Somatomedin C and other hormones, as well as blood metabolites, were measured during the dry period and during lactation in dairy cows, given different amounts of energy and protein, to study metabolic and endocrine adaptations. Somatomedin C, specifically measured by radioimmunoassay after separation from its binding protein, did not exhibit typical diurnal variations, in contrast to somatotropin and insulin, which increased particularly after concentrate intake. Somatomedin C markedly decreased at parturition and reached lowest values around the peak of lactation, while levels of somatotropin, nonesterified fatty acids and ketone bodies were high and those of glucose, insulin, thyroxine and triiodothyronine were low. Thereafter somatomedin C values slowly increased up to the 12th week of lactation and remained elevated. Low energy and protein balances were characterized by particularly low somatomedin C concentrations. An additional protein deficit at peak lactation, when cows were already provided with low amounts of energy, did not further decrease somatomedin C levels. However, when high amounts of energy were given in the form of starch or crystalline fat, somatomedin C increased. Overall, there was a positive correlation of somatomedin C primarily with energy, but also with protein balances and a negative correlation with milk yield. Conversely, somatotropin increased markedly after parturition and was positively correlated with milk production and negatively with protein and energy balances. Thus, somatomedin C levels were paradoxically low in the presence of high circulating somatotropin. Insulin most closely paralleled somatomedin C levels. Therefore the anabolic state of metabolism at the end of pregnancy was characterized by high somatomedin C and insulin and relatively low somatotropin, whereas the catabolic state of early lactation was characterized by high somatotropin, low somatomedin C, insulin and thyroid hormones.

An experiment with two groups of 24 cows during weeks 3 to 22 of lactation examined the influence of 7 (L) or 11 (H) kg concentrates per day on the prevalence of lameness. Grass silage was offered ad libitum. The cows were scored on a 1 to 5 scale for their locomotion on a weekly basis (1 = normal locomotion; 5 = severely lame). Cows scoring 3 or more were considered to be clinically lame. This allowed the prevalence of lameness, its severity and duration to be measured and statistically analysed. There were significantly more observations of lameness in the H cows than the L cows (0·077 and 0·021 observations per cow week) and the severity and duration of lameness incidents were significantly greater. The major causes of lameness were solar problems in the hind feet. The prevalence declined in both treatments as lactation progressed. The predisposing causes of the higher incidence in treatment H could have been the higher concentrate: forage ratio, the greater daily metabolizable energy intake or the greater daily crude protein intake. For treatments L and H, mean milk yields were 20·5, 23·7 kg/day; milk fat 41·7, 39·0 g/kg; milk protein 31·4, 32·0 g/kg; live-weight change -0·12, +0·11 kg/day; and condition score 2·04, 2·18.

In an experiment during weeks 3 to 26 of lactation, two groups of 12 cows were offered a mixed concentrate/grass silage diet containing 161 g crude protein per kg dry matter, and two similar groups a diet containing 198 g crude protein per kg dry matter. The concentrate: forage ratios and the daily metabolizable energy intakes were the same for all four groups. The cows in one of the two groups at each crude protein level had their hooves trimmed prior to parturition, the other group remaining untrimmed. The high protein diet significantly increased locomotion score (higher scores indicate poorer locomotion), the number and duration of clinical cases of lameness and outer toe length. Trimming of hooves reduced locomotion scores and the number and duration of clinical cases. Hoof growth was significantly increased by trimming. Mid-sole hardness was negatively correlated with locomotion score. At the two extremes, the low protein trimmed group had five cows lame for an average of 1·0 weeks, whereas the high protein untrimmed group had nine cows lame for an average of 4-2 weeks. Condition score and live-weight change were negatively correlated with locomotion score. There were no significant differences between treatments in milk solids yield.

Monthly herd recording data from Friesian cows in south-east Queensland are used to evaluate 20 models of the lactation curve, 10 being drawn from the literature and 10 being original. The curve of Wood (1967) with equation y =a nb exp(–cn),and its modificationy =a nfc/cosh(en), generally gave the lowest values for the error mean square across all seasons of calving. However, the model which predicts a constant initial yield, followed by a linear decline,y =a forn =Sc, y =a - b(n –c) forn > c, is as good as the previous two models for winter calving cows. Hence it is a useful representation of the lactation curve in south-eastern Queensland, where about 40% of cows are calved in winter. The inverse polynomial modely =nl(a +bn + en2) is a useful model for lactations commencing in the summer months.

