EFFECT OF MILK FRACTIONS ON SURVIVAL OF EQUINE SPERMATOZOA

Milk-based semen diluents are known to be practical and effective in p rotecting equine spermatozoa during storage. Due to complex compositio n of milk, the components which are beneficial or harmful to spermatoz oa are unknown. To address these unknowns the effect of various milk f ractions on motility of stallion spermatozoa was evaluated. The fracti ons tested were native phosphocaseinate (NPPC), beta-casein, whey prot ein concentrate (WPC), alpha-lactalbumin, beta-lactoglobulin, microfil trate, and ultrafiltrate. The standard reference diluents were INRA 82 , commercial skim milk, and Hank's salts solution supplemented with He pes, glucose, lactose (HGLL) supplemented with BSA. After 48 and 96 h storage at 4 or 15 degrees C some milk fractions (ultrafiltrate, micro filtrate, and a-lactalbumin fraction) decreased spermatozoal survival. Others (beta-lactoglobulin (BL) and native phosphocaseinate) were pro tective. Native phosphocaseinate (NPPC) at milk concentration afforted better protection than did the standard reference diluents. The optim al concentration of beta-lactoglobulin afforted significantly better p rotection than did BSA. The protection afforded by native phosphocasei nate was not synergistic with beta-lactoglobulin. This implies a simil ar mechanism of protective action of these two components. Semen dilut ed in HGLL supplemented with NPPC (HGLL-NPPC) or in INRA 82 and stored 24 h at 15 degrees C or 4 degrees C, respectively, produced no differ ence of spermatozoal motility. However, fertility of semen stored in H GLL-NPPC (60%) was higher (p < 0.05) than that stored in INRA 82 (36%) . (C) 1997 by Elsevier Science, Inc.