Fish meal and monensin, as supplements to grass silage, were offered either separately or together to Friesian steers from 5 to 9 months of age (period 1). At 9 months, six steers from each of the supplemented treatments were slaughtered to determine body composition. Of the remaining steers, from 9 months of age to slaughter at 490 kg live weight (LW) (period 2), six continued on each of the same treatments, whilst six received silage unsupplemented. A further group of six steers which had received fish meal and monensin during period 1, received monensin only as a supplement to their silage.

During period 1 fish-meal supplementation increased LW, empty body and carcass weight gains, and tissues gains, while monensin had no apparent effect. During period 2, continued supplementation with both fish meal and monensin significantly increased LW, empty body and carcass gains compared with the continuously unsupplemented steers, whilst fish meal and monensin separately produced intermediate increased gains. All three supplement regimes significantly reduced the time taken to reach slaughter.

The only significant effect on body composition was that steers receiving fish meal and monensin had a higher crude protein concentration in the empty body than those receiving only fish meal as a supplement. They also had the highest crude protein concentration in the carcass, although this was not significant. Steers which had their supplements withdrawn after 9 months of age generally maintained gains intermediate between those continuing to receive supplements and those steers unsupplemented throughout. Only those not continuing to receive fish meal and monensin together appeared to perform appreciably worse. Nevertheless, although time taken to reach slaughter from 4 months of age varied by as much as 96 days, there were no other significant differences in body or carcass composition, hi terms of cost effectiveness, use of monensin showed distinct advantages over fish meal.

Measurements of live weight and of ultrasonic (Scanogram) fat depth and m. longissimus cross-sectional area at the 12th/13th rib were taken at 4— to 6-week intervals from 10 to 35 months of age (23 occasions) on 15 Hereford males (bulls), 15 castrate males (steers) and 15 females (heifers) managed under grazing conditions.

Mean rates of live-weight change throughout the measurement period (0·51, 0·47 and 0·39 kg/day for bulls, steers and heifers, respectively) were significantly different. When compared at the same ages, fat depth was similar in the steers and heifers, beginning at about 3 mm and increasing to 11 mm. Fat depth changed little in the bulls, beginning at 1·7 mm and increasing to 3 mm. At the same age, bulls had larger m. longissimus cross-sectional areas than steers and steers had larger muscle cross-sectional areas than heifers.

Absolute variation within sex groups increased throughout the experiment in live weight and fat depth, but not in m. longissimus crosssectional area. Simple correlation coefficients, pooled within sex groups, of relationships between the same measurements at various measuring occasions, indicated that measurements of fat depth and of muscle cross-sectional area at 10 to 12 months of age are poor indicators of these measurements at periods of 6 months or more later in life.

When compared at the same live weights, heifers had the greatest and bulls had the smallest fat depth and, within animals, fat depth was closely related to live weight. At any live weight, m. longissimus cross-sectional area was less in heifers than in steers and bulls, which were not significantly different from each other in this trait. Equations relating fat depth and muscle area to live weight are presented and, under the conditions of this study, indicate that there is no basis for adjustment of fat depth for live weight in bulls subjected to contemporaneous selection.

The rate of passage (ROP) in the gastrointestinal tract (GIT) influences the exposure time of food to the digestion and absorption processes. Consequently, ROP affects the efficiency of nutrient utilization and energy from the diet. This study aimed to determine the physiological parameters that characterize the digestive response, such as first appearance time (FAT), ROP, mean retention time (MRT) and transit time (TT) in adult Japanese quail (Coturnix coturnix japonica), and to evaluate the effects of sex, apparent metabolizable energy corrected for nitrogen balance (AMEn) content in the diet and different types of markers on these parameters. In the first trial, we investigated the effects of sex and AMEn level (high- and low-energy diet) on the FAT parameter. Thirty-two male and 32 female Japanese quail were randomly allocated to 8 battery cages and assigned to 4 treatments in a 2 × 2 factorial design with 4 replicates of 4 birds for each treatment. To determine the FAT, ferric oxide (1%) was added to the diet, and the excreta of the quail was monitored until the first appearance of the marker. The results indicated significant differences (P < 0.05) in the FAT between males (100 min) and females (56 min), regardless of the AMEn content. In the second trial, thirty-two 32-week-old female Japanese quail in the laying phase were assigned to four treatments in a 2 × 2 factorial design, in which the main independent variables were type of marker (Cr or Ti) and AMEn level (high- and low-energy diets). In order to determine ROP (ET1%), MRT and TT (ET100%), the markers (0.5%: Cr2O3 and 0.5%: TiO2) were added to the diets, and the excreta were collected for 750 min. The excretion times for 1% (ET1%), 25% (ET25%), 50% (ET50%), 75% (ET75%) and 100% (ET100%) were estimated using cumulative excretion curves. No effect was detected for the AMEn level (P > 0.05); however, the effect of different marker types was significant (P < 0.05). This difference increased with time and ET100% was estimated to occur at 59 min. The ROP was estimated to be 68 min. The TT was estimated to be 540 min using Cr and 599 min using Ti, with an average MRT value of 0930 h. Taken together, our findings support the hypothesis that Japanese quail digestion through the GIT can be dynamic and differ based on sex or marker type.

