Resynchronization of ovulation and conception in nonpregnant dairy cows and heifers

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Show simple item record Portaluppi, M.A. Tenhouse, D.E. Stevenson, Jeffrey S. 2010-11-29T17:54:22Z 2010-11-29T17:54:22Z 2010-11-29
dc.description Dairy Research, 2006 is known as Dairy Day, 2006
dc.description.abstract Our objectives were to determine various factors influencing upfront single and multiple ovulation in response to GnRH in a timed arti-ficial insemination (TAI) protocol and subse-quent fertility after altering timing of the sec-ond GnRH injection and AI relative to PGF2α injection. Replacement heifers (n = 86) and 613 lactating cows previously inseminated were diagnosed not pregnant at biweekly in-tervals to form 77 breeding clusters spanning 36 months. At not-pregnant diagnosis (day 0), females received 100 μg of GnRH, and they received 25 mg of PGF2α 7 days later. Females in 2 treatments received GnRH 48 hr (G48) after PGF2α injection and TAI at the time of the second GnRH injection (G48 + TAI48) or 24 hr later (G48 + TAI72). Females in the third treatment received GnRH 72 hr after PGF2α, when inseminated (G72 + TAI72). Ovaries of females in 65 clusters were scanned at day 0 (first GnRH injection) and 7 days later (PGF2α injection). Ovarian struc-tures were mapped, and ovulation in response to the first GnRH injection was detected on day 7. When estrus was detected before scheduled TAI, females were inseminated; otherwise TAI conception of remaining fe-males was based on timing of GnRH and AI in 3 treatments. On day 7, 1 or more luteal struc-tures (CL) were detected in 46% of females. Conception rate was 26.5% (98/701) in fe-males that showed estrus and were insemi-nated early. Pregnancy rate was greater in fe-males that ovulated after the first GnRH injec-tion (day 0) and during nonsummer months. Compared with females in late diestrus at nonpregnant diagnosis, cows in early diestrus or those with functional cysts had greater pregnancy rates, but rates were not different from those of cows in proestrus or in metestrus or anestrus. Pregnancy rates did not differ among treatments, but a tendency was detected for a treatment × lactation number interaction. In heifers and first-lactation cows, the G72 + TAI72 treatment produced fewer pregnancies, whereas G48 + TAI48 treatment was least efficacious in older cows. In a TAI protocol for previously inseminated dairy fe-males that are diagnosed not pregnant, subse-quent timed AI pregnancy rates are greater when females are in early diestrus, ovulate in response to the first GnRH injection, or both. (Key Words: Luteolysis, Ovsynch, Ovulation, en_US
dc.publisher Kansas State University. Agricultural Experiment Station and Cooperative Extension Service en_US
dc.relation.isPartOf Diary Day, 2006 en_US
dc.relation.isPartOf Kansas Agricultural Experiment Station contribution; no. 07-118-S en_US
dc.relation.isPartOf Report of progress (Kansas State University. Agricultural Experiment Station and Cooperative Extension Service); 965 en_US
dc.subject Dairy en_US
dc.subject Luteolysis en_US
dc.subject Ovsynch en_US
dc.subject Ovulation en_US
dc.subject Pregnancy rate en_US
dc.title Resynchronization of ovulation and conception in nonpregnant dairy cows and heifers en_US
dc.type Conference paper en_US 2006 en_US
dc.citation.epage 25 en_US
dc.citation.spage 22 en_US
dc.description.conference Dairy Day, 2006, Kansas State University, Manhattan, KS, 2006
dc.contributor.authoreid jss en_US

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