One hundred and thirty-nine Scottish Half bred ewes were studied during the last 8 weeks of pregnancy, through parturition and early lactation. They were divided, on the basis of their metabolizable energy intake during this period, into low (483 MJ/ewe; L), medium (742 MJ/ewe; M) or high (974 MJ/ewe; H) feeding groups.

Ewe weight change (from mating to 12 h post lambing) was directly related to nutritional level and the number of lambs born, e.g. L ewes with triplets lost a mean 13·8 kg, while H ewes with single lambs gained 14·3 kg.

Lamb birth weight and perinatal lamb mortality levels were affected by ewe nutrition and litter size. L twins weighed 19% less at birth than H twins; L triplets weighed 26% less than H triplets. The mortality rate of L twins was 23% greater than M twins; L triplets exceeded the H triplet mortality rate by 87%.

Ewe energy feeding during late pregnancy affected the mean daily weight gain of lambs for at least 3 weeks after birth. H single, twin and triplet lambs grew 12%, 15% and 16% faster than M lambs and 19%, 31 % and 31 % faster than L lambs respectively.

The H group produced 33 % more lamb live weight at 3 weeks of age for every lamb born than did the L group.

Lamb serum immunoglobulin levels were related to litter size but did not reflect the differences in ewe feeding during late pregnancy.

Effects of creep food presentation on feeding behaviour and intake were studied with eight litters of eight to 10 Yorkshire × Landrace piglets in the 3rd and 4th weeks after birth, before weaning at 4 weeks of age. In each week, four treatments were applied, each for 24 h: a single two-space feeder unchanged from the previous day; a clean feeder with fresh food supplied at 09.00 h; a clean feeder with fresh food supplied at three times during the day; and three feeders (six feeding spaces) providing increased access to food throughout the day. There were no significant differences between the first three treatments in time spent at the feeder (recorded by video over 24 h) or food intake of piglets. However, the fourth treatment increased average intake in week 3 to 2·1 times the average of the other treatments, and in week four to 1·4 times. In week 3, most piglets spent more time at the feeder when access was increased, while in week 4 the effect was restricted to piglets which ate very little. This suggested that imitative learning was important in the initiation of feeding. Analysis of both litter means and within-Utter variation showed that piglets which ate more solid food before weaning gained more weight in the 2 weeks after weaning. However, this correlation was confounded by correlations of both measures with birth weight and other variables. Causal links between creep feeding and post-weaning weight gain remain to be demonstrated.

The origin of myristic acid in mammalian cells and the regulation of its endogenous cellular low concentration are not known. Another intriguing question is the potential metabolic properties of endogenous myristic acid as compared with exogenous myristic acid. In the present paper, we hypothesised and demonstrated that, in liver cells, in addition to the usual fatty acid synthase (FAS) pathway that produces predominantly palmitic acid and minor amounts of myristic acid, part of endogenous cellular myristic acid also comes from a shortening of palmitic acid, likely by peroxisomal β-oxidation and from lauric acid by elongation. From a nutritional point of view, C16:0 is universally found in natural fats and its shortening to myristic acid could contribute to a non-negligible source of this fatty acid (FA) in the organism. Then, we measured the distribution of endogenously synthesised myristic acid in lipid species and compared it with that of exogenous myristic acid. Our results do not support the hypothesis of different metabolic fates of endogenous and exogenous myristic acid and suggest that whatever the origin of myristic acid, its cellular concentration and lipid distribution are highly regulated.

There is some evidence to show that loose housing during gestation has a negative influence on the welfare of sows subsequently in farrowing crates. However, little is known about the effects of the gestation housing on the initial responses of gilts to the farrowing crate or of the effects on gilt welfare throughout lactation. The objective of this experiment was to evaluate three gestation housing systems (1) stalls (ST); (2) loose-bedded (LB) and (3) loose-unbedded (LU) pens for their effect on behaviour, heart rate and skin lesion scores of gilts in farrowing crates. During the 1st h in the farrowing crate, LB gilts were more active, while ST gilts were more vocal. Although heart rates during the 1st h did not differ significantly between treatments, LB and LU gilts had significantly higher mean heart rates during the first 5 min in the crate, compared with 35 min later. Posture changes during the first 24 h did not differ between treatments. However, there was a significant reduction in the number of posture changes made by ST gilts but not LB or LU gilts by day 8. Increases in the skin lesion score of gilts in all three treatments were observed after 24 h in the crate, further increases were observed post farrowing in both loose treatments. Although no significant differences in the skin lesion score were observed during lactation, LB gilts were weaned with lower lesion scores than LU or ST gilts. Gilts from both loose treatments experienced greater distress at first introduction to the farrowing crate. However, the change in environment also had an adverse affect on the welfare of ST gilts. Skin damage and continuing discomfort of the loose-housed gilts post farrowing suggests that they experienced more stress at parturition. Bedding during gestation had a beneficial effect on skin health in the farrowing crate that persisted until weaning.