Thirty-five Assaf intact male lambs were divided into three groups and offered an all-concentrate pelleted diet based on barley and maize and supplemented with either toasted soya bean meal, herring meal or toasted soya bean meal plus methionine to contain 20% crude protein. The live-weight gains to a slaughter weight of 57 kg were 425, 440 and 394 g/day, and the feed conversion ratios were 3·12, 3·07 and 3·38 kg dry matter/kg gain, respectively. It is concluded that, with toasted soya bean meal as the protein supplement, it is possible to obtain high growth rates that do not diifer significantly from those obtained with herring meal.

This experiment was designed to investigate the effects of meal-time feeding and protein restriction on performance, gait score (GS) and carcass and bone traits in broilers. A total of 420 1-day-old chicks were wing banded and randomly distributed into 21 pens with 20 chicks each. At 7 days of age, chicks were weighed and randomly assigned to one of the three treatments: (1) control (C) feed (23.02% crude protein (CP)) was available ad libitum; (2) meal-time feeding (MF); control feed was available from 0100 to 0900 h and from 1500 to 2300 h. Food was withdrawn from 0900 to 1500 h and whole wheat (10 g/bird per day) was dispersed on the floor from 7 to 21 days; and (3) low-protein (LP) diet (19.71% CP) was fed to the chicks from 7 to 21 days. All of the groups were fed ad libitum from 1 to 7 days of age and from 21 to 45 days of age with a standard commercial diet. Individual body weight was measured on days 7, 21 and 45. Feed consumption was measured from 7 to 21 days and from 21 to 45 days. Forty-two chicks were humanly slaughtered and eviscerated for bone evaluation, on days 21 and 45. Also carcass characteristics were determined on day 45. Control group body weight was significantly higher (P < 0.05) at 21 and 45 days of age than the MF and LP groups, which did not differ. Feed intake was reduced by meal-time feeding and LP diet (P < 0.01). Feed efficiency was the best in the MF group during the period of 21 to 45 days of age (P < 0.01). In the control group, shank was significantly longer than that of the LP group and tibia breaking strength was higher than that of the MF group at 21 days (P < 0.05). However, shank width, tibia wet weight and tibia mid-diaphysis ash percentage of the MF group were significantly lower than those of the C and LP groups at 21 days of age (P < 0.05). GS, shank and carcass and tibia bone traits on day 45 were not significant among groups. No compensatory growth and walking ability improvement were observed at 45 days of age for broilers fed with MF and LP between 7 and 21 days of age.

This work set out to establish the response equations for hepatic blood flows in sheep and the contribution of hepatic arterial flow to hepatic venous blood flow due to changes in intake levels at constant diet composition. The FLORA (FLuxes across Organs and tissues in Ruminant Animals) database was used, and meta-analysis performed. The meta-analysis involved selection of published papers, identification of studies, description and coding of the selected dataset and statistical analysis using a covariance model. Meta-analyses were carried out using a within-study approach. To ensure absence of bias, the analysis incorporated interfering variables and factors studied in between-study comparisons. Variables concerned diet composition; qualitative factors concerned the physiological state of the animals and the methods used to measure blood flow. The results obtained showed that hepatic blood flows were positively related to intake in sheep. The magnitude of the response (as indicated by the slope) varied with the level of intake and the blood vessel (portal, hepatic venous or arterial). Nine linear relationships were established for the portal, hepatic venous and arterial blood flows as a function of dry matter intake (DMI) with below- and above-maintenance levels considered separately. Data obtained at below- and above-maintenance levels were considered together and four quadratic relationships were established for hepatic blood flows as a function of DMI. These relationships expressed a strong effect of intake on hepatic blood flows. The contribution of hepatic arterial to hepatic venous blood flow averaged 18.2%, with a wide variability. It did not vary significantly with level of intake. Although in between-study comparisons the arterial/venous blood flow was positively influenced by the organic matter digestibility of the diet, the relationships we obtained were robust. They can be used in models of net hepatic nutrient fluxes to predict variations and absolute values of hepatic blood flows from variations and absolute values of DMI.

