Effect of incubation temperature variation and genetic selection on broiler chicken growth performance, skeletal muscle growth characteristics, and meat yield
Type of DegreeMaster's Thesis
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Throughout the last 5 decades, the broiler industry has focused its efforts toward higher meat yields and more efficient production, leading to the adoption of state-of-the-art technology for production and as a way of furthering our knowledge about physiological and nutritional factors that affect broiler production. Currently, topics such as incubation temperature and molecular aspects concerning muscle growth and their importance on growth performance are a target as a way to increase productivity. Therefore, one experiment was conducted to determine whether subtle changes in incubation temperature may impact growth performance and carcass yield when applied during crucial stages of myogenesis. Eggs from 3 different tray locations (Bottom, BOT; Middle, MID; Top, TOP) were exposed to the treatment temperature (± 0.3 ºC) from d 4 to 11 of incubation and were exposed to the same temperature (< ± 0.1 °C) from d 1 to 3 and 12 to 18 of incubation and before hatching. Subtle changes in incubation temperature during primary and secondary myogenesis did not affect broiler growth performance. However, broilers from BOT trays had heavier breast and tender weights than those from MID trays. These results indicate that variations in incubation temperature as little as 0.3 ºC among incubator tray locations during myogenesis, can significantly impact broiler meat yields. The second experiment attempted to elucidate the differences in myogenic stem cell populations (Myf-5+, MyoD+, Pax7+, Myf-5+:MyoD+, MyoD+:Pax7+, and Myf-5+:MyoD+:Pax7+) and muscle fiber characteristics between 2 muscle types and sexes in 2 different genetic strains of chickens, Red Ranger (RR), and Ross 708 x Ross 708 (ROSS). Muscle cross sectional area was similar among the 2 strains and sexes. Myofiber distributions were different between muscle types and chicken strains. BF muscles had higher number of smaller myofibers compared to PM. Furthermore, RR chickens had higher number of smaller myofibers compared to fast-growing ROSS broilers. Differences in cross-sectional area, nuclear density, and populations of Myf-5+ and Pax7+ were mainly between muscle types. ROSS broilers exhibited a 27% larger population of Myf-5+:MyoD+:Pax7+ stem cells compared with RR. These results indicated that ROSS and RR chickens have similar myogenic stem cell populations on d 43 and that perhaps major differences in performance are due to changes in gene expression profile during early stages of post-hatch growth. Future research should evaluate changes in myogenic stem cell populations as a result of changes in incubation temperature during myogenesis and the subsequent effects on broiler growth performance. These data will allow for the development of practical management interventions during the incubation period that might positively impact broiler growth efficiency and meat yield.