1. Twelve sets of 3 litter-sister Large White gilts were mated at first oestrus after reaching 250 lb. live-weight and given daily during 3 successive pregnancies either 6 lb. (A), 3 lb. (B) or 3 lb. for 76 days then 6 lb. until parturition (C) of the same meal mixture. During an 8-week lactation all were given 4 lb. meal plus 0·8 lb. per piglet suckled.

2. There was a significant linear increase in numbers born with successive parities (P<0·05) but no significant differences between treatment or sister groups. There was a highly significant difference between treatment groups in mean piglet birth weight (P< 0·001) but no parity effect; mean birth weights were 2·76, 2·40 and 2·58 Ib. for Groups A, B and C respectively. Differences between sister groups in mean piglet birth weight were also significant (P<0·05).

3. Post-natal litter performance was poor for all groups, probably because of the presence of E. coli, but there was no evidence of treatment effects other than on 3-week weight of third litters, which was significantly greater in Group C than in A or B (P<0·05). There were no significant effects on either number or weight of piglets at 8 weeks.

Random regression models were used to analyse the daily growth data for a total of 25 pigs of two commercial crossbred types between 75 and 140 days of age. A visual imaging system placed above a feeding station provided daily the plan area and length measurements of different body parts. Daily live-weight measurements of the pigs were obtained from a platform balance integrated into an electronic feeding station. Growth curves associated with different measures, pigs and types were compared. Significant differences in the age growth curves between the pig types could only be found in the ham width measurements (P < 0.05). The linear measure of ham width showed the greatest difference between the two types, and the lowest coefficient of variation among individual animals. Size measures were shown to be a more consistent indicator of pig performance during growth than live weight: pigs with a relatively large surface area or ham width at the early growth stage also have relatively large surface area or ham width at later stages and the between-animal variation in these measurements remains constant with age. Gain in live weight relative to increase in size differed significantly between the two pig types (P < 0.05). Pigs of the two types had significantly different shapes, but the change of shape during growth did not differ significantly between them. The allometric relationships between surface area and ham width1.85 and between body length and ham width0.85 indicate that the ham widths of pigs increase faster in proportion to full body measures. Variations between individual animals in size increase and shape change are significant (P < 0.05). The analysis suggests that VIA size and shape measurements provide valid descriptors of pig growth.

Eleven sun-cured hays with crude protein (CP) and neutral-detergent fibre (NDF) concentrations ranging from 57 to 207 and 428 to 744 g/kg dry matter (DM) respectively, were used to study the relationship between the DM and NDF degradation characteristics and the voluntary DM intake (VDMI) by sheep.

The VDMI was measured in the last 10 days of a 21-day period using 50 mature ewes in five groups of 10 ewes per group, with a mean live weight (LAY) of 55 kg and ranged from 41·2 to 69·8 g/day per kg LW075. Disappearanc e rates of DM and NDF were measured by incubating samples in nylon bags in the rumens of three hay-fed rumen-cannulated ewes for 3, 6, 9, 15, 24, 48 and 72 h and by fitting the exponential model Y = a + b (1 — e-ct) to the results. Potential degradabilities (defined as a + b) for DM and NDF ranged from 679 to 868 and from 445 to 808 g/kg respectively.

