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.

The objective of this study was to investigate the effect of low food intake on post-weaning fertility and hormone concentrations in primiparous sows. One hundred and forty primiparous sows (Landrace × Large White) were randomly assigned to one of four treatment groups: (A) restricted to 3 kg food per day during lactation and 2 kg food per day post weaning (no. = 36); (B) restricted to 3 kg food per day during lactation and ad libitum feeding post weaning (no. = 33); (C) ad libitum feeding throughout with a mean voluntary food intake of 3·7 kg/day during lactation (no. = 36); and (D) ad libitum feeding throughout with a mean voluntary food intake of 4·9 kg/ day during lactation (no. = 35). Litters were standardized at eight to 10 pigs at 2 days post partum and were weaned at 27·2 (s.e. 0·5) days post partum. After weaning, sows were observed twice daily for signs of oestrus and were mated on the day(s) of standing oestrus. Six sows from each group were fitted with indwelling jugular cannulae 2 days before weaning. Blood samples were collected 1 day before weaning (W−l), 1 day after weaning (W+l) and 4 days after weaning (W+4), and these sows were slaughtered on W+4. Ovaries were recovered, follicles and corpora lutea were counted, and folUcular fluid collected. Sows given food at a restricted level (groups A and B) lost more backfat during lactation than sows given food ad libitum (groups C and D) (P < 0·01). Piglet weaning weights, weaning to conception intervals and the proportion of sows ovulating by W+4 were not significantly different among groups. In sows that did not ovulate, numbers of large follicles were not significantly different among groups but the low food intake (groups A, B and C) sows had more medium-sized follicles than high food intake (group D) sows (P < 0·01). FolUcular fluid concentrations of oestradiol, progesterone and insulin-like growth factor-1 (IGF-1) did not differ among groups (P > 0·05). Plasma non-esterified fatty acids concentrations were greater in groups C and D than in groups A and B on W−l, W+l and W+4. Serum insulin and plasma glucose concentrations were lower in groups C and D than in groups A and B on W−l and W+l, but were similar among groups on W+4. Serum growth hormone concentrations were lower in group D than group A and B on W−l and W+l but not W+4. Concentrations of IGF-1 in serum were greater in groups C and D than groups A and B on W−l and W+l but not W+4. It is concluded that low food intakes during lactation and post weaning affected body condition, serum hormones and metabolites and ovarian function of primiparous sows without dramatically affecting ovarian hormones or reproductive performance.

An experiment was carried out to study the effect of changes in either the quality or the quantity of dietary protein intake on the excretion of nitrogen (N) compounds in the chicken. Thirty-two White Rock male broilers (1 day old) were raised in batteries and fed a commercial starter diet for 9 days. Then they were randomly divided into eight groups each of four birds, of similar body weight (mean live weight: 178 (s.e. 1·9) g), and individually housed in metabolism cages. Following a paired-feeding design based on metabolic body weight (kg M0·75), each group of birds was given, for an experimental period of20 days, each of four levels of protein (60, 120, 180 or 240 g/kg: 5 days each) in two groups of isoenergetic (14·5 kj metabolizable energy per g dry matter) and semisynthetic diets based on soya-bean meal, known to be first limiting in methionine, either unsupplemented (diets S) or supplemented with 2 g/kg DL-methionine (diets SM). Excreta were collected every 3 days for 48 h, frozen and stored at −20°C. The excreta samples were subjected to chemical analysis for uric acid by a rapid high-performance liquid chromatographic method, for urea and ammonia by a colorimetric method, and for total N by the Kjeldahl procedure. In general, the excretion of major N compounds was markedly affected by either the quality or the content of dietary protein. Overall, the excretion of total N, uric acid-N, ammonia-N and urea-N significantly (P < 0·05) decreased with improvement in dietary protein quality and significantly (P < 0·05) increased with increase in protein intake. Regression equations were obtained relating the excretion of uric acid, urea, ammonia and total N on protein supply. For the partition ofN compounds output, the ratios of uric acid-N and ammonia-N to total N significantly (P < 0·05) decreased on improving dietary protein quality and increased or remained unchanged, respectively, with the increase in dietary protein content. The use of the ratio of ammonia-N to total N is recommended as a rapid, easy and accurate indicator of dietary protein adequacy, as an alternative to measures based on total N balance, without the need for separation of urine and faeces.

