To investigate the effects of energy source and protein level of diets on milk protein content, 12 multiparous Holstein-Friesian cows were used in a 4 × 4 Latin square change-over experiment with 4-week periods. Four diets were offered, with ad libitum silage as proportionately 0·40 of the diet, and the remaining 0·60 as one of four concentrates, two based on barley and two on molassed sugar-beet pulp. Two protein levels were achieved by altering the amounts of digestible undegraded protein in the concentrates, with all diets formulated to supply equal quantities of rumen degradable protein. There was no effect of diet on dry-matter intakes. Both starch and high dietary protein levels significantly increased milk protein concentration (P < 0·05), but had no effects on milk fat and lactose concentrations. Mean milk yields were significantly higher (P < 0·05) with increased dietary protein. Dietary protein significantly affected the yields of milk protein (P < 0·01) and lactose (P < 0·05) but not that of fat. Urinary allantoin excretion was significantly greater with both high protein (P < 0·05) and starch-based diets (P < 0·05). No significant interaction effects were found. It is concluded that dietary effects were due largely to differences in supply of rumen degradable protein; increases in milk protein concentration were therefore brought about by increasing the protein supply to the animal.

A study was conducted to examine the effect of fine grinding or sodium hydroxide treatment of wheat, and increasing concentrate food level, on milk production. Two concentrates based either on ground wheat (450 g/kg, GW) or sodium hydroxide treated wheat (500 g/kg, SW) were offered at four concentrate levels of 2·5, 5·0, 7·5 and 10·0 kg dry matter (DM) per day to 24 dairy cows in a three-period, change-over design experiment. On average, across all concentrate food levels, silage DM intake was significantly (P < 0·01) higher with the SW concentrates, reflecting a significantly lower silage substitution rate with SW relative to GW concentrates (P < 0·01). Milk yield was also significantly higher with the SW concentrates (P < 0·05), although marginal responses to increased concentrate food level were similar (P > 0·05). Milk protein concentration increased linearly with increasing concentrate food level (P < 0·001), with a significantly greater response with the GW relative to the SW concentrate (0·59 v. 0·24 g/kg (P < 0·05) increase per kg additional concentrate). However, milk protein concentration was also significantly lower with the GW concentrate at low food levels (P < 0·05). Milk fat concentrations were similar with the two concentrate types with significant reductions in milk fat concentration with increasing concentrate food level (P < 0·05). Blood urea (P < 0·001) and β-hydroxybutyrate (P < 0·05) concentrations were significantly lower in animals offered the SW concentrate. Apparent digestibility coefficients were unaffected by either concentrate type or concentrate food level (P > 0·05), although modified acid-detergent fibre apparent digestibility was significantly reduced with increasing concentrate food level (P < 0·001). Results indicate that, at similar levels of concentrate feeding, silage intake and milk yield were significantly greater with SW compared with GW concentrates (P < 0·05 or greater). Increases in milk protein concentration with increasing concentrate food level were significantly greater with GW than with SW concentrates (P < 0·05).

An experiment was conducted to examine the effect of method and level of concentrate feeding on milk production characteristics in dairy cows offered a grass silage-based diet. Twelve treatments were used with 24 Holstein/Friesian dairy cows in a four-period change-over design experiment. Treatments consisted of three methods of concentrate feeding (twice daily, four times daily or complete diet) and four levels of concentrate feeding (2, 4, 6 or 8 kg/day). Offering a complete diet significantly reduced silage substitution rate (0·28 kg silage dry matter (DM) per kg concentrate DM) compared with concentrates offered twice daily (0·50 kg silage DM per kg concentrate DM; P < 0·01). Method of concentrate feeding had no significant effect on milk yield or milk fat concentration (P > 0·05), although the response in milk protein concentration to increased concentrate food level was significantly greater with twice and four times daily concentrate feeding than with complete diet feeding (0·59, 0·56 and 0·44 g/kg per kg increase in concentrate food level; P < 0·05). Increasing concentrate inclusion level significantly reduced silage DM intake (P < 0·001) but significantly increased (P < 0·001) total DM intake. Milk yield and milk protein concentration were significantly increased (P < 0·001) and milk fat concentration significantly reduced (P < 0·02) with increasing concentrate inclusion level. Total ration apparent digestibility coefficients were unaffected (P > 0·05) by either method of feeding or concentrate inclusion level. However, modified acid-detergent fibre apparent digestibility decreased significantly with increasing concentrate inclusion (P < 0·01). Results suggested that offering complete diets, with concentrates comprising on average 0·33 of total DM intake, increased both silage and total DM intake although this was not reflected in either increased milk yield or improvements in milk composition.