The VDMI was significantly correlated with the soluble fraction of DM (aDM; P < 0·05) and the rate of degradation of DM (cDM; P < 0·01) and NDF (cNDF; P < 0·01). The inclusion of aDM and cDM ni a multiple regression model resulted in the equation: VDMI = 21·3 + 0·0733 (s.e. 0·01577) aDM + 138 (s.e. 26·0) cDM (R2 = 0·897; residual s.d. = 2·79), with a significant increase of the variance explained by one single degradation characteristic (P < 0·05). The prediction was not improved by adding the constant cNDF to the equation (P > 0·05). These results indicate the possibility of predicting the VDMI of hays by sheep from the rumen soluble fraction (aDM) and the rate of degradation (cDM) of DM.

The effect of energy supply on physical composition of body weight gain between 45 and 100 kg was studied in Large White castrated males (cLW), crossbred Pietrain × Large White castrated males (cPPX) and boars (bPPX). The pigs were either given food ad libitum and kept in individual pens in experiment 1, or allocated to four energy levels (0·70, 0·80, 0·90, and 1·00 ad libitum) and kept in metabolism cages in experiment 2. Daily protein supplies were calculated to be the same at the four energy levels within each type of pig and non-limiting for growth. Five additional animals for each type of pig were slaughtered at 45 kg. Daily tissue gain was measured according to the comparative slaughter technique. The daily lean gain increased with metabolizable energy (ME) intake according to a linear-plateau relationship whereas the daily fat gain increased linearly. The type of pig significantly affected the slope of the relationship between lean gain and ME intake (from 15 to 22 g per extra MJ ME) but not the slope of the relationship between fat gain and ME intake (10 g per extra MJ ME on average). Increased energy intake was associated with increased fatness of body-weight gain, which was higher in cLW and cPP× than in bPP×.

The present study was undertaken to determine the Heal and total tract apparent digestibility and hindgut disappearance of dietary components and energy in a barley-based diet which included either lucerne or white-clover meal (proportionately 0·10 and 0·20). The experiment was conducted as a 5 × 5 change-over design with growing pigs fitted with simple t-shaped cannulas posterior to the ileo-caecal valve. The Heal and total tract apparent digestibilities of organic matter (OM), crude protein, crude fat, nitrogen-free extractives and energy were significantly reduced ivith increasing inclusion of lucerne and white-clover meal in the diet (P < 0·05). The total tract apparent digestibility of total fibre (TF) was significantly reduced with lucerne meal inclusion (P < 0·05), while the Heal apparent digestibility of TF was unaffected by lucerne and white-clover meal inclusion. Hindgut apparent digestibility (proportion of total tract apparent digestibility) of OM and energy was approximately 0·10, 0·70 and 0·70 for barley, lucerne and white-clover meal, respectively.

Both the Heal and total tract apparent digestibility of OM and energy were significantly higher for the control diet compared with lucerne and white-clover meal (P < 0·05). There was also a significantly higher apparent digestibility of OM, TF, crude fibre and energy in the total tract for white-clover meal compared with lucerne meal (P < 0·05). For neutral- and acid-detergent fibre a similar pattern was observed, however the effect was not significant.

The dietary digestible energy content was significantly reduced (F < 0·05), both at the ileum and over the total tract, with increasing inclusion offorage meal.

The aim of this study was to compare low doses of microencapsulated v. pharmacological ZnO in the diet of piglets on growth performance, ileum health status and architecture. One hundred and forty-four piglets weaned at 28 days and divided in 36 pens (two males and two females per pen), received a basal diet (control, Zn at 50 mg/kg) or the basal diet with ZnO at 3000 mg/kg (pZnO), or with lipid microencapsulated ZnO at 150 or 400 mg/kg (mZnO-300 and mZnO-800, respectively). After 14 and 42 days, three pigs per sex per treatment were euthanized to collect the ileum mucosa for immunohistochemistry, histomorphology, inflammatory cytokines and tight junction components gene expression. Data were analyzed with one-way ANOVA. At 0 to 14 days, the pZnO and mZnO-800 groups had greater average daily gain compared with control (P<0.05). Gain to feed ratio (G:F) in the same time interval was higher in pZnO group compared with control thus resulting in higher BW (P<0.05). At day 14, ileum villi height in mZnO-800 pigs was 343 µm v. 309 and 317 µm in control and pZnO, respectively (P<0.01) and villi:crypts ratio (V:C), as well as cells positive to proliferating cell nuclear antigen (PCNA), were greater in all treated groups compared with control (P<0.01). In mZnO-800 group, interferon-γ mRNA was the lowest (P=0.02), and both pharmacological ZnO and mZnO reduced tumor necrosis factor-α protein level (P<0.0001). Compared with pZnO group, mZnO-800 increased occludin and zonula occludens-1 protein level (1.6-fold and 1.3-fold, respectively; P<0.001). At day 42, both groups receiving microencapsulated ZnO had 1.7 kg greater BW than control and did not differ from pZnO group (P=0.01); ileum villi height and V:C ratio were the greatest for pZnO compared with the other groups, whereas PCNA-positive cells were the most numerous in mZnO-800 group (P<0.001). In conclusion, pigs receiving low doses of microencapsulated ZnO had G:F comparable with those receiving pharmacological level of ZnO in the overall post-weaning phase. Moreover, in the first 2 weeks post-weaning, microencapsulated ZnO effect on inflammatory status and ileum structure and integrity was comparable with pharmacological ZnO.

