A concentrate containing ground barley, soya-bean meal and fish meal was compared with one containing dried molassed sugar-beet pellets, dried distillers' grains and fish meal, in its influence on lameness in housed dairy cattle. Two groups of 24 cows were offered the diets in a 60:40 concentrate dry matter: grass silage dry matter ratio during weeks 3 to 26 of lactation. The same daily amounts of metabolizable energy and crude protein were offered to the two groups. The barley-based concentrate diet significantly increased locomotion score (indicating poorer locomotion), and the number and duration of clinical cases of lameness, compared with the sugar-beet concentrate diet. Hoof growth, wear, shape and hardness were not significantly affected by the diets. There were 16/24 cows with a locomotion score of 3 or over (1 to 5 scale) for an average of 7·3 weeks on the barley concentrate compared with 10/24 cows for 3·7 weeks on the sugar-beet concentrate. There was no significant difference between treatments in milk production or live-weight gain.

The effect of recombinantly derived bovine somatotropin (bST) treatment on milk production and pasture intake was examined in 16 New Zealand Friesian cows from low or high genetic merit (breeding index) selection lines. Recombinantly derived bST was administered by 2-weekly injection of a controlled release formulation for a period of 4 weeks (weeks 16 to 19 of lactation) at a dose rate equivalent to 50 mg/day. During this period the animals were housed for 18 days with food intake being measured over the last 8 days. Treatment with bST resulted in significantly higher yields of milk, fat and protein compared with the controls. Cows from the low breeding index (LBI) line were more responsive to exogenous bST than cows of the high breeding index (HBI) line in both milk and fat yield. Milk composition was not affected by bST treatment. There was a significant increase of proportionately 0·108 in intake of freshly cut pasture between bST-treated and untreated animals during days 16 to 23 of treatment. Thus, no significant difference in calculated energy balance was observed between the bSTtreated and untreated cows. This study indicates that the genetic background of cows may be an important determinant of their response to bST treatment and that such treatment rapidly alters voluntary intake in pasture-fed cows.

Four concentrate supplements differing in crude protein (CP) and undegradable protein (UDP) content were offered to 16 lactating Friesian cows together with grass silage (dry matter (DM) 196 g/kg, pH 4·38, CP 160 g/kg DM, in vitro DM digestibility 0·68) ad libitum in a Latin-square trial with 3-week periods. The supplement treatments were: (1) barley 122 g CP per kg DM, degradability (dg) 0·77; (2) barley/soya-bean meal 210 g CP per kg DM, dg 0·69; (3) barley/soya-bean meal/fish meal 190 g CP per kg DM, dg 0·61; (4) barley/soya-bean meal/fish meal 219 g CP per kg DM, dg 0·59. Supplements were given at 8 kg/day. Total daily intakes of silage (kg DM), CP and UDP (g) on treatments 1 to 4 were 7·77, 2087, 375; 8·35, 2804, 655; 8·29, 2676, 717; 8·70, 2917, 826, respectively. Milk yield (kg/day) and yields of fat, protein and lactose (g/day) on the four treatments were 21·3, 791, 617, 984; 23·0, 816, 688, 1055; 23·0, 818, 696, 1050; 23·6, 813, 735, 1071 for treatments 1 to 4 respectively. Yield and concentration of protein and lactose were significantly lower on treatment 1 than on the other treatments, while the of blood metabolites indicated treatment effects on blood glucose, non-esterified fatty acids, plasma protein and urea. Digestibility of organic matter and non-ammonia nitrogen (NAN) flow to the abomasum (g/day), measured in sheep given a fixed silage/supplement ratio at maintenance, were 0·81 and 18·4, 0·81 and 20·8, 0·82 and 21·4, 0·82 and 22·4 for treatments 1 to 4 respectively. The NAN flow was significantly greater on treatment 4 than on treatment 1.

