In the winter feeding phase of a lifetime study of spring-born cattle managed in a 20-month beef system, a total of four feeding treatments were imposed by increasing the level of concentrate supplement offered with ad libitum grass silage. The objective was to achieve a difference in live weight at the end of the winter of about 25 kg between food treatments. A multifactorial design was used with three animal factors — maturity (early maturing Hereford crosses v. late maturing Charolais crosses), sex (heifer v. steer) and method of rearing (suckled calves v. bucket-reared calves).

There were no significant differences between breeds but highly significant (P < 0·001) differences for method of rearing and sex. As a consequence live-weight differences at the end of the winter between breed types (18 kg) were less than the difference between the sexes (23 kg) and for method of rearing (25 kg) although all were highly significant. Although suckled animals had significantly lower growth rates they were still significantly fatter at the end of the winter as were heifers and Hereford crosses. Differences in dry-matter intake were reflected in growth rate.

Plane of winter nutrition had a highly significant effect (P < 0·001) on live weight and condition score at the end of the winter resulting in increments of about 23 kg and 0·12 units of condition for each level of feeding.

Interactions between the main production variables were not significant with the exception of feeding level and method of rearing. Suckled animals showed a significant (Y < 0·001) reduction in winter gain (proportionately 0·85 for that of bucket-reared animals) when offered the same diet. This reduction ranged proportionately between 0·25 and 0·08 for the lowest and highest daily levels of concentrate supplementation respectively. An extra 1 kg concentrates per day was required for suckled animals to achieve similar live-weight gains to bucket-reared animals.

Thirty-six individually penned lambs (mean live weight 32·4 (s.d. 2·27) kg) were offered maize silage ad libitum and one of three concentrate mixes, two of which contained extracted rapeseed meal (control and HR) and the other fish meal (FM). The concentrates were given according to live weight and in sufficient quantities to provide proportionately about 0·4 of the dry matter (DM) intake of the lambs. The dietary concentrations of the nitrogen (N) g/kg DM were 22·4, 27·4 and 27·5 and of the rumen undegradable N 6·6, 7·3 and 11·6 for the control, HR and FM diets, respectively. All lambs were slaughtered at 45 kg live weight and chemical composition of the empty body and some of the component parts determined. A further 12 lambs were slaughtered at the beginning of the experiment to establish body composition before the dietary treatments were imposed.

The HR lambs had lower fleece.free empty body (FFEB) gains than either control or FM lambs (P < 0·05). This reduced gain of HR lambs was particularly associated with a reduction in fat deposition (P < 0·01) such that the FFEBs contained less fat than control and FM lambs (P < 0·01). The efficiency of conversion of metabolizable energy for growth (kg) was worse than both the control (P < 0·01) and the FM (P < 0·001) diets. The FFEBs of HR lambs also contained more ash (P < 0·05) than the lambs receiving the other diets.

The FM diet was associated with greater gains of fat and energy in the guts compared with the control diet (P < 0·05) and FM lambs had a better kg, value than control lambs (P < 0·05). There was no evidence that FM lambs had better N retention than lambs on the other two treatments.

Three wilted silages (dry matter concentration of approximately 300 g/kg) were prepared from early-bloom lucerne which received no additive (MG-0), or was treated with a mixture of carboxylic salts (Maxgrass) at either 4 (MG-4) or 8 (MG-8) l/t fresh crop. Silages were stored in tower silos. Resulting silages were offered ad libitum to growing Holstein steers without supplementation. Untreated silage (MG-0) exhibited an extensive, predominantly lactic acid fermentation. The nitrogen (N) fraction was highly soluble, relative to the crop at ensiling. Silage fermentation and protein solublization were restricted by Maxgrass application. Maxgrass application reduced aerobic stability of silage removed from the upper third of silos but not of silage from the lower portion of silos. Apparent digestibility showed a quadratic response to level of Maxgrass application (P < 0·05). Voluntary intake was not affected by Maxgrass addition (P > 0·005) but intake of all silages was high (30 g/kg live weight (LW)). There was a positive linear response (P < 0·05) in LW gain to Maxgrass application with gains of 0·74, 0·86 and 0·87 kg/day being achieved in steers given MG-0, MG-4 and MG-8 silages, respectively. Degradability of silage N determined in nylon bags in situ was unaffected by Maxgrass application. However, the immediately degradable N fraction was reduced by Maxgrass application (linear effect, P < 0·001; quadratic effect, P < 0·05). Benefits in animal performance due to Maxgrass application were attributed to improved N composition while restricted carbohydrate fermentation during ensiling was considered to be of secondary importance.

