Regressions of progeny growth rate and slaughter age on bull weight for age (400-day) record were estimated from data on 63 Hereford bulls. The bulls had been weight-recorded by the Meat and Livestock Commission and subsequently progeny-tested by the Milk Marketing Board on 1300 crossbred British Friesian steers. Interpretation of the regressions led to estimates of 16 to 35% (± 9 to 17%) for the ‘effective’ heritability of400-day weight. These are lower than the average in the literature and may indicate that farm records with natural rearing of bulls are less reliable than tests with uniform rearing and feeding conditions.

Feedlot performance and carcass characteristics were examined in bulls and steers with and without a subdermal Silastic capsule containing oestradiol-17β-dipropionate. Castration and/or oestrogen treatment was imposed at approximately 8 months of age. The implants were removed 56 days before slaughter, i.e. 140 days after the trial commenced. Bulls gained more rapidly (12·9%), converted food to live-weight gain more efficiently (18·0%) and yielded leaner carcasses than did steers (P < 0·05). The oestrogenic implant elevated serum oestradiol concentrations substantially (> ninefold) over that of bulls and steers and induced a castration-response in the former. Serum luteinizing hormone, testosterone and testicular growth were suppressed (P < 0·05) during the first 140 days of the trial in bulls, but returned to normal following implant removal. This response was paralleled by a reduction in average daily gain (P < 0·05) and food: gain ratio (P < 0·10). Contrary to expectations, average daily gain and food: gain ratio were not significantly improved in implanted steers. Oestrogen treatment reduced hot carcass weight, loin eye area and quality grade in both bulls and steers; the last as a result of decreased marbling and internal fat deposition. Results of this study suggest that excessive oestrogen as provided in this study via the implant fails to improve feedlot performance and carcass merit in steers and may, in fact, diminish the inherent anabolic attributes of the intact male. Additional studies are required to understand the complex interactions of androgens and oestrogens in the regulation of body growth and composition of male cattle.

Two forms of supplement, barley or dried grass pellets (G) were given to weaned lambs, set-stocked at pasture, at three stocking rates (43·5, 60 and 87 per hectare). The supplements were given either from weaning or from the time growth rate fell below a target value. The supplements significantly increased the proportion of lambs reaching the target weight (35 kg) and G was significantly better than barley, but slightly more G was given. The substitution value of supplement for herbage was 0·48 ± 0·12 and there was no difference in this value between barley and G. The proportion of lambs reaching the target slaughter weight was not influenced by whether the supplement was offered at weaning or delayed until lamb growth declined below a target level. Increase in stocking rate depressed the herbage intake and growth rate of the unsupplemented control lambs.

The behaviour of eight litters of Large White × Landrace piglets aged 3 weeks was scored in flat-deck cages every 2min for 12 h during the day, noting the frequences of 11 behaviour patterns. Similar observations were made at 6 weeks of age, and five main activities at the two ages were compared. There was a significant decrease in the frequency of aggressive encounters between the two ages, while the other activities remained at the same frequencies. The proportion of scores devoted to the main activities is given.

