EFFECTS OF CONVENTIONAL OR BMR CORN SILAGE FED AT TWO LEVELS ON INTAKE, MILK YIELD AND COMPOSITION, AND RUMEN FERMENTATION OF HOLSTEIN DAIRY COW
Open Access
- Author:
- Edwards, Travis D.
- Graduate Program:
- Animal Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- August 29, 2008
- Committee Members:
- Gabriella Anne Varga, Thesis Advisor/Co-Advisor
Gabriella Anne Varga, Thesis Advisor/Co-Advisor
Arlyn Judson Heinrichs, Thesis Advisor/Co-Advisor
Chad Daniel Dechow, Thesis Advisor/Co-Advisor - Keywords:
- BMR
corn silage
milk yield - Abstract:
- The objectives of this study were to evaluate the effects of Brown Mid Rib (BMR) vs. conventional corn silage fed at two levels on production and rumen fermentation. Eight lactating (DIM=160; four rumen-cannulated) Holstein dairy cows were used in a replicated 4  4 Latin-Square design with 2  2 factorial dietary arrangement (silage type and level). The diets were formulated to contain either 35 or 50% of ration DM from corn silage, using conventional (CONV) and BMR genotype silage. The diets contained 16% CP, 34% NDF and 28% forage NDF; DM basis. Each experimental period was 14 d, 7 d adaptation and 7 d sampling period. Daily milk weights were collected, with sampling from four consecutive milkings the last two days of each period for components. Rumen samples were taken at set points over the last 24 hours of the sampling period. Intake was higher (level effect: P≤0.01) for cows consuming the 35% vs. 50% level of corn silage inclusion (28.2 vs. 26.4 kg/d). There was an interaction (P≤0.01) on DMI such that cows on the BMR silage maintained DMI (27.5 kg/d) on both levels of corn silage inclusion while those provided CONV reduced DMI (28.8 vs. 25.4 kg/d). Cows fed the BMR corn silage at 50% produced significantly more milk (corn silage type effect: P≤0.05) than cows fed the CONV hybrid at 50% (48.6 vs. 43.64 kg/d). Efficiency for converting feed to milk was greater (level effect: P≤0.05) for 50% vs. 35% inclusion rate (1.76 vs. 1.67, respectively)). Yields or percentages of milk fat, protein, and lactose were not significantly different across diets. Rumen pH and ammonia concentration were similar across treatments. No differences in VFA profiles were observed except that concentrations of isobutyrate and isovalerate were higher (corn silage type effect: P≤0.05) for cows fed CONV vs. BMR corn silage. Feeding BMR corn silage at 50% of ration DM did not affect DMI and maintained milk yield compared with CONV corn silage. Efficiency of converting feed to milk however was affected more by the level of corn silage inclusion in the ration than type of corn silage.