A line of mice, at its limit to selection for high body weight did not decline in performance over 11 generations of random mating, neither did it respond when selection was renewed. The experiment tested a method of improving body weight by a scheme which had earlier increased litter size under similar circumstances. The scheme was to derive partially inbred lines from the plateaued line, to select during inbreeding and, finally, to cross the best inbreds. Body weight was not increased, but the study allowed further examination of the residual genetic variance in the line.

During inbreeding, the inbred lines became clearly differentiated in body weight, proving that loci controlling body weight had not become fixed. There was also a significant response to selection for a lower body weight during inbreeding. The pattern of results suggested the segregation of recessive genes, detrimental to high body weight but which selection had become inefficient at removing. A genetic model compatible with the results accommodated several such recessives, perhaps as many as 10, each with an effect of about two-thirds of a standard deviation (or some equivalent combination of gene number and effect), and at frequencies of around 0·2. Nevertheless, the total improvement in body weight to be gained by their elimination was only half a gram, or less than 2 %. Thus, substantial genetic effects can occur at individual loci despite trivially low heritabilities and negligible potential gains.

With the aim of carrying out chimaerism and somatic cell–midblastula transition (MBT) embryos co-culture experiments in freshwater fish species, we evaluated the effect of osmolarity and composition of two media commonly used in cell fish culture on MBT zebrafish embryos and their further development and survival. To this end, wild zebrafish dechorionated embryos in midblastula stage were cultured for 6 days (Experiment 1: 189 embryos) or 1 h (Experiment 2: 150 embryos) in three different media: Hanks’ 10% (H-10), 35 mOsm; Hanks’ 100% (CH), 315 mOsm; and L-15 with serum (L-15: 315 mOsm). High osmolarity affected the survival rate (6 days: L-15: 45.1% v. CH: 72.34% v. H-10: 100%, P < 0.05; after 6 days: 0% both in L-15 and CH) and slowed their developmental timing. Embryos showed tail deformation (curly) as well as body paralysis at 48 h when they showed tail movements at 28 h. Differences in tail deformation were observed between high-osmolarity groups (CH: 85.10% v. L-15: 98.04%; P < 0.05). In Experiment 2, no effects on survival rate were observed. Teratogenic effects were only observed in L-15 (L-15: 12.98% v. CH: 0%; P< 0.05). Loss of motility was not detected in any group at 48 h. Optimum osmolar condition for cultured cells and also embryonic cells is around 315 mOsm and so, during chimaerism experiments (usually practised at MBT stage), present results indicate that midblastula embryos can acceptably bear the effects caused by 315 mOsm (CH) for 1 h, even though this involves a certain delay in developmental timing.

Reproductive performance of purebred Angus (A) and Criollo (C) cows and crossbred CA and AC cows in the temperate area of Buenos Aires, Argentina, was assessed through the study of reproductive rates, calving date, first insemination date, number of inseminations and weight related variables. The herd was grazed on pastures all year round. Matings were by artificial insemination with visual oestrus detection, from October to December. Heifers first calving was at 3 years of age. All traits were analysed with general linear models including, as corresponded, fixed effects of dam and calf genetic groups, calving year and month, dam physiological status, calving age and first order interactions. Female genetic group adjusted means were used to estimate direct (gl) and maternal (gM) breed differences and heterosis (hl) effects on reproductive traits. Weaning rate was mostly determined by oestrons detection rate. Due to the inhibitory effects of nursing on reproduction, female genetic group effects were significant for suckling cows only: mean oestrous detection rate was higher (P < 0·05) for crossbred cows (AC: 91·2 (s.e. 5-1) %; CA: 88·4 (s.e. 2·9) %) than for A (76·3 (s.e. 2·0) %) and C (49·9 (s.e. 3·3) %); direct breed effects favoured A (glA - g1c = 26·4 (s.e. 3·7) %; P < 0·001) and h1 was 26·7 (s.e. 3·4) % (P < 0·001). When only oestrous-detected cows were considered, direct breed effects were significant only for pregnancy rate fg1A —g1c = 8·5 (s.e. 4·4) %) whereas h1 was significant for pregnancy (8·3 (s.e. 3·8) %), calving (9·3 (s.e. 4·1) %) and weaning (10·1 (s.e. 4·1) %) rates (P < 0·05). Criollo cows calved later than crossbred (≍19 days) and A (≍15 days) cows mainly due to longer post-partum anoestrous. For calving date, direct breed effects favoured A (g1A — g1c = 20·8 (s.e. 5·9) days; P <0·0·001) and h1 was 11·4 (s.e. 2·8) days (P < 0·001). Low reproductive performance in C was not associated with live iveight at the beginning of mating. This genetic group was the latest in showing oestrous behaviour, even when not suckling. Number of inseminations was similar for the four genetic groups. These results sustain the principle of utilizing Fl Criollo-Angus cows to improve beef herd productivity, whereas they do not support the recommendation of using purebred Criollo females under this type of production system.

