Scottish Blackface sheep have been selected for either increased or decreased predicted carcass lean content at 20 weeks of age, using an index combining ultrasonic backfat depth and body weight. The index was designed to alter carcass lean content without changing body weight. After 4 years there have been large responses in the index and fat depth, the proportional difference between the divergent lines in fat depth is 0·28, but body weight and ultrasonic muscle depth have not changed between the lines. The realized heritability for the index is 0·45. Heritabilities for the index, ultrasonic fat depth, body weight and ultrasonic muscle depth, calculated using multivariate restricted maximum likelihood, are 0·47 (s.e. = 0·14), 0·39 (s.e. 0·13), 0·23 (s.e. 0·12) and 0·36 (s.e. 0·14), respectively. The selected lines will be used to investigate relationships between carcass lean content, viability and maternal performance under the harsh environmental conditions encountered in the Scottish hill environment.

Sixteen male and 16 female lambs were used to compare the performance and carcass composition of Texel- and Suffolk-sired lambs out of Finnish Landrace × Dorset Horn ewes. Lambs were weaned at 6 weeks of age and individually fed an all-concentrate diet ad libitum to slaughter at 30 kg (females) and 36 kg (males). At slaughter, offal weights were recorded and carcass left sides jointed and dissected.

Breed types did not differ in weight at weaning, growth iate, age at slaughter, daily feed intake or feed conversion rate. Texels had heavier carcasses (17·2 v. 16·4 kg: P <0·01) and higher dressing percentages (50·7 v. 49·2: P <0·05) than Suffolks. Texel-cross carcasses had 2·9% more lean (P <0·05), but 3·8% less total fat CP <0·01).

The results indicate the suitability of Texel-sired lambs for intensive lamb production.

1. Two experiments concerned with the voluntary intake of food by artificially reared lambs are described and the results discussed.

2. When the diets were pelleted the addition of finely ground oat husks to form as much as 40% of the diet had practically no effect on live weight gain since the lambs controlled their consumption to achieve the same energy intake on the various diets. When the diets were given as a meal, the addition of 20% oat husks caused food intake to increase, digestible dry-matter intake to remain the same and growth rate to be somewhat poorer; but the addition of 40% oat husks caused no further increase in intake so that digestible drymatter intake fell markedly and growth rate was much reduced. It is argued that the relationship between food intake and digestibility is dependent on the physical form of the diet.

3. Addition of beef tallow to the meal diets had very little effect on the lambs' performance.

4. Lambs which had received a restricted quantity of milk replacer from birth to 11·4 kg live weight had a slower growth rate and poorer food conversion efficiency during the subsequent feeding period (13·6–34·1 kg) than lambs which had received milk ad libitum. This effect was greater with meal diets containing 40% oat husks than with more concentrated diets.

5. On a pelleted diet containing 85% barley a conversion ratio of 3·21 was achieved over the whole fattening period, indicating the commercial feasibility of intensive lamb production on cereal diets.

Ten littermate pairs were used to study the effects of light and heavy birth weight on the development of muscle tissue, growth rate, body composition and the estimated milk consumption of piglets reared on the sow to 6·5 kg live weight.

Neither average daily gain to 6·5 kg nor body composition at the latter weight were significantly affected by birth weight. Birth weight also had no effect on the weight or deoxyribonucleic acid content of the semitendinosus musde at 6·5kg. However, pigs of hght birth weight -were lighter at 2\ days of age (P < 0·01) and older at 65 kg (P < 0·01) than those of heavy birth weight.

Pigs of heavy birth weight consumed more milk per suckle than their lighter birth weight littermates (P < 0·01). However, the relative milk consumption (g/kg live weight) of both groups was similar.

