Impactos do peso ao nascimento sobre parâmetros testiculares em suínos avaliados nos períodos neonatal e pós-puberal

Abstract

The aim of this study was to investigate the effects of low birth weight on some testicular parameters evaluated in neonatal and postpubertal boars. Forty-eight littermate male piglets (Agroceres PIC), born to 4th- 6th parity sows and in litters of 10 to 15 piglets (litter average birth weight of 1.25 kg to 1.65 kg), were individually identified as falling into two birth weight categories: high (HW: 1.80 to 2.15 kg) and low (LW: 0.75 to 1.10 kg) birth weight littermates. Two sub-sets of 12 animals from each experimental group underwent orchiectomy at eight days or eight months of age and the testes were collected for morphometrical and biometrical evaluations. LW animals had lower body weight (BW), testicular weight (TW) and volume (TV) and body biometrical measures in both ages evaluated (p<0.05), except for abdominal circumference that was similar between groups at eight months of age. The gonadossomatic index also differed between groups at eight days (p<0.05). No statistical differences were observed in the seminiferous cords/tubules (SC/ST) diameter, Sertoli cells number per cross section of SC/ST and cross section number of SC/ST per testis area in both ages. At eight days of age, LW animals showed lower Sertoli, Leydig and germ cell number per testis (p<0.05). However these differences were not maintained when those values were divided by their respective average testis weight. At eight months old, the number of type A spermatogonia and preleptotene primary spermatocytes were similar between experimental groups (p>0.05). However, LW males presented fewer pachytene primary spermatocytes and round spermatids numbers, which influenced the total number of spermatogenic cells that was also reduced in this group (p<0.05). The efficiency of spermatogenesis was similar in both groups, however LW animals presented a reduced number of sperm per testis (p<0.05). Furthermore, low birth weight did not affect somatic and germ cell proliferation in both ages analyzed. Significant correlations between BW, TW and TV were observed at eight days of age. BW and TW were also correlated to the total number of Sertoli cells at this age. At eight months, TW was positively correlated to TV, and birth weight to BW (p<0.05). These results suggest that low birth weight have negative effects on testis development in pigs, however the differences observed in low birth weight animals may not be mediated by a compromised organogenesis and yet to the smaller size of the animal. Therefore, studies are necessary to further address this question.