There is a lack of knowledge about the genetic background of eczema due to insect bite hypersensitivity, also called summer eczema, in horses. The condition is known in several horse breeds and countries and it causes reduced welfare of the horse and economic losses to the owner. The aim of this study was to estimate genetic parameters for summer eczema in Swedish-born Icelandic horses. A questionnaire was sent to owners of horses sired by stallions with more than 50 offspring born in Sweden between 1991 and 2001. Variance components of summer eczema classified as healthy, mild, moderate or severe were estimated using the threshold methodology with sire models. In addition, summer eczema was analysed as a binary trait (healthy v. affected). The analyses included 1250 horses sired by 33 stallions. The prevalence of summer eczema was 8%, with a range of 0% to 30% in different paternal half-sib groups. Offspring of dams suffering from eczema had a higher risk of developing eczema. The heritability for severity of summer eczema was estimated at 0.3 (s.d. < 0.2) with a threshold sire model. In contrast to the age of the horse, different geographic areas and gender were significantly associated with severity of the eczema. We conclude that genetic selection could decrease the prevalence of summer eczema among Swedish-born Icelandic horses. The amount and quality of data are, however, crucial for the possibility to introduce a genetic evaluation of summer eczema. The symptoms should be classified in several classes according to severity, and this classification could be made by the horse owner.

Pikeperch (Sander lucioperca) is a highly valuable fish in Europe. However, development of aquaculture of pikeperch is highly limited due to seasonality of production. This can be overcome by the controlled reproduction of domesticated fish. The first steps of domestication process may induce changes at anatomical, physiological and molecular levels, thereby affecting a variety of biological functions. While there is abundant literature on their effects on stress and growth for example, these effects on reproduction received limited attention notably in pikeperch, a promising candidate for the development of aquaculture. To answer the question of this life-history effect on pikeperch’s reproduction, we compared two groups (weight: 1 kg) originated from Czech Republic and with the same domestication level (F0). The first group was a recirculating aquatic system cultured one (2 years, previously fed with artificial diet, never exposed to natural changes in temperature/photoperiod conditions) and the second one was a pond cultured group (3 to 4 years, bred under natural feeding and temperature/photoperiod). The wild group successfully spawned, while the farmed one did not spawn at all. During the program, gonadosomatic indexes of both males and females were significantly higher for the wild fish, as well as the sexual steroids. Gene expression analysis revealed significantly lower LH transcript levels at the pituitary level for the farmed females and lower FSH transcript levels at the pituitary level for the males. In conclusion this study showed that the previous rearing conditions (e.g. culture system, age, diet, etc.) alter the further progress of gametogenesis and the reproductive performances in response to controlled photothermal program for both sexes in pikeperch.