Twenty-five Border Leicester ♂ × Blackface ♀ wether lambs aged about 4 months and weighing on average 28·5 kg were allocated to be treated with the naturally occurring steroid testosterone or trenbolone acetate or nandrolone phenylpropionate which are steroids synthetically produced. Treatment groups were as follows: untreated controls (C); 50 mg testosterone (T); 50 mg trenbolone acetate (TA); 50 mg testosterone + 50 mg trenbolone acetate (TTA) or 50 mg nandrolone phenylpropionate (N). Implants were given at 100 and again at 63 days before slaughter. The lambs were offered to appetite a good quality diet containing, per kg dry matter, an estimated 11·0 MJ metabolizable energy and 185 g crude protein. Comparisons were made for the main effects of T and TA and also interactions between T and TA. Effects due to N were assessed statistically against untreated controls. Treatment with T, on average, increased live-weight gain (LWG), empty body weight (EBW) and reduced backfat thickness and the weight (g/kg EBW) of perirenal and retroperitoneal fat. Main effects due to TA were increases in killing-out ratio and depth of the gigot joint and reductions in backfat thickness. Treatment with N increased the empty body weight and (g/kg) carcass ash. Non-significant (P > 0·05) trends were suggested for increases in carcass crude protein due to T and TA treatments. T and TA but not N treatments exhibited marked androgenic activity in increasing the weight (mg/kg EBW) of the accessary vesicular gland. TA and N, but not T, reduced the weight (g/kg EBW) of the thymus gland.

The maximum binding capacity of post-morte m skeletal muscle (m. gluteus) for (3H)-dexamethasone was reduced by TA but increased by T and N. These results suggest differences in the binding capacity of corticosteroid receptors which may be related to differences in the effects of T and TA on protein metabolism in skeletal muscle.

Forty-five local Omani ram, wether and ewe lambs were reared from birth until slaughter at 18, 28 or 38 kg live weight (five of each ‘sex’ at each weight group) on an ad libitum concentrate diet and Rhodesgrass hay.

Ram lambs grew faster from birth and reached predetermined slaughter weights earlier than wether and ewe lambs. At 28 kg live weight, ram lambs had: heavier heads, feet, reticulo-rumens and livers; higher muscle and bone and lower fat proportions in the carcass; lower muscle: bone and higher muscle: fat ratios; higher proportions of carcass but lower non-carcass fat than had wether and ewe lambs. The head, feet, alimentary tract, liver and heart of Omani sheep grew at a lower rate; the skin grew at a similar rate and the carcass grew at a rate faster than empty body weight (EBW). Relative to EBW, muscle grew at a similar rate, fat faster and bone slower. Both carcass and non-carcass fats grew at a rate higher than that of the growth of EBW, with non-carcass fat growing at a higher rate than that of carcass fat. The growth rate of omental fat was the fastest followed by kidney, mesenteric, subcutaneous, tail, scrotal, intermuscular and pelvic fats respectively.

This study demonstrated that Omani sheep have good potential for growth if they are managed and fed satisfactorily. Omani sheep are early maturing for which reason it is recommended that they be slaughtered at lighter weights to avoid higher fat content in the carcass. Castration in Omani sheep is not recommended for production of meat lambs under intensive systems as it resulted in reduced growth rates and deposition of excess fat at lower slaughter weights.

