Effects of Nutritional Restriction during Laying Period of Fat and Lean Line Broiler Breeder Hens on Meat Quality Traits of Offspring

The offspring meat quality of hens undergoing a 25% dietary restriction treatment during the laying period were evaluated in fat and lean line breeder. A total of 768 female birds (384/line) were randomly assigned to four groups (12 replicates/group, 16 birds/replicates). Maternal feed restriction (MFR) and normal started at 27 weeks of age. Offspring broilers were fed ad libitum. The offspring meat quality traits and muscle fiber morphology in different periods were measured. At birth, significant interactions were found on breast muscle fiber morphology (p < 0.05). At 28 days, MFR decreased breast water content and increased thigh crude fat content, and significant interactions were observed on breast crude fat and protein contents (p < 0.05). At 56 days, MFR affected morphology of peroneus longus muscle tissue, and significant interactions were found on thigh redness at 48 h and amino acid contents in breast and thigh muscle (p < 0.05). Overall, MRF may lead to offspring birth sarcopenia. Such offspring grow more easily to deposit fat in a nutritious environment, but they will self-regulate adverse symptoms during growth and development. The two lines respond differently to maternal nutritional disturbance due to different nutritional requirements and metabolic patterns.

Whole-genome bisulfite sequencing of abdominal adipose reveals DNA-methylation pattern variations in broiler lines divergently selected for fatness

The methylation status of pivotal genes involved in fat deposition in chickens has been extensively studied. However, the whole-genome DNA methylation profiles of broiler abdominal adipose tissue remain poorly understood. Using whole-genome bisulfite sequencing, we generated DNA methylation profiles of chicken abdominal adipose tissue from Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF). We aimed to explore whether DNA methylation was associated with abdominal fat deposition in broilers. The whole-genome DNA methylation profiles of fat- and lean-line broiler abdominal adipose tissue were constructed. The DNA methylation levels of functional genomic regions in the fat broiler were higher than those in the lean broiler, especially in the 3ʹUTRs and exons in the non-CG contexts. Additionally, we identified 29,631 differentially methylated regions and, subsequently, annotated 6,484 and 2,016 differentially methylated genes (DMG) in the gene body and promoter regions between the two lines, respectively. Functional annotation showed that the DMG in promoter regions were significantly enriched mainly in the triglyceride catabolic process, lipid-metabolism-related pathways, and extracellular matrix signal pathways. When the DMG in promoter regions and differentially expressed genes were integrated, we identified 30 genes with DNA methylation levels that negatively correlated with their mRNA expression, of which CMSS1 reached significant levels (FDR &lt; 0.05). These 30 genes were mainly involved in fatty acid metabolism, PPAR signaling, Wnt signaling pathways, transmembrane transport, RNA degradation, and Glycosaminoglycan degradation. Comparing the DNA methylation profiles between fat- and lean-line broilers demonstrated that DNA methylation is involved in regulating broiler abdominal fat deposition. Our study offers a basis for further exploring the underlying mechanisms of abdominal adipose deposition in broilers.

Rabbit Lines Divergently Selected for Total Body Fat Content: Correlated Responses on Growth Performance and Carcass Traits

The aim of this experiment was to study the effect of divergently selected rabbits for total body fat content (fat index) on growth performance and carcass traits. The fat index was determined at 10 weeks of age by computed tomography and lasted for four consecutive generations. The rabbits with the lowest fat index belonged to the lean line and those of the highest values belonged to the fat line. At generation four, 60 rabbits/line were housed in wire-mesh cages and fed with commercial pellet ad libitum from weaning (5 w of age) to slaughtering (11 w of age). Growth performance, dressing out percentage and carcass adiposity were measured. The lean line showed a better feed conversion ratio (p < 0.001) than the fat line. Furthermore, the carcass of the lean rabbits had the highest proportion of fore (p < 0.020) and hind (p < 0.006) parts. On the contrary, rabbits of the fat line had the highest carcass adiposity (p < 0.001). The divergent selection for total body fat content showed to be effective for both lean and fat lines. Selection for lower total body fat content could be useful for terminal male lines, while the selection for higher total body fat content could be an advantage for rabbit does in providing fat (energy) reserves.