Milk production and food intake records were available on individual animals from a high-yielding Holstein-Friesian herd in which selection had been practised on fat plus protein yield using nationally available artificial insemination sires. The relationship between sires and maternal grandsires' transmitting ability (ICC), expressed as a pedigree index (sire ICC + 0·5 maternal grandsire ICC), and offspring performance for milk production traits, food intake, and gross efficiency (milk energy (MJ)/total energy intake (MJ)) was investigated. The data comprised 475 26-week (data set 1) and 293 38-week (data set 2, a subset of 1) records, and for each data set analyses were conducted on heifers, cows and pooled lactations. Regressions of fat plus protein yield, fat yield, protein yield, and milk yield on their corresponding pedigree index were not far from the theoretical expectation (for a full lactation) of 1, for heifers (0·71 (s.e. 0·20), 0·72 (s.e. 0·20), 0·74 (s.e. 0·21) and 0·75 (s.e. 0·19), respectively), but slightly lower for the pooled lactations (0·57 (s.e. 0·20), 0·55 (s.e. 0·20), 0·67 (s.e. 0·19) and 0·64 (s.e. 0·15)) in data set 1. Regressions of fat plus protein yield, food intake and gross efficiency on pedigree index for fat plus protein yield, each trait expressed as a ratio of herd mean, were 1·31 (s.e. 0·37), 0·38 (s.e. 0·19) and 1·04 (s.e. 0·35) for heifers and 0·89 (s.e. 0·31), 0·48 (s.e. 0·18) and 0·59 (s.e. 0·26) respectively, for pooled lactations, in data set 1. Regressions for cow lactations were lower. Similar results were obtained with data set 2. In this study, a genetic increase of proportionately 0·1 in fat plus protein yield of daughters of sires of high genetic merit for fat plus protein yield, was accompanied by a proportional genetic increase of 0·029 in food intake and a 0·079 proportional genetic increase in efficiency.

Reproductive data of 139 Simmentaler heifers, previously subjected to different levels of winter and summer nutrition, over a 3-year period, were analysed. Pregnancy rates of 77% and 96% were achieved during the first and second seasons for the two groups of heifers, respectively. Winter and summer nutritional levels affected the number of heifers culled, but had little effect on conception. There were no significant differences in the weight at mating between the heifers that conceived and those that failed to conceive. Mean date of conception was within 30 days and 20 days of the commencement of the breeding season for the first and second season, respectively. Post-weaning nutrition played a relatively minor role in affecting the time of conception. Birth weights of the progeny were not affected by treatment. Calf birth weight was however, significantly (P < 0·05) correlated with the weight of the dam at mating. Sixty-three % of the heifers produced three calves in 3 years, 35% produced two calves in 3 years and only two heifers produced one calf in 3 years. The data supported the original hypothesis that the emphasis, when heifers are bred at 2 years of age, should be shifted away from a physiological base to one where management and grazing strategy are more important in rendering the enterprise economically viable.

Two experiments were made to determine the effects on digestion characteristics and live-weight (LW) gain of cattle consuming bermudagrass of supplementing with ground maize, soya-bean meal or a maizegluten— blood meal mix alone or maize plus the protein supplements. Experiment 1 was a Latin-square design with 14-day periods using six beef cows fitted with rumen and duodenal cannulas (490 kg). Cows were given bermudagrass hay at 12·7 g/kg LW alone (control, C) or with 2·4 g/kg LW of ground maize (M), 0·98 g/kg LW of soya-bean meal (S), 0·53 g/kg LW of maize-gluten plus 0·17 g/kg (dry matter basis) of blood meal (GB), M plus S (M + S) or M plus GB (M + GB). Nitrogen (N) intake was 106, 123, 143, 148, 166 and 166 g/day; total N at the duodenum was 101, 124, 117, 126, 140 and 161 (s.e. 5·91) g/day; and post-ruminal N disappearance was 61, 77, 72, 84, 87 and 110 (s.e. 5·6) g/day for C, M, S, GB, M + S and M + GB, respectively. In experiment 2, 96 crossbred beef heifers (203 kg LW) implanted with 200 mg testosterone and 20 mg oestradiol benzoate were allotted to 12 groups by LW (two groups per treatment). Heifers grazed bermudagrass paddocks for 84 days in two 42-day periods and supplement treatments were those in experiment 1. A period × treatment interaction in LW gain was noted (P < 0·05). LW gain was 0·78, 0·81, 0·79, 0·76, 0·70 and 0·95 kg in period 1 and 0·46, 0·51, 0·56, 0·53, 0·64 and 0·61 kg in period 2 for C, M, S, GB, M + S and M + GB, respectively (s.e. 0·049). In conclusion, duodenal flow and post-ruminal disappearance of N were similar for the protein sources when offered singularly, but when given with maize values were greater for the mix of protein meals high in ruminal undegradable protein as compared with soya-bean meal. LW gain by heifer calves grazing bermudagrass was increased only by supplementation with ground maize plus the protein meal mix of low ruminal degradability.

