Thesis
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
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/102683
Abstract
Phosphorus (P) excretion by dairy cows is a growing environmental concern. To examine the impact of partially substituting bluegrass straw for alfalfa hay to reduce dietary P in early to mid-lactation (114 days in milk), 24 dairy cows were used. Cows were fed a control TMR (C) or aTMR in which 10% of alfalfa hay DM was replaced by bluegrass straw (BGS) for 3 wk, diets were switched and cows fed for another 3 wk. Daily feed intake and orts were measured, milk, fecal, and blood samples were collected on d 2, 16, and 37 and analyzed for milk composition, fecal P and nitrogen (N), blood urea N and serum P. In vitro digestibility of feed was determined using an Ankom DaisyTM Incubator. Feed sorting was assessed by comparing particle size distribution of fresh TMR and 24 h refusals. Chewing activity was estimated during two 30-min periods weekly. Inclusion of BGS in the diet reduced the concentration of crude protein and P but ADF and NDF were unaffected. Average dry matter intake (DMI) was higher on the BGS than the C diet (P<0.05) whereas total in vitro digestibility, feed costs, income-over feed cost, milk fat, milk protein, milk lactose, blood urea N, blood P, fecal P and N, and feeding behavior were unaffected. Feed sorting occurred for both diets, but was unaffected by inclusion of BGS. Milk yield averaged 37 kg for C vs. 35 kg for BGS (P<0.05). Yield of fat-corrected milk and percent solids-not-fat were decreased in cows fed BGS (P<0.05). Income from milk was reduced by inclusion of BGS in the diet (P<0.05; $15.56/cow/d for C vs. $14.62/cow/d for BGS). Feed sorting occurred in both diets but was unaffected by inclusion of BGS. In conclusion, partial substitution of BGS for alfalfa hay in diets of early to mid-lactation cows reduced the %P and N in the diet. Although DMI of cows was increased by adding BGS to the diet, milk yield was reduced. Partial replacement of alfalfa hay with BGS may help reduce dietary P and N and aide in nutrient management
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Details
- Title
- 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
- Creators
- Andrina Christine Huisman
- Contributors
- Ronald L. Kincaid (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Animal Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525197701842
- Language
- English
- Resource Type
- Thesis