The effects of inclusion in the diet of different sources of soya bean meal (SBM) on growth performance, total tract apparent digestibility (TTAD) and apparent ileal digestibility (AID) of major dietary components and mucosal ileum morphology were studied in Iberian pigs weaned at 30 days of age. From 30 to 51 days of age (phase I), there was a control diet based on regular soya bean meal (R-SBM; 44% CP) of Argentina (ARG) origin and five extra diets in which a high-protein soya bean meal (HP-SBM; 49% CP) of the USA or ARG origin, either ground (990 μm) or micronized (60 μm), or a soya protein concentrate (SPC; 65% CP) substituted the R-SBM. From 51 to 61 days of age (phase II), all pigs were fed a common commercial diet in mash form. The following pre-planned orthogonal contrasts were conducted: (1) R-SBM v. all the other diets, (2) SPC v. all the HP-SBM diets, (3) micronized HP-SBM v. ground HP-SBM, (4) HP-SBM of ARG origin v. HP-SBM of US origin and (5) interaction between source and the degree of grinding of the HP-SBM. Dietary treatment did not affect growth performance of the pigs at any age but from 30 to 51 days of age, post weaning diarrhoea (PWD) was higher (P<0.001) and the TTAD and AID of all nutrients were lower for pigs fed the R-SBM diet than for pigs fed the HP-SBM or the SPC diets. However, no differences between the HP-SBM and the SPC containing diets were detected for any trait. The TTAD of organic matter (P=0.07) and gross energy (GE) (P=0.05) tended to be higher for the micronized HP-SBM than for the ground HP-SBM and that of GE was higher (P<0.05) for US meal than for the ARG meal. Pigs fed R-SBM had lower villus height (P<0.01) than pigs fed HP-SBM or SPC but no differences in ileal mucosal morphology were detected between SPC and HP-SBM containing diets. It is concluded that feeding the HP-SBM or SPC-reduced PWD and improved nutrient digestibility and ileal morphology as compared with feeding the R-SBM, but had no effect on pig performance. The inclusion in the diet of added value soya products (micronized SBM or SPC) in substitution of the R-SBM increased the TTAD of all nutrients and reduced PWD but had no advantage in terms of growth performance over the use of ground HP-SBM.

Apparent ileal digestibility (AID) of energy, dry matter (DM), nitrogen (N) and amino acids and standardized ileal digestibility (SID) of amino acids in low quality soybean meals with different CP concentration (SBM 44% CP and SBM 48% CP) with or without 400 U β-mannanase/kg supplementation were evaluated in 20 cannulated barrows ((Landrace×Yorkshire)×Duroc) with an average BW of 25.08±3.42 kg. A N-free diet was used to determine basal endogenous losses of amino acids. The supplementation of β-mannanase improved (P<0.05) AID of DM compared with non-supplemented diet. However, enzyme supplementation did not improve (P>0.05) AID of N and energy. The type of SBM (SBM 44% CP v. SBM 48% CP) had no effect on AID of DM, N and energy. β-mannanase improved (P<0.05) AID of sum of essential amino acids, arginine, histidine, lysine, valine and glycine. The SID of lysine was higher (P<0.05) in enzyme supplemented than in non-supplemented diets. Larger AID and SID of threonine and proline (P<0.05) were observed in SBM 48% CP than in SBM 44% CP. In conclusion, the supplementation of enzyme improved AID of arginine, histidine, lysine, valine and glycine, but it did not cause marked difference in SID of these amino acids except for lysine. The low nutrient digestibility of the SBM sources used in the present experiment might have favoured the positive effect of β-mannanase supplementation.