A simple model was derived relating the phenotypic effect (g) of a major gene to observed values of the population mean and variance for a trait, at specified values of the major gene frequency and at specified basal values of the population mean and variance (in the absence of the major gene). This model was applied to a total of 549 observed values of ovulation rate in ewes of the Cambridge breed at Bangor under a range of assumptions. The mean values of ovulation rate were 2·44 for 243 ewes of 1 year of age and 37·54 for 306 ewes of 2 and 3 years of age with a coefficient of variation for both age sets of 0·50.

The results indicate a minimum value for g, in this data set, of 1·07 for 1 year old and 1·72 for 2 and 3 year old ewes. The results are also consistent with a frequency value in the region of 0·3 to 0·4, with the absence of dominance and with a reasonable concordance with Hardy-Weinburg equilibrium. The results also indicate that the value of g varies according to the background phenotype since it is lower for younger as compared with older ewes.

The hypothesis that increasing the amount of straw offered and allowing animals to refuse proportionately more than 0·1 to 0·2 would increase intake and quality of the straw consumed was tested in two experiments with castrated goats (aged 6 to 31 months) and one with wether sheep (aged 6 to 18 months). Each trial (over 21 to 42 days following 14 to 35 days preliminary feeding) involved individually feeding long barley straw and concentrate supplement (15 g dry matter (DM) per kg live weight (M075) daily) and monitoring the quantity and quality of straw offered and straw refused. The results supported the hypothesis. In experiment 1, with 18 goats per treatment, those allowed to refuse 500 rather than 200 g straw per kg DM offered consumed more (18·9 and 14·4 g DM per kg M75 per day, s.e.d. 0·70) and their straw refusals contained more digestible organic matter (DOM) in vitro (347 and 320 g/kg DM, s.e.d. 7·7). For both treatments, refusals were less digestible in vitro than the straw offered (412 g DOM per kg DM). Thirty-six goats in experiment 2 (over 42 days) offered increasing amounts of straw (18, 54 and 90 g DM per kg M075 per day) consumed more (15·5, 22·8 and 26·2 g DM per kg M per day, s.e.d. 0·74), refused more (125, 566 and 703 g/kg DM offered) and the refusals were of increasing digestibility in vitro (354, 370 and 403 g DOM per kg DM, s.e.d. 14·5). All refused straw was inferior to that offered (443 g DOM per kg DM). The estimated intake of straw DOM was markedly improved by offering more straw (7·2, 12·8 and 14·5 g per kg M75 per day). Experiment 3, using 30 wethers over 21 days fed as in experiment 2, showed similar treatment responses, although absolute intakes of straw were lower. The responses observed are comparable to improvements in intake following treatment of straw with alkali. Further research is required to determine optimum feeding rates as affected by straw quality and animal productivity level. Practical feeding strategies will also need to consider utilizing refused straw.

Two experiments were conducted to investigate the basis for an increase in ovulation rate in ewes given improved nutrition prior to mating.

Sixteen wether sheep were used in the first experiment in order to screen physiological and nutritional variables likely to be affected by protein and energy intake. They were given low protein (LP) and high protein (HP) diets (19·1 and 35·2 g nitrogen per kg dry matter (DM)) each at four levels of energy intake (range 7·67 to 27·06 MJ gross energy per day). Effects of treatment on digestibility and partition of digestion between the rumen and intestines were small but increased nitrogen intake increased both nitrogen retention and the concentration of some essential amino acids (EAA) in plasma. The dietary treatments imposed on the wethers had been given to 800 ewes previously in a separate trial designed to predict ovulatory response to dietary and energy intakes. When the variables measured in the wether sheep were compared with predicted ovulation for ewes given the same treatments, the strongest relationship was with plasma concentrations of branched-chain amino acids (BCAA; r = 0·95; P < 0·001). Correlations with other EAA were weaker (r = 0·61; P < 001) and were not significantly related to concentrations of non-essential amino acids (NEAA) in plasma (r = −0·21).

