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.

Forty crossbred heifers, mated to one sire, that calved in a 20-day period were used to study the effect of varying time and level of post-partum nutrition on productivity. Heifers were individually fed for 90 days post partum beginning at parturition: (1) proportionately 1·3 National Research Council (NRC) 1984 recommendations for 45 days followed by 0·7 NRC for 45 days (130·70); (2) 1·0 NRC for 90 days (100·100); and (3) 0·7 NRC for 45 days followed by 1·3 NRC for 45 days (70·130). Milk production, growth and body condition were estimated periodically during the lactation. The 130·70 heifers maintained their weight during the first 45 days of lactation, while the 100·100 and the 70·130 heifers lost weight (−0·33 and 0·60 kg/day, respectively). During the second 45-day period, the 100·100 and 70·130 heifers gained weight (0·24 and 0·72 kg/day, respectively) while the 130·70 heifers lost weight (−0·39 kg/day). Visual condition scores paralleled weight changes during both phases of the feeding period. Milk production varied according to nutrient intake and treatment differences were greatest at 45 days post partum (8·1, 7·3 and 6·1 kg/day for 130·70, 100·100 and 70·130, respectively). Calf weight gains were unaffected by dam nutrition. Days to first oestrus, days to conception or services per conception were not significantly different (P > 0·05) among treatment groups. Based on this experiment, neither of the alternate feeding systems resulted in decreased performance when compared with feeding at a constant level. Therefore, it appears that latitude exists in the way heifers can be fed early in their first lactation, without adversely affecting production.

Straw from six varieties of oat and 12 varieties of wheat were divided into their botanical fractions of leaf plus leaf sheath, internodes, nodes and chaff, and the rumen degradabilities of the individual fractions determined by the nylon bag method.

The proportions of the fractions varied between varieties, but more so within wheat than within oat straw. The proportion of leaf plus leaf sheath varied from 0·27 to 0·37 for wheat and 0·29 to 0·33 for oats with the proportion of stem ranging from 0·41 to 0·51 for wheat and from 0·55 to 0·60 for oats. There were also differences in degradation characteristics, more evident in wheat than in oats. The 48-h degradability varied from 570 to 650 g/kg for wheat leaf plus leaf sheath and from 300 to 380 g/kg for wheat stem. The respective ranges for oat straws were from 480 to 530 and from 250 to 280.

Generally, the wheat straw varieties, and in particular leaf from wheat straw, were of a higher degradability than oat straw. The mean 48-h degradabilities of wheat and oat leaf were 615 and 501 g/kg respectively. There was no relationship between the nitrogen content of leaves or stems and their degradability.

Three diets containing 0, 45 or 90 g fish meal dry matter (DM) per kg diet DM were given to lambs in sufficient quantities to provide energy for maintenance and 150 g daily gain. The lambs grew directly from 30 to 40 kg live weight (C) or were given a maintenance diet only such that they remained at 30 kg live weight for 12 weeks before being allowed to proceed to 40 kg (R). The 48 lambs were slaughtered at 40 kg. Preliminary slaughter groups provided data upon the fleece-free empty body weights for both C and R lambs at 30 kg live weight.

There were no significant diet × growth pattern interactions. R lambs ate more DM (P < 0·01) and had greater fleece-free empty body gains (P < 0·01) than C lambs. The inclusion of fish meal in the diet increased fleece and offal weights (P < 0·05) and fleece-free empty body gains (P < 0·01). Much of the response was confined to the first increment of fish meal. The preceding growth pattern had little effect upon the response of the lambs to dietary supplements of fish meal.

Thirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs, aged about 5 months, were divided into two groups on the basis of live weight, such that group G1 contained the 16 lightest lambs and group G2 the 16 heaviest. Lambs in group G1 were subdivided equally at random either to be sham-implanted controls (Group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (OE) (group T1) at 24 kg initial live weight. The lambs in group G2 were also subdivided into two groups (groups C2 and T2), and similarly treated approximately 1 month later at 37 kg initial live weight. The lambs were offered ad libitum a diet containing an estimated 12·5 MJ metabolizable energy (ME) per kg dry matter (DM) and 140 g/kg DM crude protein. Comparisons were made for the main effects of hormonal treatment and initial live weight. Both hormonal treatment and initial live weight gave increases for DM intake, gut fill, empty body weight, carcass weight and, in the half carcass side weight, weights of dissected lean tissue, bone and intermuscular fat and chemically determined DM, crude protein and lipid. Weights of mm. semitendinosus, longissimus dorsi, supraspinatus and gastrocnemius were also increased due to hormonal treatment and in group G2 lambs compared with those in group G1. When expressed as a proportion of carcass side weight, hormonal treatment effects were not significant for individual muscles and dissected carcass lean, bone and fat and chemically determined lipid and ash. Variable effects on other body components were recorded for both treatments in the absence of any significant interactions. The responses to hormonal treatment were essentially similar in groups G1 and G2. The question is raised as to the contribution of the greater food intake in implanted lambs to the maintenance of fatness in these animals.