Two groups of eight Charolais heifers were used to examine the effect of feeding level during the post-weaning winter on the grazing behaviour and herbage intake over three periods during the first 2 months of grazing. The winter diets (L and H) were given to achieve a mean difference of 50 kg between groups at turn-out. The heifers were set-stocked together on a hill pasture where sward height was maintained at 12 cm.

The winter live-weight gains were 0·31 and 0·70 (s.e. 0·032) kg/day for L and H heifers respectively, and spring gains 1·94 and 1·66 (s.e. 0·082) kg/day respectively. Intakes increased throughout the spring grazing for both groups. Absolute intakes were lower for L than for H heifers only during the first period (P < 0·05). Intake per kg live weight was higher in L than in H heifers (23·0 v. 21·1 (s.e. 0·54) g organic matter (OM) per kg live weight). Bite weights of H heifers were constant throughout (434, (s.e. 12·9) mg OM), while bite weights ofL heifers only reached those of H heifers in the last period. Bite weight was linearly related to live weight. Bite rates were not different between groups, but L heifers compensated for lower bite weight by grazing longer and they increased their grazing time after turn-out faster than H heifers. Grazing time was mainly responsible for higher relative intakes in L heifers, and thus, partly, for compensatory gain observed.

1. Two experiments have been carried out to study the nutritive value of dilute solutions of fatty acids (consisting mainly of ammonium acetate) when incorporated in the diet of lactating Jersey cows.

The first, a continuous trial, extended over a total of 17 weeks and involved five pairs of cows. One cow in each pair received the treatment and one the control diet. The second trial, of change-over design, involved four pairs of cows; one cow in each pair received one or other of the experimental diets alternately over four 28-day periods.

2. The cows received basic diets comprising hay ad libitum and concentrates regulated according to milk yield. On the control treatment cows received water and a concentrate containing an appropriate percentage of groundnut cake; on treatment cows received a dilute solution of salts and an ‘all-cereal’ concentrate. The treatment provided cows with approximately 30% of their total DCP intake as ammonia-N and with 270 to 310 g of acetate and 43 to 49 g of propionate/day from the salt solution.

3. Solutions of salts have been offered to the cows at various concentrations in the range 0·25 to 2·6% (w/v) as a substitute for drinking water. Nineteen of the 20 cows consumed solutions of 1·4% concentration in normal quantities equivalent to water.

4. Treatment was associated with an appreciable depression in the yield of cows producing 13 to 14 kg of milk per head/day, but had little effect on the yield of cows producing 10 to U kg or less. This result has been discussed with reference to the role of the ammonia-N as a substitute for protein-N.

5. Treatment significantly increased the fat content of the milk produced by these Jersey cows above the high control level of 5·4%. Total milk fat production was also increased. This result has been discussed with reference to the role of acetate in dairy cow diets.

The fatty acid composition of longissimus thoracis (LT) muscle and adipose tissues (subcutaneous and intermuscular fat) from castrated and entire male Boer goat bucks was investigated. Sixty Boer bucks in groups of between three and five animals were slaughtered at 5, 15, 30, 45, 60, 75, 90 and 105 kg live weight (5 and 15 kg animals were not castrated). The fatty acid composition of LT muscle from castrated and entire Boers was significantly affected by slaughter weight. The fatty acid content ofLT muscle and subcutaneous and intermuscular fat from both castrated and entire Boer bucks was primarily composed of oleic acid followed by palmitic and stearic acid. Both oleic and palmitic acid increased with slaughter weight whereas stearic acid decreased. LT muscle from castrated Boer bucks contained higher amounts of desirable fatty acids. In contrast to slaughter weight, castration of Boer bucks resulted in only minor changes in fatty acid composition of adipose tissues. It can be concluded that slaughter weight plays a role in changing the fatty acid composition ofLT muscle and adipose tissues from Boer bucks.

