Insemination management for a one-injection prostaglandin F(2)alpha synchronization system. II. One versus two inseminations following detection of estrus.
Following detection of estrus in an estrus synchronization system, 216 dairy heifers were inseminated (A.I.) randomly either soon after detected estrus (1X) or soon after detected estrus and again 10 to 12 h later (2X). Average h from detection of estrus to A.I. was 1.8+/-0 for 1X and 1.1+/-0 and 11.1+/-0.4 for 2X. During the regimen, heifers were checked visually for estrus daily for five consecutive days with 16.0 and 17.3% showing estrus and receiving A.I. in the 1X and 2X groups, respectively. Those not seen in estrus were injected with 25 mg PGF(2)alpha with observations for estrus and A.I. continuing for five more days. Response rates as indicated by estrus following prostaglandin F(2)alpha (PGF(2)alpha) were 74.7 and 75.8% for 1X and 2X, respectively. Percentages of heifers in estrus <24, 25 to 48, 49 to 72, 73 to 96 and >96 h after PGF(2)alpha were 3.7, 22.8, 47.1, 15.4 and 11.0, respectively. Based on rectal palpation for pregnancy between 45 and 60 days after A.I., conception rates of 70.2% for 1X and 68.6% for 2X did not differ significantly (P>0.05). Progesterone concentrations at injection for heifers not responding to PGF(2)alpha were lower than was seen in responding heifers (2.7 vs 5.8 ng/ml) (P<0.01). Data from the present experiment supports the conclusion of an earlier experiment that satisfactory conception can be achieved with a single, established daily insemination period.
Wahome
J N
JN
Department of Dairy Science Mississippi State University Mississippi State, MS 39762 USA.
Stuart
M J
MJ
Smith
A E
AE
Hearne
W R
WR
Fuquay
J W
JW