The benefits of feeding some bluegrass straw to late lactation dairy cows included a slight reduction in daily feed costs (using actual feed intakes and current ingredient costs): 10% bluegrass straw reduced feed costs by 5 cents/day/cow whereas 15% bluegrass straw reduced feed costs by 20 cents/day/cow. The reduction in feed costs was less than expected because cows fed bluegrass straw tended to eat more feed, presumably to compensate for the lower net energy of the TMR. Another benefit to feeding bluegrass straw is reduced crude protein intake of cows and, therefore, lowered nitrogen excretion. The predicted nitrogen excretion was reduced 46 g/day for cows fed 10% bluegrass straw and 69 g/day for cows fed 15% bluegrass straw. Because much of the excreted nitrogen eventually is released into the air as ammonia, reducing nitrogen intakes without affecting milk yield provides an environmental benefit.
Incorporation of bluegrass straw in dairy total mixed rations could be an important new market for bluegrass seed producers. In the Pacific Northwest region of Washington, Oregon, and Idaho, there are approximately 781,000 dairy cows and an approximately equal number of growing replacement heifers. If bluegrass straw was included at the rate of 4 lb/head/day for mature cows and 2 lb/head/day for growing heifers, the annual potential use of bluegrass straw would be 855,195 tons. At $55/ton, this equals about $47 million. Although universal acceptance of bluegrass straw in dairy rations is not expected, bluegrass straw may be widely used as an ingredient in diets of dairy cattle because it is a much lower price roughage source, and it contains much lower concentrations of nitrogen and phosphorus which complements high-phosphorus byproducts in diets.
The objectives were to determine the level at which bluegrass straw can be added to diets of lactating cows without adversely affecting milk production and composition, calculate a phosphorus balance with cows fed bluegrass straw and determine the reduction in phosphorus excretion that results, determine the level at which bluegrass straw can be included in diets of growing dairy heifers, and estimate the impact on feed costs and phosphorus balance when bluegrass straw is incorporated into dairy diets.
Thirty multiparous Holstein cows were assigned to a randomized complete design and fed one of three levels of bluegrass straw (0, 10 and 15% of TMR, DMB). At the start of the study, the cows were 219 days in milk with an average milk yield of 41 kg per day. Cows were fed their respective treatment diet for 62 d with the first 12 d serving as an adaptation period. Individual feed intakes and milk yields were recorded daily. Samples of blood, milk, and feces were collected on d 1, 37, and 62.
Bluegrass straw for growing heifers was done using 36 heifers fed diets containing 0, 10 and 20% bluegrass straw. The heifers were fed the treatment diets for 60 days and body weights were recorded on days 0, 30, and 60 of the study.
Average dry matter intake (25.4 ± 0.2 kg/d) and milk yield (35.2± 0.4 kg/d) for the lactating cows were not affected by treatment but declined with time (P ≤ 0.01). Similarly, milk composition was not affected by dietary treatment but also was affected by time. The concentrations of P in the diets were 0.40, 0.40, and 0.39% DM and P intakes were 142.5, 140.5, and 136.2 g/d, respectively, similar (P ≤ 0.1) among treatments. Inclusion of bluegrass straw into the TMR did not affect the concentrations of P in feces (0.63, 0.61 and 0.66% P, DM), P digestibility, estimated using ADL as an internal marker, nor was plasma inorganic P affected. Thus, up to 15% bluegrass straw was included in a TMR fed to late lactation cows without affecting performance. However, substituting bluegrass straw for alfalfa hay reduced feed costs by 5 cents per day per cow whereas 15% bluegrass straw reduced feed costs by 20 cents per day per cow. In addition, nitrogen excretion was reduced 46 g per day for cows fed 10% bluegrass straw and 69 g per day for cows fed 15% bluegrass straw. For growing heifers, bluegrass straw added at 10% of the diet did not signicantly affect average daily gain.
Educational & Outreach Activities
O’Rourke, E. M., J. J. Michal, and R. L. Kincaid. 2007. Bluegrass straw as a partial replacement for alfalfa hay in dairy rations. J. Dairy Sci. 90(Suppl.1):333-334
E. M O’Rourke. 2007. Effect of diet on monitoring and reducing phosphorus on dairy farms [thesis]. Washington State University.
E. O’Rourke, J. Jewett, J. Michal, K. Johnson, J. Swain, and R. Kincaid. 2007. Consider bluegrass straw to help reduce hay costs. The Progressive Dairyman 21(8):2-3.
The benefits of feeding some bluegrass straw to late lactation dairy cows included a reduction in daily feed costs. Another benefit to feeding bluegrass straw was reduced crude protein intake of cows and, therefore, lowered nitrogen excretion. The predicted nitrogen excretion was reduced 46 g/day for cows fed 10% bluegrass straw and 69 g/day for cows fed 15% bluegrass straw. Because much excreted nitrogen eventually is released into the air as ammonia, reducing nitrogen intakes without affecting milk yield provides an environmental benefit. Clearly, when the price differential between alfalfa hay and bluegrass is over $100/ton and the current ration is already high in crude protein or phosphorus, bluegrass straw should be considered as a feed ingredient in dairy rations.
The economic calculations of bluegrass straw in diets included current prices for feed ingredients and actual feed intakes of the cows and heifers. Use of actual feed intakes are important because the lower energy level of bluegrass straw will often result in increased total feed intakes of cows. Because milk yield and composition were not affected by diet, only effects on feed costs were considered. Also, because bluegrass straw directly replaced alfalfa hay in the diets, using the actual prices of bluegrass straw and alfalfa hay allowed for easy cost benefits to be calculated. The bluegrass straw reduced daily feed costs by 5 cents per day per cow when fed at 10% of the diet and 20 cents per day per cow when fed at 15% of the diet. Similarly, including bluegrass straw into diets of growing heifers reduced feed costs by 5 to 10 cents per heifer per day.
No data are available on the adoption rate of using bluegrass straw on dairy farms. Discussions with consulting nutritionists and dairy producers indicate adoption is being considered.
Areas needing additional study
Areas needing additional study include use of bluegrass straw to reduce the impact of increased intakes of crude protein and phosphorus in cattle when distillers grains and solubles are fed. The tremendously expanded ethanol production has resulted in significantly increased feeding of distillers grains and solubles, which are high in crude protein and phosphorus.