The main aims of this study were to predict the increase in the accuracy of selection and the response to selection achieved by including feeding pattern traits, such as number and size of meals, as selection criteria in indices to improve growth rate, lean content of the carcass and food conversion ratio. Genetic and phenotypic parameters obtained for pigs given food ad libitum using single space electronic feeders were used to construct the indices. The predicted genetic gain in the index increased for indices with more feeding pattern traits. The inclusion of part test records for feeding patterns resulted in similar predicted correlated responses and predicted accuracy of selection to those using whole test records of daily food intake. The inclusion of feeding patterns as selection criteria resulted in indices that were less robust to inaccurate parameter estimates. It was concluded that feeding pattern traits could be used to improve the predicted accuracy of selection for the efficiency of lean growth but the most effective and robust index would include only daily gain, backfat depth, daily food intake and mean number of visits to the feeders per day. These traits may also be useful in reducing the length of the test period necessary for accurate measures of food intake, so increasing the potential intensity of selection using a given number of feeders.

A quantitative trait locus (QTL) for increased loin muscularity (TM-QTL) has previously been identified in purebred Texel sheep. Crossbred lambs born out of Mule ewes mated to heterozygous Texel sires for the TM-QTL were evaluated for a range of carcass traits. Lambs were genotyped and classified as carriers (n = 62) of a single copy of the TM-QTL and non-carriers (n = 49). In this study, the effects of the TM-QTL on carcass attributes were investigated using subjective classification scores for conformation and fatness, and measurements from a video image analysis (VIA) system. In addition, refined prediction equations to estimate weights of primal joints (leg, chump, loin, breast and shoulder) were obtained by calibrating the VIA system against computer tomography (CT) measurements in the loin region. The new refined prediction models increased the accuracy of prediction of all primal cuts on an average of 16% compared to previously derived standard VIA prediction equations. The coefficient of determination (R2) of the VIA system to predict in vivo CT measurements ranged from 0.39 to 0.72 for measurements of Musculus longissimus lumborum (MLL) area, width and depth, lumbar spine length, loin muscle volume and loin muscularity index. Using VIA estimates of CT-measured loin muscle traits, a significant increase in depth (+2.7%) of the MLL was found to be associated with the TM-QTL. Conformation and fatness scores and the shape of the carcass measured as individual lengths, widths and areas by VIA were not significantly influenced by the TM-QTL. Primal meat yields estimated using both standard and refined VIA prediction equations were not significantly affected by the TM-QTL. However, carcass ‘compactness’ was found to have significantly increased in carrier lambs. The weight of the dissected MLL estimated using VIA information was greater (+2.6%) for carriers compared to non-carriers. To conclude, neither the current industry carcass evaluation system for conformation and fatness nor the standard VIA system is able to identify the effect of the TM-QTL in the loin region in the moment. However, the calibration of the VIA system against CT measurements resulted in improved VIA prediction equations for primal meat yields and also showed moderate potential to estimate loin muscle traits measured by CT and to detect, partially, the effect of the TM-QTL on these traits.

Individually penned Finnish Landrace × Dorset Horn and Suffolk × Scottish Halfbred ewes were used to study the effects of supplementing diets based on ad libitum swedes. Supplementing a pregnancy diet of ad libitum swedes plus 225 g of hay with 454 g of a barley/soya bean meal supplement per day had no effect on swede intake or ewe performance in terms of the birth weight and survival of lambs born. Level of swede intake during late pregnancy was constant.

In early lactation, ewes offered ad libitum swedes plus 225 g hay per day were supplemented with 454 g of either barley or soya bean meal daily. Soya bean meal supplementation resulted in a 014 increase in swede intake to give a daily intake of 113g dry matter per kgM 0·7·5 and a total live-weight gain of 218kg in early lactation compared with a loss of 2·53 kg by barley-supplemented ewes. Lamb daily gain increased by 54g per day. The results are discussed in relation to trends towards the housing of ewes and current feeding practices for lactating ewes.

