In two experiments Red Danish dairy calves of both sexes, and of two lines selected for high (H) and low (L) milk fat production (proportional difference 0·22), were tested at 4 months and again at 10 months of age for their growth hormone (GH) release following intravenous administration of either thyrotropin releasing hormone (TRH, experiment 1: 0·15 μig/kg live weight, no. = 16 H + 10 L) or arginine hydrochloride (ARG, experiment 2: 0·10 g/kg live weight, no. = 19 H + 10 L). The GH response was measured in serial blood samples for 0·5 h prior to and for 2 h following intravenous injections. The response peak, measured as the geometric mean of the 5-, 10- and 15-min samples following TRH was greater in the line selected for high yield, at 10 months (H, 42·4 μg/l; L, 20·6 μig/l; P < 0.01) but not at 4 months of age (H, 25·4 μg/l; L, 18·6 μg/l; P > 0·05). The response peak following arginine measured in the 20-, 30- and 45-min samples was smaller than the peak following TRH and did not differ between selection lines, although there was a tendency for H calves to have a larger release at 10 months of age. After puberty (10 months) male calves responded more to both secretagogues than females, while there was no difference before puberty (4 months). These results suggest that GH release may be useful as a juvenile predictor of dairy merit, but results need to be confirmed in further and larger studies.

Responses of selection for milk production and secondary traits were predicted in open nucleus schemes using a deterministic model. Secondary traits considered were: traits recorded during lactation (e.g. mastitis resistance; calving ease); traits recorded in the nucleus only (e.g. food intake); traits recorded early in life (e.g. growth rate); and traits recorded late in life (e.g. longevity). Also, genotype × environment interactions between nucleus and commercial herds and predictors of merit in juveniles were considered.

Extension of the breeding goal to include an uncorrelated secondary trait, which was recorded at each lactation, had the same heritability as milk production (assumed throughout to be 0·25) and half its economic value, increased total economic gain by a factor of 0·12. This increase was only 0·04, if the heritability of the secondary trait was 0·1. The situation for traits of low heritability was not improved by progeny testing of young bulls due to the short optimized generation intervals. Gain increased only by a factor of 0·04, if the economic value was 0·25.

Including a secondary trait of heritability 0·25 and a genetic correlation with yield of 0·5 in the index, only increased economic response rates by a factor of 0·04. However, when the genetic correlation was –0·5 the benefits were greater with increases of 0·09, 0·10 and 0·22 for heritabilities of 0·05, 0·10 and 0·25, respectively. Hence, including traits with low heritability but with strong negative correlations with yield, which might apply to fertility and disease resistance, increased rates of gain moderately.

If an uncorrelated secondary trait was recorded in the nucleus only, e.g. food intake, and had half the economic value of milk production, total gains increased by a factor of 0·10. Hence, recording of secondary traits can be restricted to the nucleus with only minor loss of gain. The extra economic benefit was greatest from secondary traits measured early in life compared with late in life, e.g. longevity, with benefits increased by factors of 0·24 and 0·06, respectively.

Open nucleus schemes are robust in the presence of genotype × environment interactions between nucleus and commercial herds, if the breeding value estimation method accounts for these interactions, juvenile indicator traits of milk production may increase rates of gain by a factor of 0·11, if the heritability of the indicator trait is 0·25 and the correlation with milk production is 0·5.

Three silages were prepared from the primary growth of a predominantly perennial ryegrass sward (dry matter (DM) 175 g/kg; crude protein 142 g/kg DM; water-soluble carbohydrates (WSC) 243 g/kg DM). Herbage was wilted for 24 h and then treated with either an inoculant/enzyme preparation (Lactobacillus plantarum, Streptococcus faecium and Pediococcus acidilactici), formic acid applied at 4·2 lit (Add F, BP Chemicals) or no additive. Time series analysis of laboratory silages revealed that different patterns of fermentation had been achieved: formic acid treatment resulted in high levels of residual WSC and low levels of lactic acid, indicative of an inhibited fermentation, whilst treatment with the inoculant/enzyme preparation resulted in high levels of lactic acid with a low level of residual sugars, as expected with an enhanced fermentation. Analysis of the material ‘as fed’ showed that losses in the WSC content of the formic acid-treated silage had occurred in the clamp. Secondary fermentation of lactic to acetic acid was apparent in the untreated silage, but not in the inoculant/enzyme-treated silage. Digestibility, as determined using Greyface wether lambs, was marginally higher for both additive treatments when compared with the untreated silage. An evaluation of the silages for milk production was carried out at three levels of concentrate supplementation using 18 Ayrshire × British Friesian cows in a replicated 3×3 Latin-square design experiment. Treatment with formic acid resulted in significantly higher DM intakes, but this was not reflected in milk energy output. Cows offered the inoculant/enzyme-treated silage partitioned energy away from milk production toward body tissue deposition (average milk yields 19·9, 19·9 and 15·2 kg/day, and weight gain 0·26, 0·38 and 0·81 kg/day for the untreated, formic acid and inoculant/enzyme-treated silages respectively). The reason for this is not clear, but it is postulated that microbial capture of degraded nitrogen may have been impaired with the inoculant/enzyme-treated silage, resulting in an imbalance in metabolizable protein: metabolizable energy.