The time taken to lie down and stand up was determined for dry sows from different housing systems and related to physical and genetic parameters. In experiment 1, the times taken to lie down by 32 sows in two dry-sow housing conditions were measured. Sows housed long-term in stalls took longer to lie down than group-housed sows (20·42 v. 9·28 s, P < 0·001). Group-housed sows took longer to lie down in the open than to lie down against a wall (11·07 v. 7·48 s, P = 0·004). The length of time taken for stall-housed sows to lie down had strongest association with body length (P = 0·033, R2 = 0·718). The length of time taken for group-housed sows to lie down in the open had strongest association with the proportional weight of the extensor carpi radialis, (P = 0·001, R2 = 0·915). In experiment 2, the times taken for 30 sows in stalls to lie down and stand up were measured and genotype differences investigated. There were no differences between genotypes in total times taken to stand up or lie down, but total times taken to stand up quickly and lie down had strongest association with body length (P = 0·032, R2 = 0·185, and P < 0·001, R2 = 0·574 respectively). The results indicate that sows housed long-term in gestation stalls experience difficulty of movement when standing up quickly and lying down. Although the chronic effects of lack of exercise and the acute effects offloor type may contribute to this difficulty, the major factor is likely to be space restriction as the times taken to lie down and stand up quickly both increase as body length, and hence dynamic space requirement, increases. Lying down in an unrestricted environment is under muscular control and the degree of control depends on the proportion of muscle weight to total body weight. The factors affecting lying down and standing up should be considered when designing dry-sow and farrowing accommodation.

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.

Wild red deer (Cervus elaphus) hinds were subjected to one of five post-capture management strategies during the period from capture in late pregnancy in March, until weaning in September. The treatments were: remained enclosed at the capture site; relocated to a remote site; relocated to a conventional deer farm on improved pasture; relocated to a conventional deer farm and grazed with farmed hinds; housed prior to calving on a conventional deer farm site. For a further year, all hinds were managed under conventional deer farm conditions. There was considerable evidence, based on mortality and behaviour, to suggest that initial housing of the hinds following capture compromised their welfare. Deaths of hinds (seven out of 20) occurred in this group, associated with bullying during the housed period. Hinds on this treatment also showed a higher frequency of aggressive interactions compared with the groups directly moved to the deer farm (11% v. 2% respectively of scans conducted at 10-min intervals over 6h; P < 0·001) and a reduced level of lying behaviour (15% v. 34 to 47% of scans; P < 0·001) during the gestation period. Similarly, during the calving period, this group lay the least (27% v. 43 to 72% of scans; P < 0·001) and the mean number of interactions between hinds reached 11·7 compared with 1·5 to 4·9 (F < 0·001) in the other groups over a continuous 6-h recording period. The two groups of hinds relocated directly onto sown swards were generally similar to one another in terms of behaviour and performance. However, the group mixed with farmed hinds suffered from considerable calf losses in year 1 due to disease (four out of 12). Losses of hinds over winter in year 1 (nine out of 90) occurred principally amongst those animals which had not become habituated to human presence or supplementary feeding in the summer, i.e. groups remaining enclosed at the capture site or relocated to a remote site. When all hinds were treated similarly in year 2 the hinds from these same two groups, together with those initially housed indoors, showed more hind-hind interactions overall than the two groups located directly onto the deer farm (7·2 v. 3·1 interactions per hind over a 4-h period; P < 0·02) and it is suggested that these hinds had not yet adapted to their new environment. An ACTH stimulation test conducted during year 2 supported the view that the two groups of hinds most recently introduced into the managed system were subject to a chronic stressor at the time of testing, since administration of ACTH did not elicit a significant increase in plasma cortisol concentrations (mean values pre- and post-ACTH 188 and 217 nmol/l respectively). In contrast, the mean plasma cortisol concentrations of the two groups managed under extensive farm conditions from the outset, showed a significant rise (pre- and post-ACTH, 261 and 376 nmol/l respectively; P < 0·01). From this it is concluded that their adaptation to the farm environment had already occurred. The live-weight gains of the wild hinds calves (229 g/day) on the improved pastures in the 1st year of the study were below that for farmed hinds calves (282 g/day; P < 0·05), suggesting that they were not habituated to the management system. However, by the end of year 2 animal performance was comparable with that of farmed hinds and calf growth rates reached 276 g/day. Thus while housing wild red deer immediately after capture is associated with poor welfare, analysis of behaviour, adrenal response and animal production over a longer period suggests that by the end of the study few important differences remained between the groups.