Post-weaning growth rate in pigs is frequently poor and variable. Choice feeding may offer the opportunity to rectify this. In experiment 1, 24 mixed sex groups of 16 pigs weaned with an average weight of 6·8 kg were blocked on weaning weight and assigned at random to the following treatments: (A) starter diet (18·3 g/kg lysine and 16·6 MJ digestible energy (DE) per kg) for 11 days followed by link diet (15·0 g/kg lysine and 15·3 MJ DE per kg) to 27 days; (B) starter diet and link diet offered in a free choice to 27 days; and (C) starter diet and weaner diet (13·0 g/kg lysine and 14·3 MJ DE per kg) offered in a free choice to 27 days. In experiment 2, 66 pigs were weaned at 6·3 kg, blocked as individuals on sex and weight and were randomly assigned to treatments as in experiment 1. In experiment 3, 24 single sex groups of 16 pigs were formed from pigs weaned at 7·8 kg. The groups were blocked on the basis of weaning weight and randomly assigned to the following treatments: (A) starter diet for 11 days followed by link diet to 26 days, (B) starter diet and link diet offered in a free choice to 26 days and (C) starter diet and link diet offered in a free choice to 26 days with feeder position rotated twice weekly. In experiments 1 and 3 pigs were offered a common weaner diet (14·1 g/kg lysine and 14·4 MJ DE per kg) following the experimental period. In experiment 1, daily gain was 406, 410 and 397 g/day (s.e. 6·6; P > 0·05) and food coversion efficiency (FCE) was 1·24, 1·21 and 1·27 g/g (s.e. 0·01; P < 0·01) during the period from day 0 to 27 for treatments A, B and C, respectively. The proportion of the diet selected as starter diet was 0·20, 0·50 and 0·47 (s.e. 0·023; P < 0·001) for treatments A, B and C, respectively. Within-pen variation in pig weight was similar for all treatments at day 14, 27 and 56 (P > 0·05), respectively. In experiment 2, daily gain was 403, 436 and 394 g/day (s.e. 13·0; P = 0·07) and FCE was 1·19, 1·16 and 1·24 g/g (s.e. 0·02; P < 0·05) during the period from day 0 to 26 for treatments A, B and C, respectively. The proportion of the diet selected as starter diet was 0·20, 0·57 and 0·53 (s.e. 0·024; P < 0·001) for treatments A, B and C, respectively. In experiment 3, daily gain was 465, 486 and 488 g/day (s.e.9·4; P > 0·05) and FCE was 1·14, 1·11 and 1·07 g/g (s.e. 0·015; P < 0·01) during the period from day 0 to 26 for treatments A, B and C, respectively. The proportion of the diet selected as starter diet was 0·21, 0·49 and 0·55 (s.e. 0·022; P < 0·001) for treatments A, B and C, respectively. Pig weight at day 49 was 36·4, 37·1 and 37·3 kg (s.e. 0·27; P = 0·09). It was concluded from these experiments that choice feeding did improve pig performance when a choice of starter and link diet was offered.

Test-day records for average flow rate (AFR) from the routine dairy recording from Bavarian Fleckvieh cows were analysed. Two data sets with observations on approximately 20 000 cows each were sampled from the total data set. For the estimation of variance parameters, a two-step approach was applied. In a first step multiple-trait restricted maximum likelihood (REML) analyses were carried out. For each of the first three lactations, six time periods with up to 33 days were defined. An algorithm for iterative summing of expanded part matrices was applied in order to combine the estimates. In a second step covariance functions (CF) for additive-genetic variances and non-genetic animal variances were derived using second-order Legendre polynomials plus an exponential term. Estimates of test-day heritability for AFR ranged from 0.21 to 0.40, and were largest in lactation 1. For lactations 1 and 3, heritabilities decreased considerably towards the end of lactation. Genetic correlation estimates within lactation decreased as the distance between days in milk (DIM) increased. Genetic correlations between corresponding DIM in the three lactations were generally large, ranging from 0.80 to 0.99. The largest estimates were found between DIM from lactations 2 and 3. Results from this study suggest that including AFR data from second and third lactations in genetic evaluation systems could the improve accuracy of genetic selection.

The expected annual selection response is a function of selection intensity (i), generation interval (t) and precision (p) of breeding value estimation. These three parameters may, under certain conditions, be reduced to functions of one variable, y, the mean age of breeding animals at culling, which is a simple function of the annual replacement rate. When the number of breeding males and females are different, i and t become functions of two variables ym and yf, the mean ages of males and females at culling. The values of y (or of ym and yt) giving the maximum selection response are established for different domestic species: for individual selection, where the ratio i/t is to be maximized, for selection on a repeatable criterion connected to female reproduction (prolificacy, milk or egg production), where the maximum of ip/t is to be determined, and for male progeny-testing. The results show that, the more prolific a species is, the more rapid the renewal of breeding animals must be and that the renewal should be more rapid for males than for females, particularly in species of low prolificacy. When selecting on female performances which are repeated in time, the optimum renewal rate of females is lowered relative to individual selection on a criterion measured once. Numerical values have been calculated for different species, with given reproduction parameters for each one.