This study was done to evaluate the effects of two sublethal doses of gossypol (4 and 20 mg/kg of BW, every other day) on some amino and fatty acid concentrations in male rabbit seminal plasma. Rabbits were chosen as an experimental animal owing to the fact that they are excellent model for reproductive toxicological effects. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the tested product, and a recovery period (second 8 weeks) where all drugs were withdrawn. Results showed that total amino acids (TAA), total essential amino acids (EAA), total non-essential amino acids (non-EAA) and EAA/non-EAA ratio were decreased in a dose-dependent manner during gossypol treatment. The deleterious effect on TAA concentrations was mainly due to the reduction in total EAA. However, these concentrations regained their normal values after gossypol cessation. Basic, acidic, neutral amino acids and basic/acidic amino acids ratio decreased in a dose-dependent manner by gossypol treatment. Additionally, gossypol administration caused decreases in total unsaturated fatty acids (USFA) and increases in total saturated fatty acids (SFA) and the SFA/USFA ratio in a dose-dependent manner. During the recovery period, total SFA and USFA showed significant reduction and significant increase, respectively, after gossypol withdrawal. In conclusion, gossypol administration affected rabbit seminal plasma concentrations of amino and fatty acids in a dose-dependant manner. Gossypol reduced TAA, total EAA and total non-EAA. Additionally, gossypol caused decreases in total USFA and increases in total SFA. These deleterious effects were associated with poor-quality semen observed in our previous studies.

Data obtained from a detailed base from a commercial breeding company of Landrace and Large White purebred nucleus sows were used to estimate genetic parameters of piglet number born alive (NBA) following artificial insemination and natural service. Heritabilities were small but significantly different from zero, and similar to literature estimates. The genetic correlation (rG) of NBA after AI or natural service using pooled data was 0·71 and was significantly different from one (P<0·01) but not significantly different between breeds (P>0·1). It is concluded that mating type may result in a re-ranking of sow genetic merit for NBA.

The objective of this study was to examine genetic changes in reproduction traits in sows (total number born (TNB), number born alive (NBA), average piglet birth weight (ABW) and number of piglets weaned (NW), body weight prior to mating (MW), gestation length (GL) and daily food intake during lactation (DFI)) in lines of Large White pigs divergently selected over 4 years for high and low post-weaning growth rate on a restricted ration. Heritabilities and repeatabilities of the reproduction traits were also determined. The analyses were carried out on 913 litter records using average information-restricted maximum likelihood method applied to single trait animal models. Estimates of heritability for most traits were small, except for ABW (0·33) and MW (0·35). Estimates of repeatability were slightly higher than those of heritability for TNB, NBA and NW, but they were almost identical for ABW, MW, GL and DFI. After 4 years of selection, the high growth line sows had significantly heavier body weight prior to mating and produced significantly more piglets born alive with heavier average birth weight than the low line sows. There were, however, no statistical differences between the selected lines in TNB or NW. The lower food intake of high relative to low line sows during lactation was not significant, indicating that daily food intake differences found between grower pigs in the high and low lines (2·71 v. 2·76 kg/day, s.e.d. 0·024) on ad libitum feeding were not fully expressed in lactating sows. It is concluded that selection for growth rate on the restricted ration resulted in beneficial effects on important measures of reproductive performance of thea sows.