Composition of Intestinal Microbiota in Two Lines of Rainbow Trout (Oncorhynchus Mykiss) Divergently Selected for Muscle Fat Content

Background:Recently, studies suggest that gut microbiota contributes to the development of obesity in mammals. In rainbow trout, little is known about the role of intestinal microbiota in host physiology.Objective:The aim of this study was to investigate the link between intestinal microbiota and adiposity, by high-throughput 16S RNA gene based illumina Miseq sequencing in two rainbow trout lines divergently selected for muscle lipid content. Fish from these two lines of rainbow trout are known to have a differing lipid metabolism.Methods:Samples from the two lines (L for lean and F for fat) were collected from Midgut (M) and Hindgut (H) in juvenile fish (18 months) to compare intestinal microbiota diversity.Results:Whatever the lines and intestinal localisation,Proteobacteria,FirmicutesandActinobacteriaare the dominant phyla in the bacterial community of rainbow trout (at least 97%). The results indicate that richness and diversity indexes as well as bacterial composition are comparable between all groups even though 6 specific OTUs were identified in the intestinal microbiota of fish from the fat line and 2 OTUs were specific to the microbiota of fish from the lean line. Our work contributes to a better understanding in microbial diversity in intestinal microbiota of rainbow trout.Conclusion:Altogether, our study indicates that no major modification of the intestinal microbiota is induced by selection for muscle lipid content and associated metabolic changes. Finally, we identified members of core microbiota in rainbow trout.

Genetic analyses of carcass composition, as assessed by X-ray computer tomography, and meat quality traits in Scottish Blackface sheep

Genetic parameters for carcass composition and meat quality traits were estimated in Scottish Blackface sheep, previously divergently selected for carcass lean content (LEAN and FAT lines). Computerized X-ray tomography (CT) was used to obtain non-destructive in vivo estimates of the carcass composition of 700 lambs, at ca. 24 weeks of age, with tissue areas and image densities obtained for fat, muscle and bone components of the carcass. Comprehensive measures of meat quality and carcass fatness were made on 350 male lambs, at ca. 8 months of age, which had previously been CT scanned. Meat quality traits included intramuscular fat content, initial and final pH of the meat, colour attributes, shear force, dry matter, moisture and nitrogen proportions, and taste panel assessments of the cooked meat. FAT line animals were significantly (P<0·05) fatter than the LEAN line animals in all measures of fatness (from CT and slaughter data), although the differences were modest and generally proportionately less than 0·1. Correspondingly, the LEAN line animals were superior to the FAT line animals in muscling measurements. Compared with the LEAN line, the FAT line had lower muscle density (as indicated by the relative darkness of the scan image), greater estimated subcutaneous fat (predicted from fat classification score) at slaughter, more intramuscular fat content, a more ‘yellow’ as opposed to ‘red’ muscle colour, and juicer meat (all P<0·05). All CT tissue areas were moderately to highly heritable, with h2 values ranging from 0·23 to 0·76. Likewise, meat quality traits were also moderately heritable. Muscle density was the CT trait most consistently related to meat quality traits, and genetic correlations of muscle density with live weight, fat class, subcutaneous fat score, dry matter proportion, juiciness, flavour and overall liking were all moderately to strongly negative, and significantly different from zero. In addition, intramuscular fat content was positively genetically correlated with juiciness and flavour, and negatively genetically correlated with shear force value. The results of this study demonstrate that altering carcass fatness will simultaneously change muscle density (indicative of changes in intramuscular fatness), and aspects of intramuscular fat content, muscle colour and juiciness. The heritabilities for the meat quality traits indicate ample opportunities for altering most meat quality traits. Moreover, it appears that colour, intramuscular fat content, juiciness, overall liking and flavour may be adequately predicted, both genetically and phenotypically, from measures of muscle density. Thus, genetic improvement of carcass composition and meat quality is feasible using in vivo measurements.

Inheritance of faecal egg counts during early lactation in Scottish Blackface ewes facing mixed, natural nematode infections

This paper presents an analysis of nematode faecal egg counts from Scottish Blackface ewes facing mixed, natural nematode infections (predominantly Teladorsagia circumcincta). The data set comprised 1445 measurements on 421 ewes taken at 4 and 6 weeks post-lambing, over a 4-year period. The ewes, themselves, were the progeny of 73 sires and 285 dams. Only Strongyle eggs were consistently present, and faecal egg counts from this genera ranged from zero (0·4 of all measurements) to 3388 eggs per g. Faecal egg counts were significantly affected by the number of lambs reared and suckled (increasing reproductive burden led to higher counts) by ewe age (older ewes had lower counts) and by previous selection history (ewes from a line previously selected for increased carcass fatness had lower faecal egg counts than ewes from a conversely selected lean line). The heritability of log-transformed faecal egg counts was 0·23 (s.e. 005) and the repeatability, including both within- and between-year permanent environmental effects, was 0·25 (s.e. 004). The apparent presence or absence of infection had a heritability of 015 (s.e. 007) on the observed scale and 0·39 (s.e. 016) when analysed as a binomial threshold trait. The genetic correlation between average 4-week weight of lamb suckled by the ewe and faecal egg counts was 0·24 (s.e. 010). The results suggest that faecal egg counts during early lactation are heritable and influenced by the reproductive performance of the ewe. Selection to reduce nematode faecal egg output from ewes during this period should be successful in reducing pasture larval contamination.