An 18-week experiment investigated the effects of type of diet and frequency of watering on the performance of growing cattle given food at maintenance (metabolizable energy (ME) allowance (MJ) = 8·3 + 0·091 M where M = live weight of the animal). Three diets with 20: 80 (low, L), 50:50 (medium, M) and 80: 20 (high, H) roughage to concentrate ratios (10·2, 7·8 and 5·4 MJME per kg dry matter) were used in combination with free access to water for 2·5 h once daily or once every 3rd day. A completely randomized-block design with a 3 (diets) × 2 (watering frequencies) factorial arrangement of treatments was used. Five animals were allocated per treatment (average weight 245 (s.d. 21·6) kg).

Dry-matter intake increased as the roughage content of the diet increased (P < 0·05) but was not affected by the watering regime (P > 0·05). Total water intake was found to be positively correlated with dry-matter intake and increased with dietary roughage level. Animals watered daily drank more (P < 0·05) water (12·6 v. 10·0 kg/day) than those watered every 3rd day. The apparent digestibility of the diets decreased as the amount of roughage increased (diet L 734g/kg, M471 g/kg and H 433 g/kg). Similar apparent digestibilities were observed under the two watering frequencies (546 g/kg and 547 g/kg).

Type of diet significantly (P < 0·05) affected the final weights of the steers. Animals given diet H were proportionately 0·07 heavier than those offered diet L corresponding to total weight changes of −0·8 and +18·4 kg respectively. Carcass weight, backfat thickness and eye muscle area were not affected by the treatments. The chemical composition of the 9 to 11th rib joint was only affected by diet H which gave less fat (P < 0·05). Water, fat, protein and ash content averaged 607,118,190 and 84 g/kg respectively.

A study was carried out to evaluate the effect of horizontal walking upon CO2 production rate by the carbon dioxide dilution rate technique. This was used as an indicator of animal energy expenditure. Two groups of three 18-month-old Aberdeen-Angus steers were assigned to two experiments. Average weights were 290 (s.e. 7·6) kg and 285 (s.e. 1·0) kg for experiments 1 and 2 respectively. Animals were allocated to individual pens and given 5·0 and 4·5 kg dry matter of a mixed diet for experiments 1 and 2 respectively. After a 45-day training period they were assigned to three walking treatments: 0 (T0), 3 (T3) and 6 (T2) km at 3 km/hfor 3 days in a Latin square design (3 × 3). 14C labelled sodium bicarbonate (5·4 μCi/h), diluted in carbonate-bicarbonate buffer sterile solution 0·1 mol/l, was infused for 92 h intraperitoneally with portable peristaltic pumps carried by the animals. The CO2 production rate was calculated as the ratio between the rate of infusion (μCi/h) and the specific activity of CO2 (μCi/ml CO2) in saliva samples, which were taken, in experiment 1, as an average of the day (09.00 to 16.00 h) and the night (16.00 to 09.00 h of the following day). In experiment 2 the day was divided as follows: prior to activity (09.00 to 13.00 h), activity (14.00 and 15.00 h) and post activity (16.00 h). CO2 production rate (ml CO2 per h per kg M0·75) at resting was 817 (412 kj/kg M0·75), increasing during walking to 1·46 of the resting level (T1 and T2, experiment 2) with no differences between the 1st and 2nd h of activity. One hour post activity, the CO2 production rate returned in T2 to the level of T0 but in T2 remained at 1·28 times that of T0. The average CO2 production rate during a complete day or night (experiment 1) was not affected significantly by the activity. Assuming that CO2 production rate during walking is 1·46 of resting (experiment 2) and remains at that level even at lower speeds, it can be estimated that a daily 6 km walk would increase resting energy expenditure from 1·04 when walking takes 2 h, as in this experiment (3 km/h), to 1·11 when the animal spends 6h(1 km/h).

