Effect of temperature manipulation during incubation on body weight, plasma parameters, muscle histology, and expression of myogenic genes in breast muscle of embryos and broiler chickens from two commercial strains.

1. This study evaluated the effect of a higher incubation temperature on body weight, plasma profile, histology and expression of myogenin (MYOG), insulin-like growth factor-I (IGF-I) and vascular endothelial growth factor A (VEGFA) genes in breast muscle of embryos and broilers from two commercial strains.2. A total of 784 eggs from Ross 308 and Cobb 500 broiler breeder flocks were used. Half of the eggs per strain were incubated at control temperature (37.8°C), whereas the other half were exposed to heat treatment (HT) of 38.8°C between embryonic day (ED) 10 and 14, for 6 h/day. Embryos and chicks were sampled on ED 19 and at hatch. A total of 480, one-day-old chicks per strain and incubation temperature were reared up to 42 d post-hatch.3. The HT increased hatch weight of Ross chicks and 42-d body weight of broilers from both strains. Lower plasma triacylglycerol levels were measured for HT embryos and broilers on ED 19 and 42 d post-hatch, respectively. HT reduced plasma T3 levels in Ross embryos and broilers for the same periods. Hepatic TBARS concentrations were elevated by HT compared to the control incubation.4. The HT reduced breast muscle VEGFA gene expression of Cobb embryos on ED 19, whereas expression was stimulated in day-old chicks. At 42 d post-hatch, fibre area was increased by HT regardless of strain. Compared to the control incubation, HT increased the breast yield of Ross broilers and leg yield of Cobb. Ross-HT broilers had a higher pH at 24 h after slaughter and better water holding capacity than Cobb-HT broilers.5. These results suggested that HT increased body weight, fibre area, IGF-I gene expression and lowered plasma triacylglycerol levels of broiler chickens from both strains at 42 d. However, HT influenced the expression of VEGF-A and MYOG genes and meat quality differently between the broiler strains.

GnRH or eCG treatment fails to restore reproductive function in GnRH immunized ewes.

This study was designed to evaluate the potential of using eCG or GnRH in restoring reproductive functions in GnRH immunized ewes. Thirty-three multiparous Kivircik ewes were randomly assigned into either control group (n=11) or immunization group (n=22). Ewes were immunized against GnRH by injecting with a cocktail of ovalbumin-LHRH-7 (ovalbumin-GnRH-7) and thioredoxin-LHRH-7 (thioredoxin-GnRH-7) fusion proteins generated by recombinant DNA technology in April. 500 IU eCG or 0.008 mg GnRH analogue was used to induce ovulations. Serum GnRH antibodies were present in animals of the immunized group beginning the second week after the first immunization and maintained throughout the study (14 months). Immunization caused anestrus in immunized ewes. eCG or GnRH analogue administration given after 14 days progestagen (20 mg fluorogestone acetate, FGA) treatment during breeding season (mid July) did not induce ovulation in these ewes. Two more attempts with single or multiple eCG injections failed to induce ovulation in this group as well. It appears that the gonadotropin stimulation was not of adequate time since neither eCG nor GnRH administration was able to restore reproductive function in immunized animals. The immunization effect lasted more than a year. These results suggest that GnRH immunization exerts its effect via the hypothalamo-pituitary axis and that more than such stimulation is required to overcome the reproductive suppression.