Effect of brachytic2 mutation in corn silage on performance and total-tract digestibility by lactating Holstein dairy cows.

Short-stature corn hybrids carrying the brachytic2 (br2) mutation have greater standability and have grain yields similar to conventional tall hybrids; thus, they are promising for grain production. Our objective was to determine if short hybrids would also be valuable as sources of silage for lactating cows. We compared corn silages (CS) from 3 novel short hybrids (SH-1,2,3) to CS from tall (Tall) and bm3 (BMR) hybrids for their effects on DMI, milk production, and total-tract nutrient digestibility. Twenty primiparous and 20 multiparous Holstein cows (150 ± 42 DIM, 35 ± 6.4 kg of milk/d, 674 ± 103 kg of BW; mean ± SD) were enrolled in an incomplete Latin square design with three 21-d experimental periods, balanced for carryover effects. Cows were fed diets with a blend of all CS for a 14-d preliminary period, and then experimental diets for 63 d. Experimental diets contained CS from Tall, BMR, SH1, SH2, or SH3, along with alfalfa silage, soybean meal, soybean hulls, ground corn, and a premix of protein, minerals, and vitamins. All diets were formulated for 18% CP and 24% forage NDF (forNDF) and fed as TMR. Data were analyzed using PROC GLIMMIX of SAS 9.4. Preplanned contrasts were Tall versus Short (Tall vs. SH-1,2,3) and BMR versus Short (BMR vs. SH-1,2,3). Compared with cows fed the diet with Tall, cows fed Short CS produced more milk, protein, and lactose, but their milk had a lower fat percentage, and ECM yield was not different. Compared with cows fed BMR CS, cows fed Short CS had greater DMI and yields of ECM, milk, protein, and lactose, but lower fat percentage, ECM/DMI, and BCS gain. Apparent total-tract digestibilities of OM, starch, and CP, but not NDF, were lower in cows fed BMR CS than those fed short hybrids. We conclude that short corn hybrids could be valuable sources of silage on dairy farms. Further studies in other growing environmental conditions seem warranted.