Effect of graded levels of high-glucosinolate mustard (Brassica juncea) meal as substitute of soya-bean meal (SBM) in broiler rabbit diets was studied. Forty weaning rabbits of Soviet Chinchilla and White Giant breed were randomly allocated to one of four experimental diets containing mustard meal (MM) 0, 80, 160 and 245 g/kg. The experiment lasted for 8 weeks. MM had 54.8 mg total glucosinolates (TGLSs) per g dry matter (DM). Diets had TGLS 3.8, 8.4 and 11.98 mg/g DM in 80, 160 and 245 g MM diets, respectively. MM-incorporated diets had higher digestible and linearly (P < 0.01) higher metabolisable energy (ME) content. However, the effect on total tract apparent digestibility of DM, and crude protein was quadratic. Average daily gain (ADG) reduced (P < 0.05) linearly with increasing MM levels in diet, still 80 and 160 g MM diets had similar ADG compared to that of SBM diet. Caecum weight reduced linearly (P < 0.05) with increasing MM levels in diet. The pH of caecal content ranged between 5.85 and 6.19, total N between 1.19 and 1.48 (g per 100 g) and total volatile fatty acids between 4.7 and 5.8 mmol per 100 g, and they were not statistically different. NH3-N ranged between 31.2 and 39.0 mg per 100 ml, and reduced linearly (P < 0.05) while trichloroacetic acid-precipitable nitrogen increased linearly (P < 0.01, ranged between 114 and 247 mg per 100 ml) with increasing MM levels in diet. Blood haemoglobin, packed cell volume and lymphocytes were higher (quadratic effects, P < 0.05) on 245 MM diet, whereas white blood cell count reduced linearly (P < 0.01). Serum aspartate aminotransferase increased linearly (P < 0.01) while alanine aminotransferase and alkaline phosphatase activity, protein, erythrocytes sedimentation rate and red blood cell counts were not affected by MM. Serum Cu, Na and K content increased linearly (P < 0.05) with increasing MM levels. Liver Cu concentration showed quadratic (P < 0.05) increase. Rabbits tolerated 8.4 mg TGLS per g diet (160 g MM per kg) during active growth without any apparent effect on health and growth. It is concluded that MM can replace up to 66% SBM protein in rabbit feeding, whereas complete replacement of SBM with MM reduced feed intake and ADG by 23% and 13%, respectively. Further studies are required to confirm these inclusion levels and glucosinolate tolerance of rabbits.

The gastrointestinal tract (GIT) of animals is capable of sensing various kinds of nutrients via G-protein coupled receptor-mediated signaling transduction pathways, and the process is known as ‘gut nutrient chemosensing’. GPR40, GPR41, GPR43 and GPR119 are chemoreceptors for free fatty acids (FFAs) and lipid derivatives, but they are not well studied in small ruminants. The objective of this study is to determine the expression of GPR40, GPR41, GPR43 and GPR119 along the GIT of kid goats under supplemental feeding (S) v. grazing (G) during early development. In total, 44 kid goats (initial weight 1.35±0.12 kg) were slaughtered for sampling (rumen, abomasum, duodenum, jejunum, ileum, cecum, colon and rectum) between days 0 and 70. The expression of GPR41 and GPR43 were measured at both mRNA and protein levels, whereas GPR40 and GPR119 were assayed at protein level only. The effects of age and feeding system on their expression were variable depending upon GIT segments, chemoreceptors and expression level (mRNA or protein), and sometimes feeding system × age interactions (P<0.05) were observed. Supplemental feeding enhanced expression of GPR40, GPR41 and GPR43 in most segments of the GIT of goats, whereas G enhanced expression of GPR119. GPR41 and GPR43 were mainly expressed in rumen, abomasum and cecum, with different responses to age and feeding system. GPR41 and GPR43 expression in abomasum at mRNA level was greatly (P<0.01) affected by both age and feeding system; whereas their expression in rumen and abomasum at protein level were different, feeding system greatly (P<0.05) affected GPR41 expression, but had no effect (P>0.05) on GPR43 expression; and there were no feeding system×age interactions (P>0.05) on GPR41 and GPR43 protein expression. The expression of GPR41 and GPR43 in rumen and abomasum linearly (P<0.01) increased with increasing age (from days 0 to 70). Meanwhile, age was the main factor affecting GPR40 expression throughout the GIT. These outcomes indicate that age and feeding system are the two factors affecting chemoreceptors for FFAs and lipid derivatives expression in the GIT of kids goats, and S enhanced the expression of chemoreceptors for FFAs, whereas G gave rise to greater expression of chemoreceptors for lipid derivatives. Our results suggest that enhanced expression of chemoreceptors for FFAs might be one of the benefits of early supplemental feeding offered to young ruminants during early development.

