title: The concurrent and carry over effects of long term changes in energy intake before insemination on pregnancy per artificial insemination in heifers.
abstract: Follicle development in a period of negative energy balance (NEB), as experienced by the postpartum dairy cow, could be affected by undesirable metabolic changes, and may contain a developmentally incompetent oocyte with an impaired potential to establish a pregnancy. A differential feeding model in heifers was developed to evaluate the concurrent and carryover effects of reduced energy intake before insemination on pregnancy per artificial insemination (P/AI). Heifers were randomly assigned to either (i) control feed intake group (CF), n=68, 1.3 times estimated maintenance energy (M) requirements for 50 days and 2.0 M for 83 days or (ii) restricted feed intake (RF), n=88, 0.65 M for 50 days and 2.0 M for 83 days. Pregnancy per AI was determined by transrectal ultrasonography at day 30 following AI. Despite significant loss of live weight (LW; 5.8±2.1 vs 70.5±2.8 kg, respectively) and body condition score (BCS; 0.05±0.03 vs 0.45±0.03) and a significant elevation in systemic concentrations of non-esterified fatty acids in RF heifers, there was no concurrent effect on P/AI (69 vs 72%) following AI at day 50. However, there was a carryover effect on P/AI as there was an 18 percentage point difference (64 vs 82%) between CF and RF heifers following AI on day 93. The results of the study indicate that a reduction in energy intake for a 50-day period pre-insemination had no concurrent effect but had a positive carryover effect on P/AI.
authors.affiliation: Animal & Grassland Research & Innovation Centre, Teagasc, Mellows Campus, Athenry, Co. Galway, Ireland; School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: M H
authors.initials: MH
authors.lastname: Parr
authors.affiliation: School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: M A
authors.initials: MA
authors.lastname: Crowe
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Lonergan
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: A C O
authors.initials: AC
authors.lastname: Evans
authors.affiliation: School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: T
authors.initials: T
authors.lastname: Fair
authors.affiliation: Animal & Grassland Research & Innovation Centre, Teagasc, Mellows Campus, Athenry, Co. Galway, Ireland. Electronic address: Michael.Diskin@teagasc.ie.
authors.forename: M G
authors.initials: MG
authors.lastname: Diskin
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D002149:Energy Intake / Q000502:physiology*; D004973:Estrus Synchronization; D005260:Female; D007315:Insemination, Artificial / Q000662:veterinary*; D011247:Pregnancy; D018873:Pregnancy Rate; D013997:Time Factors
keywords: Heifers; Negative energy balance; Pregnancy per insemination