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

Grape seed tannin extract (GPE) from wine grape pomace has many effective anti-oxidative effects and is used as a promising natural feed additive in the animal feed industry. This study investigated the effect of GPE as a source of tannin on the antioxidant capacity and testis development in Hu lambs. Twenty-seven 3-month-old ram lambs were randomly assigned to three groups. For 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 with 0.36% GPE diet, and Group II (TAN2) was fed with 0.72% GPE diet. After an 81-day feeding trial, all lambs except the heaviest and lightest in each group were humanely slaughtered and investigated. Results showed that feeding GPE did not affect the body weight, average daily gain, dry matter intake, scrotal circumference, and testis index. Meanwhile, feeding with 0.36% GPE diet increased testis weight, testis volume, and epididymis weight (P ≤ 0.05) compared with those of the control, but no difference was found between TAN1 and TAN2 groups. Copper-zinc superoxide dismutase (Cu-ZnSOD), steroid acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450scc), follicle-stimulating hormone receptor (FSHR), elongation of very long chain fatty acid protein 2 (ELOVL2), fatty acid desaturase (FADS2), and proliferating cell nuclear antigen (PCNA) mRNA in TAN1 and TAN2 groups were significantly up-regulated (P < 0.05). GPE also markedly increased the antioxidant status of testis. Compared with the control group, the treatment groups showed significantly increased superoxide dismutase (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) and total antioxidant capacity (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). Consuming 0.72% GPE also changed the fatty acid profiles in testis with increased C15:1, C22:6n3, and total n-3 fatty acids (P < 0.05) but decreased C22:5n3 (P < 0.05). Therefore, feeding lambs with GPE stimulated testis seminiferous tubule development and increased the number of Sertoli cells (10.56 ± 0.44 in control, 14.10 ± 0.57 in TAN1 and 13.60 ± 0.42, P < 0.05), and seminiferous tubule diameter (109.30 ± 4.56 μm in control, 164.49 ± 5.37 μm in TAN1 and 146.56 ± 4.53 μm in TAN2, P < 0.05). These results suggested that feeding GPE in the early reproductive development stage of lambs upregulated the expression of antioxidative, steroidogenesis, and polyunsaturated fatty acid metabolism-related genes, changed the fatty acid profiles, increased the antioxidant capacity in lamb's testis, and contributed to testis development and spermatogenesis.