CONSOMMATION ALIMENTAIRE CHEZ DES PONDEUSES DE GÉNOTYPE Cc ET cc ISSUES DE PLUSIEURS FAMILLES

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Abstract
A total of 53 laying hens a year old, with colored plumage, Cc, or white, cc, from 4 families, were studied. They were kept in individual cages and for periods of 28 days bodyweight, gain in weight, number and weight of eggs and intake of feed were recorded. The experiment was in 2 periods. During the 1st, from May to July inclusive, half the birds were given their feed as a mash and the other half as pellets. For the 2nd period, from Aug. to Oct. inclusive, the form of the feed was reversed. A considerable amount of the mash was lost by falling into the drinking water and individual correction was made to allow for this. There was no significant difference between genotypes at the C locus or between families in total intake of feed during periods of 28 days or in any of the other criteria studied. Druing the second period only, the colored hens gained more weight, attributable perhaps to their greater ability to lay down fat. There was no interaction between genotype and form of feed. Multiple regression equations were derived for estimating theoretical intake of feed from bodyweight, weight gain and weight of eggs laid during 28 days. These equations are presented in a separate paper. The difference between actual and estimated intake for each individual represents a "residual" intake which is called the individual factor. Analysis of variance of these individual factors was made with family and genotype at the C locus as controlled sources of variation; birds were grouped irrespective of the form of feed they were given. This last factor was not separated since its main effect was suppressed, and it was shown that it did not give rise to any considerable interaction. There were highly significant differences between families (P < 0.001) and between genotypes at the C locus (P < 0.01); residual intake was about 4p. 100 less for white than for colored hens. There was no significant interaction between family and genotype. These differences, associated on the one hand with a single Mendelian factor and on the other with family, suggest that it would be possible to select for this criterion.