The digestibility of oat straw treated with anhydrous ammonia was studied in four Shetland-type ponies in a 4×4 Latin square experiment. The experimental diets which contained soya bean oil meal, corn, sugarcane molasses, and 65% straw were: (1) straw treated with anhydrous ammonia, (2) untreated straw, (3) untreated straw plus urea, (4) untreated straw plus soya bean oil meal. Digestibility of the dry matter was 15% greater (P<0·01) and digestibility of cellulose 28% greater (P<0·01) in diets containing ammonia-treated straw than in those containing untreated straw. Ammonia treatment increased the nitrogen content of the straw by 50%, and nitrogen intake was 18% greater when the ponies were fed diet 1 than when fed diet 2. The nitrogen of the treated straw was utilized as efficiently as the nitrogen of the diet containing untreated straw supplemented with soya bean oil meal. However, the amount of nitrogen provided by the diet of ammonia-treated straw was not sufficient for nitrogen balance in the ponies. Ammonia treatment of oat straw did not affect the utilization of Ca, P, or Mg.

Long-day photoperiods of 16 h light (L) and 8 h dark (D) stimulate a proportional increase in live-weight (LW) gain of peripubertal Holstein heifers of 0·08 to 0·17 compared with heifers exposed to short days of less than 12 h L per day (Peters, Chapin, Leining and Tucker, 1978; Peters, Chapin, Emery and Tucker, 1980; Petitclerc, Chapin, Emery and Tucker, 1983; Zinn, Chapin and Tucker, 1986). One factor that could account for some of this variation in the magnitude of the growth response to long days is that the previous photoperiod exposure may influence the response to a subsequent different photoperiod (Moore-Ede, Sulzman and Fuller, 1982). For example, exposure to 13L: 11D induced pulsatile activity of serum luteinizing hormone (LH) in ewes previously exposed to 16L: 8D, but reduced serum LH to undetectable levels in sheep previously exposed to 8L: 16D (Robinson and Karsch, 1987). Thus, sheep exposed to identical photoperiods exhibited different responses depending on previous photoperiod exposure.

From ~35 days of age fast growing meat chickens spend extended periods sitting or lying and less time standing. In a fast-feathering parent line lower early incubation temperatures which delayed chick hatch time, improved bone ash and extended their standing time. This incubation study assessed the consequences of incubation temperatures, hatch time and chick management at hatch/take off on femoral bone ash (BA) in Cobb 500 meat chickens. Embryos were incubated under either Control (between 37.8°C and 38.2°C egg shell temperature (EST)) or a Slow start (from 37.2°C at sett (the start of incubation), reaching 37.8°C EST at day 13 incubation), temperatures. Hatched chicks were identified at 492 h (20.5 days of incubation – classified as early (E)) or, between >492 and ⩽516 h (>20.5 and ⩽21.5 days of incubation – classified as late (L)), from setting. The E hatch chicks were allocated across three post-hatch treatments; treatment 1: E hatch chicks that were sampled E at 492 h from setting; treatment 2: E hatch chicks that were fed for a further 24 h in a floorpen before being sampled L at 516 h from setting; treatment 3: E hatch chicks that spent a further 24 h in the incubator before being sampled L at 516 h from setting. All L hatch chicks formed one treatment group which was sampled L at 516 h (i.e. L hatch chicks sampled L). It is not possible to sample L hatching chicks E hence this treatment is absent from the experimental design. Slow start incubation resulted in a higher total hatch percentage with a greater proportion of chicks hatching L, compared with the Control incubation. The L hatching chicks had significantly higher BA than the E hatching chicks. Of the E hatching chicks, those sampled both E and L had significantly lower BA than E hatching chicks fed for 24 h before L sampling. The E hatch, fed and sampled L chicks had the numerically highest BA, which was not significantly different from the BA of the L hatching chicks sampled L These results demonstrate that BA at hatch can be improved, either by extending the incubation period through a Slow start incubation profile, inducing L hatch, or alternatively, via the prompt provision of feed to E hatching chicks.