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.

The effects of live weight at weaning on carcass composition were studied with 104 Scottish Blackface lambs offered two diets differing in protein: energy ratio. Groups of lambs were slaughtered at initial live weights of 24·1 (s.e. 1·48) kg (LL) and 28·9 (s.e. 1·67) kg (IL) and at 33 kg, 38 kg, 43 kg, 53 kg and mature live weight.

Lambs were offered two diets — low protein: energy ratio (LP, 122 g crude protein (CP) per kg dry matter (DM): 10·4 MJ metabolizable energy (ME) per kg DM) and high protein: energy ratio (HP, 176 g CP per kg DM: 10·4 MJ ME per kg DM). The LP diet was offered ad libitum and the HP diet was restricted to a similar mean level. Muscle, fat and bone tissues in the carcass were separated and weighed and the carcass and non-carcass component tissues were analysed for chemical fat, protein and ash.

Daily live-weight gain (DLWG) of HP lambs (148 (s.e. 8·1) g/day) was significantly higher than that of LP lambs (118 (s.e. 8·1) g/day; P < 0·05) and food conversion ratios were lower up to a live weight of 43 kg (P < 0·05). There were no differences in intake or DLWG between LL and IL lambs. Mature live weight (73·3 (s.e. 1·79) kg) was not related to weaning weight or post-weaning diet.

There was no effect of diet on carcass composition at any slaughter weight but LL lambs had a higher fat proportion than IL lambs, which was significant (P < 0·05) at 33 kg only. During the feeding period, the increment of fat tissue per unit increase in live weight (348 (s.e. 15·8) g/kg LW) was not affected by live weight at the start of the diet. The difference between LL and IL lambs in fat proportion was directly related to the difference in weight gain required to reach slaughter weight. The difference was not a function of stage of maturity but only of weaning weight, itself largely determined by pre-weaning nutrition. At higher slaughter weights the relative difference decreased and became non-significant. Hence lambs lighter at weaning would be less suitable than heavier lambs for the production of light-weight lean carcasses.

Thirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs aged about 5 months were divided into two groups on the basis of live weight such that group Gl contained the 16 lightest lambs and group G2 the 16 heaviest. Lambs in group Gl were subdivided equally at random either to be sham-implanted controls (group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (group T1) at 24 kg initial live weight. The lambs in group G2 were also subdivided into two groups (groups C2 and T2) and similarly treated approximately 1 month later at 37 kg initial live weight. The lambs were offered ad libitum a good-quality diet. They were slaughtered 60 days after implantation. Comparisons were made for the main effects of hormonal treatment and initial live weight.

Concentrations in blood of 17-β-hydroxy-trenbolone (TBOH) and oestradiol-17β (OE) measured by radioimmunoassay peaked within 1 to 3 weeks after implantation and declined thereafter. Maximum concentrations and concentrations at slaughter respectively were 1·46 and 0·32 μg/l (group T1) and 0·78 and 0·28 μg/l (T2) for TBOH and 85 and 33 μg/1 (T1) and 59 and 37 ng/l (T2) for OE. Values up to week 7 were consistently greater in implanted animals in group T1 than in group T2. Hormonal implantation decreased the concentrations of total plasma triiodothyronine and thyroxine and urea and increased values for glucose up to week 5 or 6 after implantation. The animals in group G1 compared with G2 had, on average, variably lower concentrations in plasma of triiodothyronine, thyroxine, glucose and urea.

The highest concentrations of solvent-extractable residues were obtained in samples of kidney and liver (up to about 500 ng/kg for TBOH and 180 ng/kg for OE) with intermediate levels for fat and lowest levels for muscle. Conjugated trenbolone ranging from 45 to 186 ng/kg was present in samples of kidney, liver and perinephric fat. Trenbolone acetate was detected only in samples of fat. Variable effects of live weight at implantation on residue levels were recorded.

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.

