The effect of post-ruminal fermentation on faecal output of purine bases (PB) and urinary excretion of their derivatives (PD) was studied by the infusion of yeast RNA (2·9 g/day), corn starch (100 g/day), cellulose (200 g/day) and saline solutions into the gastro-intestinal tract offour sheep (35·4 kg live weight) fitted with caecal and duodenal catheters and given 0-80 kg/day alfalfa hay. All substrates were infused into the caecum except cellulose that was infused into the proximal duodenum.

The infusion of RNA did not affect either the faecal excretion of PB or the urinary excretion of allantoin or total PD, although xanthine excretion increased significantly from <0·01 to 0·12 mmol/day.

Starch and cellulose infusions promoted a significant increase in the faecal excretion of diaminopimelic acid (206 and 159 v. 131 mg/day) and PB (4·55 and 3·62 v. 2·29 mmol/day) and modified the partitioning of total nitrogen losses between faeces and urine. The urinary excretion of allantoin and total PD were not affected by the caecal infusion of starch (6·60 and 22·9 v. 7·02 and 22·8 mmol/day) but both tended to increase with the duodenal infusion of cellulose (7·75 and 26·4 mmol/day).

It is concluded that the urinary excretion ofPD is independent of either the supply of nucleic acids to the caecum or the extent of hind gut fermentation although it may be affected by variations in the flow of undigested fibre along the small intestine.

The effects on the behavioural and physiological responses of sheep of providing rest, food and water (lairage) during 24 h of either road transport or stationary confinement (treatment) were investigated. Twenty-four hours of continuous treatment was compared with 12 h of treatment followed by either 12 h of lairage, 3 h of lairage or 3 h of food and water on the vehicle, followed by a second 12 h of treatment. A further group of sheep was kept as controls. The plasma cortisol concentration was increased at the start of the journey and after 24 h of continuous transport it was still greater than that in controls (P < 0·05). Apart from a mobilization of body energy reserves as indicated by raised plasma concentrations offree fatty acids after 12 h and β-hydroxybutyrate after 24 h there was no evidence that the welfare of the sheep during the journey was compromised after a particular time. During the lairage and immediately after the second 12-h transport period, the sheep appeared to be hungry. Although sheep transported for 24 h without lairage drank more post transport than controls, there was no biochemical evidence of dehydration during the journey. The sheep lay down during the journey and there was no apparent difference between lairage treatments in the proportion of scans spent lying down during either the second 12-h treatment period or during the first 12 h post treatment. There were fewer potentially traumatic events during the second 22 h of the 24-h journey than during the first 12 h of the journey and no apparent effect of lairage during the journey on the frequency of potentially traumatic events during the second 12-h period of transport.

There was evidence to suggest that a period of lairage during a 24-h journey can be beneficial in providing sheep with an opportunity to eat, drink and avoid the stressors associated with transport. However, providing hay and water on the vehicle during a 3-h stationary period as compared with unloading into a lairage cannot be recommended. Although sheep readily ate hay on the vehicle, they did not drink sufficient water. This resulted in dehydration and a greater plasma cortisol concentration during the remainder of the journey than in those that had been lairaged for 12 h and a greater water intake post transport than in those given either no lairage or 12 h of lairage.

