COMPARISON OF INTACT, LATE-CASTRATED, AND DIETHYLSTILBESTROL (DES)-IMPLANTED BOARS WITH BARROWS AND GILTS: NITROGEN AND ENERGY DIGESTIBILITY, NITROGEN RETENTION, CARCASS MEASUREMENTS, MUSCLE ANALYSES, AND RESIDUAL DES IN MUSCLE TISSUE

Abstract

Forty boars, eight barrows, and eight gilts were allotted in groups of four pigs each at an average weight of 13.1 kg. Metabolism studies with a portion of the animals were conducted at 15 and 50 kg liveweight. Although no statistical differences between sexes were found in these studies, barrows tended to digest more nitrogen (N) but to retain less than boars and gilts. N digestibility (DN) and retention (NR) values at 50 kg were higher than those at 15 kg. The three sexes were found to be similar in energy digestibility (DE) and metabolizable energy (ME). Significant differences were found for boars in DE and ME coefficients between the two periods, averaging 83.2 and 85.6% DE in the 15- and 50-kg periods, respectively. At 70 kg, 16 boars were implanted with 96 mg of diethylstilbestrol (DES), 16 boars were castrated, and 8 boars were left intact. Barrows had thicker backfat (P < 0.05) and lower (P < 0.05) grade index than any of the other treatments. Late-castrated boars showed a general trend to revert to the carcass characteristics of barrows but were still superior to barrows at market weight. No significant differences between treatments were found for dry matter, protein, fat, or ash content of the longissimus muscle. No residual DES was found in the muscle tissue of the implanted boars.