title: Associations of insulin resistance later in lactation on fertility of dairy cows.
abstract: The challenge of getting dairy cows pregnant during early lactation is a well-described, worldwide problem. However, specifically in farms with poor reproductive, nutritional, and environmental conditions/management, a low pregnancy rate during early lactation is followed inevitably by an increased number of nonpregnant cows after 150 days in milk, with even more difficulties to achieve pregnancy. Therefore, several studies were designed to understand and develop strategies to mitigate reduced fertility of cows during late lactation. Experiments were performed under tropical regions to determine metabolic status during lactation and association of stage of lactation on oocyte quality and fertility. Lactating cows with extended days not pregnant (e.g.,>150 days in milk) often had systemic metabolic alterations, including development of peripheral insulin resistance and various oocyte alterations, including reduced expression of genes encoding glucose transport proteins, reduced amounts of mtDNA, increased expression of mitochondria-related genes, and increased expression of apoptosis-related genes. Additionally, in vitro embryo production and pregnancy per AI were lower in late- versus early-lactation cows in some but not all studies. Notwithstanding, when a normal embryo was transferred to a cow in late lactation, the pregnancy per transfer was reasonable, reinforcing the assertion that fertility problems in late-lactation cows may be associated with oocyte quality, fertilization, and/or failure of early embryo development. In conclusion, insulin resistance may reduce oocyte competence and consequently fertility in late-lactation dairy cows.
authors.affiliation: Department of Animal Reproduction, FMVZ-USP, São Paulo, São Paulo, Brazil. Electronic address: barusell@usp.br.
authors.forename: P S
authors.initials: PS
authors.lastname: Baruselli
authors.affiliation: Department of Animal Reproduction, FMVZ-USP, São Paulo, São Paulo, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Vieira
authors.affiliation: Department of Animal Reproduction, FMVZ-USP, São Paulo, São Paulo, Brazil.
authors.forename: M F
authors.initials: MF
authors.lastname: Sá Filho
authors.affiliation: Department of Animal Reproduction, FMVZ-USP, São Paulo, São Paulo, Brazil.
authors.forename: R D
authors.initials: RD
authors.lastname: Mingoti
authors.affiliation: Department of Animal Reproduction, FMVZ-USP, São Paulo, São Paulo, Brazil.
authors.forename: R M
authors.initials: RM
authors.lastname: Ferreira
authors.affiliation: Department of Genetics and Evolution, CCBS, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
authors.forename: M R
authors.initials: MR
authors.lastname: Chiaratti
authors.affiliation: Department of Animal Science, ESALQ-USP, Piracicaba, São Paulo, Brazil.
authors.forename: L H
authors.initials: LH
authors.lastname: Oliveira
authors.affiliation: Department of Veterinary Medicine (DMV), Federal University of Lavras, Lavras, Minas Gerais, Brazil.
authors.forename: J N
authors.initials: JN
authors.lastname: Sales
authors.affiliation: Department of Animal Science, ESALQ-USP, Piracicaba, São Paulo, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Sartori
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000502:physiology*; D007333:Insulin Resistance / Q000502:physiology*; D007774:Lactation / Q000502:physiology*; D011247:Pregnancy
keywords: Cattle; Days open; Metabolic disorder; Oocyte competence; Reproduction