Responses of late-lactation cows to forage substitutes in low-forage diets supplemented with by-products

Authors: Hall, Mary Beth; CHASE, LARRY - Cornell University

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2014
Publication Date: 5/1/2014
Publication URL: https://handle.nal.usda.gov/10113/60197
Citation: Hall, M., Chase, L.E. 2014. Responses of late-lactation cows to forage substitutes in low-forage diets supplemented with by-products. Journal of Dairy Science. 97:3042-3052.

Interpretive Summary: Due to drought-induced shortages of forage and historically high feed prices in 2012, many dairy farmers sold off animals because they could not afford to feed them and profitably stay in business. When forage is limited due to drought or when feed prices are high, it would be useful for dairy farmers to know what alternative diet formulation options they can work with to feed their herds. In this study, we asked the question: How do cows perform on low-forage diets that include forage substitutes to make up the shortfall in forage and lower-cost byproducts instead of corn and soy? Late-lactation cows maintained milk production when switched from a 61% forage diet containing corn and soy to diets containing 40% forage from alfalfa and corn silages, and 12% as varying combinations of sugar beet pulp and wheat straw. No corn or soy products were fed, only byproduct feeds (corn gluten feed, distillers grains, whole cottonseed, and molasses). The cows had lower feed efficiency on the forage substitute/byproduct diets than on the higher-forage diets. This research provides dairy farmers and nutritionists with information on nontraditional diet formulations that offer viable short-term options to maintain dairy herds.

Technical Abstract: In response to drought-induced shortages of forage and increased corn and soy prices, a study was conducted to evaluate lactation response of dairy cows to lower-forage diets supplemented with forage substitutes and with byproduct feeds entirely substituted for corn grain and soybean feeds. The design was a randomized complete block. Late-lactation cows (48) were offered a high-forage diet containing corn grain and soy products in a 2-wk covariate period and 1 of 4 diets in a 4-wk feeding period. Experimental diets contained chopped wheat straw (WS)/sugar beet pulp (SBP) at 0/12, 3/9, 6/6, or 9/3 percentages of diet dry matter (DM). Corn silage (20%), alfalfa silage (20%), corn gluten feed (25.5%), distillers grains (8%), whole cottonseed (5%), cane molasses/whey blend (7%), and vitamin & minerals mix with monensin (2.5%) comprised the rest of diet DM. The WS/SBP diets averaged 16.5% crude protein (CP), 35% neutral detergent fiber (NDF), and 11% starch (DM basis). Cows consuming the experimental diets maintained a 3.5% fat- and protein-corrected milk production (35.2 kg, standard deviation [SD] = 5.6) that was numerically similar to that measured in the covariate period (35.3 kg, SD = 5.0). Intakes of DM and CP declined linearly as WS increased, whereas NDF intake increased linearly. Linear increases in time spent ruminating (from 409 to 502 min/d) and eating (from 156 to 223 min/d) were noted as WS inclusion increased. Ruminal pH was unaffected by diet. Yields of milk fat and 3.5% fat- and protein-corrected milk did not change as WS increased, but those of protein and lactose declined linearly. Phosphorous intakes were in excess of recommended amounts and decreased linearly with increasing WS inclusion. Nutritional model predictions for multiparous cows were closest to actual performance for the National Research Council 2001 (NRC) model when the metabolizable protein (MP) basis was used; primiparous cow performance was better predicted by energy-based predictions made with the NRC or Cornell Net Carbohydrate and Protein System models. Model predictions of performance showed a quadratic diet response to increasing WS. Lactating dairy cows maintained production on low-forage diets that included forage substitutes, as well as byproduct feeds that fully replaced corn grain and soybean. However, longer-term studies are needed to evaluate animal performance and to improve models to predict performance on these nontraditional diets.