Experiment 1, with rams (17·0 kg initial weight (M)), and experiment 2, with steers (203 kg M), involved 2 × 2 arrangements of treatments to compare the effect of doubling the amount of stover offered (25 or 50 g/kg M daily) and chopping (unchopped or chopped), upon intake, selection and live-weight change. The stover used was a non-bird-resistant, local variety (Dinkamash). The particle length distribution of the chopped stover (produced by a tractor-driven chaff cutter) was: <4·5 mm, 0·148; 4·5 to 8 mm, 0·157; 8 to 12 mm, 0·181; 12 to 20 mm, 0·269; 20 to 33 mm, 0·168; 33 to 54 mm, 0·040; 54 to 90 mm, 0·003; >90mm, 0·034. The stover was supplemented with minerals and cottonseed cake (sheep, 0·1 kg dry matter (DM) per day; cattle, 0·76 kg DM per day). Experiment 1, over 56 days, involved 48 Menz Highland, 18-month-old, rams, with four replicate pens containing three rams. Experiment 2, over 49 days, used 32, individually penned, Friesian × zebu yearling steers. With rams, doubling the amount offered and chopping increased intake, and the effects were additive (unchopped: 0·98 v. 2·24; chopped: 1·08 v. 1·60 (s.e. 0·071) kg DM per pen per day). With steers, there was an amount × chopping interaction (P < 0·05) (unchopped: 3·7 v. 4·7 chopped: 3·6 v. 3·9 (s.e. 0·16) kg DM per day), with chopping reducing intake of stover offered at 50 g/kg M per day. Increased intakes were associated with increased growth rate. In both experiments refused stover contained less leaf-plus-sheath than offered stover but the difference was more pronounced in rams compared with steers indicating the superior selective ability of the rams. In rams offered unchopped stover, the increase in stover intake with increasing amount offered was accounted for by a proportional 1·03 unit increase in consumption of leaf-plus-sheath and a 0·06 unit reduction in intake of stem. Doubling the amount of unchopped stover offered increased intake of both rams and steers by 0·27 unit. Chopping stover was clearly beneficial for rams but not for steers. Doubling the amount of stover offered is a simple excess-feeding strategy to apply. Excess feeding also increases the proportion of stover refused from about 0·2 to 0·5, thus generating an uneaten residue available for other purposes, e.g. mulch or compost.

This paper reports the procedures put into place in the UK for the genetic evaluation of pedigree beef cattle and estimation of genetic trends using a comprehensive model to allow critical analysis of progress made under previous data recording schemes. Live weights of Simmental, Limousin, Charolais, South Devon and Aberdeen Angus beef cattle, recorded by the Meat and Livestock Commission (MLC) from 1970 to 1992 were analysed, as part of a project to introduce best linear unbiased predictions (BLUP) of breeding value in the British beef industry. Birth weights were available from MLC or the relevant breed society, (4000 to 84000 records, depending on the breed) and 200- and 400-day weights were estimated by within-animal linear regression on all available weights (resulting in 8000 to 48000 records per breed). Animals were retrospectively assigned to contemporary groups within herds, separately for each trait, taking account of observed calving patterns. Records were adjusted to correct for heterogeneity of variance between herds. BLUP evaluations were then performed within breed, fitting a multivariate individual animal model. In addition to additive direct genetic effects, additive maternal genetic and dam permanent environmental effects were included for birth weight and 200-day weight. Unknown parents were assigned to genetic groups, based on estimated date of birth. The model included fixed effects for contemporary group, sex, month of birth, birth type (single or multiple), embryo transfer births, fostered calves, breed of dam, proportion purebred and age of dam. Genetic trends were estimated by regressing estimated breeding values for animals on their year of birth. Trends in birth weight, 200-day weight and 400-day weight between 1970 and 1992 were approximately 0·09, 0·73 and 1·38 kg per annum respectively for the Charolais breed; 0·08, 0·76 and 1·33 kg per annum for the Simmental; 0·06, 0·53 and 0·89 kg per annum for the Limousin; 0·12, 1·02 and 1·86 kg per annum for the Aberdeen Angus; and 0·03, 0·38 and 0·82 kg per annum for the South Devon breed.

Previous reports have suggested the presence of a major gene influencing prolificacy in the Cambridge sheep breed. To estimate the effect of such a gene, high and low prolificacy groups were established in a Cambridge sheep flock between lambing years 1990 and 1993. In 1990-1991 ovulation rate (OR) was used as the basis for allocating ewes into groups but for 1992-1993 litter size was used also as a secondary selection criterion. In 1990 and 1991 small groups (each with one ram) of extreme phenotype were formed. In 1992 and 1993, six high and six low groups were formed using all available ewes, increasing the number of observations but with less selection pressure for high and low prolificacy. Results from the groups were interpreted on the basis of a major gene with additive effect resulting in three distinct genotypes (CC, Cc and cc). It was assumed, because of the selection method adopted, that CC ewes were exclusively in the high groups, heterozygotes (Cc) were distributed between the high and low groups and that cc ewes were exclusively in the low groups. In 1990-1991 there was a difference in OR of 4·0 between ewes allocated to the high and low groups. In 1992-1993 the difference was 1·9. Litter size differences between groups averaged 0·73. Whilst the high group progeny had higher OR, the differences between groups were less than differences observed between groups based on selected dam records, possibly a reflexion of the young age at which progeny records were collected. Differences between the high and low groups suggest a gene effect for adult ewes of approximately 2·0, with expected OR, above a basal level of 2·0, of 4·0 and 6·0 for heterozygous and homozygous carriers respectively. The effect of the gene in young ewes (predominantly 1 to 2 years) was approximately 0·8.