The experiment measured lamb responses to supplementation of the pregnant ewe diet with vitamin E above requirement. Crossbred ewes were mated with either Suffolk or Texel rams. Twin-bearing ewes were randomly allocated (approximately 21 months of age at allocation) to one of four treatment groups (20 ewes per group, 10 mated with Suffolk and 10 with Texel rams). Treatments imposed were 50, 100, 150 or 250 IU supplementary vitamin E per ewe per day to give a four treatment by two sire-type factorial experimental design. Ewes were fed concentrates to meet energy requirements for stage of pregnancy and hay ad libitum. Diets were introduced approximately 6 weeks before lambing. Blood samples were obtained prior to introduction of diets, 17 days after introduction of diets and within 24 h of lambing from a subset of eight ewes per treatment (32 total). Colostrum samples were obtained from 10 ewes per treatment, 12 h after birth of the first lamb. All births were observed and a lamb vigour score was assigned to each lamb 5 min after birth. At 1 and 12 h after birth, rectal temperature, and at 12 h after birth, sex, crown-rump length and BW of each lamb were recorded. Mean ewe plasma α-tocopherol concentration prior to introduction of the diets was 1.5 μg/ml (s.e.m. 0.09) and did not differ between groups. There were positive linear (P < 0.001) effects of dietary vitamin E on plasma (17 days after introduction of diets) and colostrum (12 h after birth) α-tocopherol concentrations. Lamb vigour scores were superior (P < 0.001) for lambs sired by Texel rather than Suffolk rams but there were no differences as a result of vitamin E supplementation. Lamb mortality was low and unrelated to either sire or supplementary vitamin E. Lamb birth and weaning weights were also unaffected by vitamin E supplementation. Supplementing the ewe with vitamin E therefore had no effect on any lamb measurements.

The response of finishing Blackface lambs (mean initial live weight 29·6 kg) to shearing and level of concentrate supplementation on a silage-based diet was examined in two experiments. Silage intake decreased as concentrate level increased at mean rate of 0·13 and 0·26 g silage dry matter (DM) per g concentrate DM, in experiments 1 and 2 respectively, with no significant differences between unshorn and shorn lambs. Lambs gained 36, 97, 135, 193 and 224 g/day (s.e. 9·1; P < 0·001) in experiment 1 and 97,133,170,185 and 222 g/day (s.e. 9·9; P < 0·001) in experiment 2 when 0, 200, 400, 600 g/day and concentrate ad libitum were offered respectively. Shearing increased silage DM intake from a mean of 0·50 to 0·56 kg/day (s.e. 0·016; P < 0·05) in experiment 1, and from 0·80 to 0·90 kg/day (s.e. 0·013; P < 0·001) in experiment 2. There was no interaction between shearing and the level of concentrate offered. Despite higher DM intakes by shorn lambs, their live-weight gains were lower than those of unshorn lambs. Gains of unshorn and shorn lambs averaged 153 and 120 g/day (s.e. 5·8; P < 0·001) in experiment 1 and 162 and 161 g/day (s.e. 5·7; P > 0·05) in experiment 2 respectively. This appears to have resulted because shorn lambs could not fully compensate for their increased energy requirements after shearing, by increasing their DM intake. Shearing did not significantly influence carcass characteristics.

It was calculated that with lambs gaining 150 g/day, concentrate requirement was increased from 286 to 335 g/day and total DM intake from 965 to 1107 g/day as a result of shearing.