The insulin-independent and combined effects of fatty acids (FA; linoleic and oleic acids) and insulin in modulating lipid accumulation and adipogenesis in 3T3-L1 cells was investigated using a novel protocol avoiding the effects of a complex hormone ‘induction’ mixture. 3T3-L1 cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) plus serum (control) or in DMEM plus either 0.3 mmol/l linoleic or oleic acids with 0.3 mmol/l FA-free bovine serum albumin in the presence or absence of insulin. Cells were cultured for 4 to 8 days and cell number, lipid accumulation, peroxisome proliferator-activated receptor-gamma (PPAR-γ) and glucose transporter 4 (GLUT-4) protein expression were determined. Cell number appeared to be decreased in comparison with control cultures. In both oleic acid and linoleic acid-treated cells, notably in the absence (and presence) of insulin, oil-red O stain-positive cells showed abundant lipid. The percentage of cells showing lipid accumulation was greater in FA-treated cultures compared with control cells grown in DMEM plus serum (P < 0.001). Treatment with both linoleic and oleic acid-containing media evoked higher levels of PPAR-γ than observed in control cultures (P < 0.05). GLUT-4 protein also increased in response to treatment with both linoleic and oleic acid-containing media (P < 0.001). Lipid accumulation in 3T3-L1 cells occurs in response to either oleic or linoleic acids independently of the presence of insulin. Both PPAR-γ and GLUT-4 protein expression were stimulated. Both proteins are considered markers of adipogenesis, and these observations suggest that these cells had entered the physiological state broadly accepted as differentiated. Furthermore, 3T3-L1 cells can be induced to accumulate lipid in a serum-free medium supplemented with FA, without the use of induction protocols using complex hormone mixtures. We have demonstrated a novel model for the study of lipid accumulation that will improve the understanding of adipogenesis in adipocyte lineage cells.

Globally, pressure on concentrate feed resources is increasing, especially in the tropics where many countries are net importers of food. Forage plants are a possible alternative, but their use as feed ingredients for pigs raises several issues related to their higher fibre and plant secondary metabolites contents as well as their lower nutritive value. In this paper, the nutritive value of several forage species and the parameters that influence this nutritive value in relationship to the plant family, the physiological stage, the plant part and the preservation method (fresh, hay and silage) are reviewed. The influence of the breed and the physiological status of the animal on animal voluntary intake of fibre-rich ingredients, digestibility as related to gastrointestinal volume and transit time and growth performances are also discussed. The final section highlights the advantages and drawbacks of forage plants in pig diets and stresses the need for proper economic evaluation to conclude on the benefits of the use of forage plants in pig feed.

Scrapie is a naturally occurring transmissible spongiform encephalopathy in sheep and goat. It has been known for ~250 years and is characterised by the accumulation of an abnormal isoform of a host-encoded prion protein that leads to progressive neurodegeneration and death. Scrapie is recognised in two forms, classical and atypical scrapie. The susceptibility to both types of scrapie is influenced by polymorphisms of the prion protein gene (PRNP). Sheep susceptibility or resistance to classical scrapie is strongly regulated by the polymorphisms at codons 136, 154 and 171 of the PRNP. The genetic role in atypical scrapie in sheep has been defined by polymorphisms at codons 141, 154 and 171, which are associated with different degrees of risk in the occurrence of the ovine disease. Progress has been achieved in the prevention of scrapie in sheep due to efficient genetic breeding programmes based on eradication and control of the disease. In Europe, the success of these programmes has been verified by applying eradication and genetic selection plans. In general terms, the ovine selection plans aim to eliminate and reduce the susceptible allele and to enrich the resistant allele ARR. During outbreaks all susceptible animals are slaughtered, only ARR/ARR resistant rams and sheep and semi-resistant females are preserved. In the occurrence of scrapie positive goats a complete cull of the flock (stamping out) is performed with great economic loss and severe risk of extinction for the endangered breeds. The ability to select scrapie-resistant animals allows to define new breeding strategies aimed to boost genetic progress while reducing costs during scrapie outbreaks. Allelic variants of PRNP can be protective for caprine scrapie, and the knowledge of their distribution in goats has become very important. Over the past few years, the integration of genetic information on goat populations could be used to make selection decisions, commonly referred to as genetic selection. The objective of this review was to summarise the main findings of polymorphisms of the caprine prion protein (PrP) gene and to discuss the possible application of goat breeding schemes integrating genetic selection, with their relative advantages and limitations.

Optimizing milk production efficiency implies diets allowing low methane (CH4) emissions and high dairy performance. We hypothesize that nature of energy (starch v. lipids) and lipid supplement types (monounsaturated fatty acid (MUFA) v. polyunsaturated fatty acid (PUFA) mitigate CH4 emissions and can induce low milk fat content via different pathways. The main objective of this experiment was to study the effects of starch-rich or lipid-supplemented diets that induce milk fat depression (MFD) on rumen biohydrogenation (RBH) of unsaturated fatty acids (FA) and enteric CH4 emissions in dairy cows. Four multiparous lactating Holstein cows (days in milk=61±11 days) were used in a 4×4 Latin square design with four periods of 28 days. Four dietary treatments, three of which are likely to induce MFD, were based (dry matter basis) on 56% maize silage, 4% hay and 40% concentrates rich in: (1) saturated fatty acid (SFA) from Ca salts of palm oil (PALM); (2) starch from maize grain and wheat (MFD-Starch); (3) MUFA (cis-9 C18:1) from extruded rapeseeds (MFD-RS); and (4) PUFA (C18:2n-6) from extruded sunflower seeds (MFD-SF). Intake and milk production were measured daily. Milk composition and FA profile, CH4 emissions and total-tract digestibility were measured simultaneously when animals were in open-circuit respiration chambers. Fermentation parameters were analysed from rumen fluid samples taken before feeding. Dry matter intake, milk production, fat and protein contents, and CH4 emissions were similar among the four diets. We observed a higher milk SFA concentration with PALM and MFD-Starch, and lower milk MUFA and trans-10 C18:1 concentrations in comparison to MFD-RS and MFD-SF diets, while trans-11 C18:1 remained unchanged among diets. Milk total trans FA concentration was greater for MFD-SF than for PALM and MFD-Starch, with the value for MFD-RS being intermediate. Milk C18:3n-3 content was higher for MFD-RS than MFD-SF. The MFD seems more severe with MFD-SF and MFD-RS than PALM and MFD-Starch diets, because of a decrease in milk SFA concentration and a stronger shift from trans-11 C18:1 to trans-10 C18:1 in milk. The MFD-SF diet increased milk trans FA (+60%), trans-10 C18:1 (+31%), trans-10,cis-12 CLA (+27%) and PUFA (+36%) concentrations more than MFD-RS, which explains the numerically lowest milk fat yield and indicates that RBH pathways of PUFA differ between these two diets. Maize silage-based diets rich in starch or different unsaturated FA induced MFD with changes in milk FA profiles, but did not modify CH4 emissions.

Sow litter sizes have increased, subjecting more small piglets to intra-uterine growth restriction (IUGR). Research on the development and growth of IUGR pigs is limited. The objective of this study was to compare the body composition and organ development of IUGR pigs at weaning, and to estimate their growth performance from birth to 30 kg. A total of 142 IUGR and 142 normal piglets were classified at birth based on their head morphology. At weaning, 20 IUGR and 20 normal piglets were collected, a whole-body dual-energy x-ray absorption scan was performed, and the piglets were euthanized for organ measurements. Body weight (BW) was measured weekly from birth to 30 kg, rectal temperature and whole-blood glucose levels were measured weekly from birth to weaning, and blood samples were collected at days 7, 14 and 21 for IGF-1 analysis. Results showed that IUGR pigs have a similar percentage of adipose tissue (P > 0.05) compared to normal pigs at 24 days of age. Organs were smaller (P < 0.001) in IUGR pigs than in normal pigs, whereas brain, liver, lungs and adrenal glands were relatively larger (P < 0.05) in relation to the BW of IUGR pigs. Average birth weight (BiW) of normal pigs was greater (P < 0.001) compared with IUGR pigs (1.38 v. 0.75 kg), and the average daily gain (ADG) of IUGR pigs was reduced from day 0 to 14, day 0 to 28 (weaning) and from weaning to 30 kg compared to normal pigs. From birth to weaning at day 28, IUGR piglets had a 72.9 g/day greater fractional ADG (FADG) in relation to their BiW (P < 0.05), but FADG did not differ (P > 0.05) from weaning to 30 kg. Rectal temperature of IUGR piglets was greater (P < 0.05) on day 7 compared with normal piglets, and, even though blood glucose levels were decreased (P < 0.001) in IUGR piglets at day 0, neither glucose nor IGF-1 concentrations differed (P > 0.05) between IUGR and normal piglets. In conclusion, IUGR piglets exhibited some relatively larger organs at weaning compared to normal pigs, but body composition was similar between IUGR and normal pigs. In addition, IUGR pigs had a reduced ADG from birth to 30 kg, and, although they exhibited a greater FADG during nursing, IUGR pigs still require six additional days to reach a BW of 30 kg in comparison to normal pigs.

The aim of this paper was to identify pre-slaughter factors that modify total and insoluble collagen contents in bovine muscle to construct a model of collagen dynamics. The meta-analyses were performed with primary data of total (n = 1165) and insoluble (n = 1145) collagen contents from INRA experiments obtained from different muscles in young bulls, cows and steers. According to both the bibliography and meta-analyses, total collagen content and solubility were greatly affected by the muscle (type). Moreover, the pattern of the evolution of collagen characteristics was similar among Longissimus, Semitendinosus and Triceps brachii muscles in young bulls. In cows, collagen contents in the Triceps brachii muscle had delayed dynamics compared with the other muscles. Collagen characteristics differed among breeds because of variation in the maturity of the breed. Similarly, according to the meta-analyses, total and insoluble collagen content evolutions with the degree of maturity (DOM; proportion of adult weight reached at slaughter) were different in dairy and rustic breeds from those of beef breeds, especially in bulls. Although the relationships between collagen content and DOM were quantified in different muscles and sexes, the precision of the fitted equations was not sufficient for prediction. Consequently, relying on the hypotheses raised by the meta-analysis and the literature, an approach to further develop a dynamic mechanistic model of soluble and insoluble collagen content is proposed.

Variations in maternal nutrition during gestation can influence foetal growth, foetal development and permanently ‘programme’ offspring for postnatal life. The objective of this study was to analyse the effect of increased maternal nutrition during different gestation time windows on offspring growth, carcass quality, meat quality and gene expression in skeletal muscle. A total of 64 sows were assigned to the following feeding treatments: a standard control diet at a feed allocation of 2.3 kg/day throughout gestation, increased feed allowance of 4.6 kg/day from 25 to 50 days of gestation (dg), from 50 to 80 dg and from 25 to 80 dg. At weaning, Light, Medium and Heavy pigs of the same gender, within litter, were selected based on birth weight, individually penned and monitored until slaughter at 130 days post weaning. Carcass and meat quality traits of the semimembranosus (SM) muscle were recorded post mortem. A cross section of the semitendinosus (ST) muscle encompassing the deep and superficial regions were harvested from pigs (n = 18 per treatment) for RNA extraction and quantification of gene expression by real-time PCR. The results showed that doubling the feed intake from 25 to 50 dg reduced offspring growth, carcass weight, intramuscular fat content and increased drip loss of the SM muscle. Interestingly, protein phosphatase 3 catalytic subunit – α-isoform, which codes for the transcription factor calcineurin, was upregulated in the ST muscle of offspring whose mothers received increased feed allowance from 25 to 50 dg. This may provide an explanation for the previous observed increases in Type IIa muscle fibres of these offspring. Increasing the maternal feed intake from 50 to 80 dg negatively impacted pig growth and carcass weight, but produced leaner male pigs. Extending the increased maternal feed intake from 25 to 80 dg had no effect on offspring over the standard control gestation diet. Although intra-litter variation in pig weight is a problem for pig producers, increased maternal feeding offered no improvement throughout life to the lighter birth weight littermates in our study. Indeed, increased maternal nutrition at the three-gestation time windows selected provided no major benefits to the offspring.

Tail biting has several identified feeding-related risk factors. Tail biters are often said to be lighter and thinner than other pigs in the pen, possibly because of nutrition-related problems such as reduced feed intake or inability to use nutrients efficiently. This can lead to an increase in foraging behavior and tail biting. In this study, a total of 55 pigs of different ages were selected according to their tail-biting behavior (bouts/hour) and pen-feeding system to form eight experimental groups: tail-biting pigs (TB), victim pigs (V) and control pigs from a tail-biting pen (Ctb) and control pen (Cno) having either free access to feed with limited feeding space or meal feeding from a long trough. After euthanasia, a segment of jejunal cell wall was cut from 50 cm (S50) and 100 cm (S100) posterior to the bile duct. Villus height, crypt depth and villus : crypt ratio (V : C) were measured morphometrically. Blood serum concentration of minerals and plasma concentration of amino acids (AA) was determined. Villus height was greater in Cno than Ctb pigs in the proximal and mid-jejunum (P < 0.05), indicative of better ability to absorb nutrients, and increased with age in the proximal jejunum (P < 0.001). Serum mineral concentration of inorganic phosphate (Pi) and calcium (Ca) was lower in Ctb compared with Cno pigs, and that of Pi in V compared with all the other pigs. Many non-essential AA were lower in pigs from tail-biting pens, and particularly in victim pigs. Free access feeding with shared feeding space was associated with lower levels of essential AA in blood than meal feeding with simultaneous feeding space. Our data suggest that being a pig in a tail-biting pen is associated with decreased jejunal villus height and blood AA levels, possibly because of depressed absorption capacity, feeding behavior or environmental stress associated with tail biting. Victim pigs had lower concentrations of AA and Pi in plasma, possibly as a consequence of being bitten.

It is imperative to evaluate precise nutrient requirements of animals in order to optimize productivity and minimize feed cost and nutrient excretions. The current non-phytate phosphorus (NPP) recommendation for broilers is based on the papers published 30 years ago. However, today’s commercial birds are quite different from those before 30 years. Therefore, the present experiment was conducted with growing male broiler chickens to evaluate an optimal dietary NPP level of broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age. The 1-day-old chicks were fed corn–soybean meal diet containing 0.39% NPP from 1 to 3 weeks of age. At 22 days of age, 360 birds were selected and randomly allotted by BW to one of 10 dietary treatments with six replicate cages of six birds per cage for each treatment. Birds were fed the P-unsupplemented corn–soybean meal basal diet and the basal diet supplemented with inorganic P as CaHPO4·H2O ranging from 0.00% to 0.45% with 0.05% increment from 4 to 6 weeks of age. The dietary NPP levels were 0.09%, 0.14%, 0.20%, 0.24%, 0.30%, 0.34%, 0.38%, 0.45%, 0.49% and 0.54%, respectively, and the dietary Ca level was fixed at 0.90% for all treatments. The results showed that average daily gain, serum inorganic P concentration, tibia bone strength, tibia ash percentage and P percentage, tibia bone mineral content (BMC) and density (BMD), middle toe ash percentage and P percentage, middle toe BMC, total body BMC and BMD were affected (P<0.0001) by dietary NPP level, and increased linearly (P<0.0001) and quadratically (P<0.003) as dietary NPP levels increased. Optimal dietary NPP levels estimated based on fitted broken-line models (P<0.0001) of the above indices are 0.21%, 0.29%, 0.29%, 0.29%, 0.29%, 0.31%, 0.29%, 0.30%, 0.27%, 0.29% and 0.28%, respectively. It is suggested that the total body BMC and BMD, and middle toe ash P and BMC might be new, sensitive and non-invasive criteria to evaluate the dietary NPP requirements of broilers. The optimal dietary NPP level would be 0.31% for broiler chickens fed a conventional corn–soybean meal diet from 4 to 6 weeks of age.

The aim of this paper was to explore if, and in that case how, various preventive measures against mastitis influenced the whole-farm economic outcome, measured as technical efficiency, of a sample of specialised dairy farms in Sweden. In particular, the paper aimed at analysing whether a change to preventive measures applied by fully efficient farms would be a way for inefficient farms to become fully efficient. First, technical efficiency was assessed for each farm in the sample based on farm-level accounting data and the data envelopment analysis. In a second step, the effects of preventive measures against mastitis (collected through a mail questionnaire) on technical efficiency were assessed with logistic regression. Keeping cows in a loose-housing barn, stimulating udders manually during milking, and having cows standing on clean bedding during milking were found to significantly increase the probability of a farm being fully efficient. Once the farmer considers the somatic cell count (SCC) to be too high, undertaking measures such as contacting a veterinarian, checking overall hygiene routines, and culling cows with high SCC were found to significantly increase the probability of a farm being fully efficient. Thus, these measures may be plausible targets for advisory services aimed at assisting farmers to become fully efficient, especially if they are confirmed in future studies. Several common preventive measures against mastitis, that is, choice of bedding material, frequency of cleaning stalls, pre-milking, post-milking teat disinfection, applying a milking order based on the SCC of cows, and milking high-SCC cows with a separate cluster, were found to have no statistically significant effect on farm economic outcome. However, these measures may still be valuable for non-economic goals, such as increased animal welfare, and the results imply that they can be implemented without negative impact on the economic performance of the farm.

Following a pilot study, the aim of this study was to test the hypothesis whether occurrence of massaging the anogenital region of a calf by a non-maternal hind is a reliable indicator of adoption. The investigation was conducted between 28 May (1st day of calving) and 2 September (abrupt weaning of all calves) on a red deer farm at Vimperk, Czech Republic. Fifty hinds and their calves were observed but only complete data sets of sucking bouts were considered for evaluation. Massaging occurred mostly during the 1st month of the calf’s life. All filial calves were massaged repeatedly. Other calves received ano-genital massage at least twice (termed adopted), on a single occasion or not at all (termed non-filial). Filial and adopted calves behaved in a similar way but differently from non-filial calves. They sucked in an antiparallel standing position so that the hind could lick their ano-genital region more often than the non-filial calves. This occurred even when two calves were involved in the bout. When two calves were involved in the sucking bout, non-filial calves sucked from behind, between the hind’s hind legs. This position occurred more frequently with non-filial than among the filial and adopted calves. It was therefore concluded, that repeated allonursing accompanied with massaging of the ano-genital region of the sucking calf by the hind can be considered a signal of adoption. Hinds usually adopted calves older than their own progeny. The adopted calves were on average 2·5 days old. This suggests that it is most likely the calf’s activity which leads to bonding. No reciprocity was found in allosucking and/or allonursing. The fact that non-filial calves commonly initiated allosucking from a non-maternal hind during the day when she gave birth appeared crucial for establishing bonding which subsequently led to adoption. Hinds may be bonded with several calves including their own. Therefore, bonding with a non-filial calf did not principally mean failure in looking after their own progeny as shown in other studies.

The effects of reducing the feed intake of 12 winter-calving (Hereford male × British Friesian female) cows to the maintenance level for 6 weeks from week 10 of lactation were investigated during two consecutive lactation periods. Initially, six cows were in their first and six in their third lactation. In each year the period of ‘underfeeding’ was preceded by a period of ‘adequate feeding’ (maintenance plus milk production requirements) and succeeded by a period of ‘refeeding’ (2 × maintenance). Changes in body water, estimated by the dilution of tritiated water and deuterium oxide at the end of each feeding period, were used to calculate changes in body tissue. Milk yield during the period of ‘adequate feeding’ indicated that individual cows differed markedly in milk production potential. During ‘underfeeding’ milk yield was related to lactation potential. Cows of higher potential tended to maintain higher yields than those of lower potential but in doing so they incurred higher body-weight losses. The ‘refeeding’ period did not result in significant increases in milk yield. The weight losses during ‘underfeeding’ consisted mainly of fat but some cows apparently mobilized relatively large amounts of protein. More fat per unit body weight loss was mobilized by the heifers than by the cows, which, on the other hand appeared to mobilize relatively more protein. On ‘refeeding’, only a few cows were able to achieve complete tissue repletion.

Two selection indexes, one intended for lamb producers and finishers and one for store lamb producers, were derived using genetic parameters for carcass and maternal characteristics from Conington et al. (2001) and economic values from Conington et al. (2004). This paper summarizes responses to selection for lamb traits only, after 5 years of selection (1998 to 2003) on two farms using these selection indexes. The index for lamb producers and finishers, evaluated on farm 1, with a flock size of 680 ewes, includes economic weightings for maternal traits as well as carcass weight, fat and conformation grades, whereas the index for store lamb producers, evaluated on farm 2, with a flock size of 580 ewes, only includes economic values for maternal traits and lamb growth to weaning. Three selection lines of Scottish Blackface sheep per farm were created with the first lambs born to each line in 1999. These lines were selection (S), control (C) and industry (I); they were of equal size on each farm. Five top- and five average-performing ram lambs were selected each year for the S and C lines respectively using a multi-trait best linear unbiased prediction (BLUP) implementation of the indexes. The I-line used four mature rams bought from industry, selected on appearance only, i.e. adherence to breed ‘type’. Results showed that 5 years after the implementation of the index, the S line had significantly higher index scores than the C or I lines on both farms. The means (s.d.) for the average index scores in 2003 are 114 (328), 119 (371) and 451 (328) (farm 1), and −8 (146), −11 (130), and 250 (129) (farm 2) for the C, I and S lines, respectively, giving predicted net differences (S-C) of £3·38 (farm 1) and £2·58 (farm 2) per ewe. Phenotypic responses showed significant S v. C differences in weaning weight on both farms. As predicted from previous analyses, no changes in carcass quality traits were seen at farm 1 although S-line carcass weights tended to be heavier than those from the C or I lines. The results show that genetic improvement using multi-trait selection indices has been successful and it is a viable, long-term strategy to improve levels of production for hill sheep in extensive environments.

The composition and degradability of four varieties of rice straw were examined. The varieties were tall or short and early or late maturing. The straws and their botanical parts (leaf blade plus leaf sheath, internode, node and chaff) varied in acid-detergent fibre, ash and silica contents, but not in nitrogen and neutral-detergent fibre. There were some trends but no significant difference in proportions of parts between varieties. Milled samples of whole straw and its parts were either untreated, treated with a cellulase preparation plus propionic acid, treated with ammonia, or treated with cellulase then ammonia. Rumen degradability was measured by incubating the samples in polyester bags suspended in the rumen of sheep. The soluble fraction and potential degradability were greater in untreated short and early than in tall and late varieties, but rates of degradation did not vary significantly. Internode was more degradable than leaf. Cellulase and/or ammonia treatments increased the soluble fraction, especially in tall and late varieties, and increased potential degradabiiity except in internode. Degradability correlated positively with ash and silica contents.

Genes from the Chinese Meishan pig have the potential to enhance reproductive performance of European pigs. In order to allow prediction of the impact of Meishan genes in a range of alternative improvement programmes all traits of economic importance must be evaluated and genetic crossbreeding effects estimated. Entire male and female pigs of four genotypes, purebred Meishan (MS) and Large White (LW) pigs and both reciprocal Fl crossbred genotypes (MS ♂ × LW ♀ and LW ♂ × MS ♀), were farrowed in Edinburgh and subsequently performance tested at either Edinburgh or Newcastle. In Edinburgh, animals were penned in groups of four and fed ad libitum between pen mean weights of approximately 30 and 80 kg. At the end of test fat depths at the shoulder, last rib and loin were measured ultrasonically. In Newcastle, animals were penned in groups of six and fed ad libitum between pen mean weights of approximately 30 and 70 kg. Genotypic means and genetic crossbreeding effects (additive and heterosis direct effects and additive maternal effects) were estimated using restricted maximum likelihood.

When compared with the LW, the direct additive effect of genes from the MS produced increased growth rate up to the time of weaning, no change in growth rate between weaning and start of test and greatly reduced growth rate during the performance test. The maternal additive effect of genes from the MS was to reduce growth rate up to the time of weaning, with little effect thereafter. There was substantial direct heterosis for growth rate in all periods measured, but heterosis was less in males than in females during the performance test. The combined effect was such that, within sex, the LW and the two crossbred genotypes were of similar ages when they reached 70 and 80 kg, but MS pigs were 38 to 60 days older. The direct additive effect of MS genes was to increase subcutaneous fat levels and there was little evidence for the effects of maternal genes or direct heterosis on these traits. There was a direct additive effect of MS genes reducing food intake and increasing food conversion ratio and there was direct heterosis for increased food intake. There were significant interactions between genotype and sex. Male and female LW pigs had a similar performance but male MS pigs had slower growth rates on the performance test with lower food intakes, food conversion ratios and subcutaneous fat levels than the females.

One hundred and thirteen high genetic merit Holstein-Friesian heifers were used in a study to determine the effect of rearing regime, in terms of diet offered and target calving weight, on body size, reproductive performance and milk production in high genetic merit heifers. Eighty of the heifers were supplied from 11 commercial farms, the remainder were supplied from the herd at the Agricultural Research Institute of Northern Ireland. The heifers commenced the experiment at 7 weeks of age when they were allocated on the basis of source, live weight and genetic merit to one of four rearing regimes. The target weights at calving were 540 kg (treatment 1) and 620 kg (treatments 2, 3 and 4). Treatment 1 heifers were offered grass silage-based diets during the winter and grass-based diets during the summer. Treatment 2 heifers were offered the same forage base plus additional concentrate supplementation. Treatment 3 heifers were offered a straw/concentrate diet during the winter and grass-based diets during the summer. Treatment 4 heifers received the same diets as treatment 3, except for the first summer period when they remained housed and were offered a straw/concentrate diet. The heifers were mated at 14 months of age and were returned to the 11 source farms one month prior to calving. Heifers reared on treatment 1 had a lower withers height (P < 0·001) and were of a lower condition score (P < 0·001) before calving than heifers reared on treatments 2, 3 and 4. During early lactation (3 months post calving) heifers reared on treatment 1 lost less weight and condition score than the heifers reared on the other treatments. Thus at the end of the first lactation live weights did not differ significantly between the treatments. However, body length remained shorter (P < 0·01) in treatment 1 compared with treatments 2, 3 and 4. First lactation milk yield (305 days) was lower for heifers reared on treatment 1 (7222 l) compared with heifers reared on treatment 2 (8020 l) (P < 0·01), 3 (7956 l) (P < 0·01) and 4 (7901 l) (P < 0·05). Similarly, milk fat plus protein yield was lower (P < 0·05) for heifers reared on treatment 1 (511 kg) compared with treatments 2 (544 kg), 3 (544 kg) and 4 (554 kg). The interval from calving to first recorded oestrus was shorter in treatment 1 compared with treatments 2 and 3 (P < 0·05). There was a tendency (P < 0·10) for heifers reared on treatment 1 to have a shorter calving interval (394 days) compared with treatments 2 (426 days), 3 (435 days) and 4 (458 days). In conclusion increasing the live weight of Holstein-Friesian heifers at first calving from 540 to 620 kg pre-calving increased milk yield proportionally by 0·11 but tended to increase the calving interval. Diet type during the rearing period had no effect on milk fat plus protein yield or reproductive performance.