Effect of an Expansion Processed Mixture of Grain and Urea on Lactating Dairy Cows and on Nitrogen Utilization by Rumen Microorganisms PDF Download
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Author: Lyle Gene Helmer
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Author: Lyle Gene Helmer
Publisher:
ISBN:
Category :
Languages : en
Pages : 212
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Author: David Arthur Stiles
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ISBN:
Category :
Languages : en
Pages : 168
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Category : Agricultural wastes
Languages : en
Pages : 100
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ISBN:
Category :
Languages : en
Pages : 712
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ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 464
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Publisher: National Academies
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 518
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Author: Ken Kwan
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Category : Lactation
Languages : en
Pages : 288
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Publisher:
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Category : Dissertations, Academic
Languages : en
Pages : 1244
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Author: Braden M. Tye
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Category :
Languages : en
Pages :
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The objective of this experiment was to determine if nutrient utilization and energy partitioning by lactating dairy cows would differ in response to dietary corn grain (CG) types [steam-flaked corn (SFC) vs. high-moisture corn (HMC)] and to test if the types of CG would interact with slow-release urea (SRU) on lactational performance and energy utilization. Eight multiparous Holstein cows (32 ℗ł 8.2 days-in-milk) were used in a duplicated 4 ©7 4 Latin square with one square consisting of ruminally cannulated cows. A 2 ©7 2 factorial arrangement was used to test 4 dietary treatments: SFC without SRU, SFC with SRU, HMC without SRU, and HMC with SRU. The experimental diets contained 60.5% dry matter (DM) of forages, whereas 12.9% or 14.4% DM of SFC or HMC was added in the diets, respectively. The SRU was supplemented at 0.46% DM, replacing a mixture of soybean meal and canola meal in a 50:50 ratio. Feeding HMC decreased intakes of DM, crude protein, and fiber compared with SFC. Supplementation of SRU did not affect intakes of DM and nutrients, whereas it tended to increase intakes of DM or increased crude protein intake under SFC but no effect under HMC, leading to CG ©7SRU interactions on DM and crude protein intakes. Neither type of CG nor SRU supplementation affected milk production except that cows fed HMC-based diets tended to decrease energy-corrected milk yield compared to those fed SFC-based diets. Utilization of HMC in the diet had a tendency to increase dairy efficiency based on milk yield over SFC utilization. Cows fed HMC diets gained more body weight (BW) than those fed SFC diets, whereas supplementing SRU tended to reduce BW gain regardless of type of CG. Cows fed HMC diets shifted more net energy into BW compared with those fed SFC diets, whereas supplementing SRU tended to decrease a portion of net energy partitioned into BW gain under both SFC and HMC diets. Dietary treatments exerted minor impacts on ruminal fermentation profiles. Feeding HMC diets decreased fecal N excretion compared with SFC diets. In addition, supplementing SRU increased fecal N excretion under SFC, but it was decreased by SRU with HMC, leading to an interaction between CG and SRU. These collective results demonstrate that feeding HMC with SRU can be a practical option in high-forage lactation diets to maintain or improve nutrient and energy utilization efficiency and minimize negative environmental impacts.
Author: Erin Beth Recktenwald
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ISBN:
Category :
Languages : en
Pages : 0
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Two experiments were conducted to quantify urea-N kinetics and ruminal microbial populations and their nitrogen (N) transactions in lactating dairy cows under a variety of dietary nitrogen and carbohydrate conditions. In the first experiment, twelve ruminally fistulated Holstein cows were fed one of three diets to provide adequate MP supply and ruminal N balance (Control, 16.3% CP), adequate ruminal N but deficient MP supply (LoMP, 14.1% CP), or adequate MP supply but deficient ruminal N balance (LoRumN, 14.1% CP). A continuous jugular infusion of 15N15N-urea was conducted for a minimum of 72 hours to label the respective pools. Plasma, milk, urine, feces, and ruminal contents, including the liquid associated bacteria, particle associated bacteria, and protozoa, were collected before and after urea infusion for N enrichment analysis. Urea-N synthesis was greatest for cows fed the Control diets and lowest for the LoMP diets, with the LoRumN diets demonstrating intermediate urea-N synthesis regardless of the low N intake of cows on this diet. A greater proportion of urea-N entered the GIT instead being excreted in the urine of cows fed the LoRumN diet (75% vs. 63% for both the Control and LoMP diets). Approximately 8-14% of the microbial N pool was present as protozoal N, and the protozoa predated 4-17% of the total bacterial N yield, with the highest values observed for cows fed the Control diet. A second study was conducted that fed differing amounts of dietary CP (14.3 vs. 15.8%), starch (23 vs. 29%), with or without the ionophore Rumensin. Urea-N kinetics were determined by dietary CP concentration, with little impact of dietary starch or Rumensin. Microbial pool sizes and N transactions were dependent on dietary interactions, suggesting the effect of Rumensin on these populations to be mediated by rumen conditions. Overall, these studies demonstrate control over urea-N kinetics by N intake, and particularly by urea-N synthesis, over a variety of dietary conditions. Low ruminal N balance, in conjunction with starch fermentation and ionophore effects, was able to stimulate urea-N entry to the GIT, improving efficiencies of N use. The amount of recycled N contributing to microbial N supply, in addition to protozoal predation of bacteria, varied by dietary conditions.
