Genetic tolerance to heat stress could result from reduced feather coverage of broilers. The naked neck gene reduces total feather coverage by 20% to 40%. Under high ambient temperatures, naked neck broilers exhibited higher growth rate and meat yield than their normally feathered counterparts. Field trials in Israel, Egypt, Turkey, Vietnam and India have demonstrated the practical advantage of the Na gene in hot climates. The scaleless gene, at the homozygous recessive stage (sc/sc), eliminates the development of all feathers, thus producing completely naked chickens. This mutation, found in a slow-growing egg-type stock, has been introduced into fast-growing meat-type (broiler) stock, and its value to heat tolerance and the efficiency of broiler processing will be determined.
By selecting families that exhibited very low or very high rate of ascites, resistant and susceptible genotypes were established, differing in a single dominant major gene. Genomic tools are used to identify the sequence of this gene and determine his function. Broilers of the distinctive genotypes are used to decipher the physiological background of ascites. Performance traits (growth rate, body weight, meat yield and quality) and physiological traits (electrocardiography, blood oximetry, etc.) are evaluated at several ages in a series of trials, in order to predict and fully understand the consequences of selection for resistance to the ascites syndrome.
Selection on early antibody response to vaccination by Escherichia coli demonstrated the potential of breeding for immune response and disease resistance in young broilers. The divergent lines have been found to differ in several other immune functions. The selected lines differ also in frequency of DNA markers at the MHC and other genomic regions. Results indicate the feasibility of direct selection or marker-assisted-selection (MAS) for higher immunocompetence and disease resistance in young broilers.