To examine the effects of body condition and previous nutrition on the herbage intake of ewes grazing swards of different heights in autumn, 96 Scottish Blackface X Border Leicester ewes with a wide range of body condition (score 1·75 to 3·50), were initially housed and given 50 g dry matter (DM) per kg metabolic live weight (M)0·75 per day (treatment L) or 95 g DM per kg M0·75 per day (treatment H) of a pelleted dried grass diet (11·6 MJ metabolizable energy per kg DM) for 6 weeks after weaning in July. The H ewes gained more live weight (9·0 v. 2·7 kg) and body condition score (0·39 v. 0·17) than the L ewes. Half the animals from each treatment were then allocated to each of two ryegrass pastures with a sward height of 5 cm (LS) or 10 cm (HS) for a further 6-week grazing period. During the grazing period there was no significant effect of indoor feeding level on herbage intake, but the L ewes gained more live weight (6·4 v. 5·0 kg) than the H ewes. On the HS, compared with the LS sward, mean herbage intakes were higher (70·0 v. 60·5 g DM per kg M0·75) as were gains in live weight and condition score (7·9 v. 3·4 kg; 0·18 v. 0·0). There were no interactions between the effects of sward height and previous feeding level on herbage intake. Ewes in low body condition (< 2·5) at the start of the grazing period ingested the same amount of herbage on both swards (70·3 g DM per kg M0·75) whereas ewes in high body condition (> 2·5) ingested more (67·0 v. 51·6 g DM per kg M0·75) on the HS compared with the LS sward. The responses of ewes in low and high body condition to different sward heights are discussed in relation to appetite drive and aspects of grazing behaviour.

Although breed substitution is a very common method of rapidly altering the characteristics of a livestock population, within-breed selection for lamb carcass characters is becoming more widely used in the terminal sire breeds in Britain. Such selection schemes require accurate and applicable genetic parameters for the carcass traits of interest. This paper reports a genetic analysis of 11 traits measured on 3592 lamb carcasses using a derivative-free restricted maximum likelihood technique. Because of the trial design it was possible to estimate the genetic parameters of the traits at comparable fat cover, carcass weight and age at slaughter, using appropriate within-subclass covariates.

Heritability estimates for muscle depth (0·23, s.e. 0·04), muscle width (0·32, s.e. 0·05), fat depth (0·31, s.e. 0·05), caliper fat (0·23, s.e. 0·04) and conformation (0·29, s.e. 0·05) were similar in the weight and age-corrected results. Heritabilities for fat cover (0·35, s.e. 0·05), daily carcass weight gain (0·63, s.e. 0·07), and leg conformation (0·44, s.e. 0·05) were higher with slaughter at fixed weight than at fixed age. The heritabilities of traits at comparable fat cover were similar to those at comparable age at slaughter with the exception of daily carcass weight gain, fat depth, caliper fat and leg conformation.

The different measures of fat were highly correlated with each other. Conformation was moderately correlated with external fat score, carcass length and muscle depth. Muscle depth was moderately correlated with carcass length. Differences were found between genetic correlations calculated at equal weight, a common point of comparison in breeding schemes, and equal fat cover, a common end-point for slaughter lambs.

A total of 252 lambs was subjected to two contrasting growth rates (high and low) for 7 weeks commencing at 6 weeks of age, factorially arranged with two contrasting growth rates (high and low) from 13 weeks to slaughter. Growth rate was controlled either by weaning lambs at 6 weeks and feeding indoors throughout on differing levels of a concentrate diet (84 lambs in experiment 1) or by grazing at differing sward heights up to weaning at 13 weeks after which weaned lambs were grazed at differing sward heights and where necessary housed from early October and offered differing levels of concentrate and silage (168 lambs in experiment 2). Lamb slaughter weights on each growth rate treatment covered the range 40 to 48 kg live weight.

Increasing the growth rate between 6 and 13 weeks from 213 to 320 glday in experiment 1 and from 191 to 291 g/day in experiment 2 did not significantly affect the fat depth measured at various locations throughout the carcass, the weight of perinephric and retroperitoneal fat, fat grade or the total lipid content of soft tissue dissected from the shoulder joint when lambs were taken to slaughter weights. Increasing the growth rate between 13 weeks and slaughter from 136 to 338 g/day in experiment 1 and from 99 to 146 g/day in experiment 2 significantly increased the depth of carcass fat and fat grade but, though lipid content of the tissue in the shoulder also increased, this difference was not significant.

Carcass fat depth, perinephric and retroperitoneal fat, fat grade and lipid content of the shoulder tissue increased as slaughter weight increased. The effect of carcass weight on carcass fat was greater on the high plane of feeding from 13 weeks than on the low plane. For example, mean fat depth increased by 0·52 mm/kg increase in carcass weight on the high plane compared with 0·13 mm/kg on the low plane.