It has been suggested that the induction of maternal behaviour in non-pregnant ewes by treatment with oestrogen and progesterone followed by artificial, mechanical vaginocervical stimulation (VCS), could be used to produce foster mothers for orphan or triplet lambs. To investigate the reliability of the technique, 46 non-pregnant sheep of two breeds (Suffolk (S) and Scottish Blackface (BF)) and two levels of experience (nulliparous (N) and multiparous (M)) were used. All ewes were given 6 weeks of treatment with vaginal sponges containing oestradiol and progesterone, followed by 2 min of VCS and exposure to a neonatal (< 2 days old) foster lamb. Plasma oestrogen and prolactin concentrations were significantly elevated by the hormonal treatment; prolactin was significantly higher in M ewes compared with N ewes (BFN = 91, SN = 107, BFM = 301, SM = 687 μg/l, P < 0·005). Significant udder development was seen in most ewes (proportionately 1·0 M v. 0·62 N, P = 0·01) and more M ewes produced milk than N ewes (0·67 v. 0·19, P < 0·005). No ewes showed maternal behaviour to the lamb from hormone treatment alone. After VCS, one of 26 N ewes and five of 12 M ewes expressed maternal behaviour. In the M ewes, significantly more S ewes were maternal than BF ewes (proportionately 0·75 SM v. 0·25 BFM, P < 0·05). It is concluded that the technique alone is not sufficiently reliable to be a useful fostering aid. It is suggested, however, that previous exposure to neonatal lambs, handling of ewes before testing and using newborn lambs, may be fruitful areas of investigation to improve the technique.

The relationships between body weight (BW), body condition score (BCS) and internal fat deposits were studied in Latxa dairy ewes. In 2 years, the BW and BCS of 20% of the ewes in 14 flocks were recorded at the beginning of the mating period (pre-mating), and in the 1st month of lactation (post lambing). BW increased with age (BW = 54·05 × (1-e−0·988 × age), and the mature weight was not reached until 4 years, after which weight did not differ between pre-mating and post-lambing periods. Body condition score, however, differed between the two periods. The regression coefficients (b) of BW on BCS, when flock-year and age were included in the regressions, differed significantly (P < 0·05) in the pre-mating and post-lambing periods, and were 5·3 (s.e. 0·31) and 6·3 (s.e. 0·43) kg per unit BCS, respectively. The correlation coefficients (r) were 0·77 and 0·71 respectively, compared with 0·42 and 0·38 when the flock-year and age of the ewes were not included in the regression.

Thirty-seven of these ewes, with BCS between 0·75 and 4·00, were slaughtered, the weights of omental, mesenteric and kidney and channel fat recorded, and the lumbar fat thickness assessed at the last rib. The regressions between the weight of fat deposits and lumbar fat thickness and BW and BCS fitted to semi-logarithmic equations, except for mesenteric fat, in which the relationship was linear. Body condition score was a better predictor than BW for individual fat deposits, with proportionately 0·81 to 0·83 of the variation in the weight of the deposits accounted for by variation in BCS and 0·57 to 070 by variation in BW.