Carcass and meat quality traits were studied in 94 barrows of known HAL-1843 genotype (homozygote - - and heterozygote - +) from three crosses slaughtered at 90 kg and 120 kg live weight. Crosses A and B were produced from sires of which 0·5 of the genes were from a heavy-muscled × Large White line and 0·5 from pure Pietrain (A) or Duroc (B). Sows for both A and B were from a hyperprolific Large White × Landrace line and this latter line produced the pigs for cross C (control). The carcasses from cross A which were sired from boars having 0·75 of their genotype from heavy-muscled genetic lines had higher killing-out proportion, better conformation scores, greater loin depth and loin area, less carcass length and bone content, and greater lean proportion compared with cross C. The carcasses from cross B, with roughly 0·25 of Duroc genes had a significantly higher backfat thickness than either cross A or C. However their composition was not significantly different from C, since the higher backfat was counter-balanced by their better conformation. Carcass and lean weight distribution was more favourable in crosses A and B, which had significantly higher economic yields than cross C. The halothane genotype did not have a significant effect on fatness and carcass composition, although the heterozygote showed a significantly greater muscle depth. In addition, no significant effect of the halothane gene on carcass and lean weight distribution was observed. In relation to the light group of carcasses (72·8 (s.e. 4·4) kg), the heavy group (100·1 (s.e. 2·7) kg) had greater killing-out proportion, better conformation, longer carcasses, higher fatness and greater loin depth and area. These genetic lines showed a 9·6 g/kg increase in fat and a 6·1 g/kg decrease in lean for every 10 kg of increasing slaughter weight. With the slaughter weight increase the longissimus dorsi muscle became less pale due to a higher muscle pigment concentration, and the backfat had a higher proportion of oleic and lower proportion of linoleic and palmitic fatty acids. The halothane genotype had a significant effect on meat quality. The heterozygote produced much paler, softer and more exudative meat. However, the effect of cross and carcass weight was not significant for meat quality measurements determining pale, soft and exudative meat.

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.

The timing for introducing ad libitum lactation feeding around farrowing was studied in an experiment comprising 20 blocks of three littermate sows and a total of 1085 piglets in 90 farrowings. Sows were given 2·2 kg daily of a diet containing 12·1 MJ metabolizable energy and 120 g digestible crude protein per kgfrom service until ad libitum feeding was introduced either 4 days before expected farrowing (treatment BEF), the farrowing day (AT), or 3 days after farrowing (AFT). BEF and AT sows had a higher total daily food consumption during the experimental period, 5 days before farrowing to weaning at 35 (±3) days, than AFT sows (7·2, 7·2 and 6·6 kg, respectively). BEF and AT sows tended to have deeper ultrasonic backfat (BF) than AFT sows. The mobilization of body reserves during lactation was modest as reflected in negligible losses of live weight (LW) and BF, low serum concentrations of non-esterified fatty acids and creatinine, together with increasing serum urea concentrations as well as the high proportion of sows served within 8 days after weaning (over 90% of the primiparous sows). Sow rectal temperature increased on the farrowing day but was also influenced by feeding level. No cases of agalactia post partum were diagnosed. Litter size, piglet LW, piglet mortality and creep food consumption did not differ between treatments, although there was a tendency for lower LW and increased mortality, particularly of piglets crushed by the sow, in litters of AFT sows. It can be concluded that there was no advantage in delaying the introduction of ad libitumfeeding until after farrowing.