The effect of rate of growth on the development of animals is examined in terms of it being related to variation from a pattern of development described by the allometric hypothesis. For this purpose, aliometry is expressed in terms of an extension to the shape/size concept originally proposed by Mosimann.

It is shown that such an effect of rate of growth would bias estimates of the development pattern, depending on the experimental design. However, within the framework of the method, a procedure for both removing the bias and actually estimating the effect of rate of growth on development is available.

A previously described test for one type of deviation from aliometry is shown to be incorrect by simulation.

An alternative test for the adequacy of the allometry hypothesis is developed, based on factor analysis of residual matrices from multivariate analysis of variance (the latter being used so that effects of treatment and concomitant variables can be taken into account).

Although it is known that growth hormone (GH) influences body composition in ruminants, the precise role of the pattern of GH secretion is not known. We have studied the pulsatile release of GH and insulin-like growth factor 1 (IGF 1) secretion in the male progeny of rams from lines selected either for {fat genotype) or against (lean genotype) fatness. Seventy-two lambs (36 each of the fat and lean genotype) were kept on high-quality pasture and randomly allocated within genotype to treatment at 2, 3, 3·5, 4,5 or 6 months of age. The procedure, which was identical for each sampling period, was to sample each lamb through a jugular cannula every 10 min for 6 h, and then, following an overnight fast, to slaughter and analyse the carcass for fat. All blood samples were analysed for GH and samples taken each hour for total plasma IGF 1. The GH data were further analysed with the pulse detection routine PULSAR. Carcass fatness, adjusted for cold carcass weight, was greater for fat genotype animals than for the lean genotype. GH was pulsatile in all profiles but the pattern differed with time and genotype. Mean GH and pulse amplitude decreased with time but did not differ between genotype, although the lean genotype had higher mean GH at five of the six sampling periods. In contrast, GH pulse frequency and IGF 1 were significantly higher for the fat compared with the lean genotype lambs. GH mean and amplitude correlated negatively with carcass fatness in both genotypes and GH pulse frequency and total IGF 1 correlated positively with fatness for the lean genotype only. When carcass weight and genotype were fitted to these relationships, GH mean and total IGF 1 were found to have independent negative and positive effects, respectively, on carcass fatness. Because GH mean had a separate effect on fatness independent of genotype or cold carcass weight, it is likely that GH secretion influences composition by the same basic mechanism in both genotypes. However, although the slopes of these relationships did not differ significantly between the genotypes, the intercepts were significantly different indicating that over and above the basic mechanism, at any level of GH, the lean genotype lambs were leaner than the fat genotype lambs. This may indicate a measure ofGH resistance in the fat genotype lambs.

Forty-eight sucking lambs (26 males and 22 females) of the Manchega breed were used in this work. Lambs were slaughtered at 10, 12 and 14 kg live weight. Carcass degree of fatness was assessed by three assessors from colour photographs of the carcasses, using the European Union scale for light lambs (EU), the Colomer-Rocher method (CF) and another new scale developed by our group (sucking lambs scale, SL). Carcass conformation was assessed according to the Colomer-Rocher method (CC). Fatness and conformation scales were divided to give 0·25 points in each interval. Left half-carcasses were jointed and dissected into lean, fat and bone. Muscle proportion, bone proportion and whole fat proportion (obtained by addition of every fat depot: subcutaneous fat, intermuscular fat, inguinal fat and kidney knob and channel fat) were determined. Male and female carcasses showed a very different tissue composition: both groups had statistically significant differences (P < 0·05) in 20 out of 25 tissue composition variates. Males showed a higher number of variates that were well correlated with assessors’ scoring than females. Correlation coefficients between most of the tissue composition variates and assessors’ scores were higher in males. Furthermore, the number of variates that were significantly correlated with assessors’ scores was lower in females. Therefore, subjective methods for the estimation of carcass degree of fatness and of carcass conformation are poor predictors of tissue composition in female sucking lamb carcasses.

