Short communication: Does previous superovulation affect fertility in dairy heifers?

Autor:	Fernandes CAC; Universidade José do Rosário Vellano, Alfenas, MG, Brazil 37130-000; Biotran Biotecnologia, Alfenas, MG, Brazil 37130-000. Electronic address: carlos@biotran.com.br., Pereira GHS; Universidade José do Rosário Vellano, Alfenas, MG, Brazil 37130-000., Siqueira LGB; Embrapa Gado de Leite, Juiz de Fora, MG, Brazil 36038-330., Neri HLDH; Biotran Biotecnologia, Alfenas, MG, Brazil 37130-000., Viana JHM; Embrapa Recursos Genéticos e Biotecnologia, Brasília, DF, Brazil 70770-917., Palhao MP; Universidade José do Rosário Vellano, Alfenas, MG, Brazil 37130-000., Teodoro RAS; Universidade José do Rosário Vellano, Alfenas, MG, Brazil 37130-000.
Jazyk:	angličtina
Zdroj:	Journal of dairy science [J Dairy Sci] 2020 Nov; Vol. 103 (11), pp. 10862-10866. Date of Electronic Publication: 2020 Sep 10.
DOI:	10.3168/jds.2020-18386
Abstrakt:	The aim of this study was to evaluate the potential negative effects of superovulation on subsequent fertility of dairy heifers. Holstein heifers (n = 1,783), 312 to 387 d of age, and 273 to 307 kg of body weight (BW) from 2 commercial farms were enrolled. These animals were first selected to be donors (446) or nondonors (CON, n = 1,327) according to their genomic values. Nondonor heifers (CON) were artificially inseminated (AI) according to standard procedures of each farm after reaching 320 kg of BW. Donor heifers were superovulated using a fixed FSH dose (180 mg NIH-FSH-P1; Folltropin-V, Vetoquinol Brasil, Mairiporã, SP, Brazil) and embryos were collected following standard procedures. Heifers that produced fewer than 8 viable embryos after first superovulation (SOV1, n = 337) were no longer used as donors, whereas the remaining heifers (SOV2, n = 109) were superovulated a second time within an interval of 48 to 54 d. Donor heifers (SOV1 and SOV2) were AI once they reached 320 kg of BW, at least 15 d after the last embryo collection. Data on age at first AI, at conception, and at parturition, as well as the number of services per conception, were analyzed by ANOVA, using the PROC MIXED procedure of SAS (SAS Institute Inc., Cary, NC) procedure. Binomial variables (pregnancy per AI, overall pregnancy rate, open heifers at 500 d age, and late pregnancy loss) were analyzed using the GLIMMIX procedure of SAS. The heifers selected to undergo superovulation twice (SOV2) yielded more total (12.6 ± 5.3 vs. 6.8 ± 4.6; respectively) and viable embryos (8.5 ± 3.8 vs. 3.9 ± 2.8; respectively) than those superovulated only once (SOV1). Age at first AI, conception, and at parturition was greater in SOV2, but not in SOV1 compared with nondonor controls. In addition, pregnancy per first AI, overall pregnancy rate, services per conception, open heifers at 500 d of age, and occurrence of pregnancy losses after 60 d of gestation were similar among CON, SOV1, and SOV2 heifers. In summary, a single superovulation performed before heifers reach a minimum weight for breeding did not affect age at conception, calving or other indicators of reproductive efficiency. On the other hand, heifers superovulated twice were first inseminated at a later age than their birth cohorts, but had similar reproductive performance. (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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