The role of endogenous opioids and the dopaminergic system on the inhibition of luteinizing hormone (LH) secretion during early and late anoestrus, together with its modulation by the plane of nutrition were investigated in ewes with a short anoestrous season. In early anoestrus (22 March; day 0), two groups of ovariectomized, oestradiol-treated adult Rasa Aragonesa ewes, maintained under natural photoperiod at 41°N, were given enough food to provide 1·4 × (high; H; no. = 6) or 0·5 × (low; L; no. = 6) energy requirements for maintenance. The effects of administration of the opiate receptor antagonist naloxone (1 mg/kg at four 1-h intervals) (day 15) and of the dopaminergic2 receptor antagonist pimozide (0·08 mg/kg) (day 21) on LH secretion were assessed. A second experiment was carried out in late anoestrus (21 June) using the same protocol. A significant increase in LH pulse frequency after naloxone treatment for both H and L groups was detected in late anoestrus. Number ofLH pulses after naloxone injections in early anoestrus also increased in H (P < 0·05) and L ewes (P = 0·08). The effect of pimozide injection on mean LH pulse frequency was greater in early than in late anoestrus, especially in ewes receiving a high plane of nutrition (P < 0·05 and P = 0·07 for H and L ewes, respectively in April and P = 0·07 for H ewes in July). A significant increase of LH pulse amplitude was also detected in early anoestrus in H ewes (P < 0·01). These results provide evidence that endogenous opioid mechanisms are involved in the inhibition ofLH pulsatile release both in early and late anoestrus in ewes with a short seasonal anoestrus. The ability of pimozide to increase LH pulse frequency in early anoestrus could be enhanced by a high plane of nutrition in the breed studied.

The objective of this study was to assess the growth and development of carcass composition of entire male and female lambs of three British hill breeds (Scottish Blackface, Welsh Mountain, and Shetland), from weaning to approaching maturity, when kept under conditions designed to be nutritionally non-limiting. Lambs were weaned at 8 weeks of age and given a high-quality pelleted diet ad libitum until slaughter at one offive different degrees of maturity. The Gompertz growth function was used to characterize, for each genotype, the growth curve and to provide estimates of mature weight. As expected, there were significant effects of breed and sex on both food intake and growth rate. Growth rate was depressed, relative to the Gompertz fit, during the months of October to January, and intake was similarly depressed. The estimates of mature weight for the females of each breed were: Scottish Blackface, 69; Welsh Mountain, 61; Shetland, 46 kg. The mature weights of the males were found to be not significantly different from 1-3 times the mature weight offemales. Relationships between carcass composition and live weight were derived by allometric regression. This study provides the first full description of the growth and meat production potential of the three breeds.

The objective of this study was to compare the effects of melatonin implants combined with intravaginal, progestagen-impregnated pessaries with the conventional treatment of progestagen pessaries followed by pregnant mare serum gonadatrophin (PMSG) on the reproductive performance of ewes during the anoestrous period.

A commercial flock of 179 seasonally anoestrous Chios crossbred ewes was used. The ewes within the flock were randomly allocated to one of two groups. Ewes of group MP (melatonin + pessaries) received melatonin implants on 20 March (50 days before the target breeding date of 10 May) and were treated with intravaginal progestagen pessaries 35 days later (25 April). Ewes of group PP (pessaries + PMSG) were also treated with pessaries on 25 April. After 14 days the pessaries were removed from both groups and 500 i.u. PMSG was injected (i.m.) into ewes of group PP only. Fertile rams were introduced into both groups 24 h after sponge removal. Pregnancy rate and litter size were determined by ultrasound scanning 80 days after ram introduction.

Pregnancy rate at first oestrus was significantly higher in group MP than in group PP (57 v. 40%, P < 0·05). The overall conception rate during two oestrous cycles was significantly higher in group MP than in group PP (78 v. 59%, P < 0·02). The groups did not differ significantly in the mean number of foetuses per pregnant ewe that conceived during the first or second oestrus after pessary removal (1·78 and 1·87, respectively). The total number of foetuses per treated ewe was higher in group MP than in group PP (1·39 v. 1·10) as a consequence of the difference in pregnancy rate.

Four ewes fitted with ruminal and duodenal T-piece cannulae were each given six diets in a 6 × 4 factorial design. Diets or experimental treatments consisted of two ratios of forage: concentrate (700:150 (LC) and 400: 600 (HO). Forage was ammonia-treated straw and the concentrate was formulated with barley supplemented with one of three protein sources: sunflower meal, soya-bean meal or fish meal. Duodenal flows ofdigesta were estimated by the dual-phase technique using Co-EDTA and Yb acetate as liquid and solid markers. Microbial nitrogen (N) was estimated from the digesta flow of purine bases and 15N enrichment using as reference samples, bacterial isolates from the liquid (LAB) or solid (SAB) phase of rumen digesta.

