Effect of silage from a new brachytic corn hybrid with a high harvest index on feeding behavior and performance of lactating dairy cows

We compared the effects of silage from a tall-stature corn (TSC) hybrid with silage from a new short-stature corn (SSC) hybrid (due to a brachytic mutation) on DMI, feeding behavior, nutrient digestibility, and performance of lactating Holstein dairy cows. A total of 24 cows (12 per group) received identical diets for 2 wk and were then stratified according to BW, parity, DIM, and average milk production and randomly assigned to the TSC group or the SSC group. Data were collected for 70 d. Data from cows were analyzed as a completely randomized design using a mixed model procedure, and week of treatment was the repeated measure. The fixed-effects model included diet (D), week (W), and their first-order interaction (D × W), and each cow was considered a random effect. During the week before administering the experimental diets, cows in the TSC group (3.3 ± 1.5 lactations; 643 ± 61 kg BW; 85 ± 34 DIM; 47.1 ± 5.5 kg milk yield [MY]) and the SSC group (3.3 ± 1.7 lactations; 621 ± 45 kg BW; 82 ± 31 DIM; 47.1 ± 6.9 kg of MY) had similar characteristics. The 2 diets had the same CP, NDF, starch, and sugar content on a DM basis. The feeding behavior, rumination time, apparent nutrient digestibility, milk yield and composition, cheese yield traits, and BW were measured for 70 d. The SSC silage had greater NDF digestibility at 30 h (66.7% NDF vs. 60.6% NDF) and a greater level of starch (30.3% DM vs. 28.4% DM) than the TSC silage. These 2 differences corresponded to an increased energy content of the SSC silage (1.47 vs. 1.40 Mcal/kg DM as NEL at three maintenance levels). Analysis of feeding behaviors demonstrated that the SSC group had a lower DMI (25.0 vs. 26.8 kg DM/cow per day), greater meal frequency (8.3 vs. 7.4 meals/cow per day), and larger meal size (3.8 vs. 3.2 kg DM/meal). Cows in the SSC group also produced more milk (44.7 vs. 42.9 kg/cow per day) compared with TSC. The 2 groups had similar cheese yield traits. These results suggest that the brachytic corn hybrid has potential as an alternative source of high-energy corn silage for dairy farmers because it satisfies the energy requirements of lactating dairy cows and leads to improved milk production.