depth (USP2), 11·3±2·8mm; total dissected fat (kg) = 0·63 ± 0·073 USP2 —1·1 ±0·85(r = 0·85). Between mating (parity 1) and weaning (parity 2) sows gained 22kg live weight and lost 6·8mm backfat. There were significant differences between sources with respect to fatness, despite standardized feeding. It is suggested that for breeding pigs such as these, starting their reproductive life with limited fat reserves (16·4 ± 3·0mm USP2 at 92 ± 6kg live weight), a conventional fat-exploiting feeding regime is unlikely to be appropriate.

The influence of the odoriferous androstene steroids upon the response and courtship behaviour of gilts has been studied. These steroids are normally present in the submaxillary salivary glands of the boar, and have been shown previously to be an aid in the artificial insemination of gilts. Glands were excised from young boars after weaning, and at 6 months of age the ability of the boars to elicit a standing response from oestrous gilts was compared with that of littermate controls. In addition, a detailed record was made of behavioural activities performed by both gilts and boars, under a standard test procedure.

Analysis of the data showed that the presence of the glands was essential for normal behavioural patterns in both the females and the males. When confronted with a treated boar, the gilts were affected in three ways: approaching oestrus, they did not respond as early as they did to the controls; the intensity of their response was reduced; and it was held for a shorter period. The demeanour of the treated males was passive and unconcerned, i n contrast to the easily-aroused aggressive nature of the controls. The characteristic viscous salivary secretion was absent, and the scrotal sac was less pronounced and supported closer to the body.

These results suggest that elimination of the white, frothy saliva normally containing and dispersing the androstene steroids not only reduces the boar's ability to command and elicit a full sexual response from oestrous gilts, but it also reduces his own libido. In conjunction with previous work, these studies provide evidence for the pheromonal properties of androstenone and androstenol.

The milk intake of two litters of suckling piglets was measured by the turnover of tritium-labelled body water. The estimated intakes of a litter of seven piglets agree with the current knowledge of milk yield from sows, which generally rises to a maximum at the 3rd week and then declines. With a litter of four, intake rose continuously from the 1st to the 6th week. Since piglets are often weaned at 3 weeks of age, this method has few disadvantages n i practical use. During the estimation of water turnover the total body water of individual piglets can also be obtained so that information on body composition (solids, protein, fat and ash) can be derived. The efficiency of conversion of milk by piglets can thus be calculated.

Thirty Large White × (Landrace × Large White) gilts were allocated to one of three treatments such that one gilt from each of 10 litters was on each treatment. The treatments were: (i) continuous boar exposure (CB); (ii) 30-min daily boar exposure (DB); and (iii) control, which had no boar exposure (NB). The experiment started at a gilt age of 165 days, and continued until either puberty was detected or a cut-off age of 250 days was reached.

The results indicate no significant difference in age at puberty between the CB and DB groups (194·6 v. 198·7 days), although both were significantly younger at puberty than the NB group (232·1 days, P<0·01). A possible ‘boar age’ effect is discussed.

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).

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.

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