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Synchronising ovulation in dairy cows with either two treatments of gonadotropin‐releasing hormone and one of prostaglandin, or two treatments of prostaglandin
Author(s) -
JEMMESON A.
Publication year - 2000
Publication title -
australian veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.382
H-Index - 59
eISSN - 1751-0813
pISSN - 0005-0423
DOI - 10.1111/j.1751-0813.2000.tb10536.x
Subject(s) - prostaglandin , gonadotropin releasing hormone , ovulation , insemination , estrous cycle , medicine , herd , ice calving , artificial insemination , hormone , endocrinology , pregnancy rate , zoology , biology , pregnancy , andrology , lactation , luteinizing hormone , sperm , genetics
Objective To compare oestrus synchronisation using two treatments of gonadotropin‐releasing hormone (GnRH) and one of prostaglandin F 2 ∝aL(PG) with a double prostaglandin synchronisation protocol under southern Australian conditions. Design A clinical trial. Procedure Eight hundred and forty, seasonally calving, lactating dairy cows within nine herds in the Tallangatta district of northeast Victoria were randomly allocated to treatment and control groups. The treatment (GnRH) group received gonadotropin‐releasing hormone followed by prostaglandin F 2 ∝aL and then a second treatment with gonadotropin‐releasing hormone. These cows were inseminated at a fixed time after the second gonadotropin‐releasing hormone treatment. Cows in the control (PG) group received two injections of prostaglandin F 2 ∝aL, 14 days apart, and were inseminated according to detected oestrus. Results The effect of GnRH treatment on first service conception rate (CRS 1 ) and 30 day pregnancy rate (PR 30 ) varied between herd (P < 0.001 and P < 0.02, respectively). A significant difference in CRS 1 between treatment (GnRH) and control (PG) groups existed in pooled data from eight of the nine herds (38.1% vs 65.9%, P < 0.001). A significant difference also existed in PR 30 between treatment (GnRH) and control (PG) groups in pooled data from eight of the nine herds (64.1% vs 72.4%, P = 0.03). Pregnancy rates after 56 days of mating for both groups were not significantly different (79.8% vs 84.1%, P = 0.13 for treatment (GnRH) and control (PG) groups, respectively). Submission rates (proportion of cows submitted for insemination) for the treatment (GnRH) groups were 100%. There was significant variation in submission rates in the control (PG) groups. Conclusion The GnRH protocol may be of benefit in herds where a poor response to the double prostaglandin program is anticipated. However, in the majority of herds in this trial, the double prostaglandin program achieved better results with fewer inseminations.