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Productive and reproductive responses of dairy cattle to supplemental lipid and escape protein
Abstract
One hypothesis tested in the first experiment was that supplemental rumen inert fat to increase the dietary energy density would reduce length of postpartum negative energy balance (NEB), thereby reducing the interval to reinitiation of ovarian cyclicity and increasing milk yield, milk fat concentration, and luteal phase secretion of progesterone (P$\sb4$). The second hypothesis tested was that initiation of feeding supplemental fat at 4 wk postpartum would be as beneficial as starting at parturition. Increased peak and luteal phase P$\sb4$ concentrations in plasma were observed throughout the first two ovulatory cycles for cow fed calcium salts of fatty acids (CaFA). However, dry matter intake (DMI) and net EB were higher in the control group than the group fed CaFA. There were subtle changes in conception rate and other reproductive activities. Initiating the feeding of supplemental fat at 4 wk postpartum, compared with starting at parturition, enhanced DMI as a percentage of bodyweight. The hypothesis tested in the second experiment was that supplemental rumen inert fat would increase plasma P$\sb4$ concentrations in pregnant cows with functional corpora lutea even though cows were in positive EB. Feeding CaFA to the pregnant cows (130 $\pm$ 14 d of gestation) had no affect on P$\sb4$ concentrations. The hypothesis tested in the third experiment was that dietary supplementation with tallow and/or escape protein would reduce postpartum interval to first ovulation and promote higher P$\sb4$ concentration, reproductive performance, and lactational performance. The mean DMI and NEB were higher in low fat vs high fat and low escape vs high escape dietary groups during the experimental period. Total plasma concentration of cholesterol was higher in high fat vs low fat cows. Diets did not have a consistent effect on P$\sb4$ and 17-$\beta$ Estradiol concentrations in plasma during the first two ovulatory cycles. However, conception rate at first insemination was the greatest in high fat-high escape cows. In vitro data indicate that bovine luteal cells require serum cholesterol for P$\sb4$ synthesis. However, different serum cholesterol concentrations resulting from feeding diets differing in fat and escape protein did not alter the rate of in vitro P$\sb4$ synthesis in this study. The present study indicates that feeding supplemental fat did not enhance the NEB in early lactation, but did enhance ovarian steroids by which reproductive activities are varied.
Subject Area
Livestock|Anatomy & physiology|Animals
Recommended Citation
Son, Jung-Ho, "Productive and reproductive responses of dairy cattle to supplemental lipid and escape protein" (1995). ETD collection for University of Nebraska-Lincoln. AAI9528835.
https://digitalcommons.unl.edu/dissertations/AAI9528835