Eighty ewes in experiment 2 were given an LP diet, blood samples were taken and ovulation rate determined by laparoscopy. One group of 20 ewes was maintained on the diet and another group of 20 was given an HP diet starting on day 7 of the oestrous cycle. Blood samples were taken 5 days later and numbers of ova determined during the next cycle. There were no changes in the number of ova present in ewes maintained on the LP diet, but a change to the HP diet increased ovulation rate from 1·47 to 1·89 eggs per ewe. Ewes which had single or multiple ova when given the LP diet (pre-treatment) had similar concentrations of amino acids in their blood, but those given the HP diet increased blood concentrations of BCAA by proportionately 0·58 and other EAA by 0·29 whilst NEAA were unaffected. Ewes which increased their ovulation rate when given the HP diet had a greater increase in blood BCAA concentration than those which did not increase their ovulation rate. Both the concentration in blood and the magnitude of increase in BCAA concentration appear to affect the number of eggs released. This concept is supported by evidence that BCAA are able to exert regulatory effects on mammalian protein metabolism under some circumstances.

In three experiments, seven grass silages, four grass hays and winter barley straw, with and without anhydrous ammonia treatment, were offered ad libitum to a total of 134 Finn Dorset ewes in weeks 11 to 15 of pregnancy and intakes were measured. The untreated straw diet was supplemented with 300 g fresh weight of concentrates per ewe. Number of foetuses carried did not affect intakes in mid pregnancy. Organic matter digestibilities measured in vivo in week 15, ranged from 0·39 to 0·69 for hays and 0·53 to 0·79 for silages. Generally, between weeks 11 to 15 of pregnancy, hay intakes showed either little change or slight increases whereas intakes of silages or straws showed little change or slight decreases. Forage intake was higher on the better quality hays and silages and ewes gained weight and body condition, compared with losses for the poorer diets. In late pregnancy, the ewes were offered grass silage ad libitum and rations of concentrates according to a rationing programme. There were no residual effects of the mid-pregnancy treatments on lamb birth weights but ewes offered the poorer diets in mid pregnancy still tended to be lighter and thinner post partum. Equations are presented to predict the intakes of hays and silages from food and animal factors.

Twenty-four Finn ♂ × Dorset Down ♀ wether lambs about 10 weeks and weighing on average 18 kg were allocated to treatment groups as follows: untreated controls (U); 15 mg oestradiol-17β (OE) implanted subcutaneously (O); cimaterol (2 mg/kg dry matter (DM)) in the diet (C); and 15 mg OE implant + cimaterol (2 mg/kg DM in the diet) (OC). The lambs were offered a diet, restricted to 38 g/kg live weight (LW), and which contained an estimated 12·5 MJ metabolizable energy and 137 g crude protein per kg DM for the experimental period of 62 or 63 days. Comparisons were made for the main effects of OE and cimaterol and also interactions between OE and cimaterol. Treatment with OE, on average, resulted in greater LW gain, DM intake, empty body weight (EBW), body length and chest depth, weight of shoulder and loin joints and carcass crude protein, but had no effect on fat deposition in carcass or depots. As a proportion of EBW, the weights of the pituitary gland and accessory vesicular glands were increased, as was teat length in lambs treated with OE. Cimaterol treatment, on average, increased LW gain, EBW, killing-out ratio, carcass weight and its weight of crude protein and, unlike OE, decreased the weight of the pituitary gland as a proportion of EBW and reduced the weight and proportion of fat in the carcass and perirenal and retroperitoneal depots. Increases in the cross-sectional area of m. longissimus dorsi and in the weight of selected major and minor commercial joints were also obtained in cimaterol-treated lambs. The presence of significant interactions indicated that there was incomplete or no additivity between the effects of cimaterol and OE for LW gain, cross-sectional area of m. longissimus dorsi and weights of carcass and carcass crude protein, omental fat and of certain of the dissected joints. These results suggest either that the mechanisms of action of oestradiol-17β and cimaterol are not independent or that they are affected by similar metabolic or physiological processes which limit the ability of castrated male sheep to exhibit a positive response.

