In an elaborate study that included 530 early-lactation mature Holstein cows, researchers in California showed that Canadian canola meal stimulated high milk production, at least in part due to the methionine that canola meal supplies, according to an announcement from the Canola Council of Canada.
The study was published in the June issue of Animal Feed Science & Technology by researchers Hannah Gauthier, Nadia Swanepoel and Peter Robinson with the department of animal science at the University of California-Davis.
“The two most widely used vegetable protein meals on California dairy farms are canola meal and corn dried distillers grains with solubles (DDGS), with soybean meal a distant third,” Swanepoel explained. “Due to recent reductions in the soybean meal price, and given the body of research demonstrating the advantages of feeding canola meal, we wanted to determine the extent of milk yield losses if some soybean meal was added into the ration to replace some of the canola meal.”
The researchers used three diets that all contained 7.5% DDGS, which is “pretty much the maximum inclusion level used by our dairy farms based on prior studies and on-farm experience,” Robinson said. The researchers evaluated diets that contained 0%, 3.5% or 7.0% soybean meal in exchange for canola meal (Table 1). Total dietary protein levels were above National Research Council requirement levels for all diets.
According to the announcement, the feeding experiment showed that performance for production of milk, milk fat and milk protein (Table 2) was highest for the cows on the control canola meal and 3.5% soybean meal diets and lowest when the soybean meal inclusion level was increased to 7.0%.
In addition, the change in body condition score (BCS) of the cows showed a net BCS gain on the canola meal diet and a net loss on both soybean meal diets.
Analysis of blood plasma amino acid profiles among the diets demonstrated an almost 20% decline in methionine levels with the 7.0% soybean meal diet. This reduction in plasma methionine was in line with levels that previously have been demonstrated to be much lower than desired in lactating dairy cows, the researchers said.
“The most likely reason for the decline in performance with the highest dietary addition level of soybean meal was the reduction in methionine as a proportion of metabolized amino acids,” Gauthier reported.
The research was part of the Canola AgriScience Cluster, with funding provided by Agriculture & Agri-Food Canada, the Canola Council of Canada, Alberta Canola, SaskCanola and the Manitoba Canola Growers.