The performance of 273 Hereford calves from lines previously selected for lean growth rate (LGR) or lean food conversion efficiency (LFCR), on a concentrate diet, was evaluated on a grassland diet over a period of 3 years. Both bull and heifer calves were tested, and each year the performance test ran from the 1st week of May (average age of 233 days) until the 1st week of October. Carcass lean content was predicted from body weight and ultrasonic backfat depth, and lean gain was calculated from the product of live-weight gain and predicted carcass lean content. The LGR line was superior to the control (C) line for live-weight gain on test, lean gain on test and lean gain from birth until the end of test. The LFCR line performed similarly to the C line for live-weight gain on test and lean gain on test, but was inferior for total lean gain. For lean gain on test, the proportional differences between the lines were similar to those predicted from parental breeding values for LGR, but they were smaller for total lean gain. The lines did not differ significantly for either fat depth or predicted carcass lean content.

Heritabilities were high for all growth traits, e.g. 0·52 (s.e. 0·17), 0·54 (s.e. 0·17) and 0·59 (s.e. 0·17) for live-weight gain on test, lean gain on test and total lean gain, but lower for fat depth and carcass lean content, 0·25 (s.e. 0·17) and 0·14 (s.e. 0·16), respectively. Genetic correlations with LGR, measured on a concentrate diet, were 0·57 for lean gain on test and 0·56 for total lean gain. If only males were considered, these correlations rose to 0·80 and 0·70, respectively. Coheritabilities between the two environments for lean growth were close to 0·3. It is concluded that although there is some evidence for genotype × environment and genotype × sex interactions, selection for lean growth on a concentrate regimen will still be effective in improving grassland performance.

Broiler poultry litter was deep-stacked (2·5 m high) in three ways: (1) uncovered, (2) covered with 0·1524 mm clear polyethylene and (3) surface-watered to form a 2·5 cm crust upon drying. After 30 days, each litter was used to formulate two diets containing proportionately 0·25 or 0·50 poultry litter (dry-matter basis). Urea was used as the nitrogen source in the control diet. All diets contained 100 g/kg cottonseed hulls, 20 g/kg limestone and cracked maize. Each of the seven diets was offered to 12 crossbred steers (two pens per diet; initial body weight 204 kg) for 84 days. Blood was collected and body weights measured every 28 days. After 84 days, liver biopsies were obtained from four steers per diet and an additional three steers per diet were penned individually and nutrient apparent digestibilities were determined. Steers gained 1·6 kg/day on the urea diet and 1·2, 1·3 and 1·2 kg/day on the diets containing 0·25 litter, uncovered, covered or watered, respectively. Steers consuming the 0·50 litter diets gained 1·0, 0·9 and 1·0 kg/day, respectively (significant linear decrease; P < 0·01). Litter depressed (P < 0·04) apparent dry matter, organic matter and gross energy digestibilities regardless of stacking method. However, nitrogen apparent digestibility was decreased by uncovered and watered litter only. Increased proportion of litter in the diet resulted in increased serum sorbitol dehydrogenase and aspartate aminotransferase and liver copper concentrations (P < 0·07); however, clinical copper toxicosis (haemolytic crisis) was not observed. Dietary inclusion of broiler poultry litter also increased serum phosphorus and decreased serum calcium concentrations (P < 0·07). Covering deep-stacked litter preserved nitrogen quality, but improvements over uncovered litter were not of sufficient magnitude to elicit improved animal performance in this study.

To examine the possibility of reducing milk substitute costs in artificial rearing of goat kids, 36 castrated male Saanen kids at 2 days of age were randomly allocated across six treatments in a 2×3 factorial design experiment. Milk substitute was provided for the kids over a period of 28 or 39 days, and daily levels of milk substitute dry matter (DM) intake were 0·140,0·176 or 0·272 kg.

