Department of Animal Science
Date of this Version
Fall 12-2-2015
Citation
Garcia Gomez,G. 2015. Efficiency of energy utilization and fecal mineral excretion in Holstein and Jersey dairy cows. Master thesis of Animal Science UNL.
Abstract
Eight multiparous Holstein and 8 Jersey dairy cows were used to complete energy balance trials designed to determine the effect of breed on the production and energy efficiency of milk, and energy partitioning. A repeated switchback design was used to compare the effect of cow breed. Diets consisted of 24.5% corn silage, 18.4% alfalfa hay, 6.9% grass hay, with either 22.9% rolled corn and 14.8% soybean meal (CON) or 8.95% rolled corn and 28.8% reduced fat distillers grains (RFDDGS) DM-basis. Diets were offered ad libitum for a 28 d adaptation period and 95% ad libitum for a 4 d collection period. During the collection days, nutrient digestibility and energy use was measured; indirect calorimeter respiration head boxes were used to determine heat production. Across diets, Holstein had a lesser (P < 0.01) DMI as a proportion of BW than Jersey cows (3.54 vs. 4.22 ± 0.13 DMI % BW, respectively). Milk protein (3.76 % vs. 3.21% ± 0.11 for Jersey and Holstein, respectively; P < 0.01), and fat (4.97 % and 3.70 % ± 0.19 for Jersey and Holstein, respectively; P < 0.01) concentration increased with Jersey compared with Holstein cows. Nevertheless, yield of ECM per unit of DM consumed was not affected by breed and averaged 1.58 ± 0.05 kg/kg of DMI (P = 0.50). The milk energy output per kg of DMI, per kg of BW0.75, and as a proportion of GEI did not differ between breeds (P = 0.47). However, Jersey cows had a greater fecal energy output per kg of DMI, per kg BW0.75, and as proportion of GEI (P = 0.03). Consequently, ME as a proportion of GEI of Holstein was greater than that of Jersey cows (59.1 vs. 55.4 ± 0.65% for Holstein and Jersey, respectively; P < 0.01). Milk energy output as a proportion of ME was not affected by breed and averaged 47.0 ± 1.84 % of ME. Results from this study suggest that breed had no effect on any of the dairy efficiency variables measured.
Advisor: Paul J. Kononoff
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professor Paul J. Kononoff. Lincoln, Nebraska: December, 2015
Copyright (c) 2015 Gabriel Garcia Gomez