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Effect of Sperm Dose on Pregnancy per Timed AI in Brazilian Beef Cattle.
Effect of Sperm Dose on Pregnancy per Timed AI in Brazilian Beef Cattle.
Monday, July 10, 2017
Exhibit Hall (Baltimore Convention Center)
The objective of this study was to determine if beef bull fertility varied with the dose of sperm used for insemination. Pregnancy per timed AI (P/TAI) of bulls was investigated in large Brazilian beef herds. Ejaculates were collected from 5 Angus bulls by artificial vagina, and diluted to 10, 20, 20, or 40 x 106 sperm per straw in a milk-based extender. Each sperm dose was loaded into color-coded 0.5-mL straws (colors were alternated within bull among treatments), cryopreserved and stored in liquid nitrogen. Use of two 20 x 106 sperm per straw treatments was an attempt to illustrate the potential impact of random variation, as these treatments differed only in straw color. Beef cows (n=5,290) on 11 farms were synchronized for TAI using an intravaginal progesterone device-based protocol, and were randomly assigned to treatments. Each bull (dose combination) was represented in each farm, with farm personnel blind to treatments. Bull identification and straw color were recorded at the time of AI. The proportion pregnant were analyzed using generalized linear mixed models to estimate the fixed effects of bull, dose, and the bull by dose interaction. Farms were considered as a random blocking effect. Means were compared using pair-wise comparisons. No interaction between bull and sperm dose was detected (P=0.56). The P/TAI was different between bulls (P < 0.05: Table 1). No effect of sperm dose on P/TAI was revealed (43%, 45%, 43%, and 46.5% for 10, 20, 20, and 40 x 106 sperm dosages, respectively; P=0.22). The numeric range in P/TAI between the two control doses (20 x 106 sperm per straw) was 0.3 (Bull E; 434 total doses; 44.3% vs. 44.6%) to 6.4 percentage points (Bull D; 415 total doses; 47.2% vs 40.8%), providing evidence that the potential impact of random variation cannot be ignored. In conclusion, fertility differences (P/TAI) between bulls were detected (Table 1); however, dose per straw (10, 20 and 40 x 106 sperm) did not impact P/TAI.
Table 1. Pregnancy per timed AI (P/TAI) for 5 Angus bulls
Bull |
n |
P/TAI, % |
SEM |
A |
1,148 |
46.8a |
1.94 |
B |
1,136 |
47.7a |
1.95 |
C |
1,301 |
39.5c |
1.83 |
D |
807 |
45.6ab |
2.18 |
E |
898 |
42.3bc |
2.06 |
a,b,c Means within the same column not sharing a common superscript are different, P< 0.05