The energy expenditure of freely grazing cattle was investigated in the National Institute of Agricultural Technology and Agricultural Science College of Balcarce, Argentina (37° 45'S, 58° 18'W), by the CO2 entry rate technique. Two experiments were carried out in the autumn in March 1994 (experiment 1) and in April 1995 (experiment 2) with animals prepared with catheters in the parotid gland (collection of saliva) and into the peritonea for infusion of a solution of 14C. Six Angus steers (259 (s.e. 11) kg) were used in experiment 1 and seven (298 (s.e. 36) kg) in experiment 2. In experiment 1 animals grazed ryegrass pastures for 5·5 h in two periods of 1·5 h in the morning and of 4 h in the afternoon and in experiment 2 animals grazed oat pasture in one period of 1 h in the morning. Twenty hours before and during the experiments a solution ofNaH14CO3 was infused at a rate of 9·4 (experiment 1) and 8·1 (experiment 2) μiCi/h for 48 h with portable peristaltic pumps carried by each animal. Saliva samples were collected at least after the first 20 h of infusion. The first sample was collected in the corral just before grazing and two samples were collected in each grazing period. Also, in experiment 1 three samples were taken during resting (noon, 1 h after grazing and the next morning). In addition, bite frequency, pasture availability, plant height, in vitro digestibility and crude protein were measured. Carbon dioxide production was calculated as the ratio between the rate of infusion of 14C (μCi/h) and the specific activity of CO2 (μCi/l CO2) in saliva samples. Bite frequency was 59 and 28 bites per min on the respective pasture of ryegrass (148 g dry matter (DM) per m2 and 10·5 cm height) and oat (228 g DM per m2 and 27 cm height). Energy expenditure (EE, kJ/h per kg M0·75) in corrals was 14·9 (experiment 1) and 14·3 (experiment 2), increasing to 22·6 (proportionately 0·52) when grazing at 59 bites per min and to 16·6 (0·16) when grazing was at 28 bites per min. One hour after grazing at 59 bites per min (experiment 1) the EE was as high as during grazing, and in the next morning (after 5·5 h) of grazing remained at 19·7 kJ/h per kg M0·75 (0·32). No differences in energy expenditure were found between periods of grazing in experiment 1. It was concluded that the increase in energy expenditure of cattle due to the activity of grazing depends on the rate of biting. Grazing for 10 h at a moderate rate may boost EE proportionately by only 0·06, however grazing at the highest rates could easily add proportionately 0·20.

