Improving Live and Dry Body Weight Gain of Bovine Native Calves during Hot Summer Season of Egypt using Genetic Crossing Process

The objective of this research is study the importance of crossing in improving body weight gain of native cattle calves during hot summer season of Egypt. Twenty healthy calves including 10 native cattle calves and 10 F1 (produced from mating Brown Swiss♂ with Native cattle ♀) were used in the experiment. The experimental calves of two groups were the same each of age and live body weight. Experimental calves of the two groups were exposed to mild climate of winter season for 3 months followed by exposure the same calves to hot climate of summer season for 3 months. Results showed that calves body weight gains (either live or solids) improved significantly in F1 (½ Brown Swiss x ½ Native) calves due to crossing process under both winter and summer seasons. Thyroid hormones (T3 and T4) values in both two groups were found to be highly significantly lower in summer than in winter. While cortisol level in calves of the two groups was significantly higher during summer than those in winter. Dry matter intake (DMI) in two experimental groups was significantly lower during summer than those during winter. Feed conversion (FC %) was significantly higher during summer than those during winter. DMI and FC% values were improved significantly in F1 calves due to crossing process under each of winter and summer season.
It can be concluded that growth and feed performance in crossing calves are better than native cattle calves under each of winter and summer season.

Keywords: Calves, gain, crossing, hormones, hot summer, hormonal levels.