Rate of growth of the domestic fowl as determined by egg size of the dam and the length of the incubation period

Abstract

(a) The first part of this study involved four hatches from an egg laying strain of White leghorn. Hatching eggs were obtained from around 210 dams giving a total of 1,137 chicks. The correlation estimates between the mean egg weight of the dam and the mean body weight of the hatched, chicks ranged between .79 and .89. The pooled correlation estimate between the egg size and the body weight of the chick at hatching and at 2, 8, 12 and 20 weeks of age were .8U, .28, .22, .30 and .18 respectively. These estimates which are in general agreement with previous findings suggest that egg size is of little or no practical significance in selecting the chick for growth rate. Moreover, the gain in body weight of the chicks at hatching and at 2, 8, 12 and 20 weeks of age for 1 gram increase in the mean egg weight were .72, .36, 2.85, 5.77 and 6.26 grams respectively. Thus, egg size effect on the body weight of the chick in this flock appears to be of little economic importance in broiler production.

(b) A limited number of White Leghorn chicks of another egg laying strain were involved in the second part of the study. Hatched chicks were recorded at three hour intervals and were removed from tae incubator within 6 hours of hatching and immediately given access to food and water. Simple correlation and regression values were derived between the emergent period and the chick weight at hatching and at 1, 2, 3 and 12 weeks of age. Chicks of either sex which hatched earlier were slightly heavier after day old than those that hatched later. Moreover, it is considered that the length of incubation period may be indicative of the physiological rate of development since the female chicks were found to be slightly shorter in the length of incubation period than the male chicks. However, any economic advantage in using the early hatched male chicks for broiler production may be offset by the preponderance of females among the early hatched chicks apart from the extra labour cost involved in the removal and sexing of the chicks in batches.