Effect of corn silage hybrids differing in starch and NDF digestibility on lactation performance and total tract nutrient digestibility by dairy cows

Abstract Text: The objective of this study was to determine the effect of feeding a TMR containing a floury-leafy corn silage hybrid (LFY) compared to a brown midrib corn silage hybrid (BMR) for intake, lactation performance and total tract nutrient digestibility in dairy cows. Ninety-six multiparous Holstein cows, 105 ± 31 DIM and 735 ± 18 kg of body weight at trial initiation, were stratified by DIM and randomly assigned to 12 pens of 8 cows each. Pens were randomly assigned to 1 of 2 treatments, BMR or LFY, in a completely-randomized design; a 2-wk covariate period with cows fed a common non-experimental diet followed by a 14-wk treatment period with cows fed their assigned treatment diet. Data were analyzed using Proc Mixed in SAS with covariate, treatment, period, and treatment x period interaction as Fixed effects and pen within treatment as a Random effect. Starch digestibilities, in situ, in vitro and in vivo, were 10-%, 6-% and 5-% units greater (P < 0.05), respectively, for LFY compared to BMR; however, the opposite was observed (P < 0.05) for NDF digestibility at wk 13 of treatment. Cows fed BMR consumed 1.7 kg/d more dry matter than LFY (P < 0.01); feed sorting was minimal and did not differ by treatment (P > 0.10). Although milk yield was greater (P < 0.01; 49.0 vs. 46.8 kg/d) and energy- and solids-corrected milk yields tended (P < 0.10) to be 1.5 kg/d greater for BMR than LFY, feed conversions (kg milk or component-corrected milk per kg DMI) did not differ (P > 0.10). Fat-corrected milk (50.3 kg/d on average) and milk fat yield (1.84 kg/d on average) were similar (P > 0.10), as milk fat content was greater (P < 0.01) for cows fed LFY (4.05%) than BMR (3.83%). Cows fed BMR had lower (P < 0.001) MUN concentration and greater (P < 0.05) milk protein and lactose yields compared to LFY. Body weight change and condition score were unaffected (P > 0.10) by treatment. Total tract starch digestibility was greater for cows fed the LFY corn silage, however, dry matter intake and milk and protein yields were greater for cows fed the BMR corn silage.

Keywords: corn silage, fiber, starch