The group evaluated several levels of dietary crude protein (CP) from soybean meal (SBM) or heat-moisture treated canola meal (TCM) on cows getting a total mixed ration with a grass silage-based diet.
“Heat-moisture-treated canola meal increased milk and milk protein yield, decreased MUN [milk urea nitrogen] concentration, and improved protein utilization compared with SBM supplementation,” they said. “Compared with SBM, TCM supplementation also resulted in a greater decrease in CH4 emissions per kilogram of ECM [energy corrected milk].”
Canola use in TMR
“The first aim of this study was therefore to investigate the production responses to graded levels of SBM or heat-moisture-treated CM (TCM) supplementation in dairy cows fed TMR based on grass silage and crimped barley,” said researchers. The second goal examined the interplay between ruminal degradation of CP and the production of CH4, they added.
Although links have been demonstrated between the inclusion of canola meal in dairy rations and improved milk yield and milk protein amount, little work has been done with use of canola meal in a total mixed ration, said scientists.
The use of a total mixed ration, appears to show improved synchrony of degradation for protein and carbohydrates in the rumen, they said. But, that boosted efficiency in microbial protein synthesis could alter the protein supplement quality needed in regard to nitrogen (N) use.
In the experiment, 28 Swedish red cows were used in a cyclic change-over experiment and had four diet periods, said researchers. Diets were fed for 21 days.
Diets included 600 g/kg grass silage and 400 g/kg of concentrates for a dry matter (DM) basis, they said. And, the two protein supplements were fed at four levels, 0 g/kg of DM, 170 g/kg, 210 g/kg and 250 g/kg.
Cows were milked twice a day and milk yield was recorded, they said. Samples were taken at four milkings in a row. Samples were viewed for levels of fat, protein, lactose and urea.
Blood samples also were taken on day 19 of the trial, they said, and checked for amino acid levels. Fecal samples were recorded on day days 19 and 20, and CH4 and CO2 were measured with an open-circuit head chamber system.
“Overall, replacing SBM with TCM in total mixed rations based on grass silage had beneficial effects on milk production, N efficiency, and methane emissions across a wide range of dietary CP concentrations,” said the scientists.
Feed intake was not changed by the inclusion of different CP levels, researchers said, although it tended to be higher in for cows getting TCM instead of SMB.
“Total methane emissions were not influenced by diet, but emissions per kilogram of DM intake decreased quadratically, with the lowest value observed in cows fed intermediate levels of protein supplementation,” they said. “Methane emissions per kilogram of energy-corrected milk decreased more when dietary CP concentration increased in TCM diets compared with SBM diets.”
Both milk and milk protein levels were boosted linearly with the CP concentration, they said. The best responses were seen in cows getting the TCM diets when compared to the SMB feed.
Similarly, milk urea levels grew linearly with the additional CP and more was found in cows getting the SBM, the scientists said.
“Increased dietary CP concentration increased yields of ECM, milk protein, and lactose, whereas milk fat yield only tended to increase,” they said. “Increased dietary CP concentration increased MUN concentration more in cows on SBM diets than on TCM diets. Similar interactions between protein supplement and dietary CP concentration were observed for N efficiency, which decreased more on SBM diets than on TCM diets when CP concentration increased.”
Amino Acid levels in plasma also increased with the levels of CP, but behaved similarly for both protein meals, scientists said.
“Diet had no significant effect on total CH4 emissions, but emissions decreased quadratically when expressed per kilogram of DMI, with the lowest values obtained with the medium level of supplemental CP,” they added.
Source: Journal of Dairy Science
Title: Effects of soybean meal or canola meal on milk production and methane emissions in lactating dairy cows fed grass silage-based diets
Authors: H. Gidlund, M. Hetta, S.J. Krizsan, S. Lemosquet, P. Huhtanen,