Duodenal flow of purine bases (mmol/day) was lower on LC (12·9) than HC (17·7) diets but in both treatments it was depressed by fish meal (12·3) compared with either soya-bean (17·3) or sunflower meal (16·3) as supplements (s.e. 1·13). Urinary excretion of purine derivatives showed a similar trend, 8·6 v. III mmol/day in LC and HC respectively and 8·8 v. 10·4 and 10·5 mmol/day in fish meal, soya-bean and sunflower meal diets (s.e. 0·56), respectively. Variation in excretion of urinary purine derivatives was mainly associated with digestible organic matter intake with an average ratio of 1·7 (s.e. 0·11) mmol per 100 g digestible organic matter intake. Irrespective of the microbial marker used, microbial yield was higher in animals offered HC than in those offered LC and with soya-bean or sunflower meal compared with fish meal supplemented diets. The microbial purine bases/N (mmol/g) ratio varied between LAB (1·99, s.e. 0·092) and SAB (1·69, s.e. 0·071) isolates leading to different estimates of microbial-N yield (g) from duodenal purine bases (7·76 (s.e. 2·84) v. 9·13 (s.e. 3·24)), urinary excretion of allantoin (5·57 (s.e. 2·0) v. 6·57 (s.e. 2·03)) or total purine derivatives (6·43 (s.e. 2·39) v. 7·56 (s.e. 2·77)). Urinary excretion of allantoin or total purine derivatives provided consistently lower estimates of duodenal microbial-N than duodenal purine bases or 15N, although it closely reflected the pattern observed in direct measurements.

The objective of this study was to assess the growth and development of carcass composition of entire male and female lambs of three Greek dairy breeds (Boutsko, Serres and Karagouniko), from weaning to live weights approaching maturity, when kept under conditions designed to be nutritionally non-limiting. Lambs were weaned at 6 weeks of age and given a high quality pelleted food ad libitum until slaughter at one offive different degrees of maturity. As expected, there were significant effects of breed and sex on both food intake and growth rate. The Gompertz growth function was used to characterize, for each genotype, the growth curve and to provide estimates of mature weight and appeared to describe adequately growth rate. For two breeds (Serres and Karagouniko) food intake (g/day) increased in a linear fashion with time up to approximately 24 weeks of age and then remained static for the last 10 to 22 weeks of the experiment; this coincided with the increased environmental temperatures during summer. No such plateau in food intake was seen for the Boutsko sheep. The estimates of mature weight (kg) for the females of each breed were: Boutsko, 60; Serres, 66; Karagouniko, 77. These were substantially in excess (1·4 times on average) of the pre-trial calculations of mature weight. The mature weights of the males were found to be not significantly different from 1·3 times the mature weights of the females. Relationships between carcass composition and weight were derived by allometric regressions. This study provides the first full description of the growth and meat production potential of the three Greek breeds; as such it is part of an overall study that aimed to characterize (for thefirst time as far as the authors are aware) nine sheep breeds from diverse regions of the European Union.

The effect of lambing date on the subsequent onset and duration of ovarian cyclicity in Mule (Bluefaced Leicester × Scottish Blackface) ewes was investigated. Nineteen ewes which had lambed in January (16 January 1993 (s.e. 3 days)) and been weaned in February-March and 22 comparable ewes which had lambed in May (14 May 1993 (s.e. 2 days)) and been weaned on 23 August were maintained at pasture as two isolated groups. A raddled vasectomized ram was continually present with each group from 14 July 1993 to 26 May 1994 and marked (oestrous) ewes were recorded twice weekly. Ovarian activity was assessed by measuring peripheral progesterone concentrations in blood samples collected twice weekly and by laparoscopic viewing of the ovaries of all ewes during October, January and March. The onset and duration of ovarian activity were significantly affected by the previous lambing date. For January and May lambing ewes, mean dates of onset were 5 September 1993 (s.e. 2 days) v. 25 September 1993 (s.e. 4 days) (P < 0·001) and of cessation were 5 April 1994 (s.e. 5 days) v. 10 April 1994 (s.e. 3 days). Mean durations of ovarian activity were 212 (s.e. 6) and 195 (s.e. 5) days (P < 0·05) during which 12·4 (s.e. 0·29) and 11·5 (s.e. 0·38) ovarian cycles respectively were recorded. Ovulation rate was not affected by previous lambing date but was significantly lower in March compared with October (January lambing ewes 1·7 (s.e. 0·1) v. 2·3 (s.e. 0·1) (P < 0·001); May lambing ewes 1·6 (s.e. 0·1) v. 2·1 (s.e. 0·1) (P < 0·01)). Results demonstrate that (i) Mule ewes have a potential breeding season of up to 8 months duration; (ii) the onset and duration of ovarian activity can be influenced by previous lambing date; and (Hi) a seasonal decline in ovulation rate may, in practical terms, result in a lower lambing percentage for animals bred towards the end of their natural breeding period.

