Organic Zn and Cu interaction impact on sexual behaviour, semen characteristics, hormones and spermatozoal gene expression in bucks (Capra hircus)

Abstract

The reproductive performance during the transition from prepubertal to pubertal stage was evaluated in Osmanabadi breed bucks supplemented with organic Zinc (Zn) and Copper (Cu). A total number of 40 bucks aged 20 weeks were randomly assigned to 10 groups (each n = 4). The control group was maintained with basal diet, without any additional mineral supplementation. The treatment groups were supplemented with graded doses of organic Zn (Zn 20 mg, Zn 40 mg and Zn 60 mg), Cu (Cu 12.5 mg, Cu 25 mg and Cu 37.5 mg) and a combination of Zn + Cu (Zn 20 mg + Cu 12.5 mg, Zn 40 mg + Cu 25 mg and Zn 60 mg + Cu 37.5 mg), respectively for a period of 26 weeks (up to the age of 46 weeks). Sexual behaviour and scrotal biometry were recorded periodically. Blood and semen samples were collected and processed for LH estimation in blood plasma, and testosterone, T3 and T4 hormones in the seminal plasma. The mounts with ejaculation were observed earlier (P < 0.05) in the treatment bucks (from 38th week of age) than the control group (43rd week onwards). A positive correlation was observed between blood plasma LH and testosterone with total mounts (r = 0.31, P < 0.05; r = 0.51, P < 0.01) and mounts without ejaculation (r = 0.40, P < 0.01; r = 0.52, P < 0.01). A negative correlation between T4 with sperm number per ejaculation (r = −0.31, P < 0.05) and sperm concentration (r = −0.35, P < 0.05) had been noticed. Different doses of minerals showed positive interaction (P < 0.05) with sperm functional and behavioural characteristics. The spermatozoal gene expression of ODF2 and ZCCHC6 were significantly influenced by the mineral supplementation in all doses. The ZCCHC6 gene expression was positively correlated with testosterone (r = 0.50, P < 0.001) and sperm number per ejaculation (r = 0.42, P < 0.001), and ODF2 gene with T3 hormone (r = 0.34, P < 0.05). The present study indicates that the diet supplemented with organic trace minerals cause intense sexual behaviour, enhancement in sperm number per ejaculate, total motility, spermatozoal genes expression and altered LH, testosterone and T4 hormones.