Sexual development and boar taint in male pigs selected for divergent residual feed intake

Abstract Text: Improving feed efficiency and rearing entire male pigs are relevant strategies to reduce feed cost and environmental waste in pig production. The major constraint for rearing entire male pigs being boar taint, an experiment was performed to determine the consequences of a divergent selection on residual feed intake (RFI: low RFI=LRFI; high RFI=HRFI) on pubertal development and boar taint. Forty one purebred French Large White male pigs in the course of a divergent selection experiment for RFI (10th generation of selection, n = 20 or 21 per line) were recruited. Blood samples were drawn at 125, 140, 154 and 168 ± 1 days of age (mean ± SD) for plasma estradiol (E2) and testosterone (T) determination by EIA. At slaughter at 177 ± 4 days of age (108 ± 14 kg liveweight), a backfat sample was collected in the neck for androstenone and skatole determination by HPLC and genital tract was removed for testes and Cowper gland weighing after tissue trimming. All data were analyzed by ANOVA using R, including line as a fixed effect. Plasma E2 and T were log transformed for normalization and analyzed using a repeated in time model with nlme. Fat androstenone and skatole were analyzed using a generalized mixed model with lme4. Other data were analyzed using lm. Growth rate, age and liveweight did not differ between lines (P > 0.1). Testes weight was similar in both lines (LRFI: 527 ± 23 g; HRFI: 471 ± 33 g, P > 0.1) whereas Cowper glands were heavier in LRFI pigs (176 ± 10 g vs 100 ± 8 g). Fat androstenone (1.97 ± 0.31 vs 0.56 ± 0.08 µg/g pure fat) and skatole (0.14 ± 0.02 vs 0.05 ± 0.01 µg/g pure fat) were also higher in LRFI pigs (P < 0.001). The interaction age x line for E2 and T was not significant (P >0.1). Across ages, plasma T (5.0 ± 0.9 vs 2.7 ± 0.7 ng/mL plasma) and E (25.5 ± 2.9 vs 11.4 ± 1.0 pg/mL plasma) were also higher in LRFI than in HRFI pigs (P < 0.001). In both lines, both hormones increased with age (P < 0.001). Overall, these data suggest a lower testicular activity in the HRFI than in the LRFI line which is positive for meat quality but may be detrimental to the reproductive function in the HRFI line.

Keywords: boar, testosterone, estradiol, androstenone, feed efficiency