Tibetan Mastiff is one of the most archaic, ferocious and the largest dogs in the world. A total of 140 individuals from four geographically separated populations in China (Tibet, Gansu, Qinghai and Beijing) were sampled and genetic diversity was assessed using 10 microsatellite loci on eight different chromosomes. The mean number of alleles per locus ranged from 6 to 13. The mean observed and expected heterozygosities, polymorphism information content and allelic richness were 0.69, 0.79, 0.76 and 7.59, respectively, indicating relatively high genetic diversity in Tibetan Mastiff. However, a highly significant deficiency in heterozygote was observed within populations (mean FIS = 0.11, bootstrap 95% confidence interval (0.06, 0.17)) and total inbreeding (mean FIT = 0.12, bootstrap 95% confidence interval (0.06, 0.18)), along with strong inbreeding coefficients within populations (Fis > 0.09), all of which suggested that intense inbreeding practices occurred in Tibetan Mastiff. Therefore, effective and appropriate breeding management projects in present Tibetan Mastiff will be desirable and urgent. Low genetic differentiation was obtained with a mean FST of 0.01 (bootstrap 95% confidence interval (0.007, 0.019)). Additionally, the four Tibetan Mastiff populations showed close relationships in the neighbor-joining polygenetic tree based on the coancestral genetic distances. Tibetan Mastiff was investigated by using microsatellite loci at the first time, which could facilitate the better understanding of present situation at the molecular level, breed conservation and utilization in Tibetan Mastiff.

A comparison has been made between the methods for crude fibre (CF) and acid-detergent fibre (MADF) determination. In diets containing 10 to 70 % hay with or without 8 % tallow (T) or maize oil (MO), a highly significant (P < 0·001) correlation of r = 0·95 was observed between CF and MADF estimates. This high correlation confirmed a similar relationship found in silages, concentrate feeds and also hays. Similarly for rumen digesta, a correlation of r = 0·93 was found (P < 0·001). The equation for predicting CF from MADF calculated from diets and digesta data together was CF = 0·503+0·848 (+0030) MADF and the residual variation found was sufficiently small to provide useful estimates.

1. Experiment 1. Six treatment groups of one British Friesian and four South Devon × British Friesian bulls, initially 432 kg mean live weight and aged 491 days, were offered individually maize or grass silage ad libitum plus 0, 5 or 10g barley dry matter per kg live weight daily for 80 days. The silages had similar digestible dry matter and estimated metabolizable energy contents but the grass silage contained more ammonia and acetic, propionic and butyric acids. Mean values for groups receiving respectively maize and grass silage diets were for dry-matter intake 17·7, 20·3, 20·4 and 13·0, 16·6, 18·7 g/kg live weight and for live-weight gain 1·00, 1·32, 1·46 and 0·65, 0·98, 1·22kg/day. Significantly more maize than grass silage dry matter was eaten when the silages were given alone and dry-matter intakes, live-weight and carcass gains were greater for maize silage diets. Dry-matter intake, live-weight and carcass gains, efficiency of feed use and carcass quality significantly improved when barley was given.

2. Experiment 2. Six groups of five British Friesian bulls, initially 418 kg mean live weight and aged 474 days, were offered individually maize silage ad libitum with either urea or one of two quantities of aqueous ammonia mixed in at the time of feeding, plus 0 or 5 g barley dry matter per kg live weight daily for 90 days. The urea and ammonia-treated silages contained 125, 124 and 148 g crude protein per kg dry matter respectively, with pH values of 3·8, 3·9 and 4·3, and when given alone or with barley mean daily intakes (g dry matter per kg live weight) were 17·1, 18·6 for urea-treated silage diets, and 17·8, 18·8 and 16·9, 19·1 respectively for ammoniatreated silage diets. Live-weight gains were 0·69, 0·94, 0·63, 1·09, 0·64 and 1·07 kg/day. Ammonia treatment had no effect on intake or live-weight gain. Live-weight and carcass gains and carcass quality improved when barley was given.

3. The maize silage offered in Experiment 1 contained similar metabolizable energy but more starch than that in Experiment 2 and was used more efficiently for live-weight gain.