This study was conducted to determine the effects of feeding olive cake and linseed to lambs on the volatile organic compounds (VOCs) in raw and cooked meat. Four groups of eight male Appenninica lambs each were fed: conventional cereal-based concentrates (diet C), concentrates containing 20% on a dry matter (DM) basis of rolled linseed (diet L), concentrates containing 35% DM of stoned olive cake (diet OC), or concentrates containing both rolled linseed (10% DM) and stoned olive cake (17% DM; diet OCL). The longissimus dorsi muscle of each lamb was sampled at slaughter and was subjected to VOC profiling through the use of SPME-GC-MS. In the raw meat, the concentration of 3-methylpentanoic acid was higher in treatment C as compared with treatments L, OC and OCL (P<0.01). Moreover the level of nonanoic acid was greater in treatments C and OC than in treatment L (P<0.05). With respect to alcohols, in raw meat the amount of 2-phenoxyethanol in treatment OCL was lower than in treatments C (P<0.01) and OC (P<0.05), while in cooked meat the amount of 1-pentanol was higher in treatment C than in treatment OC (P<0.05). Apart from these compounds, none of the lipid oxidation-derived volatiles was significantly affected by the dietary treatment. Therefore, the results suggest that the replacement of cereal concentrates with linseed and/or olive cake did not cause appreciable changes in the production of volatile organic compounds in lamb meat.

The effect of inclusion of live yeast culture (YC, Saccharomyces cerevisiae plus growth medium) in a high concentrate diet given to buffalo (Bubalus bubalis) calves on the rumen microbial population and fermentation pattern and in sacco dry matter disappearance of dietary constituents was examined. Six rumen-fistulated buffalo calves of about 120 kg live iveight were divided into two equal groups. The control group was given a diet consisting of, on a dry-matter basis, 0·90 kg ivheat straw, 1 kg berseem (Trifolium alexandrinum) and ISO kg concentrate per day per calf and the yeast group the above diet plus 5 g YC which was put directly into the rumen via the fistula. After feeding this diet for 6 weeks (supplementation period), inclusion of YC was stopped and both groups were given the control diet for a period of 3 weeks to examine the performance of the YC group after withdrawal of YC. At week 4 of YC supplementation the pH was significantly increased (P < 0·01) and lactate concentration was decreased (P < 0·01) in the rumen fluid for up to 6 h post feeding. The number of total bacteria, total viable bacteria, cellulolytic bacteria, amylolytic bacteria and protozoa were increased proportionately by 0·554 (P < 002), 0·482 (P<0·01), 0·670 (P <0·01), 0·077 (P > 0·05) and 0·079 (P>0·05), respectively. The concentrations of total volatile fatty acids, particularly at 4 h post feeding (P < 0·01), acetate fP < 0·01) and propionate and the acetate to propionate ratio were higher in the YC compared with the control group. On YC inclusion, the concentration of ammonia-nitrogen was decreased while that of trichloracetic acid insoluble protein was marginally increased. All these differences in rumen variables started to disappear on YC withdrawal and values returned to control levels by the 3rd week after YC withdrawal. YC supplementation increased the in sacco dry-matter disappearance of various dietary components particularly after 3, 6 and 22 h incubation.

Data on 792 Chios lambs born during the 1972/73 and 1973/74 lambing seasons were used to estimate genetic and phenotypic parameters for birth weight, weaning weight, age at weaning, pre-weaning daily gain, body weight at 5, 10, 15 and 20 weeks of age, and postweaning daily gain. Body weight at 15 weeks of age had the highest heritability estimate (0·73 ± 0·17) and that of post-weaning daily gain was also high (0·56 ± 0·15). Selection for either weight at 15 weeks or post-weaning daily gain would be expected to yield a greater response than selection for pre-weaning daily gain or weaning weight. Genetic correlations among weights and/or gains were positive (approximately 0·20). Phenotypic correlations among weights and gains were generally higher than genetic correlations. However, the correlation between pre— and post-weaning daily gain was small (0·08). Likewise, post-weaning daily gain had low correlations with all weights before 10 weeks. Age at weaning had moderate negative associations with all weights but a very low positive correlation with post-weaning daily gain.