The aim of this study was to determine whether the decrease in plasma growth hormone (GH) levels during a lamb's first autumn is a function of photoperiodic or developmental changes. Wether lambs (no. = 30) from Coopworth sheep selected for low (lean) or high (fat) backfat plus a randomly selected line (control) were subjected to long (16 h light: 8 h dark) or short (8 h light: 16 h dark) photoperiod over a 5-month period after the summer solstice. The animals were regularly blood sampled to determine plasma hormone concentrations. Daily food intake and weekly live weights were measured and the animals were slaughtered at the end of the trial to determine body composition.

Food intake and growth rate were greater for sheep on long than on short photoperiod but photoperiod had no major effect on carcass composition. Mean and basal plasma GH, as well as the number and amplitude of pulses, were not affected by photoperiod, however GH secretion decreased from January to May. Plasma levels ofprolactin, insulin-like growth factor 1 (IGF-1), insulin and glucose were greater in animals under long than short photoperiod, while non-esterified fatty acids (NEFA) were unaffected by photoperiod.

Lean animals had greater mean and basal plasma GH and increased number and amplitude of pulses compared with fat animals. Prolactin concentrations were also greater in the lean than in the fat sheep, while there were no differences in insulin, glucose and NEFA levels. IGF-1 levels were higher in lean than in fat sheep under long photoperiod but lower under short photoperiod.

These results suggest that the decline in plasma GH with increasing age is not affected by photoperiod. While long photoperiod stimulates plasma prolactin and IGF-1 levels as well as intake and growth, the relationship between these parameters is unknown. Hormonal differences between lean and fat genotype sheep are found within the GH axis and prolactin but not within the gonadotropin or insulin axes.

Four ewes fitted with ruminal and duodenalT-piece cannulas were given fourdietsin a 4 × 4 factorial design. Diets consisted of 700 (HF) or 400 (LF) g/day of ammonia-treated barley straw supplemented respectively with 150 or 600 g/day of concentrate made up with barley plus either soya-bean meal (SBM) or fishmeal (FM) as the protein source, offered at 2-h intervals. Duodenal flowsof digestawere estimated by the dual-phasetechniqueusing CoEDTAand Yb-acetate as markers and (15NH4)2SO4 was infusedinto the rumento label microbial N. Bacteria were isolated from the liquid (LAB) or solid (SAB) rumendigesta. Purinebases (PB) were isolated by precipitationin an acid solution of AgN03, and microbial contribution either to the duodenalnitrogen(N) or PB were determinedby 15N measurements induodenaldigesta and bacteria.Simultaneously, therumen degradation of Nand PB contained in SBM and FM was studiedby incubating supplements in polyesterbags in the rumen.PBcontent (mmol/g dry matter)and guanine: adenine(G/A) ratio of barley strawwas 2·89 and 5·23; barley grain,7·91 and 111;SBM, 18·8 and 1·26; and FM, 58·9 and 6·96, respectively. Duodenal flow ofPB(mmol/day)was significantly higher than PB intake on all diets and G/A ratio showed a meanvalue of 0·97, similarto the ratios determined in SAB(0·80) and LAB (1·04) and muchlower than diets(1·31 to 4·32). Microbial contribution to duodenal Nflow ranged from43·3% to 61·0%, beinghigherin SBM(59·0%)thanin FM(46·7%)diets. However, microbial contribution to duodenal PB was not affected by the experimentaltreatment, accounting for proportionately 0·77 of total PB at the duodenum. Rumen degradability of PB was much higher than that of total N and in both cases degradability was higher in SBM than FM. Direct measurements of non-microbialN were significantly higher than values determined by the polyester-bagmeasurements. However, once corrected forthe endogenousN (52 mgN per kg live weight)contribution, results show edan acceptable agreement. Duodenal flow of PB non-attributable to microbes (unlabelled PB) showed a mean value of 3·25 mmol/daywithouta significanteffect of dietary treatment. However, undegradablePBsupply determinedfor0·02, 0·05 and 0·08 per h fractional out flow rates were proportionately lower than 0·025 with SBM and 0·100 with FM diets of the estimated duodenalPB flow. Despite the magnitudeof the unlabelledduodenalPB, the close agreement between G/A ratios in duodenaldigesta and bacteria suggests thatthe contribution of dietary PB to the duodenalflow was low and seemsto confirm the reliability of values obtained from polyester-bag measurements.