Experiments involving both digestion and growth trials were undertaken to compare the responses of pigs to two increments of digested energy resulting either from gut fermentation or from digestion by endogenous enzymes in the small intestine. Unmolassed sugar-beet pulp (SBP) and maize starch (MS) were selected as model materials for these two systems. A control diet was formulated to fulfil the needs of pigs for all essential nutrients apart from energy. This diet was offered according to a scale set at about twice the maintenance energy requirement. The two SBP diets contained 150 and 300 g SBP per kg (SBP15 and SBP30) and the two MS diets 100 and 200 g MS per kg (MS10 and MS20). Sixty observations were made with 10 female and 20 male growing pigs to provide information on digestion. The results showed that the energy in SBP and MS had an apparent digestibility of 0·74 and 0·98 respectively (s.e.d. 0025). The neutral-detergent fibre fraction of SBP had a digestibility of 0·81 (s.e. 0·055). Forty pigs (20 male and 20 female) were involved in the growth trial. The responses of pigs to increments of different digestible energy (DE) were measured in terms of daily carcass-weight gain. The results gave values of 435, 478, 527, 511 and 567 (s.e.d. 17·3) g/day for the control, SBP15, SBP30, MS 10 and MS20 treatments respectively. These results suggest that the apparent DE of SBP is used for carcass growth with an efficiency of 0·57 (s.e. 0·012) relative to the DE from MS.

Wool growth, staple strength and fibre diameter are reduced during pregnancy and lactation. This may be due to the increased requirement for protein for foetal growth, udder development and milk production causing a lack of amino acids for wool. Responses in wool production, ewe live weight, lamb birth weight and growth, plasma amino acids and levels of cortisol, insulin and growth hormone were measured when different sources of protein were offered. Either lupin seed (L), fish meal (F) or formaldehyde-treated egg white (E) were included in an oaten hay-based diet offered during the final 3 weeks of pregnancy and first 3 weeks of lactation. Provision of diets containing E or F resulted in significant (P < 0·001) increases in wool growth and trends towards increased staple strength (4 to 6 N/ktex) and clean fleece weights (0·17 to 0·38 kg) compared with the sheep given L. Feeding the E diet increased the concentration of cystine in plasma and sulphur in wool in late pregnancy. Feeding the F diet increased the concentrations of arginine, histidine, lysine and threonine in plasma in early lactation. Ewes given E had higher circulating insulin and increased insulin resistance, compared with sheep given L, on 2 of the 4 days of sampling during pregnancy and lactation during the treatment period. There were no treatment effects on lamb birth weight or growth but ewes given the E diet were significantly (P < 0·05, 3·3 kg) heavier than the ewes given L after 3 weeks of lactation. The results indicate that a lack of protein available for absorption in the small intestine causes reduced wool growth during late pregnancy and early lactation. Wool growth is more sensitive to a reduced protein supply than foetal growth, maternal weight or milk production.

The effects of breed type and season on semen quality and libido were examined. Tests were carried out in autumn, winter, spring and summer using 47 rams of five breeding groups, namely the the Fleisch Merino, the Ossimi, the first cross and the two parental backcrosses. All the rams were born and reared locally.

Except for the percentage of abnormal sperm cells and time to first mount, semen quality and libido were not affected by breed type. There was little consistent evidence of heterosis in any of the traits examined. All traits except time to first mount were significantly affected by season. Semen was of better quality in autumn and spring than in winter and summer. With one exception all aspects of libido were depressed in winter.

Breed × season interactions were significant in six of the 10 traits studied but showed no consistent trends.

The reproductive performance of Merino rams was not adversely affected by the environment. This indicates the feasibility of introducing new breeds so far as semen quality and male libido are concerned.

The diet self-regulation ability of goats during late lactation has been studied with regard to their production level. Two groups of seven Girgentana goats producing 1100 ± 157 g/day (H group) and 613 ± 138 g/day (L group) were housed in individual pens and were given alfalfa pelleted hay (1.5 kg), whole grains of maize (0.5 kg), barley (0.5 kg), faba bean (0.5 kg) and pelleted sunflower cake (0.5 kg) on a daily basis. During a 7-day pre-experimental period, goats received a mixed ration based on the same feeds used during the experimental period (1.5 kg of hay and 0.4 kg of each concentrate). Individual choice of feeds was continuously recorded for 7 days using a 24-h IR video surveillance system equipped with four video cameras. The nutrient intake in both groups was much higher than needed. Goats in the H group ate more (2016.3 v. 1744.3 g dry matter (DM)/day) and selected less hay (26.9% v. 34.6% DM), more high-protein feeds (faba bean and sunflower cake: 14.0% and 15.9% v. 8.8% and 7.9% DM, respectively) and less maize (21.5% v. 25.0% DM), reaching a higher CP concentration in the diet (17.3% v. 15.0% DM) compared with the goats in the L group. During the 24-h trial period, hay was more constantly selected (on average never reaching <20% of the total hourly basis feeding time, apart from the first hour after feed administration) compared with concentrate feeds. This feeding behaviour has probably exercised a ‘curative’ effect that enabled the goats to continue to take in very high levels of starch and protein, without manifesting any symptom of metabolic disease. Shifting goats from the pre-experimental diet, based on a mixture of the same feeds used during the experimental period, to the free-choice feeding caused more than 20% increase in milk production in both groups. From the results of the intake, we are unable to conclude that the goats can select their diet to meet their requirements, as goats consumed much more than needed. However, when free to choose their diet, the animals improved milk performance, despite the late-lactation stage.

