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Title Optimizing the efficiency of nutrient utilization in dairy cows
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University/Publisher University of Saskatchewan
Abstract A series of experiments were conducted to determine nutritional strategies to improve the efficiency of N utilization in dairy cows when feeding co-products including wheat-based (W-DDGS) and corn-wheat blend distillers grains with solubles (B-DDGS), and dried whey permeate (DWP). In Experiment 1, the objective was to determine the effects of replacing canola meal (CM) as the major protein source with W-DDGS on ruminal fermentation, microbial protein production, omasal nutrient flow, and animal performance. Cows were fed either a standard barley silage-based total mixed ration containing CM as the major protein supplement (0% W-DDGS, control) or diets formulated to contain 10, 15 and 20% W-DDGS (dry matter [DM] basis), with W-DDGS replacing primarily CM. Diets were isonitrogenous (18.9% crude protein [CP]). Inclusion of W-DDGS to the diet did not negatively affect ruminal fermentation, microbial protein production, and omasal nutrient flow. However, there was a 0.7- to 2.4-kg increase in DM intake, and a 1.2- to 1.8-kg increase in milk yield after the addition of W-DDGS in place of CM. In Experiment 2, the objective was to delineate the effects of including either W-DDGS or B-DDGS dried distillers grains with solubles as the major protein source in low or high CP diets fed to dairy cows on ruminal function, microbial protein synthesis, omasal nutrient flows, urea-N recycling, and milk production. The treatment factors were type of distillers co-product (W-DDGS vs. B-DDGS) and dietary CP content (15.2 vs. 17.3%; DM basis). The B-DDGS was produced from a mixture of 15% wheat and 85% corn grain. All diets were formulated to contain 10% W-DDGS or B-DDGS on a DM basis. Feeding up to 10% of dietary DM as B-DDGS or W-DDGS as the major source of protein did not have negative effects on metabolizable protein (MP) supply and milk production in dairy cows. However, reducing dietary CP content from 17.3 to 15.2% decreased milk production. This response was attributed to an insufficient supply of ruminally degradable protein (RDP) that suppressed microbial nonammonia N (NAN) synthesis in the rumen, thus decreasing intestinal MP supply. In Experiment 3, the objective was to determine the effects of replacing barley or corn starch with lactose (as DWP) in diets containing 10% W-DDGS on ruminal function, omasal nutrient flow, and lactation performance. The treatment factors were source of starch (barley vs. corn) and dietary inclusion level of DWP (0 vs. 6%; DM basis) as a partial replacement for starch. Diets were isonitrogenous (18% CP) and contained 3 or 8% total sugar. The starch content of the low sugar diet was 24% compared to 20% for the high sugar diet. Dry matter intake, and milk and milk component yields did not differ with diet. However, partially replacing dietary corn or barley starch with sugar up-regulated ruminal acetate and propionate absorption, and reduced ruminal NH3-N concentration, but had no effect on ruminal pH, microbial protein synthesis, omasal nutrient flow and production in dairy cows. In summary, data…
Subjects/Keywords dairy cow; dried distillers grains with solubles; lactose; microbial protein; milk production; nitrogen excretion; nutrient utilization efficiency; omasal nutrient flow; starch; short-chain fatty acid absorption; nitrogen metabolism; urea-N recycling
Contributors Mutsvangwa, Timothy; Buchanan, Fiona; Hamilton, Don; McKinnon, John; Christensen, Dave
Language en
Country of Publication ca
Record ID handle:10388/ETD-2013-03-973
Other Identifiers TC-SSU-201303973
Repository sask
Date Retrieved
Date Indexed 2020-07-20

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…2.3 Reducing the Environmental Cost of Dairy Production ............................................................. 13 2.4 Urea-N Recycling

…88 4. EFFCTS OF FEEDING WHEAT OR CORN-WHEAT DRIED DISTILLERS GRAINS WITH SOLUBLES IN LOW OR HIGH CRUDE PROTEIN DIETS ON RUMINAL FUNCTION, OMASAL NUTRIENT FLOW, UREA-N RECYCLING, AND PERFORMANCE IN DAIRY COWS…

…4.4.6 Nitrogen Balance and Apparent Total Tract Nutrient Digestibilities ............................... 110 4.4.7 Urea-N Recycling Kinetics ............................................................................................... 110 4.5…

…digestibility in cows fed low or high CP diets containing either wheat-based dried distillers grains with solubles (DDGS) or blend DDGS as the major protein source (n = 4) .......................... 111 xiii Table 4.7 Urea-N recycling

…Amburgh, 2006; Reynolds and Kristensen, 2008; Hristov et al., 2011a). Additionally, restricting N intake up-regulates urea-N recycling to the rumen. Besides compensating for the limited supply of dietary N to support MPS, this increase in urea-N

…x29;. A proportion of BUN is recycled to all parts of the GIT, including the rumen. Recycling of urea-N to the rumen is desirable because it is broken down by bacterial urease to NH3-N that can potentially be sequestered into microbial protein (…

…16 2.4.1 Transport of Urea-N Into The Rumen ................................................................................. 16 2.4.2 Incorporation of Recycled Urea-N into Microbial Protein ................................................. 17…

…2.4.3 Factors That Regulate Urea Recycling ............................................................................... 18 2.4.3.1 Dietary Nitrogen Supply…

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