A comparison of anabolic treatment regimes was made in 761 autumn-born Friesian steers on 14 farms. Prior to turn-out for grazing at 6 months of age and approximately 180 kg live weight, steers were weighed and divided into three equal-weight groups. Group 1 received silastic implants containing 45 mg oestradiol-17β. Group 2 received 36 mg zeranol and group 3 were untreated controls. All steers were weighed at intervals of approximately 3 months (i.e. mid summer, yarding at autumn, mid winter and pre-slaughter) and group 2 steers received a further 36 mg zeranol at the second, third and fourth weighing. At the third weighing half the cattle in each of the treatment groups 1 and 2 received 300 mg trenbolone acetate. Also at the third weighing, group 3 (controls) were subdivided into three equal-weight groups, the first of which received 45 mg oestradiol-17β and 300 mg trenbolone acetate and the second 36 mg zeranol and 300 mg trenbolone acetate. The third subgroup remained as untreated controls.

From 10 farms a 25% sample close to group mean weight at mid winter were slaughtered on the same day and subjectively assessed for subcutaneous fat score and conformation on 15-point scales. The left thin flank was separated into tissues. Samples of lean fat, liver and kidney were analysed for zeranol residues. All implant treatments resulted in higher live-weight gain, heavier slaughter weights and earlier slaughter. Trenbolone increased daily gain only during the first 3 months after treatment. Implanted carcasses were heavier both in the fore- and hindquarter but trenbolone also produced heavier forequarters. Carcasses from treated steers had more subcutaneous fat, less perinephric and retroperitoneal fat and less intermuscular fat in the thin-flank joint. Zeranol residues in implanted steers were not significantly higher than controls except in the kidney, but even these were significantly below accepted tolerance levels.

The use of oestradiol-17β was evaluated in cereal-based beef production on 14 farms with 450 bulls. Half of the bulls were implanted subcutaneously in the ear with a silastic rubber implant containing 45 mg oestradiol-17β Representative bulls close to mean weight for each group were selected for slaughter on the same day at the end of the trial for carcass measurements. The remaining bulls were slaughtered at the farmers' discretion. Where possible, slaughter live weight (208 bulls), carcass weight (412) and European Economic Community carcass classification (353) were recorded. Implanted bulls had higher gains only in the first 3 months (+76 (s.e. 17) g/day; P < 0·001) and had heavier carcasses with the extra weight in the forequarter (+2·3 (s.e. 0·61) kg; P < 0·001), better carcass shape (+0·9 (s.e. 0·3) points; P < 0·01) and more subcutaneous fat in the thin flank (+1·3 (s.e. 0·6) g/kg; P < 0·05). Implanted bulls selected for slaughter by farmers were not slaughtered earlier, but killed out better (+0·7 (s.e. 0·3) g/kg; P < 0·05) and had heavier carcasses (+4·6 (s.e. 0·5) kg; P < 0·01) of better shape (+0·8 (s.e. 0·3) points; P < 0·05).

The use of zeranol was evaluated in cereal beef production on 15 farms with 385 bulls. Half received 36 mg zeranol which was repeated after 6 months. Forty-four bulls were selected for detailed carcass assessment as above. Implanted bulls had daily gains 0·06 (s.e. 0·01) kg greater (P < 0·001) than controls. Farmers chose to slaughter implanted bulls 8·3 (s.e. 3·8) days earlier (P < 0·05) at only marginally heavier weights (+4·8 (s.e. 3·1) kg; P = 0·08). More implanted bull carcasses were distributed in better shape and higher fat classes (P < 0·01). There were no significant differences in fore- and hindquarter and thin-flank tissue proportions. Oestradiol treatment marginally decreased testis weight in slaughtered bulls whereas zeranol treatment had no significant effect although epididymal weight was decreased in zeranol treated bulls. There were no clear effects of either treatment on testicular structure, but both oestradiol and zeranol caused a degree of disruption to the epididymal epithelium. Zeranol concentrations in treated animal tissues were not significantly different from those in control animals.