Two experiments were conducted to assess preference by sheep for endophyte-infected tall fescue growing in monoculture at least 5 m away from alfalfa (fescue-middle (FM)) over endophyte-infected tall fescue growing adjacent (0.2 to 1 m; fescue–alfalfa (FA)) to alfalfa (FA), and the effect of legume scent on preference for endophyte-infected tall fescue. In Experiment 1, 10 six-month-old lambs were offered for 12 days a choice of freshly harvested FA and FM. On days 13 and 14, lambs were offered the same choice, except cages (to allow access only to scent) containing freshly harvested alfalfa were put in the feeders containing FA, whereas cages containing freshly harvested FM were included with the feeders containing FM. Forage intake was measured 1 h after feeding and at three consecutive 2-h intervals thereafter. FA contained greater (P<0.002) concentrations of the alkaloid ergovaline (360±27 ppm) and CP (8±0.4%) than FM (219±27 ppm and 6±0.4%, respectively). Lambs preferred (P<0.05) FA to FM during the 1st hour of feeding, but the differences became smaller and disappeared in later feeding periods (P<0.005). Lambs offered FA with alfalfa scent or FM with FM scent preferred (P<0.05) FA but only on the 2nd day. In Experiment 2, 10 six-month-old lambs were offered a choice of FM with cages (to allow access only to scent) containing freshly harvested alfalfa or FM for 8 days. During the following 4 days, FM in the cages was replaced with freshly harvested sainfoin. Preference was greater (P<0.05) for FM offered with alfalfa scent than for FM offered with FM scent only on days 4 and 8. When lambs were offered FM with alfalfa or sainfoin in cages, they preferred (P<0.05) tall fescue with sainfoin scent over fescue with alfalfa scent, but intake was variable across hours and days (P<0.001). It is concluded that (1) lambs adjusted their intake of and preference for FA and FM over successive feeding bouts within each day, likely owing to an attempt to balance intakes of nutrients and alkaloids and (2) olfactory cues influenced preference, but to a lesser extent than nutrients and alkaloids in endophyte-infected tall fescue.

Thirty Suffolk cross wether sheep aged about 12 months and weighing 57 kg on average were used. They had been given previously a high energy diet to produce a fat body condition and average condition score of 3·7. Animals were allocated to an initial slaughter group (IS) or to four dietary treatment groups (UL, UH, CL and CH) based on sugar-beet feed (L) or white-fish meal (H) supplemented with chopped straw and pelleted, without (UL and UH) or with (CL and CH) the β-adrenergic agonist cimaterol, to provide an estimated 20 g (L) or 130 g (H) rumen undegradable protein per kg dry matter (DM). The sheep were offered 0·3 kg of the appropriate pelleted diet in addition to 200 to 400 g of chopped barley straw to provide proportionately 0·7 of the estimated metabolizable energy requirement for maintenance and, where appropriate, 2·5 mg cimaterol per day. Comparisons were made for the main effects of dietary protein intake and cimaterol and interactions between dietary protein and cimaterol.