In three experiments pregnant ewes (mean weight 72·5 kg) were subjected to different planes of nutrition on grass silage-based diets during mid pregnancy and, in factorial designed trials with ad libitum silage or ad libitum silage + concentrates in late pregnancy. The high plane of mid-pregnancy nutrition resulted in an average gain of 11·5 kg between weeks 7 and 14 of pregnancy while the low plane gave an average loss of 3·5 kg during this period. These differences did not affect lamb birth weight but ewes on the high plane were 7·2 kg heavier after lambing than those on the low plane. The effect of plane of nutrition during mid pregnancy on silage intake during late pregnancy was variable but there was some evidence of a greater reduction in intake during the last few weeks of pregnancy following the high plane of mid-pregnancy nutrition. The higher plane of nutrition in late pregnancy resulted in higher ewe live weights as well as higher lamb birth weights and highest lamb birth weights occurred following restriction in mid pregnancy and a high plane of nutrition in late pregnancy.

Plasma 3-hydroxybutyrate levels were variable but there was little evidence of an effect of mid-pregnancy nutrition although levels appeared to be increased by the low plane of nutrition in late pregnancy.

Thirty-two Border Leicester ♂ × Scottish Blackface ♀ wether lambs aged about 5 months, were divided on the basis of live weight such that group G1 contained the 16 lightest lambs and group G2 the 16 heaviest lambs. Lambs in group G1 were subdivided equally at random to be either sham-implanted controls (group C1) or to be implanted with 35 mg trenbolone acetate (TBA) + 5 mg oestradiol-17β (OE) (group T1) at 24 kg initial live weight. Lambs in group G2 were also subdivided into two groups (C2 and T2) and similarly treated approximately 1 month later at 37 kg initial live weight. Animals were offered ad libitum, a diet containing an estimated 12·5 MJ metabolizable energy and 140 g crude protein per kg dry matter. The experimental treatments lasted for 60 days.

Samples of pre-heparin plasma were analysed for free fatty acid (FFA) and triglycerides (TG). Post-heparin plasma was analysed for lipoprotein lipase (LPL) activity. Samples of subcutaneous (SCAT), perinephric (PNAT), mesenteric (MAT) and intermuscular (IMAT) adipose tissue, liver and muscle, taken immediately post mortem, were analysed for total lipid concentration and fatty acid composition. Comparisons were made for the main effects of hormonal treatment and live weight.

Plasma FFA concentrations in heavier lambs (group G2) were significantly higher than in group G1 from week 1 pre-implantation to week 3 post implantation. Compared with group G1, animals in group G2 had significantly higher plasma TG concentrations at weeks 1, 2, 5 and 8 when data was analysed using pre-implantation values as covariates. The lipid concentration was lower in group G1 than in group G2. In group G1 compared with group G2 there were greater proportions of C12:0 and C18:2 in SCAT and C16:1 in PNAT and lesser proportions of C18:0 in SCAT and PNAT.

Significant effects due to hormonal treatment were recorded for plasma TG at weeks 1, 5, 6, 7 and 8 mainly due to increases in group T1 compared with group C1. Hormonal treatment increased the proportions of C12:0, C15:0, C16:1 and C18:1 in SCAT and C16:1 and C18:1 in IMAT; reduced the proportions of C16:0 and C18:0 in SCAT and C18:0 in MAT and IMAT and reduced the ratio of saturated to unsaturated fatty acids in SCAT and IMAT and to a lesser extent in MAT.

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.

Wool samples were collected from two groups of Merino sheep, both of which contained animals that were either heterozygous (Ww) or homozygous (WW) for white fleece. Group 1 were sampled in summer and group 2 in winter. These samples were scoured and measured for electron spin resonance initially (ESR1), following irradiation by ultraviolet light (ESR2) and then after wetting and drying the sample (ESR3).

There was no significant difference between WW and Ww sheep in each group for any of the ESR measurements (P > 0·05). However, for ESR1 there was a difference between management groups (group 1> group 2; P < 0·05). The ESR3 on ESR1 values were plotted separately for WW and Ww genotypes. The plotted ESR3 on ESR1 values in both groups showed no differentation into distinct genotype clusters. Nevertheless, for group 2 there was a slight similarity to the cross-like pattern of genotypes reported in an earlier description of this technique and the regression coefficients of ESR3 on ESR1 for WW sheep (b = −0·09 (s.e. 0·28)) differed significantly from those of Ww sheep (b = 1·31 (s.e. 0·52)) (P < 0·05).

It appears that the previously published method for differentiating between sheep that are either heterozygous or homozygous for white fleece was ineffective in this case.

