THE INFLUENCE OF DIFFERENT METHIONINE + CYSTINE LEVELS ON NEW ZEALAND WHITE RABBIT SEMEN PRODUCTION

Abstract

This experiment was carried out to study the influence of different methionine + cystine levels on diets designed to measure semen production and quality in New Zealand white rabbit males. A sample of 30 animals, distributed in a totally randomized design, was used with six treatments and five repetitions. A reference diet was formulated with 12.0% of crude protein and 0.3% of methionine + cystine and supplemented with six levels of DL-methionine 99% (0.0%, 0.101%, 0.202%, 0.303%, 0.404% and 0.505%), resulting in diets with 0.3%, 0.4%, 0.5%, 0.6%, 0.7% and 0.8% of methionine + cystine respectively. The analysis of 480 ejaculations showed that the increase on the methionine levels in diets caused a linear reduction of the total semen volume, of the volume of semen without gel and of pH. On the other hand, it did not influence the semen aspect which changed from milky to white, nor the progressive motility and vigor nor the spermatozoa concentration in the semen. A more aqueous aspect of the semen and lower progressive motility and vigor were observed during the season in which room temperature remained higher. The results lead to the conclusion that the lowest methioline + cystine level studied (0.3%) was adequate to meet the requirements of sulphur amino acids in male rabbit diet and that semen quality decreased in hot season.