Four adult ewes (mean weight 42·6 kg) fitted with oesophageal fistulae were given 5 mmol/day ofallantoin or saline solutions by intrajugular continuous infusion. The experiment was a randomized cross-over design, with two consecutive 3-day infusion periods. One kg/day fresh matter of either chopped or pelleted fescue hay was distributed over 12 meals and salivary flow estimated from dilution of Co-EDTA infused into the buccal cavity. Allantoin infusion resulted in a rapid increase in its plasma concentration (84 to 128 (s.e. 1·5) μmol/l) and urinary excretion (9·6 to 13·3 (s.e. 0·18) mmol/day) without significant differences between diets. Salivary allantoin also increased (4·6 to 6·4 (s.e. 0·60) ymol/1) in response to infusion, although the concentration of total purine derivatives in saliva was only proportionately 0·08 that of plasma. Renal and salivary clearance of oxypurines, allantoin (78 (s.e. 5·0) ml/min and 13 (s.e. 0·7) ml/h), uric acid (466 (s.e. 98·0) ml/min and 45 (s.e. 9·8) ml/h) and creatinine (104 (s.e. 3·0) ml/min and 14 (s.e. 1·1) ml/h) were constant, irrespective of diet and infusion treatments. Urinary recovery of infused allantoin averaged 0·78 (s.e. 0·031) but salivary secretion, equivalent to about 0·003 of urinary losses, was not the explanation for the incomplete recovery.

A selection experiment was established in Coopworth sheep in 1981 to breed for increased or reduced ultrasonic backfat depth (scan C). Foundation females came from four flocks recorded for scan C and live weight, with weight-adjusted scan C data within flock being used for initial screening and subsequent selection. Three groups of animals per source flock, comprising proportionally the fattest 0·12, a random sample, and the leanest 0·12, were used to establish the F, control and L lines, respectively. Ewe flock numbers from 1981 to 1992 averaged 51 per line. Foundation rams were selected in the same manner from four different farms (two sources each in 1981 and 1982) to provide F line (proportionally the fattest 0·04), control line and L line (leanest 0·04) rams for use in 1981 and 1982, with four mated per line per year. Thereafter homebred rams were selected, with 41 or 42 homebred rams being used per line until 1992. Average generation intervals were 2·13 years and annual inbreeding rates per line 0·004. Bivariate heritability estimates for log scan C and log live weight, and a univariate estimate for log scan C using restricted maximum likelihood with an animal model, were 0·28, 0·22 and 0·38, respectively (all with s.e. 0·03). There was a suggestion of lower heritabilities in the L line for log scan C after adjustment for live weight. Realized heritabilities in the F and L lines were 0·34 (s.e. 0·07) and 0·26 (s.e. 0·03), respectively. Deviations of back-transformed weight-adjusted scan C in the last 2 years ofF and L data analysed (1991 and 1992 birth years) from the control flocks were 2·08 and −0·85 mm, which corresponded to responses of +2·50 and −1·03 phenotypic standard deviations, respectively. In addition there were relatively large responses in live weight taken at scanning, with F and L lines averaging 34·0 and 40·2 kg, compared with 38·0 kg for controls in the 1991 and 1992 birth years. The genetic and phenotypic correlations between log scan C and log live weight at scanning were 0·16 (s.e. 0·07) and 0·46 (s.e. 0·01) respectively.