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 effects of three variables; polysaccharidase inclusion level (0, 5 and 10 g/kg), moisture content (500, 600 and 700 g/kg dry matter (DM), and particle size (20, 5 and 2 mm), on the quality and degradation characteristics of ensiled rice straw were investigated. The polysaccharidase product used was shown to contain a broad spectrum of activities against polysaccharides typical of plant material. The major activities present being: mixed link glucanase, xylanase and both endo- and exo-cellulase. The straw treated with polysaccharidase had a lower final pH (5·21, 4·87, 4·82; P < 0·01), higher concentrations of lactic acid (1·98, 3·90, 3·67 g/kg; P < 0·01), a lower content of neutral-detergent fibre (689, 630, 621 g/kg DM; P < 0·01) and a higher solubility, measured as washing losses from nylon bags (152, 196, 212 g/kg DM; P < 0·01) for the 0, 5 and 10 g/kg polysaccharidase treatments respectively. The samples were subsequently incubated in nylon bags in the rumen of three sheep for 8, 16, 24, 48 and 72 h to estimate degradation rate and potential degradability using the expression p = a + b (1 – e−ct) where p is degradability at time t and a, b and c are constants. While there was no effect of moisture content or physical form of the straw, the degradation rate constant (c) was increased (P < 0·01) by the addition of polysaccharidase. The maximum potential degradability (a + b), however, was not altered by any of the treatments. The values for c were 0·0498, 0·0677 and 0·0817 per h and for (a + b) were 62·4, 62·1 and 62·8 g/100 g DM for the 0, 5 and 10 g/kg polysaccharidase enzyme additions respectively. It is concluded that the use of polysaccharidase enzymes can assist in the preservation of wet straw and can result in improved degradation characteristics.

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.

Experiments were made to study the proportion, chemical composition, and rumen degradability of the morphological components of barley straw (Corgi variety) and to study the selection of these components by sheep. The proportions in the harvested straw dry matter (DM) as leaf blade, leaf sheath, stem and chaff were 128, 314, 500 and 58 g/kg DM, respectively. The different components of straw on analysis proved to have very different concentrations of nitrogen and neutral-detergent cellulase digestibility. The leaf blades had the highest and the stems the lowest values. The degradabilities of DM in the components and in the whole straw were determined by measuring DM loss from samples incubated in nylon bags for various periods in the rumen of sheep. Responses were measured using the mathematical model p = a+b (1–e−ct) where p is DM loss, (a+b) potential degradability, c the rate constant of DM loss and t is the time of incubation. DM losses decreased in the order leaf blades > leaf sheath > whole plant > chaff > stems. Leaf blades also had the highest potential degradability and rate of degradation.

In another trial, five sheep were offered unchopped barley straw ad libitum. There were five treatment periods in which sheep were allowed to leave uneaten proportionately 0·2, 0·3, 0·4, 0·5 and 0·7 of the straw on offer for assessing the animal's selection of the morphological components of that straw. The amount of leaf blade in the material consumed increased in largely a linear (P < 0·01) fashion with the amount of excess allowance. The proportion of stem eaten varied conversely. The selection of leaf sheath was less apparent. Little stem was consumed until the proportion of leaf blade in the food available decreased below proportionately 0·4. The practical significance of the study is discussed.

Two experiments were carried out with sheep, to characterize fodder beet in terms of its effects on rumen function. In experiment A, a study was made of the effects of supplementing hay with fodder beet (FB) on rumen pH and volatile fatty acid (VFA) concentration compared with two control supplements of either barley/maize (BM) or molassed sugar-beet shreds (SBP). Hay was offered with all three supplements in a 50: 50 ratio on a dry matter (DM) basis. The mean rumen pH for the fodder beet diet was 6·34 and intermediate between two controls (BM 6·20 and SBP 6·38). There was no significant difference in rumen concentration of total VFA for the three different diets (FB, SBP and BM) but there were highly significant effects due to diet for acetic and propionic acid molar proportions (P < 0·001). Molar proportion of propionic acid for diets FB, BM and SBP were 0·2064, 0·2221 and 01880 respectively. The loss of DM from nylon bags incubated in the rumen of sheep given the test diets was 471, 447 and 486 g/kg for FB, BM and SBP respectively. In experiment B, the rate of in sacco organic matter (OM) disappearance of the three supplements were compared in sheep given a constant high forage diet (900 g/day hay DM + 200 g/day compound food DM). There were highly significant differences in rates of OM disappearances for the supplements (P < 0·001). The losses of OM measured after 3 h incubation in the rumen were 767, 608, 378 and 236 g/kg for fodder beet, barley/maize, molassed sugar-beet shreds and hay respectively.

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