An experiment was designed to establish the growth response of young housed steers to the feeding of stack-ammoniated low-quality hay, and to a range of different supplements for 16 weeks, and any carry-over effects during the following 24 weeks at pasture. Ammoniated hay was offered alone (TA), or with daily supplements of either 0·75 kg barley (TLB), 1·50 kg barley (THB), 0·1125 kg fish meal (TF), 0·75 kg or 1·50 kg of a barley-based concentrate (TLC and THC, respectively). Untreated hay was offered with either urea (UU) or with a daily supplement of 0·75 or 1·50 kg concentrates (ULC and UHC respectively).

Ammoniation increased the total nitrogen concentration of the hay from 13·4 to 24·2 g/kg dry matter, and resulted in a small increase in the organic matter digestibility measured in vivo (0·597 to 0·653), compared with that measured in vitro (0·572 to 0·667). Digestibilities of the fibre fractions, measured in vivo, were also increased by ammoniation (0·626 to 0·734, 0·637 to 0·761, 0·678 to 0·771 for acid-detergent fibre, neutral-detergent fibre and cellulose, respectively). Intakes of hay were reduced by supplementation, with the exception of TF, although total intakes were increased. During the housed period, live-weight gains of steers given ammoniated hay were 0·58, 0·71, 0·81, 0·69, 0·80, 0·86 kg/day for treatments TA, TLB, THB, TF, TLC, THC, respectively. The live-weight gains of steers offered the untreated hay were 0·49, 0·66, 0·87 kg/day for treatments UU, ULC, UHC, respectively. There was no carry-over effect of treatments on live-weight gains over the grazing season (mean 0·66 kg/day). It is concluded that when high levels of supplementation are available, no benefit is to be gained by ammonia treatment of ihe hay. However, without supplementation stack ammoniation of hay produces a marked improvememt in performance, compared with the addition of urea at feeding.

The experiments were conducted to investigate the effect of sire breed and production system on serum GH, insulin, prolactin, glucose and blood urea nitrogen concentrations in growing beef cattle. A total of 187 steers, representing a wide range of maturity types, was reared to slaughter on either the 16-month or 24-month production systems in experiment 1, and blood samples for hormone and metabolite determinations were collected at 3-monthly intervals. Experiment 2 compared only the extremes of maturity type, with four early- and four late-maturing animals on each production system. Blood samples from these animals were collected hourly for 10 h on 2 or more consecutive days at six different time periods during the growth of the animals.

Although significant between-breed differences in hormone concentrations were observed in experiment 1, there were no significant correlations between growth rate and circulating hormone concentrations. These results were largely borne out by the more detailed blood sampling used in experiment 2.

Differences did occur in live-weight gain, GH and insulin concentrations between production systems, although these were largely determined by the induced changes resulting from the imposition of a store period on the animals produced through the 24-month production system.

These results indicate that between-breed differences in growth rate cannot be accounted for by differences in circulating GH, insulin and prolactin concentrations. Rather, it appears that the hormones are primarily used to enable the animal to adjust its metabolism to changes in nutrient supply.

Two experiments have been carried out to examine the effects of the fermentation quality of grass silage and the inclusion of avoparcin in the diet on the response in the performance of calves to supplementation of silage-based diets with fish meal. The eight treatments used in each experiment consisted of untreated and formic acid-treated (2·5 1/t) silages offered ad libitum and supplemented with either barley (B) or a barley/fish meal (BF) concentrate (200 g fish meal per kg), without or with 150 mg avoparcin per head daily in a 2 × 2 × 2 factorial design. All animals received 1·25 and 1·0 kg concentrates per head daily in experiments 1 and 2 respectively. In each experiment, the diets were offered to 40 castrated male cattle which were initially 126 and 110 kg live weight in experiments 1 and 2 respectively. On average over the two experiments the untreated and formic acid-treated silages contained 24·8 and 24·5 g nitrogen (N) per kg dry matter (DM); 475 and 571 g protein N per kg total N; 76 and 62 g ammonia-N per kg total N and 45-9 and 27·5 g volatile fatty acids per kg DM respectively. Silage DM intakes for the untreated silages supplemented with B and BF and the acid-treated silages supplemented with B and BF without avoparcin and for the untreated silages supplemented with B and BF and the acid-treated silages supplemented with B and BF with avoparcin were 3·0, 3·2, 3·2, 3·0, 2·9, 3·0, 3·0 and 3·2 (s.e. 0·16) kg/day respectively. Live-weight gains for the corresponding treatments were 0·97, 1·12, 0·98, 1·01, 1·00, 1·07, 1·10 and 1·13 (s.e. 0·032) kg/day respectively. It is concluded that the inclusion of fish meal in diets based on well preserved, grass silage and barley did not affect intake and produced a small response (70 g/day) in the live-weight gain of calves. The inclusion of avoparcin in the diet did not significantly affect the response to fish meal.

