This is a draft schedule. Presentation dates, times and locations may be subject to change.
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Effects of Protein Supplementation with Low to Medium Quality Forage on Reproductive Parameters in Beef Heifers in Early Pregnancy.
Effects of Protein Supplementation with Low to Medium Quality Forage on Reproductive Parameters in Beef Heifers in Early Pregnancy.
Wednesday, July 12, 2017
Exhibit Hall (Baltimore Convention Center)
A 2-yr study was conducted to investigate the effects of protein supplementation in low to medium quality forage diets on reproductive parameters during early pregnancy (-7 d to 30 d from TAI; d 0) in yearling beef heifers. Angus, Hereford, and Angus-cross yearling beef heifers (402 ± 42 kg initial BW; n=79) were stratified by initial BW and BCS and randomly assigned to 1 of 4 supplemental treatments. Supplements were formulated to provide similar CP intake; 1) low-fat dried corn distillers grain (LDG, 7.4% fat; 0.8% BW); 2) high-fat dried corn distillers grains (HDG, 9.5% fat; 0.8% BW); 3) cottonseed meal (CSM, 2.2% fat; 0.4% BW) and 4) no supplementation (CON). The basal diet consisted of low to medium quality chopped grass hay (8% CP; 55% NDF yr 1 and 70% NDF yr 2) fed ad libitum twice daily. Supplements were fed once daily and individual intakes were recorded. Diameter of dominant follicles was measured at TAI via transrectal ultrasonography. Beginning on d 2, blood samples were collected thrice weekly (MWF) to determine plasma progesterone (P4) 4 h after supplementation. Diameter of corpora lutea (CL) was measured on d 13 and 14 after TAI at the same time as Doppler ultrasound analysis of vasculature within the ovarian hilus. Supplemented heifers had greater (P ≤ 0.0001) total DMI than CON heifers. Total CP intake was greater (P ≤ 0.0001) for HDG and LDG compared to CON and CSM was intermediate. Follicles from LDG heifers tended (P = 0.06) to be larger than CSM and CON heifers, but did not differ (P = 0.41) from heifers fed HDG. However, CL diameter and plasma P4 did not differ among treatments (P ≥ 0.26). Ovarian hemodynamics (Pulsatility and Resistance Indices) did not differ (P ≥ 0.35) among treatments and conception rates at d 30 post TAI did not differ (P = 0.98) among treatments (overall 56%). Supplementing heifers with HDG, LDG, or CSM did not influence reproductive measures such as plasma P4, CL diameter, or ovarian hilus vascular resistance when compared with CON.