Abstract
The sperm concentration analysis in boar ejaculates is a quality measure in farms dedicated to the selling seminal doses and artificial insemination. The aim of this study was to determine differences in accuracy between assessment methods of sperm concentration. A total of 174 ejaculates from Duroc and Pietrain boars were analyzed. The animals belonging at the Agricultural Production Program (PPA) of the School of Agronomy at the Technological Institute of Costa Rica. The sperm concentration was estimated by 3 methods: sperm-densitometer (ED), spectrophotometer (EF) and computer assisted semen analysis (casa). The lower concentration (p<0.05) was estimated with EF (384.90±11.19 x106 spermatozoa.ml-1) and the highest with casa (432.39±20.81 x106 spermatozoa.ml-1). Concentration was analyzed using a generalized mixed model, including as explanatory variables from the model the volume of ejaculate, age of the boars, genetic line, collection interval, season and the interactions between the factors. The coefficient of variation was different (p<0.05) among methods and the highest was casa system (45.38%) while the lowest was ED method (34.78%). There were differences(p<0.05) between EF and casa estimation methods (376.65±12.06 vs 432.20±22.08 x106spermatozoa. ml-1) respectively, when the range between seminal extractions was low (≤9 days). Only casa system estimation was adjusted (p<0.05) and asymptotic level of concentration of 7.5 days was presented over the range between collections. In general, the estimation methods of concentration showed variability in the results. Duroc genetic lines presented higher sperm concentration than the Pietrain lines, independently of the estimation method. The volume of ejaculate presented a negative correlation with sperm concentration. The concentration decreases with increases the volume of ejaculate and the age of the boars.