The farming of ostriches is well established in South Africa and is gaining in popularity in agriculture around the world but few scientific data are available for rates of egg production and the factors affecting incubation and hatching. Production and hatchability of over 1200 ostrich eggs on a farm in the United Kingdom were recorded during the 1995 season. Females of breeding ages (no. = 43) were kept in 13 enclosures in sex ratios of 1: 1 or 1: 2 (M: F). Productivity of all ostriches over the laying season was 25·2% although when results from individual enclosures, and from individual birds, were examined higher rates of production were achieved although only one bird achieved her full laying potential. As group size increased productivity decreased. Overall fertility was 78·7% although fertility greater than 90% was achieved by females kept in pairs or trios. Larger group sizes had lower fertility. Mean weekly hatchability was only 24·1% with hatch of fertile eggs being 31·9%. Maximum hatchability of eggs produced from an individual female was 73% of fertile eggs. Microbial contamination of eggs was 32·6% and this was the biggest cause of failure to hatch, although rates of contamination varied between females. These results for productivity are similar to those published for ostriches in Israel and South Africa. Hatchability is lower, and microbial contamination is higher than published information although this is the most comprehensive study of ostrich production yet published. Future development of ostrich breeding programmes needs to concentrate on small breeding groups, preferably pairs, and on improvements in nest site hygiene and post-laying egg management.

Four bales of hay were chosen from a stack of hay, barn-stored for 6 months. Each bale was subdivided into four 2·5 kg sections and one section from each bale was subjected to one of four water soaking treatments: 0, 0·5, 3 or 12 h. Post treatment, the samples were shaken for 9 min under a Negretti LS45F personal dust sampler which sampled the surrounding air. The samples were than analysed for levels of respirable particules < 5 μm in size and for amounts of sodium (Na), potassium (K), phosphorus (P), magnesium (Mg), calcium (Ca) and nitrogen (N). Soaking for 30 min reduced the number of respirable particles by about 90% but also reduced the Na, K and P content of the hay. Soaking for a longer period, at least up to 12 h, did not give a significant further reduction in number of respirable particles but there was loss of Mg and further losses in Na, K, and P. These results clearly indicate that soaking for 30 min is sufficient to reduce the respirable challenge with minimum nutrient loss.

Two experiments were made to investigate the effects of road transport on stress hormone responses in pigs. In experiment 1, seven 40-kg pigs, prepared with jugular catheters, were loaded onto a livestock lorry and transported over a 2-day period on routes characterized, by means of an accelerometer, as rough or smooth. Two 100-min journeys, one rough and one smooth, separated by a 100-min rest period, were conducted each day. The experimenters travelled with the animals and blood samples were taken for hormone analysis from each pig at 20-min intervals. On the 3rd day, samples were collected from the pigs when housed in their home pen (control). Plasma concentrations of cortisol increased after loading, remained higher for longer on rough compared with smooth journeys and were higher during both journeys on day 1 compared with day 2. Concentrations of beta-endorphin increased after loading on day 1 but neither beta-endorphin nor lysine vasopressin showed clear changes in secretion pattern during rough or smooth journeys. On day 3 (control), mean concentrations of all three hormones were significantly lower than on days 1 and 2, indicating that the responses observed were not due to a diurnal rhythm. In experiment 2, six 35-kg catheterized pigs were loaded on a lorry (09.30 h) that remained stationary while blood samples were taken at 30-min intervals during the next 8 h (control). Two days later, this procedure was repeated with the vehicle in motion for 8 h. Plasma concentrations of lysine vasopressin during driving increased between 2 and 4·5 h which coincided with behavioural observations indicating that the pigs were travel sick.

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.

Five Chilean crossbred draught horses were used to study variation in work performance and biochemical and physiological parameters whilst working with a mould board plough (36 kg) for 6 h/day. The draught force, distance travelled, work done and the estimated extra energy for work were determined for each horse. The results showed that the horses used only 68·0 (s.e. 1·9)% of the total available working time ploughing a mean area of 3283 (s.e. 168) m2 with a mean depth and width of furrow of 12·6 and 22·3 cm, respectively. Estimated daily energy expenditure by the horses during work was 2·24 (s.e. 0·02) times maintenance requirements. The small changes observed in the physiological variables: heart rate, respiratory rate, packed cell volume, haemoglobin concentration and enzyme activity of creatine kinase, lactate dehydrogenase and aspartate amino transferase, showed that the horses were exercised under submaximal conditions. However, the significant increase in blood cortisol concentrations showed that horses experienced some degree of stress during ploughing work. The significant increase in blood triglycerides concentration observed after each period of work seems to demonstrate that fat mobilization is an important metabolic pathway as an energy supply for the working muscles during prolonged and low speed draught work.