The aim of this study was to investigate whether the use of sainfoin-based condensed tannins (CT) enhances feed value when given with tannin-free legumes (lucerne) to sheep. The experiments were conducted with fresh sainfoin and lucerne harvested at two stages (vegetative stage as compared with early flowering) in the first growth cycle. Fresh sainfoin and lucerne forages were combined in ratios of 100 : 0, 75 : 25, 25 : 75 and 0 : 100 (denoted S100, S75, S25 and S0, respectively). Voluntary intake, organic matter digestibility (OMD) and nitrogen (N) retention were measured in sheep fed the different sainfoin and lucerne mixtures. Loss of dry matter (DM) and N from polyester bags suspended in the rumen, abomasum and small intestine (SI) was also measured using rumen-fistulated sheep and intestinally fistulated sheep. The CT content in sainfoin (S100) decreased with increasing percentage of lucerne in the mixture (mean value from 58 g/kg DM for S100 to 18 g/kg DM for S25) and with growth stage (S100: 64 to 52 g/kg DM). OMD did not differ between different sainfoin/lucerne mixture ratios. Sainfoin and lucerne had an associative effect (significant quadratic contrast) on voluntary intake, N intake, total-tract N digestibility, N in faeces and urine (g/g N intake) and N retained (g/g N intake). Compared with lucerne mixtures (S0 and S25), high-sainfoin-content mixtures (S100 and S75) increased the in situ estimates of forage N escaping from the rumen (from 0.162, 0.188 for S0 and S25 to 0.257, 0.287 for S75 and S100) but decreased forage N intestinal digestibility (from 0.496, 0.446 for S0 and S25 to 0.469, 0.335 for S75 and S100). The amount of forage N disappearing from the bags in the SI (per g forage N) was the highest for high-sainfoin mixtures (from 0.082, 0.108 for S100 and S75 to 0.056, 0.058 for S25 and S0, P < 0.001). Rumen juice total N (tN) and ammonia N (NH3-N) values were the lowest in the high-sainfoin diet (mean tN 0.166 mg/g in S100 as compared with 0.514 mg/g in S0; mean NH3-N 0.104 mg/g in S100 as compared with 0.333 mg/g in S0, P < 0.001).

Three successive batches of fattening pigs were raised on a deep litter of straw in one room and of sawdust in another. The quantities of litter used per pig were 40 kg of straw and 81 kg of sawdust.

Once a month, the emissions of ammonia, nitrous oxide, methane, carbon dioxide and water vapour were measured continuously for 6 days consecutively.

Gaseous emissions from pig raising on sawdust-based litter and straw-based litter were respectively 12·16 and 13·61 g per pig per day for ammonia (NH3), 4·96 and 7·39 g per pig per day for methane (CH4), 2·09 and 0·03 g per pig per day for nitrous oxide (N2O), 3·15 and 2·74 kg per pig per day for water (H2O) and 1·32 and 1·30 kg per pig per day for carbon dioxide (CO2). Differences between the emissions of the two litters were significant for N2O and H2O (P 0·01).

The nitrogen content of the manures collected at the end of the experiment was 1·47 kg per pig for the straw-based litter and 1·07 kg per pig for that based on sawdust. Nitrogen emissions were calculated under the assumption that no gases volatilized from the litter or from the animals other than NH3 and N2O. With the two litters, about 50% of nitrogen excreted by the pigs was emitted into the atmosphere in the form of N2.

Forty-three entire males were used to determine the pig's tissue requirements for protein and amino acids from 8·0 to 20·0 kg, and provide information on the capacity of diets formulated with conventional ingredients to contain the same levels and balances of amino acids as ideal protein to supply these nutrients. Seven diets with similar digestible energy (15·9 MJ digestible energy (DE) per kg) and crude protein concentrations from 119 to 232 g/kg (8·7 to 17·3 g lysine per kg) were offered ad libitum between 8·0 and 200 kg live weight. The rate of protein deposition was determined by comparative slaughter. The composition of the protein deposited in the whole empty body was determined from amino acid analyses of pigs killed at 8·0 kg and from the two extreme dietary treatments at 20·0 kg. Growth performance and the rates at which protein and lysine were deposited in the empty body increased linearly with increasing dietary protein concentration up to 187 g/kg and remained relatively constant thereafter. The corresponding dietary protein and lysine intakes required to support maximal protein accretion were 178 g/day (11·7 g/MJ DE) and 13·0 g/day (0·84 g/MJ DE) respectively. Based on the maximal deposition rates for protein (91·8 g/day), and lysine (5·96 g/day) and endogenous protein loss (77middot;6 g/day) estimated from the linear component of the relationship determined between protein deposition and apparent digestible protein intake, the pig's tissue requirements for protein and lysine were only 99·4 g/day (6·5 g/MJ DE) and 6·46 g/day (0·43 g/MJ DE) respectively. This disparity between the pig's tissue protein and amino acid requirements and the dietary levels needed to support these was associated with the fact that the apparent digestibility and biological value of the dietary protein were 0·92 and 0·602 respectively. Apart from small differences in the lysine content of body protein and the methionine: lysine ratio, the average amino acid composition of pigs killed at 8·0 kg, and from the diet of highest protein concentration at 20 kg, was similar to that of ideal protein, indicating that the low utilizability of dietary protein for tissue growth and maintenance was probably associated with low amino acid digestibility and/or availability. The implications of the results with respect to expression of the growing pig's requirements for protein and amino acids are discussed.

