Effect of selection for growth rate on carcass composition and meat quality in rabbits

Abstract

The objective of the present thesis was to study the effect of the selection for growth rate on the carcass and meat quality of line R, which is a line of rabbits selected for growth rate between the 4th and 9th week of age. This line is usually used in breeding schemes, where males from line R are mated with crossbreed females from two lines selected for litter size. When the line R was in the 7th generation of selection some embryos were recovered and vitrified. The selection of the line continued and the embryos were devitrified after some generations. The offspring of the rabbits obtained from the embryos formed the control group (Group C). This group was contemporary compared with the selected group (Group S), formed with rabbits from the present generation of selection. With groups S and C, two experiments were developed. The first experiment consisted in the study of the effect of selection for growth rate on the relative growth of offal, organs, tissues, carcass linear measurements and weight of several parts of the carcass. Group C was contemporary compared with Group S, formed with animals from the 18th generation of selection. A total of 313 animals from both groups and sexes were slaughtered at 4, 9, 13, 20, and 40 weeks old. Organs, tissues and retail cuts were weighed and several carcass linear measurements were recorded. Huxley's allometric equations relating the traits to liveweight by a parameter related to the scale (b) and an allometric coefficient (k) were fitted. Butterfield's quadratic equations relating the degree of maturity of the traits and the degree of maturity of the liveweight by an allometric coefficient (q) were also fitted. Values obtained for k and q coefficients led to similar patterns of growth in most of the traits studied. Full gastrointestinal tract and organs such as liver, kidneys, and thoracic viscera were early maturing (k<1 or q>1) whereas the chilled and reference carcass where late maturing (k>1 or q<1). The re