Performance of dairy cows fed diets formulated at 2 starch concentrations with either canola meal or soybean meal as the protein supplement

Authors: SANCHEZ-DUARTE, JUAN - South Dakota State University; Kalscheur, Kenneth; CASPER, DAVID - Furst-Mcness Company; GARCIA, ALVARO - South Dakota State University

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2019
Publication Date: 9/1/2019
Citation: Sanchez-Duarte, J.I., Kalscheur, K., Casper, D.P., Garcia, A.D. 2019. Performance of dairy cows fed diets formulated at 2 starch concentrations with either canola meal or soybean meal as the protein supplement. Journal of Dairy Science. 102(9):7970–7979. https://doi.org/10.3168/jds.2018-15760.
DOI: https://doi.org/10.3168/jds.2018-15760

Interpretive Summary: Replacing soybean meal with canola meal and reducing starch by replacing corn grain with non-forage fiber sources such as soybean hulls and beet pulp in the diets of lactating dairy cows is a feeding strategy to produce milk at a lower cost. However, reducing dietary starch concentration may reduce lactation performance. In addition, milk production may be influenced by the quality of the protein supplement provided in the diet. Currently, no information is available within a single study that evaluates both protein quality and starch concentration in the diets of lactating dairy cows. The objective of this study was to evaluate the replacement of starch from corn with non-forage fiber sources from soybean hulls and beet pulp; in addition, diets were formulated with either soybean meal or canola meal as the dietary protein sources to assess the impacts of these dietary inputs on milk production, rumen fermentation, and nutrient digestion of lactating dairy cows. Results demonstrated that reducing corn grain starch with non-forage fiber sources negatively impacted the productive response of lactating dairy cows fed either soybean meal- or canola meal-based diets. This study demonstrates to dairy producers and nutritionists that dietary starch concentration impacts lactation performance in mid-lactation dairy cows, whereas diets formulated with canola meal at lower starch concentrations may lower milk protein concentration and yield.

Technical Abstract: This study was designed to evaluate the effects of substituting corn grain with non-forage fiber sources in diets containing soybean (SBM) or canola meal (CM) as the primary protein source. Sixteen Holstein cows were assigned to a replicated 4 × 4 Latin square design with 4 periods of 28 d each. Treatments were arranged as a 2 × 2 factorial with two protein sources (SBM and CM) and two dietary starch concentrations (21 and 27% DM). Diets were formulated to contain 16.5% CP and the 21% starch diets were obtained by replacing corn grain with soybean hulls and beet pulp. Protein source × starch interactions were observed for dry matter intake (DMI), milk fat and protein concentrations, milk protein yield, milk urea nitrogen, and feed efficiency (FE). Cows fed CM diets had a higher DMI when dietary starch concentration was 27% compared to 21%, but those cows had similar DMI as cows on SBM diets with any starch concentration. Milk fat percentage was decreased in cows fed CM with 27% starch compared to cows fed CM with 21% starch and cows fed SBM with 27% starch. Milk protein percentage and yield, and milk lactose percentage was least in cows fed CM with 21% starch compared with the other three diets, but FE was greater for cows fed CM with 21% starch. Milk urea nitrogen was least in cows fed CM with 27% starch compared with the other 3 diets. Cows fed diets with 27% starch produced 2.5 kg/d more milk and 1.9 kg/d more energy-corrected milk compared to cows fed 21% starch. Digestibility of dry matter (DM) and organic matter (OM) was higher in cows fed SBM diets than cows on CM diets, and cows fed 27% starch showed greater DM and OM digestibility than cows on 21% starch. Digestibility of neutral detergent fiber and acid detergent fiber was greater in diets with SBM than those with CM. Molar proportion of acetate was the lowest for cows fed CM with 21% starch compared to cows fed SBM with 21% starch, with remaining cows fed being intermediate and similar. However, propionate was highest for cows fed CM with 21% starch than cows fed SBM with 21% starch, but remaining treatments were intermediate and similar. Isobutyrate was greater for cows fed CM with 21% starch, which resulted in the lowest acetate to propionate ratio compared to cows fed remaining treatments. Overall, we confirmed that the interaction of protein with starch in CM diets can sustain similar cow performance as with the SBM diets. Decision making of starch concentration and protein source should consider feed price when SBM or CM and different starch levels are being formulated in diets for lactating dairy cows.