The objective of the study was to investigate the influence of amino acid-deficient diets and high dietary leucine levels offered for intervals of either 21 or 35 days pre-slaughter on the intramuscular fat content of pig muscle. Twenty-four hybrid gilts were offered individually ad libitum one of four diets that comprised combinations of amino acid levels (supplemented or deficient: 5·6 v. 4·0 g lysine per kg) and low or high leucine levels (10·3 v. 30·3 g leucine per kg). Live weights at the start of the study were 74·5 and 87·0 kg for pigs on the 35- and 21-day feeding regimens, respectively. There were no significant effects of dietary amino acid level, leucine level, or feeding interval on food intake, daily live-weight gain or food efficiency. Pigs given the amino acid-deficient diets had lower killing-out proportions (736 v. 747 (s.e. 3·4) g/kg; P < 0·05) and longissimus dorsi muscle areas (32·6 v. 35·7 (s.e. 0·71) cm2, P < 0·01) than those given amino acid-supplemented diets. Subjective score for longissimus dorsi colour indicated that pigs on the high leucine diet had darker muscle than those on the low leucine diet. Intramuscular fat contents of the longissimus dors i muscle at the Wth/llth rib and the 3rd/4th lumbar vertebra and of the semimembranosu s muscle were increased by 19, 18 and 18 g/kg, respectively (P < 0·05), for pigs given amino acid-deficient compared with those given amino acid-supplemented diets. Dietary leucine level had no significant effect on intramuscular fat level. Pigs given the diets for 35, compared with 21, days had higher fat levels in the semimembranosu s muscle (52 v. 30 (s.e. 5·2) g/kg; P < 0·01) but not in the other two muscle locations studied. This study suggests that relatively short-term feeding of amino acid-deficient diets can produce substantial increases in intramuscular fat levels.

Responses in gilt live weight, backfat depth and food intake during lactation and in pre-weaning piglet growth rate were examined after seven generations of divergent selection for daily food intake (DFI), lean food conversion (LFC) or lean growth rate (LGA) on ad-libitum feeding or lean growth on restricted feeding (LGS). There were 252 Large White gilts in the study. Selection for low DFI resulted in gilts with less backfat (25·7 v. 30·7 (s.e.d. 2·21) mm) at farrowing and a substantially lowerfood intake (129 v. 146 (s.e.d. 5) kg) during lactation, but similar reductions in live weight (42 (s.e.d. 6) kg) and backfat depth (8·4 (s.e.d. 1·7) mm) than with selection for high DFI. Therefore, the lower piglet growth (167 v. 295 (s.e.d. 11) g/day) with selection for low DFI compared with selection for high DFI was primarily due to lower food intake of the gilts, as energy for milk production from food was reduced. In contrast, selection for high LFC resulted in relatively smaller changes in live weight (37 v. 48 (s.e.d. 5) kg) and backfat depth (7·6 v. 8·9 (s.e.d. 1·3) mm) than selection for low LFC, which combined with a lower food intake (132 v. 148 (s.e.d. 4) kg) during lactation, resulted in lower piglet growth (181 v. 200 (s.e.d. 11) g/day). The higher food intake of high LGA gilts (137 v. 121 (s.e.d. 4) kg) compensated for the relatively lower reductions in live weight (41 v. 46 (s.e.d. 5) kg) and backfat depth (5·5 v. 6·7 (s.e.d. 1·3) mm) during lactation compared with the low LGA line, such that piglet growth was similar (195 v. 289 (s.e.d. 11) g/day) in the two selection lines. In the high and low LGS selection lines, piglet growth was similar (195 v. 186 (s.e.d. 11) g/day) as was gilt food intake (125 v. 227 (s.e.d. 5) kg) and the changes in live weight (39 v. 41 (s.e.d. 6) kg) and backfat depth (8·1 v. 7·7 (s.e.d. 2·2) mm) during lactation. An examination of the daily energy used in litter gain and the energy available from gilt food intake and mobilization of body lipid indicated that one equation to predict the amount of body lipid mobilized during lactation was not appropriate for different genotypes. Responses in gilt food intake and the changes in live weight and backfat during lactation were selection strategy dependent. However, in general, the selection strategies which reduced gilt voluntary food intake during lactation or resulted in lower live weight and backfat depth at farrowing were detrimental to piglet growth rate.