title: Milk Production and Fertility in Cattle.
abstract: Evolutionary biology provides reasons for why the intensive selection for milk production reduces reproductive success rates. There is considerable exploitable genetic variation in reproductive performance in both dairy and beef cattle, and examination of national genetic trends demonstrates that genetic gain for both reproductive performance and milk production is possible in a well-structured breeding program. Reproductive failure is often postulated to be a consequence of the greater negative energy balance associated with the genetic selection for increased milk production. However, experimental results indicate that the majority of the decline in reproductive performance cannot be attributed to early lactation energy balance, per se; reproductive success will, therefore, not be greatly improved by nutritional interventions aimed at reducing the extent of negative energy balance. Modeling can aid in better pinpointing the key physiological components governing reproductive success and, also, the impact of individual improvements on overall fertility, helping to prioritize variables for inclusion in breeding programs.
authors.affiliation: Animal & Grassland Research and Innovation Center, Teagasc, Moorepark, County Cork, Ireland; email: donagh.berry@teagasc.ie.
authors.forename: D P
authors.initials: DP
authors.lastname: Berry
authors.affiliation: INRA and.|AgroParisTech, UMR0791 Modélisation Systémique Appliqué aux Ruminants, 75231 Paris, France; email: nicolas.friggens@agroparistech.fr.
authors.forename: N C
authors.initials: NC
authors.lastname: Friggens
authors.affiliation: Division of Animal Science, University of Missouri, Columbia, Missouri 65211; email: LucyM@missouri.edu.
authors.forename: M
authors.initials: M
authors.lastname: Lucy
authors.affiliation: DairyNZ Ltd., Hamilton 3240, New Zealand; email: John.Roche@dairynz.co.nz.
authors.forename: J R
authors.initials: JR
authors.lastname: Roche
mesh_terms: D000818:Animals; D001947:Breeding; D002417:Cattle / Q000502:physiology*; D003612:Dairying; D004734:Energy Metabolism; D005260:Female; D005298:Fertility / Q000235:genetics*; D014644:Genetic Variation; D007774:Lactation; D008892:Milk / Q000378:metabolism*; D012098:Reproduction / Q000235:genetics*; D012106:Research
keywords: beef; dairy; genetics; nutrition; reproduction