To determine the effect of different levels of gonadotropin-releasing hormone (GnRH) antibody titres (AT) on plasma hormone concentrations, behaviour, testes size and performance, Friesian bull calves (no. = 72) were immunized against either human serum albumin (HSA) conjugated to Cys-Gly-GnRH (no. = 48; immunized) or HSA (no. = 24; controls) at 8 to 10 weeks of age. One booster immunization was administered on either day 28 or 56 (no. = 24 GnRH-immunized and no. = 12 control per booster day). Based on AT 1 week post respective booster, 12 immunized and six control bulls were allocated to one of three AT groups, control (C), medium (M) and high (H) with mean AT of 0·3 (s.e. 0·1), 32 (s.e. 2) and 51 (s.e. 2)% binding at a plasma dilution of 1: 160; respectively. Bulls were blood sampled and weighed every 14 days, and testicular measurements taken every 28 days, from days 0 to 533. Behaviour was observed for 4 h once weekly while bulls were together at pasture and, within AT group, for 20 min 1 week before slaughter. At slaughter, testes and carcass measurements were made. Appropriate data were analysed by ANOVA and correlation coefficients (i) determined. Behavioural data were analysed using x2. Mean AT for M and H treatment groups during the experiment were 36·5 and 44·8% binding at a 1: 160 dilution (P > 0·05, pooled s.e.d. 5·9%), respectively. Level of AT decreased (P < 0·05) mean testosterone concentrations (1·74, 1·36 and 1·21 (s.e.d. 0·17) ng/ml for the C, M and H treatment groups, respectively) and testes size (e.g. length, 10·0, 8·9 and 8·1 (s.e.d. OS) cm) in the M and H groups compared with the C bulls. There was no effect of AT level on luteinizing hormone and insulin-like growth factor-1 concentrations or on average daily gain. Bulls in the M group had the lightest testes and lowest masculinity score compared with the C and H groups (both P < 0·05). Bulls in the H group had greater backfat thickness than the C bulls (P < 0·05). Bulls in the M and H groups were less aggressive and sexually active than the C bulls (P < 0·05). In conclusion, GnRH AT in both the M and H groups persisted for the duration of the experiment, and these AT were significantly different for a critical period pre-puberty; however they both had similar effects and caused extended periods of reduced testes growth, testosterone concentrations, and aggressive and sexual behaviour compared with C bulls but there was no detrimental effect of AT on growth or carcass characteristics.

Puberty during performance test and the effect of reproductive maturity and performance on test on superovulatory response were investigated using Simmental heifers.

Three generations of Simmental heifers (no. = 110) were performance tested for beef characteristics between 23 and 49 weeks of age over 3 years successively. Embryo recoveries were performed at 52 and 61 weeks of age following the end of the performance test. The onset of puberty was observed in 26 of 30 (87%) heifers in the 3rd year. The mean age at puberty was 284·7 (s.e. 6·63) days. Age at puberty was not significantly related to daily live-weight gain (1·5 (s.e. 0·02) kg) up to the onset of puberty. Heifers experienced zero to six oestrous cycles before initiation of the first superovulatory treatments. There was a non-significant tendency (P > 0·05) for heifers that were not cyclic to produce the highest yields of viable and grade 1 embryos at the first embryo recovery.

Performance test characteristics recorded were: total food intake (1604·0 (s.e. 13·2) kg), total energy intake (1852·0 (s.e. 169·0) MJ metabolizable energy) and live-weight gain (263·9 (s.e. 2·2) kg) during test; live weight (486·5 (s.e. 31·5) kg), backfat depth (5·6 (s.e. 15) mm) and muscle score (9·6 (s.e. 0·10) units) at the end of test and estimated breeding value for the selection index (+£7·00 (s.e. 0·76)). These were used as independent variables in general linear models to study their relationship with various measures of superovulatory response. Recovery rate of ova and embryos; and the yields of viable and grade 1 embryos were not related to any aspects of performance on test.

In conclusion, superovulation and embryo recovery were affected by reproductive maturity at the time of gonadotropin treatment and these procedures may be more effective in juvenile heifers before the establishment of cyclicity. Embryo production from 12- to 15-month-old Simmental heifers following a beef performance test was not related to their performance on test.

In blood, there are many kinds of adipogenic or antiadipogenic factors such as hormones and vitamins. In this study, adipogenic activity in sera of fattened beef cattle was evaluated using cultured mouse 3T3-L1 preadipocytes. After the preadipocytes were grown to reach confluence, serum of fattened beef cattle was added into the culture medium (10%, vol/vol)for 3 days, and thereafter cellular sn-glycerol-3-phosphate dehydrogenase (GPDH) activity was determined as an index ofadipocyte differentiation. Sera were collected from 19 beef cattle (Wagyu and Wagyu × Holstein cross cattle) from three different farms at slaughter. Cellular GPDH activity was significantly different among the farms, and was affected by sex difference (i.e. sera from fattened heifers induced higher GPDH activity than those from steers). There was a positive correlation between GPDH activity and beef marbling performance (T = 0·62, P < 0·02), suggesting that serum factor(s) play a role in development of intramuscular fat deposition. Adipogenic activity was negatively correlated with serum retinol concentration (r = −0·73, P < 0·001). Neither serum cholesterol, triacylglycerol nor non-esterified fatty acid was related to adipogenic activity.

