Recombinantly derived bovine somatotropin (bST) was administered to 25 Friesian cows by 2-weekly injections of a controlled release formulation at a dose rate equivalent to 25 mg/day. Treatment commenced 7 to 11 weeks after calving and continued for 26 weeks. A comparable group of 25 cows treated only with the slow release vehicle served as a control. During the treatment period, administration of bST increased yields of milk (controls 2358 v. bST 2598 (pooled s.e. = 39·8) kg; P < 0·01), fat (107·4 v. 119·3 (pooled s.e. = 1·9) kg; (P < 0·01) and protein (84·7 v. 93·7 (pooled s.e. = 1·2) kg; (P < 0·001). Magnitude of the treatment effect was strongly influenced by season, being greatest in spring/early summer (weeks 1 to 13 of treatment) and autumn (weeks 19 to 25) but not significant during the intervening summer dry period when herbage yield was low. Voluntary intakes, as measured by indigestible marker techniques at weeks 7 to 8 and 12 to 13 of treatment, were not influenced by bST administration. However, the net loss of body condition experienced by bST-treated cows (0·3 condition score units) was not sufficient to explain their responses in yield of milk and milk components, suggesting that some responses in voluntary intake had occurred. Administration of bST had little effect on milk composition, fatty acid composition of milk fat, live weight, reproductive performance or milk yield in the subsequent lactation.

In two experiments, the effects of protected fat and fibre were studied in compound supplements for grazing dairy cows. The protected fat used consisted of calcium salts of long-chain fatty acids. In experiment 1, 17 cows (group S) were given 4 kg/day of a starchy compound and 17 (group F) 4 kg/day of a high-fibre compound containing protected fat for the first 4 weeks after turn-out to grass. No significant difference was found between groups in milk yield, but cows in group F produced milk with a higher fat content (42·6 g/kg) than did those in group S (37·1 g/kg; P < 0·01) and had higher yields of fat (0·88 v. 0·79 kg/day; (P < 0·05). In experiment 2, four groups of five cows were given 4 kg/day of starchy (S) or fibrous (F) compounds, with (P) or without (C) protected fat for the first 4 weeks after turn-out. After 4 weeks, treatments (starchy or fibrous, added fat or none) were reversed for a further period of 4 weeks. There was no significant effect on milk yield, milk protein yield, live-weight change or change in condition score, although cows on treatment SC tended to produce less milk and have greater gains in live weight and condition. For groups SC, FC, SP and FP respectively, milk fat yields (kg/day) were 0·86, 0·98, 0·99 and 1·06 (s.e.d. 0·06); milk protein contents (g/kg) were 34·4, 34·8, 34·2 and 33·0 (s.e.d. 0·68) and calculated milk energy outputs (MJ/day) were 67/2, 74·3, 74·4 and 76·6 (s.e.d. 3·04). It is concluded that substituting fibrous compounds for starchy compounds tends to increase milk fat content and yield; adding calcium salts of fatty acids to either type of compound significantly increases milk fat content and yield but tends to decrease milk protein content.

Seventy-eight British Friesian type cows, mean calving date 13 January, were used in a 3 × 2 factorial design experiment to examine the direct and residual responses to replacing 0·8 kg/day of a concentrate containing 184 g/kg crude protein with an equal quantity of fish meal when using three levels of total supplement feeding (0·8, 4·0 and 7·2 kg/day). In addition, all animals had access ad libitum to a high-quality grass silage (in vivo digestible organic matter 750 g/kg dry matter) during the treatment period. Treatments were applied from day 8 post partum until 22 April, when all animals went to pasture, giving a mean treatment period of 91 days. At pasture the animals were rotationally grazed as three groups, based on the three levels of total supplement offered during the treatment period, at the same stocking rate. The effects of treatments in terms of direct effects during the treatment periods, residual effects at pasture and also total lactation were assessed. Also during the treatment period the effects on rumen volatile fatty acid contents and blood composition were monitored. In addition, total diet digestibility and food utilization studies were carried out on six animals per treatment.

Level of supplementation significantly influenced milk output during both the treatment and full lactation periods with the total lactation responses being 2·0 and 1·0 kg milk per kg additional supplement between the food levels of 0·8 to 4·0 and 4·0 to 7·2 kg/day respectively. Level of supplementation also significantly influenced milk fat concentration during the treatment, residual and full lactation periods and milk protein concentration during the treatment period only.