An experiment was conducted during 2 years to evaluate industry Coopworth, industry Romney and Waihora Romney ewes (a strain selected for 10 years for increased ewe productivity) in a variety of nutritional and management treatment combinations. Waihora Romneys were most productive with small and inconsistent differences between industry Romneys and Coopworths. Conventional cross-classified analyses of variance did not reveal large, consistent nor economically important ewe genotype × nutritional treatment or year interactions. Additional analyses were designed to investigate whether the ewe genotypes responded to changes in the nutritional and(or) management environment with similar quantitative changes in production. A sensitive genotype would be one that responded to environmental changes with relatively large changes in productivity; a stable genotype would be one whose changes in production in response to a variable environment were smaller. By several statistical procedures designed to assess relative ‘sensitivity’ v. ‘stability’, Waihora Romney ewes appeared to be the most stable, with industry Romney and Coopworth ewes similar in their sensitivity.

Adipocyte volume rates of fatty acid synthesis, acylglycerol glycerol synthesis and lipolysis (basal and noradrenaline stimulated) along with the activities of acetyl CoA carboxylase and lipoprotein lipase were determined in subcutaneous adipose tissue, sampled by biopsy, from the rump of four breeds of sheep differing in growth and body characteristics.

Significant differences among breeds were observed for adipocyte volume, fatty acid synthesis, stimulated lipolysis rates, initial and total acetyl CoA carboxylase activity and lipoprotein lipase activity, but not for acylglycerol glycerol synthesis.

Differences in adipocyte volume did not appear to be related to the previously reported carcass fatnesses of the breeds. Similarly differences in adipocyte volume were not related to differences in either de novo fatty acid synthesis or lipolysis rates. Across breeds there was a trend toward higher acylglycerol glycerol synthesis rates associated with greater adipocyte volume although the source of fatty acids for esterification varied greatly.

Breed variation in fatness in sheep therefore appears to be a consequence of different balances of anabolic and catabolic processes in adipose tissue, with a unique pattern for each breed. Further elucidation of these patterns may lead to the identification of key sites for genetic manipulation. In addition these breed differences provide an alternative, complementary and qualitatively different, model for the study of the control of fat metabolism to that provided by nutritional or hormonal manipulations.

The effect on the morphology of the reproductive organs of ewe lambs of exposure to phyto-oestrogens for long periods of time were studied in 10 ewe lambs reared on lucerne compared with 10 controls on Italian ryegrass.

Anatomical studies of the reproductive organs showed that the ewe lambs reared on lucerne had significantly bigger reproductive tracts than the controls, the thyroids and the mammary glands were heavier and the latter showed secretory activity. The ovaries of the ewes fed on lucerne were smaller and lighter than those of the controls but no difference in ovarian activity was detected.

Microscopic examination showed specific features affecting the uterus, cervix and vagina. The prevalence of neutral mucopolysaccharides in the composition of the cervical mucus found in ewe lambs fed on lucerne indicated a decrease in viscosity of the mucus.

The change in muscle-weight distribution from birth to maturity was examined in rams and ewes from strains of Australian Merino sheep which had been selected for high or low weaning weight, and from a randomly bred control flock. The proportional distribution of total muscle weight among nine anatomically standardized muscle groups was determined for 34 mature animals. The growth of each group was then assessed relative to the growth of the total musculature, using data from 106 immature animals. Maturity coefficients were calculated separately for pre- and post-weaning growth. Several muscle groups exhibited a diphasic growth pattern.

