Correlated Responses to Selection for High or Low Incidence of Tibial Dyschondroplasia in Broilers

Abstract

Selection for a high or a low incidence of tibial dyschondroplasia (TD) at 7 wk of age was practiced for four generations in broiler breeders keeping an unselected control (C) line and using low intensity X-ray imaging for TD diagnosis. The incidence of TD, BW at 4 and 7 wk of age, age at first egg, and egg production for the first 12 wk of production were determined in the four generations. Age at initial semen production and semen volume and concentration of males were determined only in Generations 3 and 4. The TD scores and BW at 7 wk were collected on 1,366, 1,301, and 1,389 broilers from the C, high (H), and low (L) incidence of TD lines. Incidence of TD at 7 wk in the fourth generation was 16.1, 61.9, and 3.5% for the C, H, and L lines, respectively. There were no significant differences in BW between the H and L lines in Generations 1, 3, or 4. However, in Generation 2, the H line was heavier (P < .01) than the L line. Second generation H line broilers with TD were heavier than those without TD at 4 and 7 wk of age (P < .01). There were no significant differences in age at first egg, age at semen production, or in semen volume between the H and the L lines. Egg production in the L line was greater (P < .01) than that of the H line in all four generations, and semen concentration was also greater (P < .01) in Generations 3 and 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 1. TD incidence and calcium and phosphorus plasma concentrations

“…Our body weight and of TD findings do not support the hypothesis framed by Leach et al (1990) and Edwards and Sorensen (1987), that reduced body weight will also reduce the incidence of TD. Males had significantly more TD than females at 4 and 7 weeks of age in the HH, HL and LH lines, confirming previous findings (Leach and Nesheim, 1965;Wong-Valle et al, 1993). Males had significantly more TD than females at 4 and 7 weeks of age in the HH, HL and LH lines, confirming previous findings (Leach and Nesheim, 1965;Wong-Valle et al, 1993).…”

“…Detailed descriptions of lines and selection procedures have been presented by Wong-Valle et al (1993 ). A contemporary control (CC) line was maintained.…”

Estimates of Heritabilities and Genetic Correlations Between Tibial Dyschondroplasia Expression and Body Weight at Two Ages in Broilers

“…Results obtained for genetic correlations between TD expression and weight agree with conclusions reached by Wong-Valle et al (1993b), who, in their four-generation selection experiment for TD expression at 7 wk of age, did not observe significant changes in the weights of the birds. This procedure considers genetic relationships between birds and accounts for selection in the population.…”

“…Riddell and Pass (1987) noted a greater incidence of TD at 4 and 7 wk of age in the lighter-weight group of broilers. Later studies by Wong-Valle et al (1993b) reached the same conclusion. Later studies by Wong-Valle et al (1993b) reached the same conclusion.…”

Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 2. Processing yield

“…However studies by Riddell (1975) showed that excessive weight on the proximal tibia was not a primary factor in TD. In a recent study Wong-Valle et al (1993b) did not note any differences in body weight between high (H) and low (L) incidence of TD lines in generation 1, 3 or 4. In a recent study Wong-Valle et al (1993b) did not note any differences in body weight between high (H) and low (L) incidence of TD lines in generation 1, 3 or 4.…”