The dairy study used 30 mature Holstein cows that initially were 219 days in milk with an average milk yield of 90 pounds per day. Bluegrass straw (0, 10 or 15 percent) replaced alfalfa hay in a total mixed ration (TMR) (see Table 1* for components of the TMR fed). Substituting bluegrass straw for alfalfa hay did not statistically affect milk yields or feed intakes after 62 days on feed. Efficiency of milk yield was somewhat low because the cows were in later lactation and gaining bodyweight.
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 percent bluegrass straw reduced feed costs by 5 cents per day per cow whereas 15 percent bluegrass straw reduced feed costs by 20 cents per day per 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 (see Table 2*). 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 grams per day for cows fed 10 percent bluegrass straw and 69 grams per day for cows fed 15 percent 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.
Bluegrass straw is not for all feeding situations. The high fiber and low protein content of bluegrass straw reduces its feeding value and could reduce milk yield of cows in early lactation, which is why we used cows in the last third of their lactation. Also, the chemical composition, particularly the crude protein, of bluegrass straw is variable so a chemical analysis is recommended (see Table 3*). However, when the price differential between alfalfa hay and bluegrass is over $100 per ton and if the current TMR is already high in crude protein (CP), bluegrass straw is worth considering for late-lactation cows.
When purchasing bluegrass straw it is helpful to have a chemical analysis to examine. The variation in protein and fiber content between growers within a season is large. The amount of ash and soil contamination is also variable. However, with knowledge of the hay quality, cattle diets can be created to save considerable amounts of money and not compromise cattle performance. PD
References omitted but are available upon request.
*Tables omitted but are available upon request to editor@progressivedairy.com.
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