Growing heifers (experiment 1) and wether lambs (experiments 2 and 3) were offered ammoniated cereal straw with or without a protein meal. The effects of supplementation with long-chain fatty acids (LCFA; as calcium salts of LCFA (CaLCFA) or fat prills) on nutrient utilization were studied.

Intake of the basal diet (g/kg live weight) was unaffected by the protein meal, but was often reduced by supplementation with LCFA, especially fat prills. Live-weight gain was increased both by supplementation with protein meal and CaLCFA. Fat prills only increased live-weight gain in the presence of protein meal and depressed live-weight gain in the absence of protein meal. There were small differences between the two sources of LCFA in their apparent effects on rumen fermentation.

Supplementation with protein meal increased relative protein content (P < 0·05) and tended to increase water content (P > 0·05) in the wethers in experiment 3 (corrected to equal empty-body weight at slaughter). Of the LCFA, only CaLCFA tended to increase relative body fat content (by proportionately 0·23; (P > 0·05) but decreased relative protein and water content by 0·05 and 0·06 (P < 0·05).

Supplementation of straw-based diets with as little as 20 g CaLCFA per kg food dry matter improved live-weight gain and efficiency of nutrient utilization of ruminants, particularly when offered in combination with a protein meal. There appeared to be marked differences in the effects of CaLCFA and fat prills on food intake, productivity and to some extent body composition.

During the first 2 weeks after kidding, 27 multiparous British Saanen goats were offered 1·5 kg hay (98 g crude protein (CP) per kg dry matter (DM)) and from 0·45 increasing to 0·70 kg concentrates (152 g CP per kg DM) daily. Week 2 was used as a covariance period. At week 3 of lactation all the goats were allocated to one of three groups and were offered hay ad libitum and 1 kg concentrates containing 117 (LP), 152 (MP) or 185 (HP) g CP per kg DM daily to week 15. During weeks 4 to 15, hay intake and milk yield were highest in the HP group. With increasing protein in the concentrates, hay DM intake was 1·20, 1·19 and 1·37 (s.e. 0·060) kg/day respectively and milk yield was 3·04, 3·21 and 3·36 (s.e. 0·080) kg/day respectively (linear response P < 001). There was no significant effect on the concentration of solids-not-fat, fat, total nitrogen or casein in milk. The digestibility of dietary organic matter, acid-detergent fibre and total nitrogen measured after week 15 was significantly greater with HP than with LP (P < 0·05), with MP values being intermediate (linear response P < 005). The rate of passage of ytterbium-labelled hay was unaffected by the treatments. The results indicate that, with lactating goats given hay and concentrates, beneficial responses may be expected to increasing concentrate CP to at least 185 g CP per kg DM.

Two experiments were conducted to determine the effect of including sucrose in diets on energy utilization by growing pigs. In the first experiment, the digestible energy (DE) content of sucrose was determined as 15·6 MJ/kg, indicating that gross energy was 0·96 digested. In the second experiment, iso-energetic diets were used to determine the effects of sucrose on growth and nutrient utilization. Sucrose was used to replace wheat gradually in four iso-energetic diets (15 MJ DE, 0·75 g lysine per MJ DE for pigs from 20 to 50 kg live weight and 15·1 MJ DE, 0·67 g lysine per MJ DE for pigs from 50 to 80 kg live weight). Pigs were fed ad libitum. Food intake (P < 0·01) and carcass daily gain (P < 0·05) increased with sucrose inclusion, independently of the level of sucrose in the diet. Food conversion ratio of male (boar) pigs on a carcass basis was unaffected by sucrose inclusion but increased with female pigs (P < 0·01). Killing-out proportion increased linearly with sucrose inclusion (P < 0·01). Sucrose inclusion improved energy retention (P < 0·05) and increased fat deposition (P < 0·05) but protein deposition was not affected. The weight of the full viscera (P < 0·01), empty digestive tract (P < 0·05), stomach (P < 0·01) and large intestine (P < 0·05) decreased with increasing sucrose inclusion. Sucrose did not affect blood triglycerides or cholesterol concentration (P > 0·05). Sucrose inclusion decreased the crude fibre and crude protein content of the diet and energy utilization was improved. Differences in gut fill indicated that sucrose-based diets were rapidly digested and absorbed.

