Fatty acid profile in the breast and thigh muscles of the slow- and fast-growing birds under the same management system

The aim of the study was to assess the effect of feeding the same diet to different breeds of chickens and at different ages on fatty acid (FA) composition of the breast and thigh muscles. A total of 150 chickens comprising 50 each of red jungle fowl (RJ) and village chicken (VC), the slow-growing birds, and the commercial broiler (CB), fast-growing birds, were used for this study. Ten chickens from each breed were serially euthanized at days 1, 10, 20, 56, and 120 post hatch, and pectoralis major and bicep femoris were harvested to represent the breast and thigh muscles respectively. It was revealed that the breast muscle concentrations of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and total polyunsaturated fatty acids (PUFA) are significantly different (p<0.05) among the breeds. Also, the FA composition of breast and thigh muscles among RJ, VC, and CB at various ages studied varied significantly (p<0.05) but without a definite pattern. The composition of MUFA was lower, but that of PUFA was higher in the RJ and VC than in the CB breast muscles. Within the breeds, the composition of total MUFA decreased, while that of PUFA increased with age. The total MUFA and PUFA showed no significant difference (p>0.05) between the breast and thigh muscles at different ages evaluated. This study suggests that slow-growing birds (RJ and VC) might be better sources of desirable FA than the fast-growing birds, CB.

Genomic Landscape of Long Terminal Repeat Retrotransposons (LTR-RTs) and Solo LTRs as Shaped by Ectopic Recombination in Chicken and Zebra Finch

Transposable elements (TEs) are nearly ubiquitous among eukaryotic genomes, but TE contents vary dramatically among phylogenetic lineages. Several mechanisms have been proposed as drivers of TE dynamics in genomes, including the fixation/loss of a particular TE insertion by selection or drift as well as structural changes in the genome due to mutation (e.g., recombination). In particular, recombination can have a significant and directional effect on the genomic TE landscape. For example, ectopic recombination removes internal regions of long terminal repeat retrotransposons (LTR-RTs) as well as one long terminal repeat (LTR), resulting in a solo LTR. In this study, we focus on the intra-species dynamics of LTR-RTs and solo LTRs in bird genomes. The distribution of LTR-RTs and solo LTRs in birds is intriguing because avian recombination rates vary widely within a given genome. We used published linkage maps and whole genome assemblies to study the relationship between recombination rates and LTR-removal events in the chicken and zebra finch. We hypothesized that regions with low recombination rates would harbor more full-length LTR-RTs (and fewer solo LTRs) than regions with high recombination rates. We tested this hypothesis by comparing the ratio of full-length LTR-RTs and solo LTRs across chromosomes, across non-overlapping megabase windows, and across physical features (i.e., centromeres and telomeres). The chicken data statistically supported the hypothesis that recombination rates are inversely correlated with the ratio of full-length to solo LTRs at both the chromosome level and in 1-Mb non-overlapping windows. We also found that the ratio of full-length to solo LTRs near chicken telomeres was significantly lower than those ratios near centromeres. Our results suggest a potential role of ectopic recombination in shaping the chicken LTR-RT genomic landscape.