Increasing the level of milk substitute offered had no significant effect on intake of concentrate up to weaning, but did significantly reduce the total intake of concentrate through to slaughter. Weaning after 39 days, as opposed to 28 days, also significantly reduced the total intake of concentrates. However, there was no difference when the same total quantity of milk substitute was consumed over different periods. Increasing the daily intake of milk substitute significantly increased daily live-weight gain to weaning, but tended to increase the time taken by kids to regain their weaning weight following cessation of milk substitute intake. However, milk substitute level and weaning age did not significantly affect overall daily live-weight gain or the length of time taken to reach 28 kg.

Eight additional kids were slaughtered at 2 days of age to develop regression equations relating initial body composition to live weight. These relationships were similar to others published for 2-day-old Saanen kids. Treatments had no significant effect on overall rates of fat, crude protein, water, ash and energy gain or on final body composition, carcass weight or carcass composition when kids were slaughtered at a live weight of 28 kg. These data suggest that savings in milk substitute may be achieved by reducing the weaning age and/or the daily intake level.

Two groups of 10 lactating does were housed separately, in isolation from bucks. Does in one group (T) were implanted with melatonin; the second group (U) were not implanted. After 30 days, five implanted and five non-implanted bucks were introduced, singly, into both groups of females each day. Subsamples of milk were taken from the daily output of each doe on 3 days each week for progesterone analysis.

Mean milk progesterone concentration during anoestrus varied significantly amongst individuals (P < 0·001), but the difference between T and U groups was not significant (1·51 and 1·93 (s.e.d. 0·52) μg/l, respectively). Elevated progesterone levels, indicative of a short oestrous cycle and commencing days 2 to 5 after male exposure, were observed in most does. Mean progesterone concentrations were 9·9 and 9·6 (s.e.d. 1·32) μg/l in T and U does respectively. Most does showed a second short cycle starting at 12 to 18 days, (mean concentration 8·4 and 10·6 (s.e.d. 1·64) ng/l, respectively). Untreated does then returned to anoestrus until mated at 63·1 (s.e. 0·94) days after male introduction. In contrast, T does either became pregnant or had a normal oestrous cycle, followed by a repeat cycle or pregnancy (mean onset 21·7 (s.e. 2·22) days after male introduction). The mean time of effective mating for group T does was 37·3 (s.e. 5·91) days, 26 days earlier than for U does (P < 0·001). Mean progesterone concentration in early pregnancy was 65·7 (s.e. 5·78) and 67·6 (s.e. 5·41) μg/l in T and U does, respectively. Males did not become sexually active until after the onset of luteal activity in the females, although treated males were earlier than untreated. There were no significant differences in lactation pattern associated with the progesterone profiles in the two groups.

The introduction of males during late anoestrus initiates short luteal cycles. Only those does closest to onset of the breeding season, in this case induced by melatonin, continue to cycle normally and mating success may require early stimulation of sexual activity in males.

Eighty castrated male lambs were allocated to either an initial slaughter group (no. = 16) or one of eight treatment groups (no. = 8). Ammoniated barley straw was offered ad libitum. This was supplemented with sodium (Na) propionate (0 or 20 g/day), formaldehyde-treated casein, (protected casein, 0 or 50 g/day) and/or calcium (Ca) salts of long-chain fatty acids (Ca soap, 0 or 30 g/day), as a factorial design. Measurements were made of food intake, live-weight gain and wool growth, rumen fluid parameters and changes in body composition over a period of 155 days.

Food intake (g dry matter per kg live weight) was lower in the groups supplemented with Ca soap and Na propionate. Fleece-free live-weight gain was increased by supplementation with protected casein and Ca soap, but was not affected by Na propionate. Supplementation with protected casein increased wool yield. Adjusted means for water, protein and ash content of the body (adjusted to mean fleece/digesta-free body weight at slaughter of 27·1 kg) were affected significantly by the second-order interaction between the supplements. Adjusted body water and protein mass were lower when Na propionate was given alone or with Ca soap and protected casein. Fat mass tended to be higher under those conditions. Supplementation with Ca soap increased adjusted fat and gross energy contents and decreased adjusted protein and water mass. Supplementation with protected casein decreased total body fat and increased adjusted protein mass in the body. The partitioning of water, protein, fat, ash and energy between the carcass and non-carcass residues was affected to a small extent also. These results demonstrate interactive effects of the supplements used, on nutrient partitioning in lambs offered straw-based diets.

The objective of this work was to determine the apparent bioavailability of magnesium from four different types of calcined magnesites of Greek origin. These four types (A, B, C, D) were different in particle size fractions and production process. The solubility of the above four magnesium samples and their fractions were determined: (a) in the laboratory using ammonium nitrate solution after 24-h shaking and (b) in vivo using a nylon bag technique after 24-h incubation.

