EFFECT OF DECREASING THE LEVEL OF CRUDE PROTEIN IN NAKED NECK BROILERS .1. INDEXES OF PRODUCTIVE PERFORMANCE

A total of 312 chickens of both sexes from an experimental strain (Whi te Plymouth Rock) where two genotypes were segregated: heterozygous na ked neck (Nana+) and their normal half sibs (na+na+ )from 1 to 49 days of age were used to evaluate their performance with a control diet an d another low in crude protein (CP) both being isoenergetic according to a triphasic feeding system in a 2 x 2 factorial arrangement. From 1 to 49 days of age the diet with a low level of CP affected feed conve rsion (P < 0.01) in na+na+ (2.66) chickens. The reverse occurred with Nana+ (2.37) and the protein waste per unit of live weight gain was hi gher (P < 0.05) in na+na + chickens (0.47) than Nana+ (0.42). Live wei ght gain did not differ between na+na+ genotypes (1490 g/bird) and Nan a+ (1504/bird) and the consumption was higher (P < 0.05) in na+a+ (381 9 g/bird) than in Nana+ (3656 g/bird)regardless of the diet. The resul ts obtained under the specific conditions of this experiment suggest a lower protein requirement for naked neck chickens (Nana+) compared to their normal half sibs (na+na+).