Effects of supplement type on performance, reproductive, and physiological responses of Brahman-crossbred females

¹ University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865; University of Florida - Animal Sciences, Gainesville 32611
² University of Florida - IFAS, Range Cattle Research and Education Center, Ona 33865
³ University of Florida - Animal Sciences, Gainesville 32611
⁴ University of Minnesota - North Central Research and Outreach Center, Grand Rapids 55744

^* To whom correspondence should be addressed. E-mail: jdarthington{at}ifas.ufl.edu.

	Abstract

Two experiments were conducted to compare the performance and physiological responses of forage-fed beef females supplemented with either a molasses-based (ML) or a citrus pulp-based (CT) supplement. In Exp. 1, BW gain, reproductive performance, and concentrations of blood urea nitrogen (BUN), plasma glucose, insulin, IGF-I, and progesterone (P4) were assessed in 60 Brahman x Angus heifers supplemented 3 times weekly with either ML or CT. Supplement intakes were formulated to be iso-caloric and iso-nitrogenous. Reproductive performance was not affected by treatments, but mean BW gain was greater (P < 0.01) for heifers fed CT than for those fed ML (0.40 vs. 0.30 kg/d). Mean plasma concentrations of glucose, insulin, and IGF-I were greater (P < 0.05) for heifers fed CT, whereas BUN was greater (P < 0.05) for heifers fed ML. Mean plasma P4 concentration did not differ between treatments, but both groups had lower plasma P4 concentrations during days that supplements were offered (P < 0.01). In Exp. 2, forage DMI and concentrations of BUN, plasma glucose, insulin, IGF-I, and P4 were assessed in 24 Brahman x British mature cows supplemented with the same treatments described in Exp. 1. Overall forage DMI did not differ between treatments, but a day effect and a treatment x day interaction were detected (P < 0.05). Both groups consumed less forage during the days that supplements were offered (P < 0.01), and forage DMI for cows fed CT was less (P < 0.05) than for cows fed ML during these days. No differences were detected in any blood or plasma measurement. In addition, no differences in concentrations of P4 were detected between CT and ML-fed cows. We concluded that CT-supplemented heifers had greater BW gain compared to ML-supplemented heifers, but no differences in reproductive performance were observed. We also observed that CT-supplemented cows had a greater variability in forage DMI compared to ML-supplemented cows.

Key Words: Heifer growth, Pregnancy, Supplementation

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