Solubility was correlated with apparent bioavailability as determined in a balance experiment with five wether sheep in a 5×5 Latin-square design.

Sheep were kept in metabolism cages and were given daily a basal diet (500 g hay + 700 g concentrate) plus 2 g magnesium supplements from types A to D. The magnesium bioavailability of the basal diet was used as a base for the determination of the bioavailability of magnesium in A, B, C and D supplements.

Magnesium apparent bioavailability of the basal diet was found to be 0·203 and, for the supplements A, B, C and D, 0·381, 0·339, 0·315 and 0·292 respectively. The solubility of supplements A, B, C and D in ammonium nitrate solution and in vivo (using the nylon-bag technique) was found to be 0·812, 0·805, 0·784 and 0·773 or 0·294, 0·152, 0·102 and 0·200 respectively.

The solubilities of the magnesium supplements in ammonium nitrate solution and in vivo both reflected dietary bioavailability differences up to a point, but neither was well enough correlated with the apparent bioavailability as determined by the balance experiment, this being judged to be the most precise method for bioavailability determination.

Sixty castrated male lambs fca. 37 kg) were allocated to an initial slaughter group (no. = 12) or to one of six treatment groups (no. = 8). Chopped oaten hay (sprayed with 10 g urea per kg) was offered ad libitum with 57 gjday chopped lucerne hay. Additional supplements were 0 or 57 g/day formaldehyde-treated casein (protected casein) and volatile fatty acids (VFAs) at ca. 1·45 MJ gross energy per day. The VFAs given were acetate or propionate or a mixture of these (molar ratio 4: 1). Daily food intake and weekly live-weight (LW) gain were measured and rumen fluid and blood were collected. The lambs were shorn, slaughtered and body composition was determined.

Food intake (g/kg LW) was not affected by treatments. Supplementation with protected casein increased LW gain and wool growth. Supplementation with propionate reduced LW gain, but not when given with protected casein. Plasma concentrations of urea-nitrogen and insulin were increased, and plasma somatotropin decreased in lambs given protected casein. Final body content of water, fat, protein and gross energy, adjusted to the mean fleece/digesta-free body weight of 36·5 kg, was not affected by the treatments. The partitioning of water, fat and energy between the carcass and the rest of the body was affected by the treatments. Excretion of VFAs in urine was measured in two sheep in experiment 2, and was negligible compared with the quantity of VFAs given. It is concluded that energy from salts of VFAs, in particular propionate, is used inefficiently for body-weight gain in lambs given low-protein roughage diets. The nutritional treatments had only marginal effects on the composition of body gain.

Thirty-six wether lambs were given food hourly consisting of mature chopped oaten hay, sprayed with 10 g urea per kg hay. A pelleted supplement was given containing 0 or 75 g/day fish meal and 0 or ca. 1·5 MJ/day gross energy as acetate or propionate in a 2 × 3 factorial design. Dry matter (DM) digestibility, nitrogen retention and urinary allantoin excretion were determined over 7 days. Tissue protein kinetics were estimated using 15N-glycine. Net fluxes of acetate, bicarbonate and glucose were estimated with continuous infusion of 14C-acetate, 14C-bicarbonate and 3H-glucose respectively.

Intake of oaten hay (g DM per kg live weight per day) was reduced by supplementation. Live-weight gain was lower in lambs supplemented with propionate than in lambs given the basal diet only. Supplementation with fish meal increased DM digestibility, live-weight gain and wool growth. Daily excretion of urinary allantoin did not differ between groups of lambs. Nitrogen retention and protein flux were reduced in lambs supplemented with acetate or propionate and were increased in lambs given fish meal. Plasma acetate concentrations were higher for lambs supplemented with acetate. However, net flux of acetate did not differ between groups of lambs. The net flux of glucose was increased by supplementation with propionate and with fish meal. Plasma levels of β-hydroxybutyrate were reduced in lambs supplemented with propionate.

Availability of propionate and glucose were not limiting live-weight gain in these lambs. Also, a high ratio of acetate to propionate did not reduce the apparent efficiency of nutrient use.

Scottish Blackface sheep have been selected for either increased or decreased predicted carcass lean content at 20 weeks of age, using an index combining ultrasonic backfat depth and body weight. The index was designed to alter carcass lean content without changing body weight. After 4 years there have been large responses in the index and fat depth, the proportional difference between the divergent lines in fat depth is 0·28, but body weight and ultrasonic muscle depth have not changed between the lines. The realized heritability for the index is 0·45. Heritabilities for the index, ultrasonic fat depth, body weight and ultrasonic muscle depth, calculated using multivariate restricted maximum likelihood, are 0·47 (s.e. = 0·14), 0·39 (s.e. 0·13), 0·23 (s.e. 0·12) and 0·36 (s.e. 0·14), respectively. The selected lines will be used to investigate relationships between carcass lean content, viability and maternal performance under the harsh environmental conditions encountered in the Scottish hill environment.