Comparing the effect of plane of feeding and carcass weight on carcass fat depth the high finishing plane of feeding had an effect equivalent to an increase of 3·8 kg carcass weight. The equivalent figure for the depth of tissue over the 12th rib was 2·8 kg while in relation to fat grade the effect was smaller at 1·0 kg carcass weight.

Fatty acid synthetase and lipoprotein lipase activities, lipid content of adipose tissue and the fatty acid composition of subcutaneous fat, sampled by biopsy at the 13th rib, were measured in 20-week-old rams from lines of Texel-Oxford (TO) and Scottish Blackface (SB) sheep, both divergently selected for carcass lean content. A total of 150 animals were measured, with close to equal numbers of animals per selection line-breed combination.

In both breeds, the high (lean) selection lines had significantly lower backfat depths (TO : 0·5 mm and SB : 0·6 mm, s.e.d. 0·2) than the low (fat) lines. The lipid content of subcutaneous fat was 65 mg lipid per g fat tissue wet weight (s.e.d. 24) greater in TO rams than in SB rams. The TO low line had a higher lipid content than the high selection line (426 v. 448 (s.e.d. 36)) and although the SB selection lines did not differ, the selection line with breed interaction was not significant. SB rams had higher fatty acid synthetase activity (3·1 v. 2·6 (s.e.d. 0·3) on a log scale) but there were no differences between selection lines. Lipoprotein lipase activities were similar between breeds and selection lines. The lower concentration of myristic acid (C14:0) of TO rams compared with SB rams (0·9 (s.e.d. 0·3)) was the only breed or selection line difference which was statistically significant for fatty acid composition of subcutaneous fat.

Lipid content of subcutaneous fat and lipoprotein lipase activity were highly correlated and both were positively correlated with performance test traits, especially with backfat depth. The correlation between backfat depth and fatty acid synthetase activity was not different from zero. Performance test traits, lipid content of subcutaneous fat and lipoprotein lipase activity were positively correlated with the unsaturated fatty acids, with the exception of C18 :1 when correlations were negative.

Distribution of tissue weight in the musculature and skeleton was studied in ram, wether and ewe Omani sheep raised under an intensive management system and slaughtered over the range 18 to 38 kg live weight. Ram lambs had higher muscle weight in the forequarters than wether and ewe lambs whereas the latter ‘sexes’ had heavier hindquarters and slightly more muscle in the muscle groups of proximal hind- and forelimbs and those surrounding the spinal column. Some of the neck region muscles, e.g. m. splenius and m. longissimus capitis et atlantis, were more developed in ram than in wether and ewe lambs. The proportions in the side muscle weight of some muscles (mainly in the hindquarter) decreased with increased slaughter weight whereas others (mainly in forequarter) increased, with the majority of the muscles showing no significant slaughter weight effects. The magnitude of change in proportions of individual muscles with increased slaughter weight was small and unlikely to have a commercial impact on meat production from Omani sheep.

As a proportion of total carcass bone, the axial skeleton and the hindlimb decreased with increased slaughter weight whereas the forelimb did not show a significant change. Ram lambs had heavier individual bones than wether and ewe lambs and higher proportions of the axial skeleton and lower proportions of the hindlimb than wethers at 28 kg live weight. There were few differences between the various ‘sexes’ in length, width or circumference of bones. Except for the 12th rib, individual bones, in all sexes, grew at a rate lower than empty body weight.

It is suggested that future improvement of Omani sheep should take into consideration the high proportion of bone in the carcass of these animals as well as the relatively higher proportion of bone in the limbs than in the axial skeleton.

Twenty-five primigravid ewes were used in a preliminary study to investigate the effect of bovine somatotropin (bST) between 97 and 124 days of gestation, on maternaland foetal growthand development. Five ewes (reference group) were slaughteredat 96 days of gestation, and the remaining ewes were injected daily with saline (control group: no = 10) or 0·1 mg/kgbody weight of bST (bST group: no. = 10). Following bST treatment, five control- and five bST groupewes were slaughtered (slaughter group). The remaining ewes (production group) were allowed to lamb, after which the lambs were slaughtered within 2 h of birth. Bovine somatotropin reducedthe proportion of maternal body fat, but had no major impacton wool growth, maternal gain and gross skeletal measurements, and foetal growth and development. Maternal bST treatment tended to affect the number of placentomes. It should, however, be emphasized that these results are based on small numbers of animals and that further research in this area is required.