Surgical castration in pig husbandry is criticized for welfare reasons. Thus, it is necessary to evaluate alternative ways of rearing male pigs, such as entire or immunocastrated animals. Immunocastration is a vaccination directed against gonadotropin-releasing hormone (GnRH) to suppress the production of sexual hormones. This study aimed at investigating the effects of these two methods of castration in comparison with intact male pigs on blood T-lymphocyte subsets and function, the immunoglobulin (Ig) response to an influenza vaccine and health markers during sexual development. A total of 70 animals were allocated to three experimental groups: entire (E), surgically castrated at 5 to 6 days of age (SC), and immunized against GnRH at 3 and 4 months of age (IC). Blood samples were collected at 3, 4 and 5 months. At slaughter, global health status and body and spleen weights were measured. Results showed that SC male pigs had fewer blood lymphocytes than E pigs at 4 and 5 months (P<0.05), whereas IC pigs did not differ significantly from E pigs. The percentages of CD3+, CD3+CD4+ and CD3+CD8+ lymphocytes were not altered by treatment (P>0.1). Compared with E pigs, the SC pigs had a higher percentage of CD3+CD4+CD8+ cells at 4 months, whereas the IC pigs had a higher percentage at 5 months (P<0.05). Regarding γδT cells, SC pigs had a lower percentage than E pigs at 4 and 5 months (P<0.05), whereas IC pigs did not differ significantly from E pigs at any age. However, there were no consequences on T-lymphocyte proliferation and total IgG or anti-influenza Ig. At slaughter, relative spleen weight was decreased in IC pigs, whereas pneumonia score was decreased in SC pigs relatively to E pigs. Overall, no clear functional consequences of either method on commercial pig immune abilities were demonstrated, but more investigations are required to ascertain this conclusion.

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.

Forty-eight Large White × Landrace weanling pigs weighing initially 9·69 (s.e. 013) kg were used to evaluate the dietary methionine requirements of weanling European pigs reared under a humid, lowland, tropical environment. Response criteria used were growth rate, efficiency of food conversion, carcass quality, and the weights of some organs and individual muscles. The pigs (three male castrates and three females per treatment) were given a cassava flour-soya bean meal diet containing 202 g crude protein per kg dry matter and supplemented with increments of multiples of 0·8 g DL-methionine per kg diet. Total dietary methionine levels ranged from 2·3 to 7·9 g per kg diet dry matter. All diets contained 14·75 MJ digestible energy per kg dry matter. The experiment lasted 42 days, at the end of which the pigs were slaughtered at an average live weight of 17 kg.

Growth rate and feed efficiency were significantly improved when the basal diet was supplemented with DL-methionine (P< 0·001). No significant treatment differences in organ weight were found. Methionine requirement was significantly influenced by sex and age of the pigs, with castrates having lower requirements than females. Pooled estimated methionine requirements for optimum growth rate and efficiency of food conversion were 4·0 and 4·3 g/kg diet dry matter respectively. Maximum proportion of lean was recorded on the diet containing 3·1 g total methionine per kg dry matter.

A simple and general procedure for calculating the equilibrium improvement lag in a livestock dissemination system is presented. The lag is conveniently measured in terms of the number of years of genetic change that it represents, and depends on the age and on the genetic superiority of the parents used in each step of the dissemination system. The total lag is the sum of the lags in all steps, weighting each step by the proportion of genes going through it.

Seventy-two, 4-month-old, British Friesian steers were used to investigate the effects of feeding a supplement of fish meal on the voluntary intake and live-weight gain by young growing cattle given a well preserved ryegrass silage. The silage was offered either alone or mixed with 50,100 or 150 g fish meal per kg silage dry matter (DM) and the diets were offered either ad libitum or intakes were restricted to 16, 19 or 22 g dietary DM per kg live weight (LW). Intakes were recorded daily, LW weekly and in vivo apparent digestibility over one 7-day period during the 132-day trial.