Amine-organic buffers (BESKOH and TESTRIS) were compared for their ability to be used for buck semen dilution in a freezing procedure. BESKOH showed better results (P < 0·05) at the time of dilution and after chilling at +5°C (72% motility v. 54% at dilution and 62% v. 39% after chilling). After freezing and thawing, none of the variables measured (motility, normal acrosome ridge and normal swelling) was significantly different. A washing procedure was necessary when freezing was undertaken and egg yolk addition was necessary to avoid cold shock as the temperature lowered during chilling. There were no significant differences between a 3% and 12% level of egg yolk addition.

Two experiments were made to study the effects of a mist or large-droplet water spray for different lengths of time, on pig behaviour in lairage prior to slaughter and on subsequent carcass Quality. Water spraying caused more pigs to stand, chew the pen walls and root around the pen floor compared with unsprayed controls, and they also tended to fight more. The sprayed pigs produced meat of superior quality in terms of m. longissimus dorsi rate of acidification and colour. It is suggested that these benefits were due to the effects of evaporative cooling and increased water intake.

In an experiment of factorial design, female rabbits were given four diets, containing 13·0, 11·4, 10·4 and 9·7 kJ digestible energy (DE) per g and subjected to two remating intervals (R) of 1 to 2 days (intensive) or 9 days (semi-intensive) from parturition. The experiment lasted for 2 years during which 352 does produced a total of 1254 litters. The only major differences due to diet were that the diet with the highest energy concentration, and which contained 35 g/kg added fat, promoted a significantly higher energy intake in lactation (111 v. an average of 94 MJ DE) than the other diets, and thereby increased litter weight at weaning at 28 days (3·48 v. 2·99 kg). Diet and R showed no major interactive effects. The intensive treatment significantly reduced parturition interval (46 v. 52 days) and increased the output of weaned rabbits per doe per year (35 v. 29). As actual R was more variable than the theoretical R imposed by the treatments, further analyses were made by dividing the does into four groups according to the actual R. In these analyses, the effects of R on current and subsequent lactation performance were assessed separately. The main difference between the groups was that litter size increased significantly with R (e.g. litter size at birth in subsequent parities was 8·0, 9·2, 9·7 and 9·0 for mean intervals of 2, 10, 16 and 37 days). However, the same pattern of differences occurred in the current parity, indicating that it was litter size that affected R, rather than the reverse (i.e. does with small litters conceived earlier than those with larger litters).

A proline-free, chemically defined amino acid basal diet was compared with this same diet fortified with 4g L-proline per kg when given to 5-kg pigs. During a 28-day feeding period, daily gain, food intake, and gain: food ratio of pigs given the proline-free diet were not different (P > 0·05) from those of pigs given the proline-supplemented diet. Young pigs can apparently synthesize adequate quantities of proline endogenously to meet their needs for both growth and maintenance.

The effect of level of barley feeding (200, 400 or 600 g fresh matter per ewe per day) on the change in body condition, between weaning and mating, of ewes offered barley straw treated with ammonia was examined in experiment 1. In experiment 2, a 2 × 2 factorial design was used with two levels of restriction of metabolizable energy in lactation (proportionately 0·85 and 0·70 of the requirements) followed by two levels of feeding of barley (250 or 500 g) in the main experimental period. In experiment 1 the intake of straw was significantly lower when 600 glday was offered, and ewes given 200 g/day barky had significantly lower gain in live weight and body condition score. In experiment 2 the level of energy intake in lactation did not affect the intakes of straw, but the current level of barley feeding did.

Zeolite, cellulose acetate phthalate (CAP) and maize starch were used as the coating materials for encapsulating pancreatic protease, which was proposed as an additive to enhance the food efficiency and growth rate of weanling pigs. In this study, microcapsules were formed by the process of coacervation in liquid paraffin media, where the deposition time was in the range of 20 to 60 min, and the concentrations of CAP, zeolite and maize starch were 20, 40 and 120 g/kg respectively. Hardening by n-hexane was achieved with 15 min of stirring. Microcapsules generated by this method were 20 to 30 mesh in diameter. They were stable for at least 3 h in simulated gastric conditions (pH 3·97), but disintegrated rapidly under simulated intestinal conditions (pH 6·82).