The replacement of 0·8 kg conventional concentrate by 0·8 kg fish meal significantly increased milk yield during the final 21 days on treatment (mean yield per day 20·6 and 21·9 (s.e. 0·44) kg for without and with fish meal treatments respectively) but there were no significant residual or total lactation effects. From the data it was calculated that at low levels of supplementation 0·8 kg fish meal could be used to replace 1·9 kg conventional concentrate but at more moderate levels of nutrition any substitution would be much lower and uneconomic.

The effects of pregnancy status (non-pregnant, early to mid (1 to 5 months) and late (> 6 months)) and month of pregnancy on live weight, carcass weight, dressing proportion, bruising and muscle properties were examined in 237 Shorthorn and Brahman crossbred cows (mean live weight 424 kg, 62% pregnant). The cows were transported 1155 km to an abattoir and given access to food and water until slaughter. Mustering to slaughter periods were 5, 6 or 7 days.

The mean gross hot carcass weights for the 89 non-pregnant, 108 early to mid pregnant and 40 late pregnant cows were 207, 199 and 187 kg (P < 0·05). Their respective dressing proportions were 487, 469 and 443 g/kg (P < 0·05). Among the pregnant cows, carcass weight and dressing proportion decreased by 2·95 kg and 6 g/kg, respectively, for each month of pregnancy (P < 0·05).

Cows in late pregnancy had lower mean initial yield (IY) and peak force (PF) shear values for m.longissimus dorsi (LD) than non-pregnant cows. The late-pregnant cows also had the greatest mean pH 24 h post mortem (pH24) and ultimate pH (pHu) values (P < 0·05). They also had a greater proportion of carcasses with high pHu values than the early to mid-pregnant and non-pregnant cows (0·30 v. 0·157 v. 0·079; (P < 005). Among the pregnant cows, mean pH24 increased by proportionately 0·038 and the proportion of high pH24 carcasses by 0·055 for each month of pregnancy (P < 0·05). Pregnancy status had no significant effect on mean fat depth, bruise score, PF-IY value or cooking loss.

The economic values of cattle production traits differ with different production circumstances. This sensitivity implies that (1) production circumstances influence the revenue of breeding programmes, and (2) losses in revenue of breeding programmes occur when circumstances used in defining breeding goals are incorrect with regard to actual production circumstances at the moments of expression of genetic superiorities. In this study, these effects are quantified for a set of genotype and index traits, including milk production traits, food intake capacity and live weight. Twenty-four situations of production circumstances were studied, including alternative output limitations, milk production levels, roughage qualities and product (milk, beef) and production-factor (food) prices.

Results indicate that type of output limitation is the most important factor in determining revenue. Also, incorrect prediction of type of limitation leads to highest losses in revenue found (proportionately 0·01 to 0·06 of revenue). Losses in revenue due to incorrect prediction of production circumstances seem too low to justify complete diversification of cattle breeding goals within a breeding organization, except for different types of output limitations.

The incidence of twin calvings and double ovulations was studied in two Milking Shorthorn herds and one Friesian herd, each with above-average annual twin calving rates (average 0·031, compared with a national rate of 0·01). The proportions of double ovulations were calculated from records comprising 1237 cow × years (cows over 2·0 years of age); means were 0·08, 0·27 and 0·50, for three groups which had previously produced 0, 1 or >1 sets of twins, respectively. All cows (whether still present or no longer in the herd) were then allocated a twin production status, to indicate the number of twin sets (0, 1 or >1) produced, or produced so far, in their lifetime. There were records from 1559 cows, with sire and dam also known. Twin production status was significantly influenced by dam group (P < 0·01), i.e. the twin production status of the cow's dam. Sires were classified into two groups, according to whether any daughters had produced two or more sets of twins. After allowing for ascertainment, sires in the two groups were found to differ (P < 0·01) by 0·06 in the probability of their daughters producing at least one set of twins in their lifetime (i.e. 0·08 to 0·14). One sire and dam combination in particular had prolific daughters with a probability of 0·39 of producing at least one set of twins in their lifetime (compared with a probability of 0-07 for the other extreme combination). The possibility of these observations being explained by the segregation of a single recessive gene was considered, but the necessary interaction between sire group and dam group was not significant.