We investigated the effect of offering supplementary dietary fibres to suckling piglets on their behaviour and performance before weaning. From 5 to 22 days of age, suckling piglets were offered a high-fibre diet (HF; 5% cellulose; n=5 litters), or a control low-fibre diet (n=5 litters). Piglets were housed with the sows in individual farrowing pens, and had access to maternal milk until weaning, at 23 days of age. Behaviours of six focal piglets per pen were scored at 6, 16 and 21 days of age. All piglets were individually weighed at 5, 15 and 20 days of age and feed intake was measured daily at the pen level. Piglets on the HF diet were more active than controls (P=0.05), and spent more time suckling or massaging the udder (P=0.01) and interacting with pen mates (P=0.008). Time spent manipulating pen mates, which may reflect re-directed foraging activity in the absence of substrate, accounted for most of the time spent interacting with pen mates (⩾73% of total time spent interacting). Dietary fibres had no effect on BW and feed intake. In conclusion, inclusion of cellulose in the supplemental diet of suckling piglets affects behaviour, with no deleterious effects on performance before weaning.

These studies were conducted to determine whether dietary homoarginine, derived from guanidination of synthetic lysine, affects the measurement of apparent and true ileal amino acid digestibility in the pig and to determine the optimal ratio of o-methylisourea (OMIU) to free synthetic lysine in the guanidination reaction that produces homoarginine. In two preliminary experiments, specific amounts of lysine were weighed and added to a solution of 0·6 mol/l OMIU to produce OMIU to free synthetic lysine ratios of 2:1, 1·5:1, 1·4:1, 1·3:1, 1·2:1, 1·1:1 and 1·0:1. The mixture was incubated at a pH of 10·5 and a temperature of 20±1°C for 6 days. The highest yield of homoarginine (proportionately 0·995) was produced with an OMIU to free synthetic lysine ratio of 1·5:1. The serum concentrations of homoarginine and lysine were measured in two test pigs at various times after consuming a single meal containing either homoarginine or lysine. Blood samples were taken before and 0·5, 1·5, 2·5, 4·5, 6·0, 7·5, and 11·5 h after feeding. Thirty minutes after feeding the homoarginine-containing diet, the homoarginine concentration in serum was 0·013 mmol/dl, and increased to a maximum of 0·031 mmol/dl 1·5 h after feeding. Thirty minutes after feeding the lysine-containing diet, the serum lysine concentration was 0·011 mmol/dl and also reached its maximum concentration of 0·025 mmol/dl 1·5 h after feeding. The timing of the changes in concentration of homoarginine and lysine related to feeding were similar, which suggests that homoarginine is absorbed and metabolized in a similar manner to lysine. Six Large White×Landrace barrows, weighing 68·5±3·5 kg and fitted with a simple T-cannula at the distal ileum as well as a jugular vein catheter, were used to determine the effects of homoarginine on endogenous amino acid flows and apparent and true ileal amino acid digestibility. The experimental design was a doubly replicated 3×3 Latin-square design with the three treatments consisting of a lysine-free, zein-based diet and jugular infusion of a lysine solution; a lysine-free, zein-based diet supplemented with homoarginine; and a lysine-free, zein-based diet supplemented with l-lysine. There were no significant differences in endogenous ileal lysine flow for pigs receiving the different treatments (396·6, 407·6, and 360·4 mg/kg DMI, respectively, P=0·71). In addition, with the exception of phenylalanine (P=0·04), there were no significant differences (P>0·10) in the apparent and true ileal digestibility of crude protein and amino acids among the three treatments. Therefore, it would appear that the presence of dietary homoarginine, derived from guanidination of synthetic lysine, does not affect endogenous amino acid losses or the digestibility of crude protein as well as most amino acids. These results are therefore supportive of the use of the homoarginine method as a means of measuring true ileal lysine digestibility.

