Semen quality, total protein content and protein profiles of seminal plasma of alpaca (vicugna pacos) fed different diets

Advances in reproductive technologies reveal seminal plasma (SP) as a nutritive- protective medium for spermatozoa suspended in it. This complex physiological fluid contains various organic and inorganic components among which, a variety of proteins adsorb into plasma membrane during epididymal maturation and at ejaculation, affecting spermatozoal membrane stability and functions including fertilization. The potential influence of SP proteins on male reproduction has drawn attention because of their association with semen freezability and breeding scores in ruminants. Despite the relevance of SP proteins with fertility, studies on their precise natures and factors affecting their quantities and qualities are limited in alpacas. Therefore, this study was conducted to evaluate changes in total protein (TP) content and protein profiles (PP) of SP along with semen quality of alpacas maintained with different diets. Five alpaca males were used to collect semen with an artificial vagina. Semen was collected once in a week, over a period of 6 months from March to September, 2009. The study period had four sessions with four types of diets: I.hay; II.hay+ pasture grazing; III. Sheep concentrate (gross protein 16%, lipids 2.7%, fiber 10%, +pasture grazing; IV. horse concentrate (gross protein 12%, lipids 3%, fiber 11%,) + pasture grazing. After proper evaluation of semen quality, samples were centrifuged (3500 r.p.m., 40 min) to separate SP to perform biochemical study including gel electrophoresis. The SDS electrophoresis was performed using two concentrations of polyacrylamide (14% and 16%) in the gel of separation. The gels were colored with cromassie brilliant blue and the intensity was analyzed with Sante Dicom Viewer and Image J program. In this study there were great variations in TP and PP of SP along with semen quality of individual alpacas. TP (g/dl) were 4.5±4.04, 3.21±3.08, 3.06±2.93 and 6.38±2.83 in the sessions I, II, III and IV, respectively. Motility and concentration of spermatozoa were lower (18.5±8.8%, 10.44±23.35X106/ml respectively) during session IV. Assessment of the electrophoretic profiles of SP proteins showed a total of 7 bands having molecular weights from 200 to 14.00 kDa. Surprisingly, all bands were not present in all alpacas SP. Semen from males fed a high quality diet markedly differed and showed protein bands with molecular weights from 10 to 14 kDa and 31 to 45 kDa compared to semen of the other males. Moreover, there were significant changes in the percentage and quantity of similar protein profiles during the four sessions. Protein fractions of low molecular weights (14.40 to 31.00 kDa) were highest during session II and this fraction showed a positive correlation with sperm motility and concentration throughout the study. These results demonstrate that there are marked changes in semen quality, TP and PP of SP of alpaca depending on diets. In ruminants, SP proteins vary with individual animal, season of collection, temperature, nutrition and stress, and are originated from seminal vesicles, which are normally absent in camelides. The origin, composition and function of SP proteins remain a mystery in alpacas. For successful preservation of alpaca semen we should define good quality semen before processing by determining the biological and biochemical makeup of SP. This study could help us to define different protein profiles in alpaca SP and could lead us to find out functions and the specific sources of these proteins in future.