Forty-nine bulls, 27 Limousin × Friesian and 22 Charolais × Friesian, were evaluated and slaughtered in four batches of about equal size over 4 weeks. Each batch was of one breed. Age, live weight at evaluation and subjective assessments of fatness and conformation were recorded together with fat and muscle measurements by the Delphi, Meritronics, Scanogram, Vetscan, Kaijo Denki, Warren and the Velocity of Sound ultrasonic machines. Experienced operators were used to assess the performance of machine/operator combinations likely to be achieved in bull performance testing in the field. Fat thicknesses and areas, and m. longissimus areas were taken at the 10th rib and 13th rib, and 3rd lumbar regions by most machines. For the Delphi and Meritronics machines, fat thicknesses only were taken; for the Velocity of Sound machine, time interval measurements and anatomical distances were taken at the shoulder, mid back, lumbar and hind limb regions. The left side of each carcass was fully separated into lean, subcutaneous fat, intermuscular fat, bone and waste. All measurements were examined as potential predictors of carcass composition in step-wise regression in a model which included week of evaluation, breed and live weight at evaluation as the first independent variable. On the whole, scanning machines had a higher precision than A-mode machines, with the Velocity of Sound machine achieving the highest precision for carcass lean (g/kg) (residual s.d. = 13·0) and fat (g/kg) (residual s.d. = 14·1). None of the linear and area measurements taken on the carcass achieved the degree of precision of the Velocity of Sound, Scanogram and Vetscan machines.

Four silages were prepared from perennial ryegrass: two unwilted, ensiled either without (UWN) or with formic acid additive (UWA) and two wilted for either 19 (WS) or 43 h (WL) prior to ensiling. The influence of conservation method on digestion in the rumen and the flow of organic mater (OM) and nitrogen (N) to the small intestine was studied using young steers fitted with rumen and duodenal T-piece cannulae. The silages were well preserved and of similar chemical composition despite a 1·5-fold increase in dry matter (DM) following wilting. The unwilted silages had a higher concentration of fermentation acids and a lower concentration of soluble N in the DM. Polyester bag studies showed that significantly more DM was potentially degradable but the degradation rate was slower in the rumen of steers fed UWA and WS silages (P < 0·05), however, rate of passage was not significantly different for the four treatments. Conservation method had little effect on post-feeding rumen ammonia concentration but feeding unwilted silages caused a greater depression in post-feeding rumen pH (P < 0·05). Wilting lowered N digestibility in the whole tract (P < 0·05), but had no effect on apparent digestion or degradability of N in the rumen as measured by the polyester bag method. Apparent OM digestibility in the whole tract was lower in steers given wilted rather than unwilted silages (P < 0·05), but disappearance of apparently digestible OM in the rumen was greatest for the 19 h wilted silage (WS, P < 0·05). It is concluded that, provided unwilted silage is well preserved, the use of formic acid has little effect on digestion of silage by steers and the effects of wilting are confined to a reduction in whole tract digestibility.

A crossmothering experiment was conducted to measure the direct and the maternal components of the response to divergent selection for yearling growth rate in beef cattle. The animals were from three closed lines of Angus cattle. Two lines had been selected since 1974 for either high (high-line) or low (low-line) average daily gain from birth to yearling, and the third line was maintained as a randomly bred control-line. A total of 221 female calves born between 1984 and 1987 was used in the crossmothering experiment, and an additional 113 cows bearing calves in 1988 were used to obtain more records of milk production.

On average, high-line calves born in 1984-87 were 45 kg heavier at weaning (200 days of age) than low-line calves and 65 kg heavier at yearling age, corresponding to a proportional divergence in daily weight gain of 0·29 and 0·32 respectively. The direct component of the response to selection was 0·82 (s.e. 0-05) of the divergence in body weight at weaning and 0·89 (s.e. 0·05) at yearling age. The maternal component was 0·18 (s.e. 0·06) and 0·11 (s.e. 0·04) for weaning and yearling weight respectively. Over the years 1984-88, high-line dams produced 1·15 times the milk of low-line dams and only 1·03 times that of control-line dams. There were small differences in the composition of milk sampled in 1984 which resulted in the milk of high-line dams having a higher content of metabolizable energy (ME) than that of control-line dams. The ME in the milk consumed by the calves from the three selection lines was sufficient to fuel similar proportions of their pre-weaning growth and indicated that the expression of the maternal component of the selection response may be via small differences in the quantity and quality of the milk produced by the dams. Expression of the direct component appeared to be at least partially via differences in appetite of the calves. These results, together with results for sheep, mice and rats, show that the direct component of the response to selection for growth is much larger than the maternal component.