Animal health planning activities are not always providing a satisfactory positive impact on herd health and welfare. Moreover, evaluating the impact of advisory programmes is complex due to multiple interacting elements that influence its outcome. Therefore, measuring solely health outcomes is not sufficient: the whole process of the implementation and use of such programmes should be evaluated. In order to evaluate the impact of an intervention with a Herd Health and Production Management (HHPM) programme a process evaluation framework was designed and used. The intervention involved 20 organic dairy cattle farmers and their advisors, in both France and Sweden. In both countries 20 organic dairy farms were selected as control herds. The evaluation of the HHPM programme was based on: (a) the compliance to the programme; (b) the programme’s functions influencing herd health management practices and stimulating dialogue between farmers and advisors; (c) its effectiveness in terms of improving herd health compared with control farms. Complete compliance to the programme was fulfilled by 21 out of 40 farmers–advisors. Results from a questionnaire showed that the programme functioned as intended (e.g. by allowing early identification of herd health problems), stimulated change in farmers’ herd health management practices and farmer–advisor dialogue. Even though the majority of the users perceived that the programme contributed to herd health improvements, no significant differences in health outcomes were found when compared with control farms 12 months after the start of the intervention. The programme allowed creating an environment promoting the exchange of information between farmers and advisors, necessary to define pertinent advice in a farm-specific situation. Future research should aim at improving methods for the evaluation of the effect of advisory programmes, by identifying early indicators for effective advice and developing methods to evaluate the quality of advisory situations without interfering with them.

Seasonal fluctuations in oestrous activity and live weight were studied in ewes of the Marwari breed indigenous to the Rajasthan Desert in north-western India. Of the ewes examined 80 to 100% were in oestrus every month of the year, indicating thereby the non-seasonality of female reproductive activity in this breed. On average, each ewe exhibited heat 18 times a year. The incidence of silent heats was low (4·2 %). The average length of an oestrous cycle was 17 days, while the actual period of oestrus varied from 24 to 48 h with an average of 36 h. No seasonal effect on these activities could be observed. The maximum and minimum body weights of the animals were recorded during the autumn (October) and summer (June) months respectively. The body weights differed significantly (P<0·05) between months. Sexual activity in these animals is, therefore, apparently not affected by changes in body weight. The continuous nature of oestrous activity in Marwari sheep may be economically exploited by regulating the lambing season according o t the prevailing ecological conditions and market demands, without the use of hormones.

Two feeding trials were carried out with Israeli Friesian male calves, commencing at an average age of 7 to 10 days, and covering a suckling period of 30 days followed by a further 90 days. A conventional starter, or one that contained cotton hulls, was used. In each experiment one group of 10 animals served as a control and a similar group was monensin-supplemented. No coccidia were found in the animals. In experiments 1 and 2 monensin supplementation was associated with increased daily gains of 10% and 47% during the suckling period and of 6% and 17% during the next 90 days, but only the differences obtained in experiment 2 were significant. In both experiments, dry-matter intake relative to body weight was higher with monensin supplementation in period 1, but reduced in period 2. The effect of monensin on molar proportions of acetic and propionic acids was smaller than that reported by previous authors for older cattle.

A separate digestibility trial showed that monensin administered to suckling calves, either with milk replacer or directly into the rumen, improved dry-matter digestibility, increased the excretion of amylase, and tended to reduce that of trypsin and chymotrypsin.

The milk production of dairy goats under various regimes of mother-young contact from day 4 post partum were studied during the first 2 months of lactation, together with the prolactin (PRL) and growth hormone (GH) responses to udder stimulation. In the control group, 13 goats and their kids were left in permanent contact and did not undergo milking. In two additional groups, goats were machine milked once a day in the morning (at 0800 h) and kids were allowed 10 hours (from 1000 to 2000 h; 10H group, n = 11) or 5 h (from 1000 to 2000 h; 5H group, n = 11) of mother-young interaction per day. In the last group (MO, n = 10), mothers were permanently separated from their kids on day 4 post partum and milked once a day. Milk production during a 24-h period at 37 days post partum performed by controlled nursing and weighing of the kids (groups with kids) or by two machine milking 12 h apart (milking only group) revealed a higher production in the three groups with some mother-young contact than in the MO group. Total milk collected by milking over the 2 months of the study did not differ between the three groups that underwent milking. Kid weights at 2 months were 3.4 to 4.8 kg. lighter in the groups that underwent milking than in the control group. Hormonal profiles were significantly affected by restricted mother-young contact, with highest pre-stimulation concentrations of PRL and GH in the 5H group. Restricting mother-young contact from the first week postpartum can permit an early collection of milk without major effects on kid growth, when compared with one daily milking in goats totally separated from their young.

