Key Findings
The growing season in the northeast United States is relatively short and characterized by periods of low forage biomass production during early spring, mid-summer, and late fall. Opportunities exist to fill gaps in forage productivity by growing nutritious, high yielding annual crops, such as brassicas.
Forage canola results in high biomass production and exceptional nutritive value and is emerging as an attractive option for dairy farmers in New Hampshire.
There's a substantial reduction in enteric methane emissions in cows that graze on forage canola, and a the research shows a marginal reduction in milk production and milk fat.
About the Co-Author
Andre Brito, Professor of Agriculture, Nutrition, and Food Systems
Contact information: Andre.Brito@unh.edu
603-862-1341, Brito Lab website
This research was published in the INSPIRED: A Publication of the New Hampshire Agricultural Experiment Station (Winter 2021)
Researchers: L.H. Silva, J. Sacramento, D. Reyes, Y. Geng, M. Ghelichkhan, S. Dillard, K. Soder, A.F. Brito
Focus group interviews and surveys indicate that profitable strategies to maximize forage utilization are challenging to 75% of organic dairy farmers. Moreover, there continue to be knowledge gaps about optimal annual species or rotations for milk production and farm profitability. Forage canola seems to be an excellent candidate to be tested in grazing studies because it led to the highest N use efficiency in cows and ability to mitigate methane emissions in lactating dairy cows. Our objective was to investigate how grazing forage canola affected milk production, milk composition, nutrient digestibility and enteric methane emissions during the fall season.
Brassicas, which collectively include turnip, swede, rapeseed, kale, canola, among others, have emerged as promising annual crops for grazing because of their high productivity, digestibility, nutritional value (>20% crude protein; Dillard et al., 2018), winter hardiness, and decreased enteric methane emissions in sheep (Sun et al., 2012). Brassicas can also extend the grazing season during the fall, thus offering a unique opportunity for dairy farmers to capitalize on cheaper high-forage diets.
However, forage-based diets have been shown to result in greater methane emission intensity than typical total mixed rations (TMR) fed across the United States (Hristov et al., 2013). Enteric fermentation is the largest source of human derived methane emissions in the country, accounting for approximately 25% of the total (EPA, 2019). Recently, a rumen-simulated in vitro study done at the USDA ARS Pasture Lab in Pennsylvania showed up to an 84% reduction in methane emissions when using canola, rapeseed, and turnip brassicas in feed (Dillard et al., 2018).
Research was conducted at the UNH Organic Dairy Research Farm where twenty organic Jersey cows were paired by parity, milk production, or days in milk and, within pair, randomly assigned to a control (CTRL) or a forage canola (CAN) diet in a randomized complete block design. Cows in the CTRL group (n = 10) were kept in the barn all day long and were fed TMR, while CAN cows (n = 10) stayed in the barn during the day receiving a TMR and had access to canola pasture from 6 p.m. to 5 a.m. next day. Diets were formulated to contain (dry matter basis) a 60:40 forage:concentrate ratio. In the canola diet, 67% of the TMR baleage was replaced by grazed canola resulting in approximately 40% of canola in the total ration dry matter. The experiment lasted seven weeks, with the first two weeks used for baseline data collection (all cows received the same TMR) followed by five weeks of measurements with sample collection during weeks three and five. Two forage canola fields were established and cows grazed within a strip grazing management. A fresh strip of forage canola pasture was offered daily immediately after the pm milking for cows assigned to the canola diet.
Forage canola mass yield averaged 6,016 lb/acre and had a nutritional value averaging (dry matter basis) 24.1% crude protein, 16.6% neutral detergent fiber, 2.6% starch, and 17.7% total sugars. These results indicate that forage canola is an excellent feed source.
As expected, intake of TMR was 53% greater in cows assigned to the control diet compared with those assigned to the CAN diet (Table 1). Intake of forage canola via grazing averaged 14.2 lb. Diets did not affect intake of pellet grain and total dry matter intake. Milk production and 4% fat-corrected milk production indicated some tendency to increase in control cows, which may be explained by decreased digestibility of neutral detergent fiber in cows grazing forage canola. Milk fat yield tended to be lower in cows fed canola, but milk protein percentage was greater, likely caused by a dilution effect.
Enteric methane production, yield and intensity decreased by 32%, 30%, and 28%, respectively, in canola diets. These reductions were likely due to the presence of glucosinolates in forage canola, which have been shown to be negatively correlated with methane production in the rumen. Canola fed cows also had a greater rumen proportion of propionate, known to be a hydrogen sink resulting in less substrate for methanogenesis in the
This material is based upon work supported by the NH Agricultural Experiment Station, through joint funding of the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 1017808, and the state of New Hampshire. Authors include L.H. Silva, J. Sacramento, D. Reyes, Y. Geng, M. Ghelichkhan, S. Dillard, K. Soder, and A.F. Brito.
