Accessory Sperm Numbers for Cattle Inseminated with Protamine Sulfate Microcapsules

¹ Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315

A study utilizing two morphologically distinct sperm populations in a heterospermic trial was conducted to evaluate the effect of microencapsulation on accessory sperm number in artificially inseminated cattle. Inseminates consisted of an equal number (100 x 10⁶) of morphologically normal and tapered sperm. In reciprocal inseminates, one of the two sperm types was encapsulated in protamine sulfate microcapsules, and the other type was unencapsulated. Insemination of both sperm types that were unencapsulated served as the control. Thirty-one embryos were nonsurgically recovered 6 d postinsemination, and accessory sperm within the zona pellucida were counted and morphologically classified as normal or tapered. Microencapsulated sperm contributed 25.7% of the accessory sperm obtained for inseminates containing microcapsules. Microencapsulation did not affect the total number of accessory sperm per embryo; however, encapsulation did reduce accessory sperm for the specific sperm type encapsulated. The proportion of morphologically normal to total accessory sperm recovered were 65.8% when both sperm types were unencapsulated, 35.4% when normal sperm were encapsulated, and 80.6% when the tapered sperm were encapsulated. High accessory sperm numbers per embryo were related to embryo quality (P < .01). Mean accessory sperm and standard deviations for degenerate embryos and for embryos classified fair to poor, good, and excellent were 1.7 ± 2.9, 11.1 ± 8.6 24.9 ± 33.9, and 84.3 ± 58.3. We conclude that sperm inseminated in protamine sulfate microcapsules can be released and can attach to the zona pellucida of ova in vivo. Microencapsulation failed to increase accessory sperm numbers under conditions of this experiment in which insemination was 12 h after estrus was first detected.

Key Words: accessory sperm • microencapsulation • embryo quality

Submitted on August 12, 1991
Accepted on October 16, 1991