Effect of lysine and methionine on libido and semen characteristics of bucks
The aim of this experiment was to study the influence of dietary lysine and methionine levels on the libido and semen quality of bucks. Forty crossbred Hyla HYLA rabbit males (10-12 months old) were subjected to four diets (15% crude protein) differing in lysine and methionine content (diet A 0.64 and 0.58%; diet B 0.75 and 0.58%; diet C 0.64 and 0.65%; diet D 0.75 and 0.65 of lysine and methionine +cystine, respectively). Two successive ejaculates were collected once a week for 12 consecutive months. Semen evaluations of for volume, colour, pH, motility, concentration and percentage of live spermatozoa were performed every two weeks. Dietary supplementation with lysine and methionine affected few parameters and there was little variation in the values. Never experienced large oscillations. Diets with higher lysine contents increased live sperm concentration from 77.1 to 78.2% in the second ejaculate and reduced the necessary interval between mating and ejaculation (sec. 20.8 vs 21.3 and 22.6 vs 23.1 for ejaculates I and 11, respectively). Supplementation with methionine increased the motility of ejaculate 11 (72.7 vs 71.2%) and reduced libido at the first sampling (sec. 21.4 vs 20.6 sec.). No significant differences in the reproduction parameters (fertility -75.2% on average-, total born/litter and born alive itter - 7.7 alive on average) were found for does inseminated with the semen of bucks undergoing dietary treatments (100 Al /treatment).
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