Rumen degradability of dry matter (DM), organic matter (OM), nitrogen (N), neutral-detergent fibre (NDF), hemicellulose, cellulose and lignin was evaluated with the in situ technique for maize silage and cocksfoot, timothy, fescue, lucerne and meadow hays. The degradability of each of the six forages was studied separately, each forage being used in turn as the main component of the diet offered to four fistulated cows. For each forage 300 g were mordanted with sodium dichromate and placed in the rumen when the same forage was studied. Faecal grab samples were collected to measure the forage transit time. Digestibility was evaluated using both lignin as an indicator and by an in vitro method.

Rumen outflow rate was higher for cocksfoot and lucerne hays than for maize silage and the meadow, timothy and fescue hays (P < 0·01). The effective degradabilities of DM and OM were higher in maize silage, fescue and lucerne than in cocksfoot, timothy or meadow hay (P < 0·01). Effective degradability of N was highest in lucerne and lowest in timothy and meadow hay (P < 0·01). The degradability of NDF, hemicellulose and cellulose for fescue was always the highest of the six forages (P < 0·01; P < 0·05; F < 0·01 respectively).

Rumen outflow rate was statistically correlated with the c value of DM (r = 0·47), N (r = 0·54), NDF (r = 0·43) and hemicellulose (r = 0·43). High correlations were observed between rate constants of degradation of NDF and hemicellulose, cellulose or lignin (0·93, 0·75 and 0·79 respectively). The regression between in vitro and lignin-derived digestibility was highly significant (P < 0·001, r2 = 0·902 residual s.e. 0·017). The multiple regression analysis between lignin-based digestibility and degradability coefficients, effective degradability and coefficients of faecal chromium excretion was highly significant (r = 0·748; residual s.e. = 0·03).

Three groups of lambs of about 25 kg live weight were given a concentrate diet either on its own (eight lambs) or supplemented with 10 g/kg ammonium chloride (eight lambs) or 20 g/kg sodium bicarbonate (12 lambs). At about 45 kg live weight the lambs were killed and their body composition was determined. The composition of their gains was also determined using information obtained from a fourth group of lambs (eight lambs) which were killed at the start of the experiment. Lambs given the ammonium chloride diet showed a reduction in blood pH while those given the sodium bicarbonate diet showed an increase to levels seen in lambs given forage diets. There were also marked effects on calcium (Ca), phosphorus (P) and magnesium retention with retentions being reduced in those given the ammonium chloride diet and increased in those given the bicarbonate diet. The average rates of retention of Ca and P in lambs given the bicarbonate diet were 9·1 and 5·9 g/kg empty-body weight gain and are comparable with rates seen in lambs given forage diets. These results suggest that dietary induced changes in blood acid-base status is a major factor contributing to the lower rates of retentions of these minerals in lambs given cereal-based diets.

A dynamic, mechanistic model of lamb metabolism and growth was developed for the purpose of evaluating hypotheses regarding the mechanisms of action of growth promotants. The model relates tissue growth to DNA accretion and protein turn-over. State variables include circulating amino acids, glucose, lipids and acetate; four protein pools (carcass, viscera, other tissues and wool) and storage triacylglycerol are also included. Equations are mainly of the Michaelis-Menten form, allowing for nutrient utilization patterns to be determined by relative tissue affinities for substrates (ko.5), enzymatic capacities (Vmax) and substrate concentrations ([S]). Protein degradation rates are defined as first-order with respect to protein. The model adequately simulated growth from 20 to 40 kg empty body weight. Simulated changes in nutrient input yielded reasonable energy balance response patterns, although theoretical growth efficiencies were greater than those observed in practice. Variations in volatile fatty acid absorption patterns were accommodated well, with predicted nitrogen retention closely approximating experimental observations. The model also responded appropriately to changes in dietary protein level, with body fat varying inversely with amino acid absorption. In summary, the model was found to perform adequately for the purpose of examining mechanisms responsible for alteration of growth and body composition.