Replacing grass silage with maize silage results in a fundamental change in the ratio of structural to non-structural carbohydrates with commensurate changes in rumen fermentation patterns and nutrient utilisation. This study investigated the effects of feeding four forage mixtures, namely grass silage (G); 67 g/100 g grass silage + 33 g/100 g maize silage (GGM); 67 g/100 g maize silage + 33/100 g grass silage (MMG); maize silage (M) to four ruminally and duodenally canulated Holstein Friesian steers. All diets were formulated to be isonitrogenous (22.4 g N/kg DM) using a concentrate mixture. Dietary dry matter (DM) and organic matter (OM) digestibility increased with ascending maize silage inclusion (P < 0.1) whereas starch and neutral detergent fibre digestibility declined (P < 0.05). Ratio of non-glucogenic to glucogenic precursors in the rumen fluid increased with maize silage inclusion (P < 0.01) with a commensurate reduction in rumen pH (P < 0.05). Mean circulating concentrations of insulin were greatest and similar in diets MMG and GGM, lower in diet M and lowest in diet G (P < 0.01). There were no effects of diet on the mean circulating concentration of growth hormone (GH), or the frequency, amplitude and duration of GH pulses, or the mean circulating concentrations of IGF-1. Increasing levels of DM, OM and starch intakes with the substitution of grass silage with maize silage affected overall digestion, nutrient partitioning and subsequent circulating concentrations of insulin.

The objectives of this study were to analyze the trend of within-breed genetic diversity and identify major causes leading to loss of genetic diversity in Guernsey breed in three countries. Pedigree files of Canadian (GCN), South African (GSA) and American (GUS) Guernsey populations containing 130 927, 18 593 and 1 851 624 records, respectively, were analyzed. Several parameters derived from the in-depth pedigree analyses were used to measure trends and current levels of genetic diversity. Pedigree completeness index of GCN, GSA and GUS populations, in the most recent year (2007), was 97%, 74% and 79%, respectively, considering four generations back in the analysis. The rate of inbreeding in each population was 0.19%, 0.16% and 0.17% between 2002 and 2007, respectively. For the same period, the estimated effective population size for GCN, GSA and GUS was 46, 57 and 46, respectively. The estimated percentage of genetic diversity lost within each population over the last four decades was 8%, 3% and 5%, respectively. The relative proportion of genetic diversity lost due to random genetic drift in the three populations was 93%, 91% and 86%, respectively. In conclusion, the results suggested that GCN and GUS have lost more genetic diversity than GSA over the past four decades, and this loss is gaining momentum due to increasing rates of inbreeding. Therefore, strategies such as optimum contribution selection and migration of genetic material are advised to increase effective population size, particularly in GCN and GUS.

Women who were themselves small-for-gestational age (SGA) are at a greater risk of adulthood diseases such as non-insulin-dependent diabetes mellitus (NIDDM), and twice at risk of having an SGA baby themselves. The aim of this study was to examine the intergenerational pig. Low (L) and normal (N) birth weight female piglets were followed throughout their first pregnancy (generation 1 (G1)). After they had given birth, the growth and development of the lightest (l) and heaviest (n) female piglet from each litter were monitored until approximately 5 months of age (generation 2 (G2)). A glucose tolerance test (GTT) was conducted on G1 pig at ∼6 months of age and again during late pregnancy; a GTT was also conducted on G2 pigs at ∼4 months of age. G1 L offspring exhibited impaired glucose metabolism in later life compared to their G1 N sibling but in the next generation a similar scenario was only observed between l and n offspring born to G1 L mothers. Despite G1 L mothers showing greater glucose intolerance in late pregnancy and a decreased litter size, average piglet birth weight was reduced and there was also a large variation in litter weight; this suggests that they were, to some extent, prioritising their nutrient intake towards themselves rather than promoting their reproductive performance. There were numerous relationships between body shape at birth and glucose curve characteristics in later life, which can, to some extent, be used to predict neonatal outcome. In conclusion, intergenerational effects are partly seen in the pig. It is likely that some of the intergenerational influences may be masked due to the pig being a litter-bearing species.

Classification of pig carcasses in the European Community (EC) is based on the lean meat percentage of the carcasses. The lean meat percentage is predicted from instrumental carcass measurements, such as fat and muscle depth measurements, obtained in the slaughterline. The prediction formula for an instrument is derived from the data of a dissection experiment. When the relationship between percentage lean and instrumental carcass measurements differs between subpopulations, such as sexes or breeds, accuracy of prediction may differ between these subpopulations. In particular for some subpopulations predicted lean meat percentages may be systematically too low and for other subpopulations systematically too high. Producers or buyers that largely specialize in subpopulations where the percentage lean is underestimated, are put at a financial disadvantage.

The aim of this paper is to gain insight, on the basis of real data, into the effects of differences between subpopulations on the accuracy of the predicted percentage lean meat of pig carcasses. A simulation study was performed based on data from dissection trials in The Netherlands, comprising gilts and castrated males, and trials in Spain, comprising different genetic types. The possible gain in accuracy, i.e. reduction of prediction bias and mean squared prediction error, by the use of separate prediction formulae for (some of) the subpopulations was determined.