Furthermore, serum retinol concentration was negatively correlated with beef marbling performance. These data imply that retinol level in blood during the fattening period may influence intramuscular fat deposition of beef cattle through its antiadipogenic action on preadipocytes present in muscle tissues.

The effect of transportation on energy metabolism in young calves was assessed at two feeding levels by indirect calorimetry during a 5·5-day experimental period. Twenty-six Holstein-Friesian male calves were assigned in a 2 × 2 factorial arrangement of treatments. Calves were fed below or near the maintenance requirements (270 or 420 k) metabolizable energy per kg M0·75 per day). At 5 days of age, 13 calves were transported. The applied transportation procedure was aimed to mimic common transport of young calves. The other 13 calves were controls. Metabolizability of dietary energy was low (0·808), but similar for control and transported calves. Despite the similar salivary cortisol concentrations after transportation, heat production was higher by 23 kJ/kg M0·75 per day in transported than in control calves. Calves were not in a steady-state regarding their energy metabolism. Heat production decreased with time. Both transportation and feeding level influenced the decline in heat production with time. Only during the first 3 days after transportation was heat production enhanced, suggesting a relatively short-term effect of transportation in young calves. The impact of transportation on heat production and time related alterations in heat production were not related to the calfs activity.

Because of the evidence that growth hormone gene transfer in pigs and mice can result in widespread pathological changes and more general concerns that transgenesis techniques themselves may have deleterious effects, a study was undertaken to compare the behaviour of two populations of immature female sheep, one of transgenic and one of control animals. The gene transferred was that for human alpha-1 antitrypsin factor. In the first part of the study the behaviour of 25 transgenic (T) and 25 control (C) sheep was compared in three separate situations: competition for a limited quantity of supplementary concentrate, six categories of normal behaviour on pasture and movement order when driven through a crush. With two minor exceptions (idling and ‘other’ behaviour in focally sampled animals), none of the differences observed between the two populations was significant and in most cases the mean values observed for T and C sheep were very similar. In the second part 25 T and 25 C sheep (different individuals from those in part 1) were compared in straw-littered covered pens for both normal behaviour and competition for a complete diet provided in a trough. The only significant differences in the seven categories of normal behaviour were a lower incidence of idling and ‘other’ behaviour in T sheep. There was a difference between T and C sheep in their social interaction under very competitive conditions (the T sheep reached food less quickly). The behavioural differences found in this study were all slight. Overall, the findings suggest that the gene transferred had no detectable deleterious effects on the normal behaviour of immature animals.

Two groups of 28 Finnish Landrace (FL) lambs were given (group Mg) or denied (group O) access to a magnesium (Mg)-rich mineral mixture to establish its role in the hitherto frequent development of diarrhoea in the flock. Diarrhoea developed in most lambs but became marginally worse in group Mg (P < 0·05) by weaning. At weaning, 28% of the lambs had salivary sodium: potassium (Na: K) ratios < 4 indicating Na deficiency but pasture was not low in Na (60·9 mmol/kg dry matter (DM)) and providing the mineral mixture (which also contained Na) did not alleviate the deficiency. Raised plasma pepsinogen (PP) concentrations were indicative ofabomasal parasitism and all lambs were drenched with levamisole. Groups were subdivided at weaning, either continuing on their previous treatments (groups Mg/Mg and O/O) or being offered pure salt (NaCl) (groups Mg/Na and O/Na). Mineral consumption was measured from weaning and varied widely between groups and with time for the first 2 weeks. Early consumption was maximal at 19·6 g per head per day in group Mg/Mg and zero in group Mg/Na and faecal DM was significantly lower in the former group (165 v. 223 (s.d. 16·9) g/kg DM). All groups showed an improvement in Na status after weaning followed by a decline and NaCl consumption showed opposite changes about a mean of 6·3 g per head per day: faecal DM became uniformly low (ca. 200 g/kg fresh weight) in all groups. A further rise in PP prompted a second treatment with levamisole 6 weeks after weaning. When salivary Na: K was low (1 and 7 weeks after weaning), a significant relationship (P = 0·002) was found between salivary K (mmol/l), faecal DM (g/kg) and plasma pepsinogen (PP U per l;):

K = 22·9 + 4·5 PP – 0·047 DM (d.f. 82: r = 0·34).