For animals fed ad libitum, the absolute intake of dietary DM increased linearly with an increase in the level of fish-meal supplementation such that intake when the highest level of fish meal was given was significantly higher (P < 0·01) than when silage was given alone. However, DM intake per unit LW (approx. 24 g DM per kg LW) was not affected significantly (P > 0·05).

Inclusion of fish meal in the diet did not affect the apparent digestibility of dietary DM, organic matter, acid-detergent or neutral-detergent fibre (NDF) although there was a trend for slightly higher (P > 0·05) gross energy apparent digestibility when fish meal was given. Increasing the level of feeding reduced NDF digestibility. The coefficients measured at the 22 g and ad libitum levels of intake were lower (P < 0·01 and P < 0·05 respectively) than that measured at the 16 g DM per kg LW level.

Animals given silage alone to appetite achieved LW gains of 0·6 kg/day. LW gains increased linearly with increasing level of feeding (P < 0·001) and increasing level offish-meal supplementation (P < 0·001).

The efficiency of utilization of absorbed essential amino acids (AA) was studied in wether lambs (35 to 40 kg live weight) given dried grass and dried grass: barley pelleted diets over an intake range from maintenance (M) to 2·5 M energy intake. Each animal was prepared with a duodenal and Heal simple (T-shaped) cannulafor the collection of digesta entering and leaving the small intestine and with a catheter into the abomasum for the infusion of digesta phase markers (103Ru phenanthroline and 51 Cr ethylene diamine tetra acetic acid). The efficiencies of utilization of total AA and individual essential AA (EAA) were calculated from the ratios of the regressions describing AA retention per unit nitrogen (N) intake (assessed using the N retention data obtained in the present study and the AA composition of N retention derived during an accompanying comparative slaughter experiment) and AA absorption per unit N intake. These ratios for total EAA were 0·5 for the grass diet and 0·59 for the grass plus barley diet. Values for individual EAA ranged from 0·32 for threonine in sheep given the grass diet to 0·88 for arginine in sheep given the grass: barley diet. Whilst the ratios for total and individual EAA were generally higher for the grass: barley diet the very wide 95% confidence limits associated with these derived values make any between-diet or between-EAA comparisons equivocal. The data appear to support the introduction by the Agricultural and Food Research Council (1992), of a scaling factor to reduce the high efficiency of utilization of AA used previously.

The effect of botanical diversity on supply of polyunsaturated fatty acids (PUFA) to ruminants in vitro, and the fatty acid (FA) composition of muscle in lambs was investigated. Six plant species, commonly grown as part of UK herbal ley mixtures (Trifolium pratense, Lotus corniculatus, Achillea millefolium, Centaurea nigra, Plantago lanceolata and Prunella vulgaris), were assessed for FA profile, and in vitro biohydrogenation of constituent PUFA, to estimate intestinal supply of PUFA available for absorption by ruminants. Modelling the in vitro data suggested that L. corniculatus and P. vulgaris had the greatest potential to increase 18:3n-3 supply to ruminants, having the highest amounts escaping in vitro biohydrogenation. Biodiverse pastures were established using the six selected species, under-sown in a perennial ryegrass-based sward. Lambs were grazed (~50 days) on biodiverse or control pastures and the effects on the FA composition of musculus longissimus thoracis (lean and subcutaneous fat) and musculus semimembranosus (lean) were determined. Biodiverse pasture increased 18:2n-6 and 18:3n-3 contents of m. semimembranosus (+14.8 and +7.2 mg/100 g tissue, respectively) and the subcutaneous fat of m. longissimus thoracis (+158 and +166 mg/100 g tissue, respectively) relative to feeding a perennial ryegrass pasture. However, there was no effect on total concentrations of saturated FA in the tissues studied. It was concluded that enhancing biodiversity had a positive impact on muscle FA profile reflected by increased levels of total PUFA.