We concluded that marked bias in the predicted percentage lean meat may occur between subpopulations when a single overall prediction formula is employed. Systematic differences in predicted percentage lean between subpopulations that are overestimated and underestimated may exceed 4% and for selected values of instrumental measurements may run up to 6%. Bias between subpopulations may be eliminated, and prediction accuracy may be markedly improved, when separate prediction formulae are used. With the use of separate formulae the root mean squared prediction error may be reduced by 13 to 26% of the expected value when a single prediction formula is used for all pig carcasses.

These are substantial reductions on a national scale. This suggests that there will be a commercial interest in the use of separate prediction formulae for different subpopulations. In the near future, when the use of implants becomes more reliable, subpopulations will be recognized automatically in the slaughterline and use of different prediction formulae will become practically feasible. Some possible consequences for the EC regulations and national safeguards for quality of prediction formulae are discussed.

Maturing patterns are established for 26 body organs using data from 35 rams of two strains of Merinos of different mature size (97 and 120 kg).

The proportion of shorn full live weight represented by each structure at maturity was very similar for all organs except the head, hide and distal limbs which were relatively heavier in the small strain. and small intestine and blood which were relatively heavier in the large strain.

All organs were early maturing relative to shorn full live weight except the hide and the penis plus bladder, which matured at the same rate as live weight. The maturity coefficients differed between strains only for the head, thyroid and omasum.

Differences in the proportion of live weight comprised by each organ in the two strains were compared at the same shorn full live weight and at the same proportion of mature shorn full live weight. Differences in the various portions of the alimentary tract and other internal organs, with the exception of the kidneys, which were evident in comparisons at the same weight, were reduced when compared at the same proportion of maturity. The difference between strains for head, hide and distal limbs was greater at equal maturity than at equal weight suggesting a functional relationship to body weight rather than to ultimate mature body size.

It was concluded in genetic comparisons of animals of different mature size, the most appropriate basis of comparison of relative organ weight will be at the same proportion of mature live weight.

Social learning from peers can trigger herd-wide intoxication with white locoweed (Oxytropis sericea), an alkaloid-synthesizing herbaceous legume that grows on rangelands of western North America. We conducted an experiment to test the hypothesis that restriction of the area allocated to animals to feed in would inhibit social facilitation of locoweed ingestion in yearling heifers. Eight heifers that avoided white locoweed (LA) and eight heifers that readily consumed it (LE) were selected from a pool of 40 cross-bred heifers and were randomly assigned to the social facilitation or social interference treatment groups. We conducted 200 10-min feeding trials in three 5-day phases (pre-treatment, treatment, post-treatment) during which animals were presented with a set of bowls arrayed in a test arena, some of which contained ground wheat straw and others contained air-dried ground white locoweed. During the pre-treatment (days 1 to 5) and the post-treatment phases (days 11 to 15) non-social trials were conducted in which the feeding behavior of individual animals was investigated in an 80 m2 arena containing 12 feeding bowls. During the treatment phase (days 6 to 10) social learning trials were conducted in which LA + LE pairs from the social interference group were exposed to 12 bowls of food distributed in an 80 m2 arena intended to induce social interference, and LA + LE pairs from the social facilitation group were exposed to 36 bowls of food distributed in a 240 m2 arena intended to permit social facilitation. During pre-treatment phase, LA heifers consumed detectably less locoweed and wheat straw and exhibited lower preference for locoweed than LE (P ⩽ 0.05) although wheat straw preference of LA and LE was similar. During social learning trials (treatment phase), LA in the social interference group visited similar number of locoweed bowls (mean ± s.e.m.: 0.2 ± 0.12) as they had during non-social learning (0.2 ± 0.20). Conversely, LA heifers in the social facilitation group visited detectably more locoweed bowls during social learning trials (1.6 ± 0.46) compared with the pre-treatment phase (0.2 ± 0.16). Correlation between daily number of locoweed bowls visited by LA and LE during social learning trials was detected in the social facilitation (r = 0.70; P < 0.01), but not in the social interference group (r = 0.15; P = 0.52). During testing trials (post-treatment phase), locoweed and wheat straw intake and preference of LA and LE in both treatment groups was similar. Manipulation of the feeding environment delayed, but did not inhibit social learning of toxic weed ingestion in this study.