Selection for high and low weaning weight resulted in an increase and decrease respectively in total muscle weight in mature animals, but had no effect on mature muscle-weight distribution. There were no significant strain effects on maturing patterns of muscle groups, except during the pre-weaning growth of muscles around the spinal column and those connecting the thorax to the forelimb. When compared at the same stage of maturity there was little difference between the strains in muscle-weight distribution. However, at the same weight the larger mature-size strain had a more immature pattern of muscle-weight distribution.

The total muscle weight of mature rams was greater than that of mature ewes. Sex also had an effect on muscle-weight distribution at maturity for seven of the nine muscle groups. At maturity rams had a higher proportion of their muscle weight in those muscle groups associated with the neck and thorax, and a lower proportion in those associated with the limbs. Sex affected the pre-weaning maturing pattern of the muscles of the spinal column, and the post-weaning maturing pattern of all muscle groups, with the exception of those muscles associated with the distal hindlimb, the spinal column, and those attaching the thorax to the forelimb.

Three types of high glucosinolate British rapeseed meal (RSM) — extracted, expeller and extruded — were incorporated in ewe diets at 200 g/kg; soya-bean meal (SBM) at 165 g/kg replaced RSM in a control diet. Eighty housed Suffolk-Mule ewes were divided into four equal groups and given one of four diets, A (control SBM), B (extracted RSM), C (expeller RSM) or D (extruded RSM) for one reproductive cycle. Diets A and B were compared for a second season. The ewes were given a maximum of 2·5 kg diet per day during lactation. Barley straw was available ad libitum. The ewes were mated in November and December. Lambs were weaned at 42 days of age; they were given creep food similar in composition to their dams' lactation diets.

There were no dietary effects on ewes in overall health, live weight, oestrous activity, conception, number of lambs born alive or lamb birth weights. A mean of 1·6 lambs were weaned per ewe mated and 58% of these were twins, in year 1. In year 2, 1·8 lambs were reared and 79% were twins. The mean milk yield over the first 4 weeks of lactation was 3·2 1 and there were no significant dietary effects. Fat concentration in milk was very variable, but in general was slightly depressed by the RSM diets, significantly so at three sampling dates. Protein concentration was consistently lower in milk from RSM than SBM groups, significantly lower at four of the weekly samplings. Thiocyanate levels in plasma and milk were related to glucosinolate intake, but were not associated with any detrimental effects. At all sampling dates, values for RSM groups were significantly greater than for SBM ewes. Plasma thyroxine values were similar regardless of diet

An investigation was made into a possible relationship between the relative growth potential and skeletal muscle fibre number in low birth weight Large White pigs and their heaviest birth-weight littermates. Estimates of the total fibre number of m. semitendinosus were made from 23 pairs of ‘small’ and ‘large’ littermates. Littermates were slaughtered at the same age and were of a mean live weight 86 (s.d. 15) kg. Small littermates (mean birth weight 939 (s.d. 164) g) had, on average, lower live weights at slaughter (P < 0·001) and lower muscle fibre numbers (P < 0·05) than their large littermates (mean birth weight 2085 (s.d. 343) g). However, pigs within the low birth-weight category exhibited various degrees of catch-up growth with their heaviest littermates and some individuals actually exceeded their large littermates in live weight at slaughter. The relative live weights at slaughter and relative muscle fibre numbers of small and large littermates were determined by expressing the value for the small littermate as a proportion of the corresponding value for its large littermate. No correlation existed between relative live weight at slaughter and relative muscle fibre number of small and large littermates. The small littermates were then divided into two groups by their mean value of relative small to large slaughter weight (0·84). The littermates of low relative slaughter weight (≤0·84) exhibited a large range of muscle fibre numbers although their mean fibre numbers were lower than their large littermates (P < 0·05). This large range was probably responsible for the lack of correlation mentioned above. Those small littermates which exhibited a good degree of catch-up growth (relative slaughter weight >0·84) possessed fibre numbers which were not significantly different from those of their large littermates. These results suggest that pigs which exhibit an appreciable degree of catch-up growth always contain high relative numbers of fibres in their muscles. Those which show a poor degree of catch-up growth (≤O·84) exhibit a range of fibre numbers because there may be environmental and other factors which prevent some pigs from realizing their full growth potential. The results of the present study advocate muscle fibre number as an indicator at birth of potential for post-natal growth performance.

