Submitted to: Journal of Dairy Science
Publication Type: Abstract only
Publication Acceptance Date: 7/9/2007
Publication Date: 7/9/2007
Citation: Krizsan, S.J., Broderick, G.A., Muck, R.E., Promkot, C., Colombini, S., Randby, A.T. 2007. Effect of alfalfa silage storage structure and roasting corn on production and ruminal metabolism of lactating dairy cows [abstract]. Journal of Dairy Science. 90 (supplement 1):345. Interpretive Summary:
Technical Abstract: The objective of this study was to determine if feeding roasted corn as principal concentrate source, would improve production and nutrient utilization when supplemented to lactating cows fed one of 3 different alfalfa silages (AS). Forty-two lactating Holstein cows (6 fitted with ruminal cannulas) averaging 77 DIM and producing 43 kg milk/d pretrial were assigned to 2 cyclic change-over designs. Treatments were AS, ensiled in bag, bunker, or O2-limiting tower silo supplemented with ground shelled corn (GSC) or roasted GSC (RGSC). Experimental diets contained 40% AS, 15% corn silage and 35% of either GSC or RGSC on DM basis. No significant interactions between AS and corn sources were detected for any production trait. Although chemical composition of the 3 AS was similar, feeding AS from the O2-limiting tower silo elicited positive production responses (P<0.01). Yields of 3.5% FCM and fat were increased 1.7 kg/d and 150 g/d, and milk fat content was increased 0.3%, when cows were fed diets based on AS from the O2-limiting silo compared with the other 2 AS. The responses in milk fat were paralleled by an average increase in ADF digestibility of 270 g/d for cows fed AS from the O2-limiting silo. However, ruminal concentrations of lipogenic VFA were unchanged with AS source. Cows fed RGSC consumed 0.6 kg/d more DM and yielded 30 g/d more protein and 50 g/d more lactose than cows fed GSC diets (P=0.02). There was no evidence of increased total tract digestibility of OM or starch, or reduced ruminal NH3 concentration, when feeding RGSC. Free AA increased, and isovalerate decreased in rumen fluid from cows fed RGSC diets (P<0.01). However, responses in production with roasted corn were mainly due to increased DMI, which increased the supply of energy and nutrients available for synthesis of milk and milk components.