Responses of lambs to cimaterol (CIM), diethylstylbestrol (DES) and ovine growth hormone (GH) were examined using a mechanistic model of growing lamb metabolism. All three compounds increase growth of lean tissue (protein) and decrease fat gain, although the magnitudes of these responses vary. Our working hypothesis was that observed changes in nutrient partition between lean and fat gain were caused by alteration of rate constants for turn-over of muscle protein and fat. Individual experiments were simulated whilst varying values of the protein degradation constant (Kprolein) and Vmax for lipolysis (Kfat). Optimal parameter values were found by minimizing residual errors, calculated as the deviations of model predictions from experimental values for carcass protein and fat. Fitted values of Kfat and Kprotein (expressed as proportions of controls) for each simulation were: CIM (grazing), 1·20 (s.d. 0·05) and 0·86 (s.d. 0·025); CIM (pellet-fed), 1·11 (s.d. 0·115) and 0·87 (s.d. 0·032); DES, 1·33 (s.d. 0·111) and 0·94 (s.d. 0·024); GH, 1·77 (s.d. 0·139) and 0·97 (s.d. 0·025) respectively. These results demonstrate that different mechanisms may be responsible for the changes in carcass composition due to 3-adrenergic agonists, anabolic steroids and growth hormone. CIM probably exerts its effects via changes in protein and fat metabolism, whereas DES and GH appear to act mainly through changes in adipose tissue, with little or no effect on the rate constant for protein turn-over. Carcass composition is less sensitive to manipulation of adipose tissue metabolism than to changes in muscle protein metabolism.

The present study was carried out on 1243 kids (379 Black Bengal; 568 Jamunapari × Black Bengal and 296 Beetal × Black Bengal) born between 1981 and 1986. Data were analysed to study the influence of genetic group, sex, season of birth, type of birth, birth weight, dam's weight at kidding, filial generation and parity of dam (as covariate) on survivability of kids during the pre-weaning period (0 to 90 days of age). The overall survival rates during 0 to 15, 16 to 30, 31 to 60, 61 to 90 and 0 to 90 days of age were 81·68 (s.e. 2·89), 95·55 (s.e. 2·00), 90·77 (s.e. 2·33), 93·31 (s.e. 2·59) and 69·94 (s.e. 3·65) % respectively. Variation in survival rates from 0 to 15 days of age was significant due to genetic group (P < 0·01), birth weight (P < 0·01), dam's weight at kidding and parity of dams as a covariate (P < 0·05). Season of birth (P < 0·05), weight of kids (P < 0·01) and dam's weight at kidding (P < 0·01) had significant effects on survival rate during 0 to 90 days of age. Sex and type of birth had no significant effect on survival rates. The interaction effects of genetic groups with season of birth and sex on pre-weaning survival rates were not significant in all ages except the effect between genetic group and sex during 31 to 60 days of age. An improvement in survival rates during the period of study was noticed with the increase in filial generation number from Fj to F3, although the difference was not significant except from 61 to 90 days of age (P < 0·05). Birth weight of kids had a positive linear relationship with survivability during the pre-weaning period. Summer-born kids had a significantly lower survival rate than those born in the winter and monsoon periods from 16 to 30, 61 to 90 and from 0 to 90 days of age. A negative linear relationship was observed between dam's weight at kidding and survival rates of kids from 0 to 90 days of age except the 25 to 30 kg dams deviate. Heritability estimates of survival rates during pre-weaning periods were not significantly different from zero, indicating that improvement by simple selection is probably limited.

The effect of grain processing and form of the concentrate mixture were studied on early-weaned Chios lambs (42 days of age) and Damascus kids (56 days of age). Forty-five, 36, 33 and 33 animals were used in trials 1 (lambs), 2 (lambs), 3 (kids) and 4 (kids), respectively. Within trials animals were divided on the basis of live weight and age into three groups. Treatments (three forms of concentrate mixture) were randomly allocated to one of the three groups. The treatments were: whole cereal (WGP) grains mixed with pellets made from the other ingredients of the concentrate mixture; pelleted (P), where all ingredients were ground and pelleted in 5-mm cubes; rolled cereal grains (RGP), where cereal grains were rolled and then mixed with pellets (5-mm cubes) made from the other ingredients of the concentrate mixture. Cereal grains comprised 774 g/kg concentrate mixture. Fattening diets were based on ad libitum feeding of concentrates and a daily allowance of 01 kg per animal of long lucerne hay. Digestion coefficients, outflow rate of small particles from the rumen and rumen metabolites were measured using five animals per species per treatment.