The animals on dietary treatments were slaughtered after 49 days. The animals exhibited variable reductions in live weight and weights of carcass and non-carcass components in comparison with the IS group and in response to restricted dietary energy intake. The only effect due to the elevated dietary protein provision was a smaller loss in live weight compared with the low protein diet. In contrast, compared with responses recorded in its absence, treatment with cimaterol resulted in significantly greater values for weights of cold carcass, cross-sectional area o/m. longissimus dorsi and weights of DM, crude protein and ash in the carcass with significantly smaller weights for raw fleece. In comparison with the IS group, significantly smaller changes due to cimaterol were recorded for the weights of carcass crude protein and ash. Cimaterol treatment significantly increased the weight loss of fat in the carcass and in the perirenal and retroperitoneal, but not omental, depots as components of fleece-free non-carcass fat which was also significantly reduced in total. Interactions suggested that losses in carcass weight and DM in the presence of cimaterol were less and gains in carcass protein and ash greater, on the high than on the low protein diet. The results suggest that under conditions of energy undernutrition cimaterol may induce smaller losses or larger gains in carcass but not non-carcass, crude protein at the expense of fat depletion in carcass and non-carcass fat depots.

Trials were carried out over two winters to compare red clover and grass silage for cattle finishing.

The silages were mixed to give rations containing 0,25,50,75 or 100% red clover dry-matter and were offered ad libitum to individually fed British Friesian-type steers. Significant differences in dry-matter intake occurred but the effect of silage type on animal performance was not significant. Barley supplementation had a significant effect on both total dry-matter intake and daily live-weight gain.

Krškopolje pig, the only Slovenian autochtonous breed is still relatively untapped, with almost no information available on the effect of rearing conditions or its aptitude for processing and meat product quality. In the present study, dry-fermented sausages were produced from Krškopolje pigs that were fed similar diets (with regard to ingredients, energy and protein content) but reared in either conventional (CON) or organic conditions (ECO). Sausage weight losses at the end of processing were recorded and their final pH, chemical composition (moisture, fat and protein content, proteolysis index, fat and protein oxidation, fatty acid and free fatty acid profile) were determined in addition to measurements of instrumental texture, sensory evaluation and volatile profile analysis. Compared with CON, ECO dry-fermented sausages had lower processing losses, lower pH, higher moisture, salt and thiobarbituric acid reactive substances content, less saturated fat and less free fatty acids. Volatile profile analysis showed that ECO dry-fermented sausages exhibited higher concentrations of compounds arising from lipid autooxidation and lower levels of volatile compounds resulting from microbial lipid β-oxidation, amino acid degradation and spices. Panellists perceived ECO dry-fermented sausages as saltier and less colour intensive, while both rheological and sensory analysis indicated that ECO sausages had softer texture than CON. The present results indicate that rearing of Krškopolje pigs according to organic standards induced differences in meat and fat properties which affected the quality of dry-fermented sausages, most distinctly in terms of softer texture and different volatile profile.

Alternative closed breeding schemes for beef cattle are analysed using stochastic computer simulation. Multiple ovulation and embryo transfer (MOET) schemes are compared with conventional schemes (schemes without MOET) with an equal expected number of progeny born per year. Schemes are compared for genetic gain and inbreeding obtained after 25 years of selection. The trait considered, evaluated in both sexes, has an initial heritability of 0·35. Different population sizes and numbers of sires selected are evaluated. Current realistic parameters for embryo production are assumed in MOET schemes.

After 25 years of selection, and with no control on inbreeding, cumulative genetic gains are about 50% higher in MOET schemes compared with conventional schemes. The benefit from MOET is mostly due to increased selection intensities in females. The rate of inbreeding increases by up to nearly 300% when MOET is used. This maximum percentage increase in inbreeding following the use of MOET can be reduced to about 100% when selection and mating strategies for controlling inbreeding are used. The effect of the number of sires used on the inbreeding obtained is more important than the effect of the size of the herd. In MOET schemes, increasing the number of sires selected by a factor of three, leads to reductions in inbreeding rates of 40%. When schemes of the same size are compared at similar acceptable inbreeding levels, MOET schemes give around 30% higher genetic progress than conventional schemes.

The aim of this work was to determine whether developmental changes in growth hormone (GH) secretory patterns and carcass composition were influenced by nutrition and genotype in sheep. Four-month-old wether lambs from lean (low backfat), fat (high backfat) and control selection lines were nutritionally restricted to maintain a 28 kg live weight or given food ad libitum for 24 weeks. Plasma concentrations of GH and insulin-like growth factor 1 (IGF-1) were measured at predetermined times and carcass composition of the animals determined at the end of the trial.

