| This experiment was to explore the effects of different dietary n-6/n-3 polyunsaturated fatty acids ratios on reproductive growth and performance of breeding boars before sexual maturity.Thirty two boars with body weight at 15.0±1.4 kg were divided into four groups (C, T1, T2, T3) and were respectively fed diets with different n-6/n-3 fatty acid ratios (29.06:1, 20.07:1,1:1,1:17.96) for 174 days. Each group had 8 repeat of one boar. Boars testis volume were measured at the 4,10 and 18 weeks of the test, and blood sampling of each boar was operated at 2nd and 24th week to determine the serum testosterone (T) and prostaglandin E2 (PGE2) levels. At 6.5 months age, boars were trained for semen collection, and then collecting the semen samples 2 times a week. It was for the determination of normal semen quality (response time and persistent period, semen volume, sperm density, sperm motility, etc.), total superoxide dismutase (T-SOD) activity and glutathione peroxidase (GSH-Px) activity and total antioxidant capacity (T-AOC) and malondialdehyde (MDA) content in semen, activities of acid phosphatase (ACP), fructose concentration and alpha glycosidase enzymes in seminal plasma, the fatty acid composition of sperm and expression of functional gene. The experimental results showed that:1) Different proportions of n-6/n-3 unsaturated fatty acid in diets had no significant influence for the weight gain and feed intake among each groups (P>0.05), but the boar testis volume index of T1 and T2 were significantly higher than other groups (P< 0.05).2) During the period of ejaculations, the sperm density and total sperm number per ejaculate in T2 group were significantly higher than other groups, while the sperm deformity rate and response time were the lowest (P<0.05). There was no significant difference in persistent period, sperm motility, sperm viability, PH of each group (P> 0.05). At the end of the test, the fatty acid compositions and ratio in sperm were consistent with those in diets.3) Compared with C group, the T-AOC in T1 seminal plasma was significantly higher (P< 0.05), and there was no difference between the other two treatments. The GSH-Px activity of sperm in T2 was higher than other groups (P< 0.05), but there were no difference in the T-SOD activity and MDA content of semen among groups (P>0.05). Meanwhile, ACP activity and fructose concentration of seminal plasma in T2 were significantly higher than other groups (P< 0.05). Otherwise, the concentration of testosterone and PGE2 increased after diet supplemented with fatty acid compared with C group, and reached the peak when n-6/n-3 fatty acid ratios was 1:1 (P< 0.05).4) On the gene expression, the higher expression of △6 fatty acid desaturase、 peroxisome proliferator activated receptor-a and cytochrome P450, family 11, subfamily A, polypeptide 1 (CYP11A1) in spermatozoa of T2 group were observed (P< 0.05), and the expression of carnitine fatty acyl transferase-1 (CPT-1), superoxide dismutase-1(SOD-1) and glutathione peroxidase-4 (GPx-4) in group T1 were significantly higher than others (P <0.05).In conclusion, the results of this study indicated that:The n-6/n-3 PUFAs ratio wasl:1 in the diet can promote the development of boar testis and gonad, by changing the hormone levels in the body and sperm fatty acid composition, meanwhile, improving the semen antioxidant capacity and the seminal plasma environment to enhance the reproductive performance of boars. |
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