Recent studies suggest that the use of vegetable oils at expense of fish oil in aquaculture feeds might have potential negative effects on fish redox homeostasis and adiposity. Resveratrol (RESV) is a lipid-soluble phytoalexin present in fruits and vegetables with proven in vivo antioxidant function in animals. The present study aims to assess the potential use of RESV in Atlantic salmon feeds. To this end, post-smolt salmons with an initial BW of 148±3 g were fed four experimental diets for 15 weeks. A diet low in fish oil served as a control and was supplemented with 0, 0.5, 1.5 and 2.5 g/kg of RESV, respectively. The effect of the experimental diets on animal performance, tissue fatty acid composition, and the expression of genes encoding proteins involved in antioxidant signalling, lipid peroxidation, and metabolism were studied. Resveratrol significantly reduced feed intake and final BW of the salmon. Feeding RESV did not affect the sum of saturated and monounsaturated fatty acids or total lipids in the fillet. While the content of total polyunsaturated fatty acids was not affected, the percentages of some fatty acids in the liver and fillet were changed by RESV. Furthermore, in liver, the relative expression of glutathione peroxidase 4b, nuclear factor-like 2, and arachidonate 5-lipoxygenase remained unchanged across treatment groups. In conclusion, the negative impact of dietary RESV on FI and hence reduction of the BW discourages its inclusion in low fish oil diets for Atlantic salmon.

A growth experiment with 108 lambs (breed: German Merino Landsheep) was carried out to examine the effect of gender, body weight (BW) and feeding intensity on the deposition of Fe, Zn, Cu and Mn in the empty body (whole animal minus contents of the gastrointestinal tract and bladder). The lambs (50% female and 50% male animals) were fed at three feeding levels (‘low’, ‘medium’ and ‘high’ by varying daily amounts of concentrate and hay) and slaughtered at different final BWs (30, 45 or 55 kg). Six male and six female animals were killed at a BW of 18 kg representing the animals’ BW at the beginning of the comparative slaughter experiment. There were significant main effects for the treatments growth rate and final weight on the daily rate of accretion of the trace elements examined. Feeding intensity had a marked influence on the accretion rate for Fe (P < 0.001), Zn (P < 0.001), Cu (P < 0.001) and Mn (P = 0.003). With increasing feeding intensity (low, medium, high) the daily deposition of these trace elements increased (4.4, 5.2, 6.6 mg/day for Fe; 4.9, 5.5, 6.9 mg/day for Zn; 0.20, 0.36, 0.44 mg/day for Cu; 0.14, 0.16, 0.21 mg/day for Mn). Heavier final BW led to increased daily retention of Zn (P < 0.001) and Mn (P = 0.002). Gender had a marked influence only on the accretion rate for Zn (P < 0.001). Ram lambs had a higher daily deposition of this element than female lambs. Related to 1000 g empty body gain, the following concentrations were found for the trace elements examined: Fe 26.1 mg, Zn 30.0 mg, Cu 1.41 mg and Mn 1.04 mg. A feeding influence was given for Zn (P < 0.001) and Cu (P = 0.039). Feeding level low had higher Zn and lower Cu concentrations. Male animals showed less Fe (P < 0.001) and Zn (P = 0.034) per kg empty body gain than females.

