Effect of Time of Insemination on Number of Accessory Sperm, Fertilization Rate, and Embryo Quality in Nonlactating Dairy Cattle

Abstract

Two experiments were conducted to determine the effect of insemination time on number of accessory sperm per embryo (ovum), fertilization rate, and embryo quality. Semen was collected from three fertile Holstein bulls and cryopreserved in egg yolk-citrate-glycerol. In experiment 1, cows were continuously monitored for behavioral estrus by the HeatWatch estrous detection system and were artificially inseminated (AI) with one 0.5-ml straw (25 x 10(6) sperm) at the onset of estrus (AI 0 h), 12 h after onset (AI 12 h), or received natural service at 0 h (Nat 0 h) from one of three bulls. From 150 inseminations, 115 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; Nat 0 h: n = 37) were recovered 6 or 7 d after insemination. Fertilization rates differed between treatments (AI 0 h: 67%; AI 12 h: 79%; Nat 0 h: 98%). Median accessory sperm per embryo (ovum) also differed (AI 0 h: 1; AI 12 h: 10; and Nat 0 h: 27) and paralleled the fertilization rate. Embryo quality was not affected by insemination time or natural service. In experiment 2, cows received AI at 0, 12, or 24 h (AI 24 h) after the onset of estrus as determined by HeatWatch. From 154 inseminations, 117 embryos and ova (AI 0 h: n = 39; AI 12 h: n = 39; AI 24 h: n = 39) were recovered 6 or 7 d after insemination. Fertilization rates did not differ in experiment 2 (AI 0 h: 66%; AI 12 h: 74%; AI 24 h: 82%); however, a trend toward a higher fertilization rate accompanied AI 24 h. Median accessory sperm values increased from AI 0 h (1) to AI 24 h (4). Embryo quality declined with AI at increasing intervals after onset of estrus, as percentages of excellent and good, fair and poor, and degenerate embryos were as follows: 77, 15, 8; 52, 38, 10; and 47, 19, 34 for the 0-, 12-, and 24-h inseminations, respectively. Results indicate AI 12 h after the onset of estrus provides a compromise between potential fertilization failure (AI 0 h) and embryo failure (AI 24 h), despite increased accessory sperm per embryo (ovum) after AI 24 h. Artificial insemination 12 h after onset of estrus should optimize fertility of dairy cattle through an acceptable fertilization rate, number of accessory sperm per embryo, and desirable embryo quality.

Fertility evaluation in Egyptian buffalo bulls using zona pellucida binding and in vitro fertilization assays

“…These findings were in agreement with those of Saacke et al (2000) and Dalton et al (2001). On a molecular level, sperm surface proteins are thought to participate in zona binding and fertilization (Talbot et al, 2003).…”

Development of Ovulation Synchronization and Fixed Time Artificial Insemination in Dairy Cows

“…In addition, the average milk yield per cow per lactation in Nakashunbetsu rose from 7,700 kg in 1992 to 8,100 kg in 2000. These changes might cause poor expression of estrous behavior and shortening of the duration of estrus [7][8][9][10][11][12]. As the consequence, the estrous detection has become more difficult than ever [13].…”

The Possibility of a False Positive Arising from Sperm DNA in Genetic Diagnosis of Bovine Embryos

“…Previous reports have revealed that the distribution of accessory sperm cells is very skewed, with a median of 1 to 10 per ovum/ embryo [10,11] and a mode of 0 per ovum/embryo [10]. In contrast, more than 50 accessory sperm cells per ovum/embryo were observed with low frequency, and good to excellent embryos, which are generally used for genetic diagnosis, had a higher accessory sperm number than degenerate or fair to poor embryos [10].…”

“…Saacke [10] reported that the average, median and mode accessory sperm cell numbers in the zonae pellucidae of ova and embryos were 12.0, 2.4 and 0, respectively. Dalton et al [11] also reported that the range of the accessory sperm cell number per embryo was 0 to 216. The DNA of most vertebrate sperm cells is packaged by protamines, and disulfide bonds between DNA-bound protamines help stabilize the chromatin of mature sperm cells [12].…”