From week 3 on, restrictions in dry matter (DM) intake were observed as the ad libitum treatment group had a significantly greater intake than the restricted treatment group (7·70 v. 5·80 kg DM per week, s.e.d. = 0·81). Differences in live weight between the feeding treatments were significant (P < 0·05) at week 9. The restricted feeding regime was associated with significant reductions in plasma levels of IGF-1 but had no effect (P > 0·05) on carcass weight-adjusted carcass fat proportion at the close of the trial. The effect of food restriction on GH secretory patterns was variable. Although there was initially a suppression in mean plasma GH, there was subsequently significantly higher mean plasma GH in the restricted feeding treatment. Periodogram analysis indicated that both the absolute levels of GH and the GH secretory pattern were altered by restricted feeding. In all animals, mean and basal GH concentrations, as well as the frequency and amplitude of pulses, declined from February to March and then increased from May to July (P < 0·001).

DM intake and live weight did not differ (P > 0·05) between genotypes, however the fat genotype had greater carcass fatness than lean or control genotypes (P < 0·01). There were no consistent differences between genotypes in plasma IGF-1 concentrations. In the ad libitum treatment, the lean and control genotypes had higher plasma GH levels than the f at genotype but the pattern of GH release did not vary. Under restricted feeding, both the pattern and the level of plasma GH varied between genotypes.

It is concluded that the developmental change in GH secretory patterns is affected by nutrition but not in a consistent manner. Although restricted feeding resulted in higher mean plasma GH concentrations later in the trial, this did not result in a change in carcass composition. The biological cues which lead to increased fat deposition in older lambs need further study but plasma GH levels may not he an important mechanism in this process.

The live-weight gain (LWG) of young male red deer in New Zealand naturally slows during winter and feeding diets of mainly silage appears to exacerbate this effect. We aimed to quantify the effect of feeding silage on intake and LWG during winter and the ability to improve LWG by feeding supplements, mainly in the form of barley. Seven groups of eight deer were maintained outside in gravelled enclosures and offered silage ad libitum for 94 days during winter. Six groups were given supplements (950 g barley with 50 g rapeseed meal per kg to make all diets isonitrogenous) at rates of proportionately 0·2, 0·4, 0·5, 0·6, 0·7 and 0·9 of the metabolizable energy (ME) intake of the group given only silage (0). The study also examined the effect of the winter treatments on subsequent LWG to slaughter weight whilst grazing on pasture during spring and into summer (102 days).

Increasing supplement intake resulted in a decrease in silage dry matter (DM) and ME intake (P < 0·001) and an increase in total ME intake (P < 0·01). The substitution rate for silage DM was 0·84 (s.e. 0·079). LWG during silage feeding was positively related (P < 0·01) to supplement intake with an increase of 6·21 g/day per MJ per day. LWG on pasture was not related to either supplement feeding rate or LWG during winter. LWG over the entire experiment was related (P < 0·01) to supplement feeding rate, with a final difference in live weight of 6 kg between 0 and 0·9 groups.

This study has confirmed that the LWG of young male deer is low during winter when given only silage and that feeding supplements increases total ME intake and LWG. The reduced LWG due to silage feeding was not compensated for on pasture during spring and summer, thus delaying the time to reach slaughter weight by approximately 1 month. High proportions of silage in the diet appear unsuitable for young male deer if the aim is to achieve rapid LWG during winter.

The relationships among five traits in dairy cattle (milk yield, fat yield, protein, fat % and protein %) were examined on the original and on a logarithmic scale. The data comprised the records on 5333 Red Danish cows tested at the Danish Progeny Testing Stations during the years 1960–66. None of the heritabilities or the correlations among the variates were altered appreciably by transformation. For the five traits heritability estimates were 0·56, 0·80, 0·65, 0·64 and 0·56, respectively. Phenotypic and genetic correlations among milk yield, fat yield and protein yield were all very high, about 0·95. The correlations between fat % and protein % were about 0·6. The coefficient of variation of a variate proved to be a good approximation of the standard deviation of the transformed variate even for milk, fat and protein yield with coefficients of variation of 17–18%. It was concluded that little is likely to be gained by using index selection for fat yield and protein yield. However, about 90% of the response obtainable by direct selection for fat or protein yield could be obtained merely by selection for milk yield. A large correlated response for protein yield could be obtained by selecting for fat yield.