Genetically similar nulliparous Polled Hereford heifers from a closed pedigree herd were used to evaluate the effects of dietary protein during the first and second trimester of gestation upon foetal, placental and postnatal growth. Heifers were randomly allocated into two groups at 35 days after artificial insemination (35 days post conception (dpc)) to a single bull and fed high (15.7% CP) or low (5.9% CP) protein in the first trimester (T1). At 90 dpc, half of each nutritional treatment group changed to a high- or low-protein diet for the second trimester until 180 dpc (T2). High protein intake in the second trimester increased birth weight in females (P=0.05), but there was no effect of treatment upon birth weight when taken over both sexes. Biparietal diameter was significantly increased by high protein in the second trimester with the effect being greater in the female (P=0.02), but also significant overall (P=0.05). Placental weight was positively correlated with birth weight, fibroblast volume and relative blood vessel volume (P<0.05). Placental fibroblast density was increased and trophoblast volume decreased in the high-protein first trimester treatment group (P<0.05). There was a trend for placental weight to be increased by high protein in the second trimester (P=0.06). Calves from heifers fed the high-protein treatment in the second trimester weighed significantly more on all occasions preweaning (at 1 month (P=0.0004), 2 months (P=0.006), 3 months (P=0.002), 4 months (P=0.01), 5 months (P=0.03), 6 months (P=0.001)), and grew at a faster rate over the 6-month period. By 6 months of age, the calves from heifers fed high nutrition in the second trimester weighed 33 kg heavier than those fed the low diet in the second trimester. These results suggest that dietary protein in early pregnancy alters the development of the bovine placenta and calf growth to weaning.

A 2 × 2 × 2 factorial experiment was conducted with 128 growing-finishing steer calves to examine the effects of feeding whole v. rolled barley in diets containing either a constant proportion of concentrate (0·67) or proportionately 0·33 concentrate for 56 days followed by 0·90 concentrate for 83 days, with the concentrate being given at either 08.00 or 15.30 h. Steers given hay at 08.00 h and concentrate at 15.50 h grew proportionately 0·05 faster (P < 0-05) and had better dry matter (DM): gain ratios (P < 0·05) during the first 56 days than those given concentrate at 08.00 h and hay at 09.00 h. By the end of the trial steers fed at 15.50 h had similar daily gains to steers fed at 08.00 h but required proportionately 0·02 less DM: gain (P <0·05). No significant difference in gain was detected between steers given whole (1·30 kg/day) or rolled (1·38 kg/day) barley, but those given whole barley ate proportionately 0-08 more DM daily and had a proportionately 0-15 poorer DM: gain ratio (P < 0-05). The digestibility of diets containing whole grain was reduced (P < 0-05). Thirty-six steers given whole barley bloated compared with nine given rolled barley (P < 0·05). No significant differences were found either in DM intake or in final proportion of concentrate in the diet between steers given the diet containing proportionately 0·67 concentrate throughout the feeding period and those given the variable concentrate diets. There was a trend for DM: gain ratios to be poorer for steers given the constant proportion of concentrate (6·89 v. 6·65).

An experiment was conducted to compare the voluntary intake and in vivo digestion for guanacos and sheep when offered perennial ryegrass at three different growth stages: vegetative growth (VG), emerging inflorescence (El) and mature inflorescence (MI). Dry-matter (DM) intake ranged from 1·19 to 2·12 kg/day for the guanacos and 0·79 to 1·52 kg/day for the sheep. When expressed on a metabolic live-weight (M0·75) basis, the intake of the guanacos (55·8, 43·1 and 44·1 g DM per kg M0·75 daily on the VG, El and MI grasses respectively) and the sheep (54·4, 45·7 and 47·4g DM per kg M0·75 daily respectively) were similar (s.e.d. = 3·70). Apparent digestibilities of all food constituents were also similar. In terms of food choice, the response of the two species to grass stem differed; the guanacos selected (El) or tolerated (MI) this fraction, while the sheep tolerated (El) or avoided (MI) it.