Feeding a branded, modified wet corn gluten feed to lactating dairy cows: A meta-regression approach

Abstract

Our objectives were to identify optimal dietary inclusion for Sweet Bran (SB; Cargill Inc.), a branded, modified wet corn gluten feed product, and determine whether there are other important factors to consider when feeding SB to lactating dairy cattle. Experiments where at least 2 SB concentrations were investigated (n = 12; 50 treatment means) were compiled into a database for meta-regression analysis. Experiments were screened to ensure they reported nutrient and ingredient composition of treatments and milk yield and milk component responses. The meta-regression was conducted using lmer and step functions of the lmerTest package within R (v 4.0.2). Dietary SB interacted with NDF concentration such that greater SB inclusion was associated with increased DMI, but the magnitude of this effect declined with increasing dietary NDF concentration. Milk fat percentage and protein yield were affected by an interaction between dietary forage NDF (fNDF) and SB; increasing fNDF when feeding greater SB inclusions had positive effects on milk fat concentration but negative effects on milk protein yield. Milk fat and protein yield were optimized at 26 and 11% SB inclusion, respectively. Sweet Bran supports increased DMI and milk fat yield when included at 20 to 40% of diet DM, but total diet NDF must be controlled. Results also suggest that moderate fNDF when feeding SB is important. Too little fNDF reduces milk fat percentage, whereas too much reduces protein yield. Finally, feeding greater SB concentrations reduced milk protein yield, suggesting the need to focus on AA balancing.