The chemical composition of the muscle and fatty carcass tissues of Hereford × Friesian (HE), Friesian (FR) and Charolais × Friesian (CH) steers finished on high (H) (12·6 MJ/kg dry matter) and medium (M) (10·4 MJ/kg dry matter) metabolizable energy (ME) concentration diets and slaughtered at low (L), normal (N) and heavy (W) carcass weights was determined in a 3 × 2 × 3 (no. = 9) factorial experiment. There were also pre-finishing slaughter groups of nine animals of each breed type. Target L, N and W carcass weights were 260, 300 and 340 kg, for HE and FR and 260, 320 and 380 kg, for CH, respectively.

Main effect side soft tissue weights of the finished groups were 128, 125 and 134 (s.e.d. 1·3) kg for HE, FR and CH, 133 and 125 (s.e.d. 1·1) kg for H and M and 108, 129 and 150 (s.e.d. 1·3) kg for L, N and W, respectively. Soft tissue chemical composition was 540, 562 and 590 (s.e.d. 5·0) g/kg moisture, 162, 174 and 181 (s.e.d. 1·7) g/kg protein and 288, 254 and 220 (s.e.d. 6·6) g/kg lipid for HE, FR and CH and 558 and 570 (s.e.d. 4·1) g/kg moisture, 170 and 175 (s.e.d. 1·4) g/kg protein and 262 and 246 (s.e.d. 5·4) g/kg lipid for H and M, respectively. The allometric regression coefficients for moisture, protein and lipid weights on soft tissue weight were 0·65, 0·69 and 206, respectively. The coefficients for moisture and protein weights on muscle and fat weights were < 1·0, whereas for lipid, they were >1·0. The breed differences in soft tissue chemical composition paralleled differences in physical composition. Dietary ME concentration had little effect on the chemical composition of individual tissues. For the M diet, HE, FR and CH were calculated to have similar soft tissue lipid concentrations (250 g/kg) at side soft tissue weights of 113, 125 and 157 kg, respectively. Corresponding side muscle weights at similar muscle lipid concentration (70 g/kg) would be 77, 90 and 108 kg.

Data from the Danish progeny test reports were used in an attempt to measure the genetic change in backfat thickness in the Danish Landrace breed from 1952 to 1960. Over this period the average backfat thickness of tested pigs fell from 34·2 mm. to 28·5 mm., a change of two standard deviation units.

The method used to measure genetic change depends on the differencein performance in two or more years of progeny from particular sires or dams. Environmental differences between the years are avoided by measuring performance relative to the year mean. However, allowance has to be made for selection among parents on the basis of their first set of progeny records, through adjusting the initial records by theoretical regression factors. The genetic change is then estimated as a function of the difference between the adjusted first progeny records and the records of subsequent progeny groups.

Separate estimates of the genetic change in backfat thickness were calculated in this way from the progenies of sires and of dams at each of the three stations. These were in general agreement and indicated that there was some genetic improvement in backfat thickness in the Danish Landrace from 1952 to 1960 but that not all of the observed change was genetic change. The overall estimate of the genetic change was —015±0·10 mm. per year and this represented about one-fifth of the observed change. Other less critical results are also given and these lead to the same general conclusion.

Two experiments were designed to test the possibility of partially replacing fish-meal protein in rainbow trout either with maize-gluten meal (MGM) (experiment 1) or potato protein concentrate (PPC) (experiment 2). Rainbow trout (Oncorhynchus mykiss) 30 g initial average weight were given diets containing different levels of MGM or PPC proteins ranging from 0 to 0·4 or to 0·6 of dietary protein, respectively. Substitutions of fish meal either by MGM or PPC were carried out establishing two different total dietary protein levels; 350 and 450 g/kg. Results showed that the MGM diets were acceptable and gave a significant enhancement (over 0·37 in the better case) in nutrient utilization when compared with those including only fish meal. On the contrary, diets including PPC were poorly accepted, and the growth offish and nutrient utilization were negatively correlated with dietary levels of PPC. It is concluded that levels of MGM representing around 400 g/kg diet can be used in foods for rainbow trout, whereas PPC appears not to be a suitable protein source for those fish.

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.