There were no significant differences between diets for live-weight gain in lambs. On the other hand, kids on the P diet gained more weight and had better food to gain ratio than the other two diets. Feeding the P diet resulted in a significant decrease of acetate and butyrate molar proportion ( P < 0·001) and an increase (P < 0·001) of propionate molar proportion. Similarly, feeding the P diet resulted in a significant reduction in ruminal pH (P < 0·01) and NH,-N (P < 0·05) concentration. Outflow rate (% per h) of small particles from the rumen was lower from lambs and kids on the P diet (P < 0·001). There were no significant differences between species and/or among diets for apparent digestion coefficients and nitrogen balance.

The performance of housed ewes, shorn at various stages during pregnancy and offered silages ad libitum made from grass harvested at two contrasting stages of growth, was studied. The mean increase in silage dry matter (DM) intake due to shearing (0·11 kg/day; P > 0·05) was small in comparison with that resulting from offered earlier-cut silage (0·27 kg/day; P < 0·001). The mean increase in twin lamb birth weight from ewes shorn at least 6 weeks before lambing was almost 1 kg per lamb (P < 0·01) with no significant effect on ewe live-weight change. Greatest increase in lamb birth weight (1·11 kg; P < 0·01) was produced by shearing several times during pregnancy, with least response (0·23 kg; P < 0·05) from shearing once only, 4 weeks before lambing. The effect of silage quality on lamb birth weight was not significant, despite the large difference in DM intake of the two silages. This difference in intake was reflected by ewe live-weight change over pregnancy with those ewes offered early-cut silage gaining 5·57 kg while those offered late-cut silage lost 4·53 kg (P < 0·001). There was a marked fall in respiration rate and rectal temperature after each shearing and, compared with shorn ewes, unshorn ewes had a mean gestation length which was 2·04 days shorter (P < 0·01). In terms of lamb growth rates, ewe milk yields and milk composition, the performance on all treatments after turn-out to pasture was satisfactory and no significant carry-over effect of treatments applied during pregnancy were observed during the first 5 weeks of lactation.

The proportion of whole grain consumed that was voided intact in the faeces of ewes in late pregnancy and early lactation was measured for diets based on a range of forages in two experiments. The proportions of grain voided intact varied widely between ewes and was to some extent a characteristic of the individual ewe. During late pregnancy on hay-based diets the mean proportion of grain recovered was 0·053 with a range from 0·042 to 0·063 while on silage-based diets 0·135 (range 0·082 to 0·209) was recovered. On silage-based diets after lambing 0·196 and 0·235 of grain was voided intact in the faeces. The proportion of intact grain voided was affected by forage intake. The estimated increase in the proportion of grain voided intact was 0·012 measured over a range of forages before lambing and 0·021 on silage after lambing per 100 g increase in dry matter intake. However, when the total digestibility was measured, there were no differences between feeding of whole and processed grain where proportionately 0·06 of whole grain consumed was voided intact.

An evaluation of the response to selection for prolificacy within a nucleus sheep flock of a commercial group-breeding scheme is presented. In 1979, the Romney Group Breeders formed a nucleus flock of 120 prolific ewes chosen from 12 contributing flocks. A control flock was established in 1982 from the same source. The analysis was conducted on the trait of litter size. Selection differentials are presented for each year of birth progeny group in both flocks. Expected selection response was calculated from selection differentials and was found to have an average value of 1·5% of parent mean litter size per year. Using least squares procedures the litter size performance of control and nucleus ewes of 2, 3 and 4 years of age was corrected for environmental effects. Realized response was estimated from the differences between corrected litter size means of control and nucleus flocks. Response in litter size was found to be significant within years and within ewe age groups (P < 0·05).

