Using Bluegrass Straw to Modulate the Elevated Dietary Crude Protein and Phosphorus Caused by Including Distillers Grains and Solubles in Dairy Diets

Using Bluegrass Straw to Modulate the Elevated Dietary Crude Protein and Phosphorus Caused by Including Distillers Grains and Solubles in Dairy Diets

Summary

The impact of partially substituting bluegrass straw (BGS) for alfalfa hay to reduce N and P intake in early lactation cows was determined. Cows were fed a control ration or a ration in which 10% of alfalfa hay was replaced by BGS. Feed intakes were higher for the BGS ration whereas in vitro digestibility, feed costs, income-over feed cost, fecal P and N, and feeding behavior were unaffected. Milk yield and income was reduced but not income-over-feed costs. Thus, BGS in diets of lactating cows reduced the %P and %N, N intake, and aided nutrient management.

Objectives/Performance Targets

The objectives are to determine if:
1. bluegrass straw can be used in diets to offset the increased excretion of nitrogen and phosphorus of cattle fed distillers grains & solubles.
2. bluegrass straw can be fed to cows in early to mid-lactation without affecting milk yield and composition; and
3. income over feed costs is affected when bluegrass straw is incoporated into lactation diets.

Accomplishments/Milestones

Inclusion of 10% BGS in the rations of early to mid-lactation dairy cows reduced the P and N content of the diet. However, because DMI increased in cows fed BGS, P intake was not affect although N intake was reduced. Sorting of the TMR by all cows contributed to intakes of P and N that were higher than expected. Although fecal P concentration was not affected, the %P in the diet was reduced by inclusion of BGS, giving producers an option for reducing P content of the ration. Feeding behavior and feed sorting were similar between treatment and control groups. Milk yield was reduced by inclusion of BGS but overall income over feed costs was unaffected. Reduced income from milk was compensated by the reduction in feed costs, indicating that finances are not impacted by inclusion of 10% BGS in the diet. Bluegrass straw reduced P intake and P excretion in diets of cows late lactation without affecting milk yield. The results of this study show that BGS is an acceptable feedstuffs that can be used to reduce N and P intakes of cows, particularly those in late lactation, and also can be used as a forage extender.

Publications:
Huisman, Andrina Christine. 2009. The Effects of Reducing Dietary Phosphorus and Nitrogen by the Addition of Bluegrass Straw to the Rations of Early to Mid-Lactation Holstein Dairy Cows. M.S. Thesis, Washington State University, Pullman, WA.

Huisman, A.C., S. Cobb, R.L. Kincaid, J.J. Michal, and K.A. Johnson. 2009. The effects of reducing hdietary phosphorus by the addition of bluegrass straw to the rations of early to mid-lactation Holstein dairy cows. J. Anim. Sci. 87(E-Suppl.3):157.

Huisman, A.C., S.M. Cobb, J. Michal, and R.L. Kincaid. 2008. Effects of bluegrass straw on milk yield, intakes of crude protein and phosphorus, and income over feed costs in early to mid-lactation Holstein cows. Proc. 43rd Pacific Northwest Animal Nutrition Conference, pp.201, Tacoma, WA.

Impacts and Contributions/Outcomes

At the time of the trial, alfalfa cost $270/ton whereas bluegrass straw cost $85/ton. The reduction in feed cost from incorporation of bluegrass straw into the diet was $0.24/cow/day. At the time of the study, milk prices were $0.42/kg of milk. Yield of milk was reduced in the cows fed BGS and consequently income from milk was reduced as well. Although gross income was reduced, the overall income over feed costs was unaffected by the inclusion of bluegrass straw in rations of cows in early and mid-lactation.

Within the past 12 months there has been major changes in prices of forages, feed grains, milk and fuel. For example, alfalfa hay prices declined by nearly $100/ton and milk prices are significantly lower than their recent peak. Because the price difference between bluegrass straw and alfalfa hay has narrowed considerably, from nearly $200/ton to less than $100/ton currently, farmer intested has declined as well. However, nutritionists and farm nutrient management specialists continue to express interest in this and other strategies to reduce N and P excretion and subsequent soil accumulation on livestock farms.

Collaborators: