A total of 120 Duroc×(Large White×Landrace) pigs, 50% barrows and 50% gilts, with 54.1±0.14 kg BW and 103±3 days of age, were used to study the effect of advancing the shift to a standard finisher feed from 100 to 90 and 80 kg BW on production performances and carcass and pork quality. Each of the six treatments (two sexes×three BWs at time of feeding shift) was replicated four times and the experimental unit was the pen (with five pigs for growth performance and carcass variables and three pigs for pork and fat traits). The grower (163 g CP and 9.5 g total Lys/kg) and the finisher diets (152 g CP and 7.9 g total Lys/kg) were based on maize, barley and vegetal protein concentrates, contained 13.39 MJ metabolizable energy/kg and were offered ad libitum through the trial. Pigs intended for dry-cured product elaboration were slaughtered at 170±3 days of age as average (124 and 115 kg BW for barrows and gilts, respectively). For the overall period, barrows ate more feed (P<0.001) and grew faster (P=0.03) than gilts. No effect of feed shift was observed on growth performances, although the average daily CP intake (P=0.01) and feeding costs (P=0.04) were reduced by advancing the transition to the finisher feed. Carcasses from barrows were heavier (P<0.001) and had wider backfat depth (P<0.001) than those from gilts but no significant differences were observed in the meat chemical composition. The feed change schedule did not modify carcass or meat traits. It is concluded that an early shift to the finisher feed (at 80 kg BW instead of 100 kg BW) might be an interesting strategy in pigs intended for dry-cured products because, although it neither increased body fatness nor improved pork quality, CP intake and feeding costs were reduced without impairment of growth performances. Results were similar for barrows and gilts.

Intramuscular fat (IMF) % contributes positively to the juiciness and flavour of lamb and is therefore a useful indicator of eating quality. A rapid, non-destructive method of IMF determination like computed tomography (CT) would enable pre-sorting of carcasses based on IMF% and potential eating quality. Given the loin muscle (longissimus lumborum) is easy to sample, a single measurement at this site would be useful, providing is correlates well to other muscles. To determine the ability of CT to predict IMF%, this study used 400 animals and examined 5 muscles from three sections of the carcass: from the fore-section the m. supraspinatus and m. infraspinatus, from the saddle-section the m. longissimus lumborum and from the hind-section the m. semimembranosus and m. semitendinosus. The average CT pixel density of muscle was negatively associated with IMF% and can be used to predict IMF% although precision in this study was poor. The ability of CT to predict IMF% was greatest in the m. longissimus lumborum (slope −0.07) and smallest in the m. infraspinatus (slope −0.02). The correlation coefficients of IMF% between the five muscles were variable, with the highest correlation coefficients evident between muscles of the fore section (0.67 between the m. supraspinatus and the m. infraspinatus) and the weakest correlations were between the muscle of the fore and hind section. The correlation between the m. longissimus lumborum to the other muscles was fairly consistent with values ranging between 0.34 and 0.40 (partial correlation coefficient). The correlation between the proportion of carcass fat and the IMF% of the five muscles varied and was greatest in the m. longissimus lumborum (0.41).

The significance of hepatocyte nuclear factors (HNFs) in β-cell development and function has been generally recognized in humans, as evidenced by their associations with cases of maturity onset diabetes of the young (MODY). Common Hepatocyte nuclear factor-1 alpha (HNF1A), Hepatocyte nuclear factor-1 beta (HNF1B) and Hepatocyte nuclear factor-4 alpha (HNF4A) mutations could lead to monogenic forms 3, 5 and 1 of diabetes mellitus, respectively, and were characterized by MODY in humans. In this study, multiple variants were discovered in the porcine HNF1A and HNF4A genes, and one single-nucleotide polymorphism (SNP) was detected in the HNF1B gene. Using the Iowa State University Berkshire × Yorkshire pig resource population, the HNF1A, HNF1B and HNF4A genes were mapped on chromosomes 14, 12 and 17, respectively. The linkage disequilibrium (LD) analyses indicated that most of the HNF1A variants were not in strong LD with each other; however, nearly all of them were highly significantly (P < 0.01) associated with loin muscle area (LMA). The SNPs c.327-19G>T and c.1768+40_23del were significantly (P < 0.05) associated with backfat and total lipid percentage, and the latter was also associated with muscle glycogen metabolism measures. Four major haplotypes were observed and the association analyses suggested that haplotype 3 (-CGCGD-, I indicates Insertion and D indicates Deletion) was favorable for reduced backfat, while haplotype 1 (-CACGI-) was unfavorably associated with backfat and LMA. There was no significant interaction effect on backfat among the SNPs c.327-19G>T, c.1768+40_23del of the HNF1A gene and c.646C>T of the transcription factor-7-like 2 (TCF7L2) gene. These findings suggest that the HNF1A gene has significant effects on both fatness- and meat production-related traits. No significant associations with production traits with the SNPs from the HNF1B and HNF4A genes were observed in the study.

An experimental design aiming at analysing the consequences of genetic selection from 1977 to 1998–2000 on the evolution of stress-responsive systems in the French Large White (LW) and Landrace (LR) pig populations was conducted by INRA and IFIP-Institut du Porc. Large White sows were inseminated with semen from LW boars born in 1977 (frozen semen) or in 1998 and their second-generation offspring were station-tested. Landrace sows were inseminated with semen from LR boars born in 1977 (frozen semen) or in 1999 to 2000, and their progeny was station-tested. Urinary concentration of stress hormones (cortisol and catecholamines) and traits related to carcass composition (estimated carcass lean content (ECLC) and global adiposity) and meat quality (pH 24 h) were measured. For the two populations, selection carried out since 1977 led to an increase in ECLC and a decrease in carcass adiposity. Between 1977 and 1998 to 2000, urinary concentrations of stress hormones were unchanged in the LR breed, but were decreased in the LW breed. Moreover, for the animals generated from LW boars born in 1977 and in 1998, urinary cortisol levels were negatively correlated with ECLC. Therefore, in the LW breed, selection carried out for higher ECLC resulted in a decrease in cortisol production, as well as a reduction of catecholamine production that may be responsible for the lower ultimate pH of meat. Therefore, selection carried out for increased carcass lean content led, in this breed, to large modifications in the functioning of the stress-responsive systems, thereby influencing a large range of physiological regulations and technical properties such as carcass composition and meat pH, which remained however in the normal range for acceptable meat quality.

Hypotheses on total body chemical composition were tested using data from 350 Suffolk sheep grown to a wide range of live weights, and fed in a non-limiting way, or with reduced amounts of feed, or ad libitum on feeds of reduced protein content. The sheep were from an experiment where selection used an index designed to increase the lean deposition rate while restricting the fat deposition rate. Ultrasound muscle and fat depths were the only composition measurements in the index. The animals were males and females from a selection (S) line and its unselected control (C). The protein content of the lipid-free dry matter was unaffected by live weight, sex or feeding treatment with only a very small effect of genetic line (0.762 kg/kg in S and 0.753 kg/kg in C; P < 0.05). The form of the relationship between water and protein was not affected by any of the factors; in the different kinds of sheep it was consistent with no effect other than through differences in mature protein weight. The water : protein ratio at maturity was estimated as 3.45. Over the whole dataset, lipid weight (L) increased with protein weight (P) according to L = 0.3135 × P1.850. Allowing for this scaling, fatness increased on low-protein feeds, was greater in females than in males and in C than in S (P < 0.001). Lipid content (g/kg fleece-free empty body weight) was reduced by restricted feeding only in males at the highest slaughter weight (114 kg). The lines differed in lipid content (P < 0.001) with means of 265.1 g/kg for C and 237.3 g/kg for S. Importantly, there was no interaction between line and feeding treatments. A higher proportion of total body protein was in the carcass in S than in C (0.627 v. 0.610; P < 0.001). For lipid, the difference was reversed (0.736 v. 0.744; P < 0.05). The total energy content increased quadratically with slaughter weight. At a particular weight, the energy content of gain was higher in females than in males and in C than in S. Genetic selection affected body composition at a weight favouring the distribution of protein to the carcass and lipid to the non-carcass. Once allowing for effects of genetic selection, sex and feeding treatment on fatness, simple rules can be used to generate the chemical composition of sheep.

Stress neuroendocrine systems (hypothalamic–pituitary–adrenal axis and sympathetic nervous system) were studied in 100 female pigs from each of the five main genetic lines used in Europe for pork production: Piétrain, Large White, Landrace, Duroc and Meishan. Levels of cortisol and catecholamines were measured in urine collected at the farm, after transportation to the slaughterhouse and the next morning before slaughter. With the exception of the Piétrain line that showed intermediate levels of cortisol despite its extreme leanness, a significant positive relationship was found between basal cortisol levels and fatness, both across and within (except in Piétrain and Duroc) lines. Basal cortisol levels were 2.46-fold higher in Meishan (20.46 ng/mg creatinine) than in Large White pigs (8.30 ng/mg creatinine), the two extreme breeds. Post-transportation levels were highest but proportional to basal levels, suggesting that the adrenal reactivity to adrenocorticotropic hormone is a major source of variability between lines. Levels of catecholamines were less variable between lines but correlated also with fatness, partlyviapartial correlations with cortisol levels. In serum collected at exsanguination, creatine kinase activity was correlated with muscularity across the five breeds. However, this was due to a much larger activity than expected in Piétrain pigs, although all animals were negative for the allele of the ryanodine receptor gene responsible for stress sensitivity. Serum glucose levels were inversely related to fatness. These data show that the differences between breeds or lines can be utilised by cross-breeding and that this can lead to changes in stress hormones and in turn to some degree of changes in carcass traits.

Résumé

La génomique de la volaille a bénéficié des avancements technologiques rapides acquis en génomique humaine et sur les organismes modèles. Certains outils et certains approches sont maintenant bien établis chez le poulet, y compris les cartes et marqueurs (génétiques comme physiques), mapping loci pour caractéres quantitatifs, mapping comparative, ressources expressed sequence tag et bacterial artificial chromosome, et mapping physique. De plus, la phase suivante de la découverte génétique, la génomique fonctionnelle, est en cours. Les progre`s dans le mapping de loci pour caracte`res quantitatifs de croissance et d'adiposité seront discutés pour illustrer ces nouvelles technologies et ces nouvelles approches dans l'étude de la génétique et de la physiologie avicole.

Skinfold thicknesses represent a comparatively simple and reasonably accurate assessment of body fatness which is an important part of the estimation of nutritional state. However, much emphasis is placed on the necessity to be very precise in the exact position of the skinfold being measured and there is frequently concern, also, about the variability of the measurement by different observers using different types of caliper. Fifty-three women and forty-five men had four skinfolds (biceps, triceps, supra-iliac and subscapular) measured first at the standard sites (Tanner, 1953; Edwards et al. 1955), and then at deliberately chosen sites about 20 mm distant from the ‘correct’ ones. The effect on the estimation of body fatness by this manoeuvre resulted in a difference of usually less then 1% and, at a maximum, 3%. In the light of the uncertainty of the basic assumptions which are made in extrapolating from skinfolds (or indeed densitometry, total body water, total body K, and others) to body fatness, these technical errors assume comparatively little importance.