Browsing by Author "Kwak, Wansup"

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    Lactational, metabolic, and physiological effects of dietary fats and isoacids on early lactating first-calf Holstein heifers
    Kwak, Wansup (Virginia Polytechnic Institute and State University, 1986)
    Forty four first-calf heifers were randomly selected to determine lactational and metabolic responses to high fat diets and isoacids. All heifers were allowed ad libitum consumption of a control diet for the first 2 weeks of lactation and then offered experimental diets Eor the next 4 weeks. Each 6 cows of twenty four were randomly assigned to 1) a control diet (C) with 35.2% corn silage, 14.4% alfalfa haylage and 50.4% concentrate (dry matter basis), 2) C with 2% calcium stearate (S) substituted for corn grain, 3) C with 2% tallow (T) for corn grain, and 4) C with 10% whole cottonseed (W) for corn grain, cottonseed meal and cottonseed hulls. The remaining 20 heifers were randomly assigned to diets C, S, T, and W, each with 4g/kg isoacids added (CI, SI, TI, and WI). Fat supplementation or isoacid addition did not affect milk production. Addition cf isoacid increased milk fat percentage, 4% fat-corrected milk, milk fat production (kg/day) and dry matter intake. Differences due tc isoacid were greatest when added to W. Increased milk lactose percentage and weight gain were evident in animal receiving WI compared to W ration. Fat supplementation depressed percentages cf milk fat, milk lactose and milk solids-not-fat. Milk protein percentage and somatic cell count were not affected by treatments. Plasma glucose,and glucose and epinephrine challenge parameters were not affected by diet. Peak plasma non-esterified fatty acid response to epinephrine injection, detected at 10 to 12 minites, was similar for C, S, T, and W. Concentrations of individual volatile fatty acids (VFA) and total VFA in rumen fluid were increased by fat supplements. Isoacid addition increased the amounts of isobutyrate and isovalerate; however, acetate and total VFA concentrations were decreased compared to CI when isoacids were added to high fat diets. The ratio of acetate to propionate was similar for all diets. Digestibilities cf dry matter, crude protein, and acid detergent fiber were not influenced by diet. The efficiency of energy utilization was highest for control diet. In conclusion, lactational, metabolic, and physiological responses to S, CI, and WI were favorable. Responses to W were lowest.
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    Solubility, degradability and utilization by ruminants of broiler litter processed by ensiling, deepstacking and composting
    Kwak, Wansup (Virginia Tech, 1990-01-05)
    Using ruminally, abomasally and ileally cannulated wethers, an in vivo experiment was conducted to compare supplementing ensiled, deepstacked and composted broiler litter as N sources with soybean meal. Sheep were fed isonitrogenous (10.3% CP) and isocaloric (56% TDN) corn cob-based diets. Apparent digestibility of CP was somewhat depressed by feeding deepstacked and composted litters; however, N retention was affected by N sources. Nitrogen source did not alter flow and partial digestion of DM, OM and ADF through the digestive tract of sheep, with the exception of higher OM digestion in the large intestine of sheep fed deepstacked and composted litters than ensiled litter. Diets containing soybean meal, and ensiled, deepstacked and composted litter had 12.2, 25.2, 29.1, and 25.5% protein undegradability, respectively. Feeding litter increased dietary undegraded N flow and decreased microbial N flOw, compared to feeding soybean meal. Efficiency of microbial protein synthesis was not affected by N source. Available N (g/d) in the small intestine was similar among all diets. An in situ bag experiment showed that CP of ensiled, deepstacked and composted litter consisted of 80 to 89% of soluble A fraction, 8 to 13% of degradable B fraction, and 3 to 6% of undegradable C fraction. The ruminal degradability of CP was approximately 89 to 94% for processed litters, and 75% for soybean meal. Nitrogen solubilities of ensiled, deepstacked and composted broiler litter, determined in autoclaved ruminal fluid, were 62, 59, and 41%, respectively, when that of soybean meal was 12%. Another in situ experiment was conducted to determine ruminal DM and CP characteristics of broiler litter from surface and charred areas in the deepstacks. The low DM content in charred litter reflected more susceptibility of the locally high moisture litter for charring. Surface litter contained less CP than normal litter. Charred litter had higher undegradable protein fractions and lower CP degradability than normal litter. These studies illustrated that broiler litter processed by ensiling, deepstacking and composting could be efficiently utilized as a protein source for ruminants.