Voluntary food intake (VFI) of chopped timothy hay and metabolic rate were each measured in each month of the year in six non-breeding ewes of each of three breeds. Metabolic rate was measured using indirect calorimetry over a range of food intakes and adjusted for intake to an estimated maintenance metabolic rate (MMR). The breeds compared were the Dorset Horn (DT), Scottish Blackface (BF) and Shetland (SH), the first being less seasonal in reproductive and other characteristics than the other two which are hill or northern latitude breeds. There was significant overall variation between months in VFI which was higher in the summer (July to September) than in the winter (December to February) months (P < 0·001). There was a significant breed × month interaction (P < 0·01), the seasonal effect being most strongly observed in the BF and SH ewes, whose VFI in summer was proportionately 0-1 greater than the year-round mean but was 0-1 lower in the winter. The DT ewes showed much less seasonal variation in VFI. There was no overall difference in VFI between breeeds (DT: 43-7; BF: 49-5; SH: 48-1 g dry matter per M075 live weight per day, P > 0·1). Although MMR varied significantly between months (P < 0·001), there was no systematic variation between summer and winter. There was no significant breed × month interaction, but the MMR differed significantly (P < 0·001) between breeds giving a high overall MMR in BF (DT: 322-7; BF: 356-6; SH: 324-5 kf/kg M0·75 per day). No significant correlation existed (P > 0·05) between the monthly mean MMR and VFI in any of the breeds. The causal relationship between seasonal cycles of basal metabolic rate and VFI is questioned.

An investigation was conducted to determine the effects of treatment with the GnRH agonist buserelin on day 12 post mating on the reproductive performance of ewes. There was a non-significant (P > 0·05) increase in nonreturn rate (control 0·76 v. buserelin 0·83) and litter size (control 1·51 v. buserelin 1·77) in three flocks. However, there was a significant (P < 0·05) increase in the number of twin lambs born (control 20 v. buserelin 40) and litter size (control 1·44 v. buserelin 1·68) in the yearling flock. There was no effect of buserelin on oestrous cycle length, although there was a tendency for treated animals to have a longer gestation length and heavier lambs. In a ewe lamb flock there was no effect of buserelin on non-return rate or litter size assessed post slaughter on day 31 of pregnancy. However, ovulation rate tended to be greater in the treated animals, which suggests that buserelin may have induced the formation of accessory corpora lutea. These results indicate that buserelin treatment improves embryo survival and that this effect is particularly evident in yearling ewes.

The influence of food allowance or level of food excess on diet selectivity and intake by sheep given pearl millet stover leaves, and the potential feeding value of the food leftovers (not eaten) (L) were studied. Animals were given food at four levels of L (100, 300, 500 and 700 g dry matter (DM) per day). All sheep received different food allowances (A, g DM per day) and had different L/A and A/M (g DM per kg M) ratios. An additional treatment consisted of feeding the leftovers from the two highest levels of food excess to six rams to have 300 g DM of L per day. A diet supplement was given to provide sufficient rumen degradable protein and sulphur to sustain microbial activity. Variances of organic matter (OM) digestibility (OMD, g/kg) and intake (g/kg M0·75) of both DM (DMI) and digestible OM (DOMI) of the original millet leaves were analysed using L, L/A, A/M and A/M0·75 as independent variables. Variation accounted for was highest when OMD was analysed as a function of L/A (R2 = 0·34) and when DMI was analysed as a function of A/M (R2 = 0·79) or A/M0·75 (R2 = 0·80). The response in OMD to varying L/A was best described by the equation OMD = 457 (s.e. 16) + 157 (s.e. 48) L/A. As L/A or A/M increased, L had a lower concentration of acid-detergent fibre and a higher in sacco OM disappearance. As A/M increased, DOMI and L/A increased following a diminishing return pattern. However, when A/M fell below 31·1 (s.e. 0·9) g DM per kg M, DOMI decreased linearly. No differences (P > 0·33) were observed for OMD between the original food (505 (s.e. 8) g/kg) and the re-fed leftovers (489 (s.e. 15) g/kg), but DOMI was lower with the latter (22•4 (s.e. 0·4) v. 20·3 (s.e. 0·8) g/kg M0˙75, P < 0·03). Results suggest that DOMI of millet stover should be determined at L/A much higher than the traditionally recommended (0·15), and support the hypothesis that farmers could benefit from feeding millet stover at high allowances to animals of high economic value and give the leftovers to less valuable or less selective stock.

