Replacing corn with soyhulls for late-lactation cows fed high-forage diets
The objective was to evaluate performance of 48 late-lactation multiparous Holstein cows (27.6 ± 5.90 kg milk/d, 280 ± 79 DIM) fed rations gradually substituting ground corn (C) with soyhull pellets (SH). Treatments contained 17.4% of dietary DM as C, no SH (C100:SH0); 11.6% C, 5.8% SH (C67:SH33); 5.8% C, 11.6% SH (C33:SH67), and no C, 17.4% SH (C0:SH100). Other dietary ingredients remained similar in all treatments: bermudagrass hay (6.3%, diet DM), corn silage (56%), soybean meal (15.3%), urea (0.5%), calcium carbonate (0.5%), mineral (2.5%), salt (0.5%), and yeast (1%). Fixed ingredients except forages were premixed weekly. Treatments were mixed and offered once daily as TMR. Refusals were weighed and removed before next day feeding. Cows were randomly assigned to treatments for 7 weeks following a 2-week standardization period. Intake and milk yield were recorded daily. Milk samples were collected from one 48-h collection period (2 milkings/d) during pretrial and three collection periods during trial. Milk samples were analyzed for fat, protein, SNF, MUN and SCC. Body weights and body condition scores were recorded at the beginning and end of the experimental period. Two cows were removed before the end of the study because of mastitis (treatments C100:SH0 and C0:SH100). Means were analyzed using Mixed procedures (SAS, version 9.3) for main effects of treatment and contrasts were set to test for linear, quadratic and cubic effects of levels of soyhulls substitution for corn. Treatment diets contained 56.5% ± 0.2% DM, 17.0% ± 0.2% CP, 0.91% ± 0.04% Ca, and 0.39% ± 0.02% P as analyzed (average ± standard deviation), and 1.48 Mcal/kg DM as estimated with NRC (2001). Dry matter intake was not affected by treatments (means = 20.8 kg/cow/d; SEM = 0.81), ranging from 19.6 kg for cows fed C67:SH33 to 22.3 kg for those fed C100:SH0. Milk yield averaged 23 kg/cow/d (SEM = 1.55 kg/cow/d) and was not significantly different. Milk fat (3.9%), milk protein (3.3%) and MUNs (18 mg/L) did not differ statistically. There was no evidence supporting better NPN utilization for either feedstuff. Regardless of treatment, cows gained 0.5 kg body weight/d during the study, but body condition score changes in nearly 49 days of study were negligible, averaging 0.04 unit. This study suggests that soyhull pellets can replace corn in late-lactation cows’ diets without significantly affect animal performance.
Ground corn, Soyhull pellets, Dairy cows