Dietary grape seed tannin  extract supplementation stimulated testis development, changed fatty acid profiles and increased antioxidant capacity in testis in Hu lambs in pre-puberty

Abstract Background Grape seed tannin extract (GPE) that is from wine grape pomace has many effective anti-oxidative effects and is used as a promising natural feed additive in the animal feed industry. In this study, we investigated the effect of GPE as a source of tannin on the antioxidant capacity and testis development in Hu lamb. Method: Twenty-seven 3-month-old ram lambs were randomly assigned to three groups. Within each treatment group, nine lambs were allocated to nine pens (one lamb per pen). The lambs in the control group were fed a control diet without GPE for 61 days from D21 to D80. Group I (TAN1) was fed a 0.36% GPE diet. Group II (TAN2) was fed a 0.72% GPE diet. After 81-day feeding trial, all lambs except the heaviest and lightest in each group were humanely slaughtered and investigated. Results Feeding GPE did not affect the body weight, average daily gain, dry matter intake, scrotal circumference and testis index, whereas feeding 0.36% GPE diet increased testis weight, testis volume, and epididymis weight (P < 0.05) compared with the control. Cu-ZnSOD, P450scc, P450arom, FSHR, FADS2, ELOVL2 and PCNA mRNA in TAN1 and TAN2 groups were significantly up-regulated (P < 0.05). GPE also markedly increased antioxidant status of testis. Compared with the control group, GPE significantly increased the SOD activity (314.23 ± 18.64 U/mg prot in control, 505.22 ± 63.47 U/mg prot in TAN1 and 587.88 ± 55.94 U/mg prot in TAN2, P < 0.05), T-AOC (98.23 ± 18.99 U/g prot in control, 202.15 ± 34.19 U/g prot in TAN1 and 189.57 ± 18.95 U/g prot in TAN2, P < 0.05). GPE also increased NEFAs levels (158.36 ± 26.32 mmol/kg prot in control, 205.15 ± 14.51 mmol/kg prot in TNA1 and 250.06 ± 33.82 mmol/kg prot in TAN2 P = 0.08). But, consuming GPE downregulated testicular total cholesterol concentration (3.89 ± 0.57 mmol/kg prot in TAN1, 4.21 ± 1.04 mmol/kg prot in TAN2 and 7.20 ± 1.46 mmol/kg prot, P = 0.09). Consuming 0.72% GPE also changed fatty acid profiles in testis with increased C15:1, C22:6n3 and total n-3 fatty acids (P < 0.05). Therefore, feeding lambs with 0.72% GPE stimulated testis seminiferous tubule development, increased the number of Sertoli cells (10.56 ± 0.44 vs. 13.60 ± 0.42, P < 0.05), and seminiferous tubule diameter (146.56 ± 4.53 µm vs. 109.3 ± 4.56 µm, P < 0.05). Conclusion All these results suggested that feeding GPE in the early reproductive development stage of lambs upregulated the expression of antioxidative, steroidogenesis, and PUFA metabolism-related genes; changed the fatty acids profiles, increased the antioxidant capacity in lamb’s testis; and contributed to testis development and spermatogenesis.