Poultry litter has been used as an economical nitrogen (N) source in ruminant diets. However, litter must be processed to eliminate pathogens. Broiler poultry litter was processed by three different deep-stack methods: (1) uncovered, (2) covered with 0.1524 mm clear polyethylene, and (3) aerated by placing perforated pipe 1 m apart within the stack. Stack temperature was measured for 28 days. The litter was used to formulate experimental diets (186 g litter per kg), while the control diet contained urea as the N source. All diets contained 100 g/kg cottonseed hulls, 16 to 17 g/kg limestone, varying amounts of cracked maize and added retinol. The control diet contained 131 g/kg crude protein (CP) while the litter diets contained 125 g/kg CP. The diets were offered to 16 crossbred wether lambs (37 (s.e. 6·1) kg) in individual metabolism crates for 16 days. Blood was collected at the initiation and termination of the trial. Covering litter with plastic decreased temperature ivithin the stack (P < 0·05). Maximum temperature for the uncovered, covered and aerated stacks was: 68°C, 57°C and 72°C, respectively. Dry-matter intake and dry matter, energy and neutral-detergent fibre apparent digestibilities were not different (P > 0·05) among the diets. Apparent digestibility for N was less (P < 0·05) in lambs given uncovered and aerated litter than in those given the control diet. However, N apparent digestibility in lambs given covered litter was not different from that of those given the control diet. Gross energy and N retention of the four diets were not different (P > 0·05). Covering deep-stacked broiler poultry litter improved N digestibility by proportionately 0·15 compared with uncovered litter. Serum chloride was decreased while serum urea was increased (P < 0·05) in sheep consuming the litter-containing diets. Deep-stacked broiler litter should be covered in an air-tight manner in order to maximize its nutritive value.

Two groups of five sheep (7 months of age) were moved and isolated in pens which did not allow visual and tactile contact with other sheep for 24 h. They were then moved back to their original pens where visual and tactile contact was possible. After 24 h the procedure was repeated seven times for one group (group 8-1) and thirteen times for the other group (group 14-1). One group (control) of five sheep remained in pens where visual and tactile contact was possible. When isolated the lambs spent more time standing still in an alert posture, less time eating and resting, and vocalized more than control lambs. The heart rate of the lambs increased when they were moved between pens and during isolation. The plasma concentration of cortisol was significantly increased after 1·5 h and 3 h of isolation. The plasma concentration of prolactin was increased after 1·5 h of isolation. After 3 h of isolation the number of neutrophils in the blood was increased and the numbers of T-lymphocytes (CD2), T-helper-lymphocytes (CD4) and yd-lymphocytes (T19) were decreased. After 24 h of isolation the lymphocyte blastogenic response to Con A was lower and the numbers of T-lymphocytes and T-helper-lymphocytes were still less than those in control lambs. Although there were still behavioural changes when the lambs were isolated for the seventh time, no cortisol, prolactin and leucocyte changes were found. These results suggest that stressors similar to isolation, which can occur during normal management practice, may elicit short-term leucocyte changes in lambs.

In four experiments, 189 gilts either received PMSG antiserum around the time of a PMSG- (experiments 1, 2 and 3) or PMSG/hCG-induced (experiment 4) oestrus or served as controls. Ovulation rates were not affected by treatment. There was no treatment effect on pregnancy rate (experiments 2, 3 and 4). In experiment 2, numbers of embryos in PMSG-treated control gilts were quite low and were higher (P < 0·05) in those gilts subsequently receiving anti-PMSG treatment. In experiment 3, the mean number of embryos in control gilts were higher than in experiment 2 and there was no effect of immunoneutralization of PMSG. No treatment effect was evident in PMSG/hCG treated gilts (experiment 4). These data indicate that the immunoneutralization of PMSG is unlikely to improve the reproductive performance of gilts following a gonadotropin-induced oestrus except in gilts that otherwise would have poor performance.