Central test data of two pig breeding companies were analysed to estimate sire × testing regime (S × T) interaction for ultrasonic backfat thickness (BT), life-time growth rate (GL) and growth rate during test (GT). Testing regime consisted of a combination of sex, test period and housing system (individual v. group housing). Data were analysed within five lines, with 5417, 8331, 3427, 2413 and 1263 records of progeny of 97, 162, 64, 69 and 33 sires, respectively. The data were collected from May 1983 until May 1987 (lines 1, 2 and 3) and from June 1985 until May 1987 (lines 4 and 5). Testing regime had a significant effect on BT (in three lines) and on GL and GT (in five lines). S × T interaction was significant only for BT in three lines and for GT in one line. Genetic correlations between identical traits, measured under the two testing regimes, varied from 0·64 to 1·00 for BT, from 0·65 to 1·00 for GL and from 0·62 to 1·00 for GT. Conclusively, within central test S × T interactions were relatively unimportant for BT, GT and GL.

One hundred and thirty crossbred gilts (Yorkshire × Duroc × Hampshire) were exposed to either natural (40 lux) or supplemental lighting (700 lux) beginning at 8 weeks of age. Gilts received supplemental lighting from 40-W flourescent bulbs from 05·15 to 09·00 h and 16·30 to 20·15 h from 9 September to 22 April. At 4 months of age, all gilts were exposed daily for 15 min to mature boars five times weekly. Twelve gilts from each group were slaughtered at 4, 5, 6 and 7 months of age. All gilts were bled from indwelling cannulas at 20-min intervals for 4 h the day preceding slaughter. In addition, blood samples were drawn weekly from 17 gilts in each group from 7 to 9 months of age and analysed for progesterone to determine age of puberty. Twelve of 17 gilts that received supplemental lighting reached puberty at 228 (s.e. 11) days of age whereas 11 of 16 gilts that received natural lighting reached puberty at 252 (s.e. 7) days of age (P = 0·07). No significant differences occurred in anterior pituitary gland weight or pituitary concentration of LH, mean concentrations of serum LH or number of LH secretory spikes between natural and supplemental-lighted gilts at each month (all P > 005). Concentration of oestradiol-17β and progesterone in follicular fluid was similar between treatment groups within months and follicular size (P > 0·05). Content of GnRH in the stalk-median eminence, preoptic area and hypothalamus proper were also similar between treatment groups (P > 0·05). In summary, supplemental lighting reduced the age of puberty in gilts without a detectable change in pituitary, hypothalamic or ovarian parameters.

It is common for sows in commercial practice to lose body weight during lactation and if the loss is excessive then performance may be impaired. However, there is little information on the composition of this loss of body weight. In a 2 × 2 factorial experiment gilts were given daily either 2·7 (H) or 1·5 (L) kg food during gestation and either a high (H) (mean intakes of 3·4 and 4·9 kg/day for the H-H and L-H groups, respectively) or low (L, 2·0 kg/day) food intakes during a 31-day lactation. Seventy-three animals were slaughtered at various stages over all treatments and body composition determined by chemical analysis. The content of lipid (Li, kg) and protein (Pr, kg) in the empty body were closely related to live weight (LW, kg) and depth of backfat measured by ultrasound (P2, mm); Li = 0·381 LW + 1·042 P2 - 31·099 (R = 0·95) and Pr = 0·11 LW - 013 P2 + 4·46 (R = 0·67). Prediction equations were used to predict the composition of animals from a previous experiment (Mullan and Williams, 1989). Increasing food intake prior to farrowing increased the amount of lipid (67 v. 38 kg), protein (20 v. 17 kg), water (73 v. 63 kg) and ash (5 v. 4 kg) in the empty body at farrowing. For sows given 2·0 kg/day food during lactation about half of the total loss of body weight was lipid (835 and 570 g/day for the H-L and L-L groups, respectively) and proportionately 0-10 was protein tissue (165 and 125 g/day, respectively). When sows were fed to appetite the heaviest animals lost both lipid (520 g/day) and protein (130 g/day) whereas animals in the L-H group maintained their lipid reserves but lost 65 g protein per day. This study demonstrates the considerable amounts of lipid and protein which may be mobilized by the sow during lactation to buffer the nutritional stress through a low intake of food. The body composition of the sow during the first lactation can be accurately predicted from live weight and depth of backfat.

