title: Factors affecting success of embryo collection and transfer in large dairy herds.
abstract: Our objective was to evaluate factors that affected the success of embryo transfer programs in large dairy herds. Non-lactating donor cows produced a larger number of ova/embryos (P<0.01) and viable embryos (P<0.01) than lactating cows. The interaction between season and donor class was correlated with the proportion of ova/embryos classified as fertilized (P=0.03), because lactating donors had fewer fertilized ova in the summer. There was no correlation between 305-day mature equivalent milk yield and response to superstimulation. Although the interval between superstimulation protocols was correlated with the number of ova/embryos (P=0.03), there was no correlation with the number of viable embryos. Pregnancy per embryo transfer (P/ET) in heifer recipients was correlated with embryo quality grade (P<0.01), season (P=0.04), and whether embryos were fresh or frozen/thawed (P<0.01). Lactating recipient cows tended to have a lower rate of P/ET during the summer (P=0.12 to P=0.08). Synchronization protocols tended to be (P=0.06; Herd 1) or were (P=0.02; Herd 2) correlated with P/ET. Lactating cows receiving vitrified IVF embryos had a lower (P=0.01) P/ET than those receiving fresh IVF embryos, especially in the summer (P=0.09). Milk yield was not correlated with P/ET. The use of heat abatement systems is critical to improve embryo production and P/ET. Synchronization protocols that optimized synchrony of ovulation may increase fertility of recipient cows and eliminate the need for estrous detection.
authors.affiliation: Veterinary Medicine Cooperative Extension, University of California Davis, Tulare, CA 93274, USA. rchebel@vmtrc.ucdavis.edu
authors.forename: R C
authors.initials: RC
authors.lastname: Chebel
authors.forename: D G B
authors.initials: DG
authors.lastname: Demétrio
authors.forename: J
authors.initials: J
authors.lastname: Metzger
mesh_terms: D000818:Animals; D002140:California; D002417:Cattle / Q000502:physiology*; D004624:Embryo Transfer / Q000592:standards / Q000662:veterinary*; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary*; D016015:Logistic Models; D008297:Male; D018587:Oocyte Donation / Q000662:veterinary*; D011247:Pregnancy; D012189:Retrospective Studies; D012621:Seasons; D013023:South Dakota