Nematodiasis may have caused an ion imbalance and an associated diarrhoea, inducing a craving for NaCl which was ill-met by a mixture rich in laxative Mg.

Effects of Trypanosoma vivax infection on nitrogen and energy metabolism and serum hormones and metabolites were measured using 24 castrated West African Dwarf bucks. In order to discriminate between the effect of infection and the effect of food intake level on energy and nitrogen balance, food quantity restriction was applied for isonutritional comparison; a number of the animals were not infected and served as controls. Daily dry-matter (DM) intake was measured, and energy and nitrogen balance for a 7-day period in weeks 2, 4 and 6 after infection. Weekly blood sampling for analysis of hormones and metabolites was carried out.

Infected animals had a lower DM intake, compared with control animals, viz. 38·6 (s.e. 3·2) and 16·1 (s.e. 2·0) g/kg M0·75 per day, respectively (P < 0·001). Intake of gross energy and nitrogen followed the same pattern.

Metabolizability was not changed by infection and averaged 0·44. Heat production was increased by infection with an average of 33 kJ/kg M0·75 per day. Energy and nitrogen retention were negative for all groups; infection reduced energy retention and, during week 2 and 4 after infection, also nitrogen retention. The required metabolizable energy (ME) intake for maintenance was increased in infected animals (406 and 335 kJ/kg M0·75 per day for infected and control goats respectively), based on linear regression of energy retention on ME intake. The efficiency with which energy mobilization from body stores was substituted by dietary ME was estimated at 0·809 for both infected and control animals. The relationship between nitrogen retention and energy retention was not changed by infection. Therefore no indications were found for an increased catabolism of protein due to infection. Serum thyroxine and triiodothyronine were reduced by infection; serum metabolites and insulin levels reflected the negative energy balance in infected animals.

A 4 × 4 Latin square design experiment with 3-week experimental periods was conducted with four wether sheep, each fitted with a permanent rumen cannula, to evaluate the effects of dietary protein sources and levels on fermentation and microbial activity in the rumen. Four complete diets were offered each containing (g/kg dry matter (DM)) molasses 248, grass silage 200 and barley straw 260. The control diet (C) also contained barley and soya-bean meal and the other three diets were supplemented with urea (CU), soya-bean meal (CS), and soya-bean meal and fish meal (CSF), respectively. This gave foods of similar concentrations of metabolizable energy (ME) and estimated fermentable ME (10·6 and 9·8 MJ/kg DM, respectively), but different levels (g/kg DM) of estimated effective rumen degraded dietary protein (ERDP) and digestible undegraded protein (DUP) (ERDP/DUP, 84/17, 109/17, 116/38 and 119/54 for diets C, CU, CS and CSF, respectively).