The effects of dietary protein (151 to 282 g crude protein per kg dry matter (DM)) and lysine (8·5 to 16·4 g/kg DM) on the carcass composition and energy metabolism of entire male pigs, given food close to appetite, was studied from 33 to 88 kg. Four replicates (three Landrace and one Duroc) of four littermates were used. Energy and nitrogen (N) balances were conducted at approximately 35 to 43, 58 to 65 and 78 to 85 kg and body composition was determined at slaughter. There was no effect of dietary treatment on the crude protein content of the empty body (EBW) but the DM (P < 0·001), fat (P < 0·001) and ash (P < 0·05) proportions and fat: protein ratio in EBW (P < 0·01) increased with decreasing dietary protein level. The mean maximum protein retention was 183 g/day. Retention of protein (P < 0·05) and proportion of protein energy in the gain (P < 0·01) decreased linearly and fat retention (P < 0·001) and energy content of the gain (P < 001) increased with decreasing dietary protein. The N retention values calculated from balance data were proportionately 0·21 higher at high protein intakes (509 g/day) and 0·056 higher at low protein intakes (329 g/day) than the values obtained by slaughter. Using the ideal protein system the value for the efficiency of utilization of apparently digested ideal protein for protein deposition (a2) fell linearly (P < 0·001), based on the slaughter data, as dietary protein content increased. Heat production, calculated from slaughter data, was proportionately 0·07 higher than that measured by indirect calorimetry and 0·17 higher than the computed value for heat production using the standard values of energy costs for maintenance and for protein and fat deposition.

Previous investigations have established that supplementing broiler chicken diets with appropriate endosperm cell wall degrading enzymes can improve nutrient digestion, and indicated that this could allow lower protein diets to be used. In this study the effect of enzyme supplementation on the productive value of low (192 g/kg dry matter (DM)) and high (227 g/kg DM) protein diets was studied. The diets employed were based on barley, wheat and rye, and the two enzyme preparations used, Glucanase GP 5000® and Novozym-343®, contained β3-glucanase and arabinoxylanase activities.

The high protein diet gave a higher incidence of sticky droppings, but resulted in a higher growth rate and improved food conversion ratio than the low protein diet. Enzyme supplementation reduced the incidence of sticky droppings and also improved growth rate, food intake and food conversion efficiency for both diets, with the Glucanase GP 5000 preparation generally being more effective. Enzyme supplementation improved growth rate on the low protein diet to a level equal to or better than that on the high protein diet, although this was achieved by a better food intake and an inferior food conversion ratio. This study demonstrated that supplementation with appropriate enzymes could allow a reduction in dietary protein level without affecting broiler growth rate.

Twenty-eight male fallow deer (Dama dama), 14 entire and 14 castrated (seven each 1- and 2-year-old) were slaughtered and their carcasses jointed. Each joint was separated into venison, trim A (low visible fat, diced pieces), trim B (pieces suitable only for mincing), waste and bone. Castration had a significant and cumulative effect on live and carcass weights. At 1 year of age castrated males were 80 g/kg lighter in live weight; at 2 years this difference had increased to 119 g/kg. The pattern for differences in hot and cold carcass weights was similar, being 66 and 148 g/kg lighter at 1 and 2 years old, respectively.

Castration caused small but significant shifts in the proportions of the primal joints, and the proportions of venison, trim A and trim B. Castrated males had smaller neck (9 g/kg) and saddle (10 g/kg) joints, but 18 g/kg larger legs. In the whole carcass they contained 12 g/kg more venison, but correspondingly less trim A and trim B.

Older animals had higher proportions of venison and lower proportions of bone. Venison distribution altered with age, but this was mainly a reflexion of changes in joint proportions.

The overall effect of castration was to reduce carcass weights (on which producers are paid) and reduce venison production proportionately to 0-97 and 0-88 of that achieved in 1- and 2-year-old entire males respectively. In some market situations castration may be an acceptable method of producing venison outside of the normal peak production, but the reduced production would require higher schedule prices to be economically viable for the producer.