ABSTRACT Incubating temperature and timing or duration is critical to determine the optimum protocol of thermal manipulation (TM), which underlines muscle growth improvement. Therefore, the aim of the present study is to determine the optimum period of embryonic TM that may result in the improvement of pectoral and thigh muscle myogenesis. This is done by investigating the level of mRNA expression of creatine kinase (CK) and lactate dehydrogenase (LDH). An additional goal is measuring the blood levels of CK and LDH as a biomarker of muscle injury due to the experimental thermal challenge on post-hatch day 35. The study was conducted on 1,440 fertile eggs (Ross broilers) that were divided randomly and equally into a control group and four treatment groups (TM1, TM2, TM3, and TM4). The treatment groups were daily subjected to TM at 39 ºC for 18h with 65% relative humidity (RH) during embryonic days (EDs) 7-11, 11-15, 15-18, and 7-18, respectively. Among the thermally manipulated groups that were investigated, TM1 (ED 7-11) resulted in significant improvement of mRNA expression and enzymatic concentration of CK and LDH in muscle during embryogenesis, as compared to the control. Six hours of TC showed the highest significant CK and LDH expression and concentration levels in the control as compared to TM groups. Thus, the results of this study indicate that TM during ED 7-11 improves pectoral and thigh muscles’ response to heat stress without adversely affecting their performance. This finding could be used by commercial breeders to enhance local broiler production.

ABSTRACT This study investigated the effect of a probiotic (Bacillus subtilis DSM 17299), blend of acidifiers, and their combination on the performance of broiler chicks. Two hundred and twenty unsexed one-day-old broilers (Ross 308) were randomly distributed into four groups (55 birds per group divided into 5 replicates) as 2X2 factorial arrangement including two factors, probiotic and blend of acidifiers, each of which had two levels: yes and no. Performance was determined weekly. Haemagglutination test was performed on blood samples taken on days 28 and 42 after the birds were injected twice (days 14 and 28) with 10% suspension of sheep red blood cells (SRBC). On day 42, tissue samples taken from the duodenum, jejunum and ileum were prepared for histology via scanning electron microscopy. During the first three weeks, dietary addition of probiotic significantly (p<0.05) increased body weight gain (BWG) while acidifiers significantly lowered (p<0.01) feed conversion ratio (FCR). Antibody titer against SRBC increased remarkably (p<0.01) 15 days post the first injection when probiotic was administered. The probiotic also increased (p<0.01) the number of the duodenal goblet cells, and the density of jejunal and ileal villi. Overall, the supplementation of probiotic or acidifiers enhanced the growth performance of broiler chicks, mainly during the first three weeks of age. The probiotic also improved the immune response and intestinal morphology of broilers. However, there was no evidence of synergy when probiotic and acidifiers were co-administered.

ABSTRACT The aim of this study was to determine the optimum timing of thermal manipulation during early, mid, late and long lasting embryogenesis that may result in improvement of body performance and myofiber development (fiber diameter and thickness of perimysium) of pectoral and thigh muscles by a comparative morphometrical investigation on post-hatch day 35. 1440 fertile Ross broiler eggs were divided randomly and equally into 5 treatment groups: control (no TM), TM1, TM2 TM3 and TM4 were thermally subjected to 39ºC for 18h with 65% relative humidity daily during embryonic days ED 7-11, ED 11-15, ED 15-18 and ED 7-18 respectively. Out of TM conditions that were investigated, TM1 resulted in a significant improvement of hatchability rate (95.14%)and body performance when compared to the control. On post-hatch day 35, there were significant differences in BW, skinned carcass, breast, thigh and gut weight for all groups when compared to each other with a higher significant in TM1 and TM2 when compared to those of the control. FCR in this study was lower in TM groups when compared to the control group. In TM3 and TM4 the chicks show a significantly lower value of body performance when compared with those of the control group, TM1 and TM2.The histological evaluation of Pectoral muscle revealed myofibers of different diameter (38.39-40.27 µm) and perimysial thickening (17-30.5 µm), while myofibers diameter of thigh muscle ranged between (29-32.9 µm) and the perimysial thickening ranged between (14.36-22.15 µm). Thus, these results indicate that TM duringED7-11 improved muscle growth and body performance and this finding may be applied by commercial breeders to produce more enhanced broiler chickens.