Whole-body amino acid composition was determined in six male and six female 53-day-old New Zealand White rabbits. There were no significant sex differences in whole-body amino acid compositition except for arginine and glycine where whole-body concentrations (g/16 g N) were significantly lower in the females (P < 0·05). Overall mean whole-body essential amino acid levels (relative to lysine = 100 units) were methionine = 20; cystine = 41; histidine = 50; phenylalanine = 65; tyrosine = 50; threonine = 64; leucine = 112; isoleucine = 51; valine = 62; arginine = 109. The lysine concentration of rabbit whole-body tissue was 6·12 g/16 g N. There was close agreement between rabbit whole-body amino acid composition and corresponding published values for the rat and pig, although the rabbit whole-body cystine was high and methionine concentration low compared with the rat or pig. The rabbit whole-body amino acid pattern can be regarded as approximating an ideal balance of dietary amino acids and as such indicates discrepancies in current recommendations on the essential amino acid requirements for growth in the meat rabbit.

Over a 40-day period nine rabbits were each given one of nine isocaloric diets with progressively reduced amounts of crude protein (159 to 97 g/kg) but a fixed level of lysine; the latter was slightly below the higher of the National Research Council (NRC, 1977) and Societe de Chime Organique et Biologique (AEC, 1978) recommendations. The proportion of each other essential amino acid in the diet of highest crude protein concentration was close to a balance derived from the higher of each independently determined amino acid requirement given by NRC (1977) and AEC (1978), while the proportions in the two diets of lowest crude protein level were below those in a theoretical amino acid balance based on rabbit whole-body tissue composition. When an intersecting linear regression line model was fitted to growth performance data over the period, performance was found to be similar on the first six diets (159 to 123 g crude protein per kg) but further reductions in dietary protein were accompanied by a decline in growth rate and concomitant increase in food conversion ratio. Fitting of an asymptotic model to the data showed that growth performance first declined markedly between diets four and five (130 to 120 g crude protein per kg). These findings suggest that if a balance of essential amino acids relative to lysine, based on current amino acid recommendations, is adhered to in diet formulation for the growing rabbit, several of these amino acids will be in excess of requirement

The absence of a simple, accurate method of lamb carcass composition assessment presents difficulties in satisfying an increasing consumer demand for leaner meat. Present carcass classification methods, depending on visual appraisal by trained personnel, may be perceived as subjective and consequently little support for the scheme is found within the industry. Ten carcasses of varying weight (19·9 (s.d. 5·9) kg) and side concentration of fat (303·61 (s.d. 102·70) g/kg) were assessed for impedance to the flow of an alternating current (800μΛ at 50Hz) by use of an impedance analyser. Impedance measurements were highly repeatable (> 0·90) and prediction equations for side concentration of fat and lean produced residual s.d.s of 23·25 to 18·80 g/kg and 37·10 to 18·55 g/kg respectively. Impedance measurements may provide an inexpensive, accurate and simple means of assessing lamb carcass composition

It is known that microbial activity in the hind-gut of pigs influences the amino acid composition of faeces (Mason, 1984), yet contributes little to protein nutrition (Just, Jørgensen and Fernández, 1985). This diminishes the extent to which amino acid digestibility determined by faecal collection from intact pigs adequately represents nutritional value. In order to minimize the interference of hind-gut microflora, pigs for digestibility trials have been surgically modified to create a by-pass of the large intestine by ileo-rectal anastomosis (e.g. Green, Bertrand, Duron and Maillard, 1987 and 1988). This involves transection of the ileum approximately 100 mm anterior to the ileo/caecal valve. The modification can be considered as an alternative to collecting digesta from cannulas fitted in the ileum. The attributes of ileo-rectal anastomosis are that all digesta, rather than spot samples, can be collected and the animals remain in good health for many months of trial work. There is, however, concern that because the anastomosis operation involves complete severance of the ileum, digestion in the ileum may be abnormal. Of particular concern is the by-pass of the ileo-caecal valve which is suspected to have a restraining rôle on digesta passage (Gazet and Kopp, 1964; Laplace and Borgida, 1976), and therefore a possible influence on digestibility. When using ileo-caecal valve, by fitting the anterior digesta, other workers have attempted to preserve a complete ileum, and functional ileo-caecal value, by fitting the anterior cannula immediately posterior to the valve (Laplace, 1986)