Energy and nitrogen balance partitioning was studied in sheep given whole cottonseed (WCS), vetch hay and commercial concentrates. Sheep were offered diets containing 0 (CON) and 250 g/kg WCS at maintenance (LF) and twice maintenance (HF) levels. Digested energy, metabolizable energy (ME) and heat production (HP) were measured in a balance trial combined with indirect calorimetry. Dietary ingredients were also incubated in sacco in sheep rumens. Feeding WCS resulted in decreased energy digestibility at HF (0·718 v. 0·751) but not at LF. Loss of energy as methane expressed as a proportion of gross energy intake for CON and WCS respectively was 0·078 and 0·057 at LF and 0·061 and 0·051 at HF. In both diets, HP was similar at LF. In contrast HP amounted to 0·657 of the ME for CON and only 0·61 for WCS at HF.

Apparent nitrogen digestibility was not affected by WCS consumption. Urinary nitrogen was similar for both diets at LF, but at HF it was higher in the WCS diet. Thus at HF, retained nitrogen was 045 and 0·12 of apparently digested nitrogen for CON and WCS respectively.

Ruminal degradation of organic matter was proportionately 0·87 and 0·77 of apparent digested organic matter in the total tract for the CON diet, at LF and HF respectively and 0·80 and 0·73 for the WCS diet, at LF and HF respectively. In the four groups ruminal nitrogen degradation was equal to apparent whole-tract nitrogen digestion. It was concluded that feeding WCS may decrease metabolic HP in ruminants. Utilization of WCS could be improved by taking measures to decrease urinary nitrogen losses.

The morphological development of the sheep and the goat is different and this difference is manifested from early post-natal life. The main characteristic of kid goat carcasses is their low adipose tissue, and this is considered detrimental to quality. In an attempt to determine the nutritional causes of this, a study was performed with kid goats of the Granadina breed and lambs of the Segureña breed. Six kid goats and six lambs were slaughtered at birth, while a further eight kids and eight lambs were fed a milk replacer to satiety until the 60th day of life and slaughtered on the 61st day. Dry matter (DM) and metabolizable energy (ME) intakes and apparent digestibility of energy were determined in four balance periods between 8 and 60 days of life. From the intakes of ME and comparative slaughter data it was possible to calculate energy retention (ER), heat loss (HL) and energy retained as protein (ERp) and as fat (ERf) for kids and lambs. Kid goats showed a similar apparent digestibility of energy to lambs but had lower DM and ME intakes per kg metabolic body weight (M0·75) than lambs. For kids and lambs respectively these values were: 0·93 and 0·94; 45·4 and 50·1 g/kg M0·75 per day; 937 and 1033 kJ/kg M0·75 per day. Mean values for ER, HL, ERp and ERf rates were: 263, 674, 131 and 132 kJ/kg M0·75 per day for kid goats and, 343, 690, 132 and 211 kJ/kg M0·75 per day for lambs. Together with the different intake, kid goats showed a lower rate of ER and overall, a lower rate of ERf than lambs.

In three experiments, four grass silages and four grass hays were offeredad libitum to a total of 164 Finn Dorset ewes rearing twins in the 1st month of lactation. In addition, one of three constant daily levels (300, 650 or 1000 g fresh weight per ewe) of a barley-based concentrate was offered. In the first experiment, replacement rate of silage with in vitro organic matter digestibility (OMD) of 0·65 was less than for hay (OMD 0·59), at –0·09 v. –0·62 g forage OM per g concentrates OM. Consequently, lamb growth rate was greater and ewe weight loss was less with increased concentrate level for the silage than for the hay. In the second experiment, the replacement rates of three silages (OMD 0·56, 0·60 and 0·67) were not significantly different (mean –0·29) and, once again, increased concentrate level gave significantly better ewe and lamb performance. Finally, the replacement rates for three hays (OMD 0·51, 0·59 and 0·72) were also not significantly different (mean –0·30). Equations are presented to predict the intakes of hays and silages by ewes in early lactation.