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Modulation of Luteal Activity in Postpartum Beef Cows through Changes in Dietary Lipid¹

Texas Agricultural Experiment Station^2,3,, Beeville 78102

Abstract

Studies were conducted to evaluate the normal changes in lipid metabolism occurring in the suckled Brahman crossbred female during the postpartum period (Exp. 1) and to examine the function of induced corpora lutea (CL) in postpartum cows fed diets with normal (2.8%) lipid or elevated (8%) lipid content (Exp. 2). Multiparous and primiparous females (n = 20), maintained on pasture without energy or protein supplementation, were used in Exp. 1. A linear increase (P < .001) in plasma lipid metabolites was observed between the 1st and 8th wk after calving, reaching a plateau of 221 ± 18.3 and 74 ± 3.4 mg/dl for total cholesterol and triglycerides, respectively. Seventy percent of all postpartum females exhibited luteal activity within 50 d ( = 34.7 d), and 59% of these animals exhibited short luteal phases (<12 d). In Exp. 2, primiparous and multiparous females (n = 32) were assigned to receive a control (n = 16) or high-lipid (HL) diet (n = 16; 30% whole cottonseed) between d 1 and d 38 after calving. The HL diet increased (P < .001) total cholesterol and triglycerides 1.7- and 1.4-fold, respectively, relative to controls, and increased (P < .05) the spontaneous occurrence of low-level progesterone elevations. Forty-eight-hour calf removal and gonadotropin-releasing hormone (GnRH; .22 mg/kg BW i.v.) were employed between d 21 and 26 after calving to induce ovulations. Mean concentrations of progesterone in the HL group were markedly higher (P < .01) than in controls between d 5 and 8 of the induced cycle, and average lifespan of induced CL was approximately twice that of controls (P < .01).

¹ Texas Agric. Exp. Sta. Journal Article No. 23763. Contribution to Regional Project W-112, Reproductive Performance in Domestic Ruminants.

² Beef Cattle Reprod. Lab., The Texas A&M University System.

³ The assistance of D. Jackson, J. Perez, H. Garcia, D. Walker, D. Richardson and W. McVey, Jr. is gratefully acknowledged.

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