No clinical symptoms of ill health in the animals due to the feeding of molasses were observed during the experiment. The average pH values of rumen liquors obtained at various sampling times post feeding for diets C, CU, CS and CSF were 6·40, 6·49, 6·62 and 6·47 (s.e.d. 0·06 P < 0·05) respectively and average ammonia-nitrogen concentrations were 63, 81, 90 and 113 mg/l (s.e.d. 14·9, P < 0·02) respectively. The average concentrations of total volatile fatty acids in the rumen liquor were similar across the four treatments. The molar proportions of propionate and butyrate were higher for the diet C than for the other three diets (P < 0·05), while acetate was lower (P < 0·05). Supplementing with true protein (P < 0·05), but not with urea (P > 0·05), increased the molar proportions of isobutyrate and isovalerate. Whole tract apparent digestibilities of DM and organic matter did not differ significantly across the four treatments, but neutral-detergent fibre apparent digestibility (0·677, 0·672, 0·716 and 0·728 (s.e.d. 0·017) g/kg DM for diets C, CU, CS and CSF respectively) and the proportions of hay DM that disappeared in the rumen during 24 h incubation (0·223, 0·238, 0·284 and 0·271 (s.e.d. 0·019) g/kg DM) were significantly lower for diets C and CU than CS and CSF (P < 0·05). Urinary excretion of purine derivative nitrogen was similar across the four treatments. The results obtained from the present study indicate that there were no significant differences in the microbial crude protein synthesis in the rumen when a diet containing molasses was supplemented with urea or true protein. However, the supplementation of this control diet with true protein, but not with urea, did stimulate the degradation of hay DM in the rumen and the digestion of dietary fibre in the whole tract.

A progeny test was designed to test whether genetic superiority for lean growth in terminal sires is expressed in their crossbred progeny when reared in a different environment. In each of 1986, 1987 and 1988, 22 Suffolk rams were chosen at the conclusion of an indoor, intensive performance testing regime on an index score that rated their propensity for lean growth, while constraining fat growth, at 150 days of age. Half of these rams had high index scores and half had low index scores. In each year, around 400 crossbred ewes were mated and the resulting lambs were finished on grass to one of three target live weights (35·5, 41·5, and 47·0 kg). Shoulder joints were dissected on 1505 lambs whilst half carcasses were dissected on 372 lambs. Double sampling techniques were then used to combine the data from the shoulder and half carcass more precisely to predict the lean, fat and bone weight and content in the carcass.

With each increment in target live weight, the carcasses were heavier and had proportionally more fat. The progeny of high index rams consistently had 144 (s.e.d. 32) g more lean, 66 (s.e.d. 12) g more bone, and 186 (s.e.d. 32) g less fat in a 19·7 (s.e. 0·5) kg carcass than progeny of low index rams, from the double sampling procedure. This improved composition reflected a correlated response to ram selection on the index. One standard deviation increase in ram index score corresponded to 51 g more lean and 64 g less fat in the 20 kg carcass of their crossbred offspring. These results show that the use of rams with high lean index scores in a crossbreeding system will produce lambs with leaner carcasses. Visual appraisals of fat and conformation both increased as the weight and, consequently, the fatness of the carcass increased. Offspring of high index rams were consistently scored as less fat than offspring of low index rams. But, at the lighter weights (35·5 and 41·5 kg), they were also scored lower in conformation — in effect, a penalty for their higher genetic merit for lean growth.

The relationship between total number born (TNB), ovulation rate (CL) and prenatal survival was analysed in a French Large White population. The left ovary had a significantly (P < 0·01) higher ovulation rate (7·9) than the right ovary (6·9). Prenatal survival showed an ovum wastage of 35 or 37% depending on whether referred to total number born or number born alive. No differences between parities were found in these traits. There was a negative relationship between ovulation rate at both sides (v = −0·34). There was a negative relationship between CL and prenatal survival (r = −0·37), a low correlation between CL and TNB (i = 0·19), and a high positive correlation between prenatal survival and TNB (i = 0·82). Litter size showed a quadratic relationship with ovulation rate, and the individual variation for each class of ovulation rate was found to be high. The relationship between prenatal survival and ovulation rate was found to be linear, and a high individual variation for each class of litter size was also found. The relationships between prenatal survival and litter size were quadratic, but depended much less on individual variation.

Food intake and body weight of 119 mice was measured from 3 to 18 weeks of age. Residual food intake was calculated for each week as the variation in food intake independent of variation in weight gain, weight maintained and sex. Growth efficiency and maintenance requirement were calculated by fitting curves to data from 3 to 18 weeks. The repeatability of residual food intake was low in young mice, but increased as they matured. Growth efficiency was correlated with residual food intake in very young mice. Residual food intake was not correlated with maintenance requirement in young mice, but as mice matured the correlation of residual food intake with maintenance requirement increased to 0·6. Body composition at maturity was correlated with residual food intake and maintenance requirement of mature mice, but a large proportion of the variation in residual food intake and maintenance requirement was independent of body composition. The results suggest that the age at which residual food intake is measured is important if it is to be used as a criterion for selection for efficiency.