The Baluchi breed is the most common native breed of Iran adapted to harsh environments in the eastern parts of the country. The data used in the present study, collected from two research flocks at the Abbasabad sheep breeding station in north-east Iran, included 20 534 animals descended from 363 sires, 5992 dams, 282 maternal grandsires, and 2865 maternal granddams during the period 1966 to 1989. The traits recorded were: birth weight (BW), weaning weight (WW), weight at 6 months (W6), weight at 12 months (YW), pre-weaning gain (WG), post-weaning gain (PWG), lamb fleece weight (LFW), ewe fleece weight sheared before first joining (FW1) and adult ewe fleece weight (FW). Genetic parameters, estimated with restricted maximum likelihood and a two-trait animal model, were similar in the two flocks. Direct heritabilities for the various body weight traits were moderate and varied between 0·13 and 0·32, while the maternal heritabilities were low and varied between 0·01 and 0·12. Direct and maternal genetic correlations between WW and weights at later ages were moderate to high (0·59 to 0·96). Direct heritabilities of weight gain measures varied between 0·12 and 0·19, while no significant maternal influence on either of these weight gain measures could be detected. The estimates of direct genetic correlation between WG and PWG were positive and varied between 0·54 and 0·74, while negative maternal genetic correlation (0·17 on average) between WG and PWG was detected. For LFW, direct heritability was low and no maternal heritability could be shown. For FW1, both direct and maternal genetic influences were demonstrated (0·07 to 0·26). Direct genetic correlation between LFW and FW1 was very low and close to zero, while maternal genetic correlation was positive and relatively high (0·72 on average). The relative contributions to phenotypic variance from variance components due to common environmental effects ranged from 0·01 to 0·15 for all traits. The repeatability of FW was low (0·03 to 0·12).

Oxalic acid is found in high concentrations in some plants consumed by ruminants and may cause renal toxicity. To determine whether exposure to oxalic acid affects the capacity of the rumen of sheep and goats to degrade the compound, 20 animals (10 sheep and 10 goats) were dosed with free oxalic acid by gelatin capsule twice daily for 3 weeks at one of five levels (0·0, 0·3, 0·6, 0·9 and 1·2 mmol/kg live weight (M) per day). Rumen samples were collected by stomach tube in the week prior to the start of dosing and in each week of the 3-week experiment. Oxalic acid degradation capacity was measured by adding uC-labelled oxalic acid to rumen fluid in vitro and capturing evolved 14CO2. Rates of degradation increased with increasing level of administration (2·30, 4·71, 6·74, 9·83 and 13·90 mmol of oxalic acid degraded per I rumen fluid per day for doses 0·0, 0·3, 0·6, 0·9 and 1·2 mmol/kg M per day, respectively; P < 0·001). Rates of degradation increased during the dosing period (P < 0·001) with the largest increases occurring in the 1st week of dosing. Goats showed a greater response than sheep, with a higher mean oxalic acid degradation capacity (9·04 v. 5·95 mmol of oxalic acid degraded per I rumen fluid, P < 0·05). Oxalic acid administration did not influence plasma calcium concentration or cause renal function impairment as measured by plasma creatinine concentrations. The experiment demonstrated adaptation in the rumen to potential toxins in the host diet and suggests that the rumen micro-organisms of goats may have been more adapted to degrading oxalic acid than sheep.

Six adult and six juvenile goats were used to estimate their feeding preferences when three grasses (ryegrass, barley and brome) and two legumes (clover and alfalfa) were tested. Each grass was separately tested with both clover and alfalfa. A comparison between alfalfa and clover was also performed. The plants were harvested just before their utilization, chopped into 4- to 6-cm pieces and offered to the animals in plastic baskets. Preferences were evaluated by means of a series of seven short-term trials. Each short-term trial consisted of two single-food presentations and one choice-presentation. In the first single-food presentation animals received one of the two plants to be tested. In the second single-food presentation they were offered the alternative plant species. In the choice presentation they received the two species simultaneously. During each presentation animals were allowed to eat for 20 min or take a maximum of 50 bites. In the single-food presentations bite rate, bite mass and intake rate of both juvenile and adult animals were influenced by the plant species offered. Indeed, all goats tended to display a higher intake rate and bite mass for grasses than for legumes. A grass/legume ratio of the intake rates was also computed for each grass-legume comparison. These ratios tended to be higher for juvenile than for adult goats. The results of the choice presentations indicated that food preferences were not affected by age as all goats preferred grasses to legumes and clover over alfalfa. This experiment showed that age may not play an important role in the development of food preferences.