Influence of genetic selection for antibody production against sheep bloodcells on energy metabolism in laying hens

Genetic selection in chickens has been utilized to enhance immune responses that may influence resistance to diseases. It is important, however, to in vestigate the effects of this selection on other physiological processes. T herefore, this study was conducted to determine whether selection for antib ody (Ab) production against SRBC has an effect on energy metabolism. Laying hens from three lines were used in this study, two of which were selected for 15 generations for Ab response against SRBC, and the third was nonselec ted and randombred. The hens used were from four different groups. The firs t two groups were from the lines that were selected for either high (SH) or low (SL) Ab production. The second two groups were control birds (nonselec ted) that had either high (CH) or low (CZ,) Ab titers that were similar to those in the SH and SL lines, respectively. The birds were housed in climat e-respiration chambers. Body weights and energy metabolism were measured. B ody weights of SL hens were significantly (P < 0.05) higher than those of S H hens. However, the BW for the two nonselected groups were similar but sig nificantly less than the Si, group. Energy partitioning was similar in all groups; however, ME for maintenance for the selected groups (119 kcal.kg(-0 .75).d(-1)) was numerically, but not significantly (P < 0.09), higher than that of the nonselected groups (112 kcal.kg(-0.75).d(-1)). These results su ggest that divergent selection for Ab may result in an increase in the requ irements of energy for maintenance, which is not directly related to the am ount of Ab produced. Furthermore, these results support previous findings o f the presence of a negative correlation between BW and the levels of Ab in selected lines.