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Variables Associated with Peripartum Traits in Dairy Cows. VII. Hormones, Calf Traits and Subsequent Milk Yield¹

Purdue University⁶, West Lafayette, IN 47907

Abstract

Independent effects of certain partum and peripartum traits on subsequent milk yields (Y) during days 1 to 27 (Y₂₇), 28 to 60 (Y₆₀) and 1 to 200 (Y₂₀₀) of lactation were estimated from data on 167 Holstein cows and first-calf heifers. The variables were health status, calf sex and covariates (linear, quadratic and cubic) of calf birth weight (CBW), cow age (CA), month of calving code (season) and the peripartum blood plasma concentrations (means of three samples taken from 48 hr prepartum to within 2 hr postpartum) of prolactin (PRL), progesterone (P₄), estrone (E₁), estradiol-17β (Eβ) and estradiol-17 (E). Except for Y₂₀₀ values, the measures of milk yield were positively correlated (P<.01) with each other and with CA, CBW, plasma PRL and plasma Eβ. Plasma PRL, Eβ and E₁ were positively correlated with each other and with CA (PRL and Eβ) and CBW (E₁ and Eβ). Covariates prominently and independently related to increases in Y were CA, CBW and plasma PRL (P<.01). Predicted Y₂₇, Y₆₀ and Y₂₀₀, calculated with equations of the cubic model, increased by 12.4, 6.5 and 3.7%, respectively, between CBW of 37 and 50 kg, and by 16.6, 15.9 and 14.8% between plasma PRL concentrations of 50 and 195 ng/ml. Season of calving, calf sex and health status were associated with changes in Y₂₇ but not Y₆₀ or Y₂₀₀. Within the health status group, only infectious disorders (metritis or mastitis) decreased (P<.025) milk yield adjusted for CA and cow weight (adjusted Y₆₀ and Y₂₀₀). Among all other cows, including those with dystocia alone, adjusted yields were increased by heavier calves (P<.07, Y₆₀), high plasma PRL (P<.025, Y₆₀) and below average plasma E₁ (P<.025, Y₂₀₀). It may be practical to increase milk yield by providing supplemental light prepartum to increase plasma PRL and by selecting sires to maintain CBW above average.

¹ Journal Paper No. 7812, Purdue Univ., Agr. Exp. Sta. A contribution to NC-113 entitled, "Methods for Improvement of Fertility in Cows Postpartum." This research was supported in part by a grant from the Indiana Farm Bureau Cooperative Association, Inc.

² 3300 Carpenter Rd. S.E., #85, Olympia, WA 98503.

³ Dept. of Anim. Sci., Washington State Univ., Pullman 99164.

⁴ 5006 Tamarisk Lane, Bellaire, TX 77401.

⁵ Dept. of Physiol., School of Med., Univ. of New Mexico, Albuquerque 87131.

⁶ A contribution from the Dept. of Anim. Sci.