A 2 × 2 factorial experimental design was used to compare growth in entire and castrated fallow bucks, implanted with zeranol at 6 and 9 months of age, or left as controls (no. = 10 per group). Growth pattern at pasture was assessed using 10-monthly growth periods from weaning (6 months) to 17 months. There were no overall castration or zeranol effects on growth rates from weaning to 17 months (P > 0·05), although there were significant interactions of zeranol and castration with time (P < 0·05). Zeranol-treated animals grew faster than the controls from 6 to 14 months, compared with the last 3 months (P < 0·05), indicating that the zeranol implants given at 6 and 9 months of age were no longer effective over the last 3 months of the experiment. The interaction between castration and time was significant (P < 0·05), whereby entire males grew relatively faster than the castrated males in both spring and the average of the winter and spring periods, whilst there was little difference in growth rates between entire and castrated males during the autumn period.

At 17 months of age all animals were slaughtered following a 16-hfast. Entire bucks were 46g/kg live weight and 56 g/kg carcass weight heavier than the castrated bucks at slaughter (P < 0·05), although there was no effect of zeranol treatment on either live or carcass weights (P > 0·05). The mean dressing proportion for deer in all groups was 0·61.

A subset of each treatment (no. = 5) were slaughtered and half carcasses dissected into muscle, bone and fat. When compared at the same carcass weight, both castration and treatment with zeranol significantly reduced the muscle weight and increased carcass fat weight (P < 0·05). There was no effect of either castration or zeranol treatment on the distribution of primal cuts. There were significant castration × zeranol interactions (P < 0·05) for muscle: bone and muscle: fat ratios, the entire control group having the highest muscle: bone and muscle: fat ratios.

It was concluded that there is little commercial basis for the use of the growth promotant zeranol in fallow bucks being grown for venison. Although castration resulted in lower carcass weights and muscle proportion, these disadvantages should be considered against the management advantages of easier handling and lower bruising of castrates.

Four diets were formulated to study the effect of a progressive substitution of grape pomace (GP) for alfalfa hay (AH) at the rates 0, 100, 200 and 300 g/kg total weight. The control diet contained 500 g AH and 192 g acid-detergent fibre per kg dry matter (DM). In experiment 1, 32 Californian × New Zealand White rabbits were used to determine dietary nutrient apparent digestibility. The inclusion of GP decreased the apparent digestibility of crude protein (P < 0·001) and energy (P < 0·05). However, the digestible energy (DE) contents of the diets were similar because GP had a greater gross energy content than AH. In experiment 2, 36 rabbits given the same diets as in experiment 1 were used to determine several digestive and productive traits and chemical body composition (at 20kg live weight). Dietary inclusion of GP linearly decreased ammonia (P < 0·01), total volatile fatty acid concentration (P < 0·001) and the molar proportion of acetate (P < 0·05) in the caecum. Starch content in the Heal and caecal contents was low but linearly increased (P < 0·05) with increasing dietary concentration of GP. The average daily gain (from weaning at 30 days of age to 2·0 kg live weight) was not significantly affected (P > 0·10) by the diet, but the ratio gain: food linearly decreased (P < 0·001) with the GP inclusion. Dietary inclusion of GP linearly increased (P < 0·10) the fat content of the empty body of the rabbits. The efficiency of utilization of dietary DE and protein for growth were calculated by the comparative slaughter method, using the chemical body composition data of 22 suckling rabbits slaughtered at 30 days of age for the initial body composition. The efficiency of utilization of DE was not influenced by dietary GP inclusion, but GP linearly increased (P < 0·01) digestible crude protein utilization. The decrease in crude protein apparent digestibility may be the main reason that gain: food ratio was impaired in diets containing GP substituted for AH.