Daily methane production and feed intake were measured on 160 adult ewes, which were the progeny of 20 sires and 3 sire types (Merino, dual-purpose and terminal) from a genetically diverse flock. All animals were housed in individual pens and fed a 50/50 mix of chaffed lucerne and oaten hays at 20 g/kg liveweight (LW), with feed refusals measured for at least 10 days before the first of three 22-h measurements in respiration chambers (RC). Feed was withdrawn at 1600 h on the day before each RC test to encourage the ewes to eat the entire ration provided for them in the RC. After the first 1-day RC test, the sheep were returned to their pens for a day, then given a second 1-day RC test, followed by another day in their pens, then a third RC test. After all animals had been tested, they were ranked according to methane emissions adjusted for feed intake in the RC and on the previous day, enabling 10 low and 10 high methane animals to be chosen for repeat measurement. No variation between sires nor consistent effects of LW on feed eaten (%FE, expressed as per cent of feed offered) was evident in the 10 days before the first RC measurement. However, significant differences between sires (equivalent to an estimated heritability of 41%) were identified for %FE during the 2nd and 3rd days of RC testing (2 and 4 days after the initial RC test). The analysis of all data showed that methane emissions in the RC were related to feed intake on the day of testing and the two previous days (all P<0.0005). Before correcting for feed intake on previous days, there was some variation between sires in methane yield, equivalent to an estimated heritability of 9%. Correction for feed intake on the 2 previous days halved the residual variation, allowing other effects to be detected, including effects of LW, twins reared as singles, test batch, RC and test-day effects, but estimated sire variation fell to zero. In order to avoid potential biases, statistical models of methane emissions in the RC need to consider potential confounding factors, such as those identified as significant in this study.

Genetic and phenotypic parameters and correlated responses in performance test traits were estimated for populations of Large White (LW) and British Landrace (LR) pigs tested in Edinburgh and Wye respectively, to four generations of divergent selection for lean growth rate (LGA), lean food conversion (LFC) and daily food intake (DFI) with ad-libitum feeding.

There were differences between the two populations in genetic parameters, as LW heritabilities for growth rate, daily food intake and backfat depths were higher and the correlation between growth rate and backfat was positive for LW, but negative for LR. However, heritabilities, genetic and phenotypic correlations were generally comparable between selection groups, within each population. Genetic and phenotypic correlations indicated that animals with high daily food intakes were faster growing, had positive residual food intakes (RFI), were fatter with higher food conversion ratios. RFI was highly correlated with daily food intake and food conversion ratio, but phenotypically independent of growth rate and backfat, as expected.

Selection for LGA, in LW and LR populations, increased growth rate (54 and 101 g/day), but reduced backfat (−3·9 and −2·0 mm), food conversion ratio (−0·23 and −0·25) and total food intake (−11·8 and −12·6 kg). There was no change in daily food intake in LW pigs (−19 g/day), but daily food intake increased in the LR pigs (69 g/day). With selection for LFC in LW and LR populations, there was no response in groivth rate (9 and 9 g/day), but backfat (−4·1 and −2·1 mm), total (−6·6 and −11·8 kg) and daily food intake (−90 and −172 g) were reduced, as animals had lower food conversion ratios (−0·13 and −0·22). LW and LR pigs selected for DFI ate more food in total (6·8 and 5·9 kg) and on a daily basis (314 and 230 g), grew faster (94 and 51 g/day) and had higher food conversion ratios (0·12 and 0·13). Backfat was increased in LW pigs (3·7 mm), but not in the LR population.

In general, efficiency of lean growth was improved by increasing groivth rate, with little change in daily food intake from selection for LGA, but was primarily due to reduced daily food intake with selection on LFC.