title: Influence of postpartum weight and body condition change on duration of anestrus by undernourished suckled beef heifers.
abstract: Two experiments were conducted to determine the relationship between change in weight and body condition on postpartum interval of thin first-calf beef heifers. Twenty-nine (Exp. I) and 36 (Exp. II) Angus and Angus-sired crossbred heifers were limit-fed to reduce their condition score (BCS) to 4 (scale of 1 to 9) at calving. After calving, heifers were assigned to one of four daily ME intakes (range of 198 to 305 kcal ME/kg BW.75) designed to create a range of BCS changes. Each unit change in BCS was associated (R2 = .72; P < .0001) with a 33-kg weight change. Mean postpartum interval (PPI) from calving to initiation of luteal activity was 121 +/- 6.0 d. As dietary energy density increased, PPI decreased (P < .01). Condition score at calving (CCS) accounted for a greater proportion of the variation (R2 = .37) associated with PPI than did condition score change from calving to d 90 postpartum (CSCH90; R2 = .27) or weight change from calving to d 90 postpartum (WTCH90; R2 = .17). The "best fit" equation (R2 = .56) for predicting PPI included CCS and CSCH90: PPI = 244.5 - 28.28(CCS) - 23.07(CSCH90) + 6.36(CSCH90(2)). Maximum reduction in PPI occurred when heifers gained 1.8 units of BCS during the first 90 d of lactation. Gaining BCS at a faster rate was of no additional benefit.
authors.affiliation: Department of Animal Science, University of Missouri, Columbia 65211, USA.
authors.forename: D L
authors.initials: DL
authors.lastname: Lalman
authors.forename: D H
authors.initials: DH
authors.lastname: Keisler
authors.forename: J E
authors.initials: JE
authors.lastname: Williams
authors.forename: E J
authors.initials: EJ
authors.lastname: Scholljegerdes
authors.forename: D M
authors.initials: DM
authors.lastname: Mallett
mesh_terms: D000375:Aging / Q000378:metabolism / Q000502:physiology; D000780:Anestrus / Q000502:physiology*; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight / Q000502:physiology*; D002417:Cattle; D002418:Cattle Diseases / Q000378:metabolism / Q000503:physiopathology*; D004032:Diet / Q000662:veterinary; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D007774:Lactation / Q000502:physiology*; D009748:Nutrition Disorders / Q000378:metabolism / Q000503:physiopathology / Q000662:veterinary*; D049590:Postpartum Period / Q000502:physiology*; D011897:Random Allocation; D012044:Regression Analysis