In earlier studies with pigs the P-adrenergic agonist Ro 16·8714 ((3-AG) enhanced the efficiency of nitrogen (N) retention. Therefore effects of Ro 16·8714 were studied on growth rate, body composition, N, fat and energy retention in pigs fed isoenergetically, but given different amounts of protein (112 or 138 g/kg diet) without (groups LP and NP) or with 60 mg Ro 16·8714 per kg diet (groups LPP and NPP) from 60 to 100 kg live weight. Weight gain (898, 927, 855 and 810 g/day in NP, NPp, LP and LPp) decreased, whereas food: gain ratio (2·94, 2·82, 3·04 and 3·24 kg/kg in NP, NPP, LP and LPP) was increased by low protein intake (P < 0·05) and both weight gain and food conversion were modified by the interaction (P × P) of protein intake and Ro 16·8714 (P < 0·05). Killing-out proportion (820, 830, 830 and 830 g/kg in groups NP, NPp, LP and LPP) was modified by protein intake and Ro 16·8714 (P < 0·05). Carcass growth rate (760, 814, 748 and 723 g/day in NP, NPP, LP and LPP) was modified by protein intake and by P × p (P < 0·05), while non-carcass growth rate (90, 77, 76 and 56 g/day in NP, NPP, LP and LPP) was changed by protein intake and by Ro 16·8714 (P < 0·05). Compared with NP, weights of kidneys (−0·025 kg), small intestine (−0·26 kg) and large intestine (−0·17 kg) were decreased by low protein feeding, and weights of heart, spleen and stomach decreased in response to Ro 16·8714 (-002, -0·02 and -0·06 kg; P < 0·05) while both low protein intake and Ro 16·8714 reduced liver weight (−0·12 and −0·23 kg, respectively; P < 0·05) and blood volume obtained at slaughter (-0·12 and -0·23 kg; P < 0·05). Carcass N (1813, 1970, 1786 and 1825 g in NP NPp, LP and LPP) increased in response to Ro 16-8714, but was reduced by low protein intake (P < 0·05), while noncarcass N (330, 309, 312 and 285 g in NP, NPp, LP and LPP) was decreased by both low protein intake and Ro 16-8714 (P < 0·01). Carcass and non-carcass fat (22·1, 19·9, 23·4 and 23·0 kg, respectively 1·51, 1·41, 1·59 and 1·68 kg in NP, NPp, LP and LPP) increased with low protein feeding (P < 0·05), but were not significantly influenced by Ro 16·8714. The efficiency of N retention (295, 363, 321 and 327 g/kg N retained: N intake in NP, NPp, LP and LPP) was enhanced by Ro 16·8714 (P > 0·05) whereas the efficiency of energy retention was not influenced by Ro 16·8714 and protein intake. In conclusion, an adequate intake of protein is necessary for optimum expression of many, but not all, effects of the P-adrenergic agonist Ro 16·8714.

Six experiments involving the artificial insemination (AI) of a total of 300 female red deer (hinds) with frozen-thawed red deer semen (collected by electro-ejaculation) were conducted over 3 years. Insemination took place at fixed times following various oestrous synchronization procedures using progesterone withdrawal and treatment with pregnant mare's serum gonadotropin (PMSG). In the 1st year, the experiments evaluated basic AI techniques in which pregnancy rates were 45% in 20 hinds receiving two inseminations per vaginam (PV) and 56% in 27 hinds inseminated by the laparoscopic intrauterine method (IU). In the 2nd year, the experiments involved comparisons of the progesterone regime, one or two PV inseminations, and the timing of a single PV insemination. There was no effect of replacement of the progesterone device after 9 days and withdrawal 3 days later compared with the use of one device for the whole period in two experiments. The pregnancy rate for a double PV insemination was significantly higher than for a single PV insemination (58 and 34%; P < 0·05) and there was also a small effect of timing of insemination relative to the synchronization treatment. In the 3rd year all hinds were inseminated by the IU method. The experiments involved a comparison of various times of AI following progesterone withdrawal and a comparison of the progesterone regime. The overall pregnancy rate for 63 hinds inseminated was 56% with no difference between three times of insemination (48, 52 and 55 h). In the second experiment, the difference in pregnancy rate between treatment with progesterone for 15 days and 12 days (44 and 72% for 18 hinds per group) was not significant, but the interaction between the length of progesterone treatment and insemination time was significant (P < 0·05), with the 12-day progesterone/55 h insemination giving a much higher pregnancy rate than the 15-day/55 h insemination (89 and 20% respectively). Although no experiments involved direct comparisons of the routes of insemination, overall pregnancy rates were 56% for IU, 53% for double PV and 35% for single PV inseminations.