Date of Award
Master of Science
Three experiments were conducted to determine the effects of feed additives on the performance, energy digestibility, and body composition of first-cycle laying hens fed two concentrations of dietary energy. The first and second experiments were 8 wk in duration. The first experiment contained two dietary energy levels (2,750 and 2,850 kcal/kg) with or without the addition of a mannose rich fraction (MRF) from a specific strain of yeast. As expected, no differences in performance parameters including egg production, egg weight, and egg mass were detected, although increased dietary energy, but not MRF resulted in increased total and percentage of hen fat mass as determined by DXA analysis. A similar response to dietary energy was observed for abdominal fat pad weight, but significance was not achieved (p = 0.12). Mannose rich fraction treatment increased nitrogen corrected apparent metabolizable energy (AMEn) but the increased dietary energy did not appear to be stored as increased fat within the hen. The second experiment contained the same two dietary energy levels (2,750 and 2,850 kcal/kg) with or without the addition of an Aspergillus niger derived product created from solid-state fermentation (SSF) containing various enzyme activities. There was a significant SSF by dietary energy interaction (p = 0.02) on fat mass of hens in which reduced dietary energy without SSF resulted in reduced fat mass, but reduced dietary energy with SSF resulted in increased fat mass. Both dietary energy and SSF resulted in a significant (p < 0.01) increase in AMEn. Again, no differences in performance parameters including egg production, egg weight, and egg mass were detected in experiment 2. In these two 8 wk experiments, laying hen performance parameters were unaffected, despite, significant differences in body composition and dietary AMEn suggesting that short term performance is a poor indicator of energy and feed additive status The third experiment was 16 wk and hens were fed two concentrations of dietary energy (2,850 and 2,950 kcal/kg) with three SSF inclusions (0%, 0.2%, and 0.4%). A significant effect of SSF on HDEP (p ¡Ü 0.01) was seen in which the 200 SSF and 400 SSF fed birds resulted in a 1% decrease in egg production compared to the control hens. The solid-state fermentation product had a significant (p = 0.02) effect on egg mass in which birds fed the 200 SSF and 400 SSF diets produced 1 g less egg mass than the control hens (due to lower egg production and not egg weight). The solid-state fermentation product also had a significant (p = 0.02) effect on feed efficiency in which laying hens fed the 200 SSF diet consumed 9 g/kg more feed to produce an egg than the control hens. There were significant (p ¡Ü 0.01) effects of dietary energy on 16 wk fat mass and AFP in which the high energy (HE) fed birds contained more fat than the low energy (LE) fed birds. There was a significant (p ¡Ü 0.01) interaction of energy and SSF in which the 0.2% SSF treatment resulted in the highest AMEn in the high energy diet, but the 0.4% SSF treatment resulted in the highest AMEn in the lower energy diet. During the 16 wk experiment SSF treatment improved AMEn, but negatively impacted egg production, and did not influence body composition.
Gareis, Alysha, "Effects of two feed additives on performance, energy digestibility, and body composition of first-cycle laying hens fed two concentrations of dietary energy" (2014). Graduate Theses and Dissertations. 14138.