Organic dairy producers must follow many rules that seem to heighten the struggles every dairy faces. One of these regulations requires all organic dairy cattle to spend a minimum of 120 days each year on pasture, which in some areas can be the entire grazing season. Providing quality forage for that amount of time is no easy feat, especially with the limited fertilizer options available to organic producers. A team of researchers at Utah State University, University of Idaho and the USDA Agricultural Research Service received funding through the Western Sustainable Agriculture Research and Education (SARE) program and the National Institute of Food and Agriculture’s (NIFA) Organic Agriculture Research and Extension Initiative (OREI). The researchers have been interested in learning if grass-legume pastures can help decrease the need for fertilizer on pastures and increase the efficiency of Jersey replacement heifers.
Phase 1
This project began in 2012 when a team of researchers from Utah State University and the Forage and Range Research Laboratory – co-led by Blair Waldron, Earl Creech and Dale ZoBell – conducted a study on how grass-legume pastures would affect beef steer growth and economic returns. The team wanted to learn if adding legumes to a pasture would improve forage quality without the use of expensive fertilizers.
They compared four pastures: tall fescue with fertilizer, without fertilizer, with alfalfa and with birdsfoot trefoil (BFT). The general findings of this study were that the fields with BFT resulted in the greatest weight gains from the steers and had the highest economic return.
The research team believed this was due, in part, to the low levels of condensed tannins found in BFT. Low levels of condensed tannins “bind the protein so it’s non-bloating,” Waldron says. “Research has shown these levels also increase protein digestion, so less is lost through excretion.”
However, the steers did not grow as efficiently as the team expected, which prompted two new research questions: What grass-BFT mix would provide the most energy to the cattle and maximize feed efficiency, and did the low levels of condensed tannins really have an impact?
Phase 2
Waldron and Creech were joined by Dr. Clay Isom as co-leader and many other new researchers. When the opportunity came to continue the study, the team knew their research could be helpful to organic dairy producers looking to raise replacement heifers on pasture. They switched from a beef steer model to organic Jersey replacement heifers. Members of the team were analyzing the forage, the animal performance and behavior, the environmental impact and the economics of these pastures.
Jacob Hadfield, a graduate student focusing on animal science, summed up the main purpose of the study. “Can producers build pastures with high enough nutritional quality that they can raise replacement heifers on pasture without having to spend extra money?” Hadfield says. “If a producer already has this resource, pasture is going to be much cheaper than organic feed.”
The set-up
To ensure a producer was making the most economically beneficial choice, the team chose four grasses with varying levels of energy to pair with BFT. They chose to use Cache meadow bromegrass, QuickDraw orchardgrass, Fawn tall fescue and Amazon perennial ryegrass. They built eight pastures – one pasture for each individual grass and another pasture for each grass with BFT. Each pasture received Chilean nitrate yearly as an approved organic source of nitrogen. The pastures without BFT received a second round of nitrate each year. The heifers were put in a rotational grazing system, and all data points were taken after a 12-hour fast.
The findings
Ultimately, this study showed the researchers that BFT had an overall positive impact. The team analyzed the bodyweight, blood urea nitrogen levels and other growth measures and found that the fields with BFT almost always outperformed the grass-only pastures.
The largest difference came when comparing bodyweights. Each pasture with BFT saw significantly higher gains than the pastures that only contained the corresponding grass. This contributed to the greater economic returns also shown in the mixed pastures. “I think it's a great opportunity for producers to be able to lower their costs overall,” Hadfield says.
The team was also interested in how the low levels of condensed tannins affected the heifers. “Because dairy is known to have high blood urea nitrogen on grazing,” Waldron says, “we wanted to see if the condensed tannins would reduce that.” The team did not find the large impact they thought they might. The levels of condensed tannins may have been too low, or there could have been a genetic element in play. A new phase of this research is nearing completion, analyzing four different dairy breeds and what role genetics may have played in these findings.
Determining which grass would be the best to pair with BFT was a bit tricky. The higher-energy grasses like perennial ryegrass had a lower yield. Even though the heifers gained more on these pastures, the lowered carrying capacity balanced out the economics. Producers need to decide which grass to pair based on their specific growing conditions and carrying capacity.
Recommendations
“A lot of people in the West are afraid of using BFT,” Waldron says. He has had producers tell him that BFT will not survive grazing. “That’s probably true under conventional grazing, but under rotational grazing there’s no reason it won’t persist.”
Waldron recommends starting on a different paddock each year when using a rotational grazing method. This means a different area will be grazed last each year, helping the BFT to persist for the next season.
Both Waldron and Hadfield emphasized the importance of resting the BFT pastures for the month of September. “It’s not like alfalfa,” Waldron says. “It doesn’t put root reserves in throughout the year – it does it in the fall right before winter. You have to rest it in September. Wait for a frost and then you can go back in and graze it.”
Adding BFT to the mix increases growth and economic returns for producers raising replacement heifers on pasture. The increased nutritional quality and forage can’t be ignored. Even though this study was an organic model, traditional producers shouldn’t overlook these findings. “It’s not just for the organic producers,” Waldron says. “Now it’s for all dairy producers.”
