Effect of different amino acid patterns on semen quality of boars fed with low-protein diets

The objective of the present study was to determine the effect of different amino acid patterns on the semen quality of boars fed with low-protein diets. Twenty-four boars were randomly divided into 4 groups (HP, LP1, LP2, and LP3). HP boars received 17% crude protein diet with a lysine:threonine:tryptophan:arginine (Lys:Thr:Trp:Arg) ratio of 100:50:20:104. Other boars received 13% CP and similar Lys levels (0.84%) with Lys:Thr:Trp:Arg ratios of 100:50:20:71, 100:76:38:71, and 100:76:38:120 for LP1, LP2, and LP3, respectively. These results showed sperm motility in the LP3 group was higher than in HP group during the 13-22 week period. The total sperm number, acrosome integrity ratio, and the effective total sperm number in LP3 and LP2 was higher than in other groups, and the abnormality ratio was lower than in other groups during the 13-18 week period. During 19-22 week period, in LP1 and LP3 groups, total sperm number and effective total sperm number were higher than in other groups, abnormality ratio was lower, and acrosome integrity ratio was higher than in the HP group. Nitric oxide synthase activity of seminal plasma and nitric oxide concentration of spermatozoa were significantly higher in the LP3 group than in other groups. Furthermore, mRNA expression of androgen receptor in testes was up-regulated in LP3. In conclusion, we suggest that the optimum ratio of Lys:Thr:Trp:Arg in a 13% CP diet for boars is 100:76:38:120, which results in similar or better reproductive performances than a 17% CP diet.