Barley (Hordeum vulgare, L.) harvested at boot (5/7/88) and soft dough (6/6/88) stages of maturity was ensiled for nutritive comparisons. Boot stage was wilted and soft dough was direct cut at 15 (SD-Lo) and 25 cm (SD-Hi) above ground. Yields (kg DM/ha) were 3690, 8750 and 6287 for boot, SD-Lo and SD-Hi respectively. Digestibilities (%) of DM, CP and ADF were 74.7, 74.5 and 70.8 for boot; 61.9, 50.4 and 44.7 for SD-Lo; and 62.3, 47.2 and 49.7 for SD-Hi, respectively. Calculated TDN was 71.2, 62.0 and 62.8 for boot, SD-Lo and SD-Hi, respectively. Thirty-six lactating Holstein cows were fed boot silage at 75 and 60% of diet DM, SD-Lo fed at 75 and 60 and SD-Hi fed at 75 and 60, respectively. Milk yields (kg/d) were greatest for high concentrate diets and averaged 25.7, 28.3, 24.8, 26.3, 25.7 and 26.9, respectively. There were no differences among diets for DM intake or 4% FCM. Boot silage had a greater In Situ rumen degradability of DM, CP, ADF and NDF (68.6, 89.3, 44.2 and 45.1% respectively) than SD-Lo (57.8, 76.9, 20.9 and 24.2%) and SD-Hi (62.5, 80.0, 22.8 and 26.4%). Predictability of ruminal degradability of complete diets from weighted averages of single ingredients determined separately was low. In Situ incubation of single ingredients resulted in underestimation of DM and overestimation of CP degradability compared with complete diet incubation. / Master of Science

Two experiments were conducted to study the utilization of poor quality hay by ruminants. In the first experiment, several nitrogen supplements were compared under practical conditions when fed to stocker cattle receiving a hay diet. Sixty cattle were wintered on fescue hay with one of five supplements: 1) none, 2) liquid urea-molasses supplement injected into the bales, 3) liquid-supplement self-fed in lick-tank, 4) mixture of deep-stacked broiler litter and ground corn grain and 5) soybean meal. Preliminary observations showed that the liquid supplement injected into bales was poorly distributed. Highest daily weight gains were for the animals supplemented with urea-molasses self-fed, litter or soybean meal. Compensatory gains under spring-grazing conditions subsequently suppressed these differences. Feed intake was low for all treatments. Feed efficiency was best for the soybean-meal group but feed cost per unit of gain was lowest for the broiler litter supplemented group. In a second experiment, urea and carbohydrates were supplemented to a fescue hay diet fed to lambs cannulated at the rumen, abomasum and ileum. The treatment diets were: 1) hay, alone or supplemented with 2) urea, 3) urea and molasses and 4) urea and corn. Chromic oxide and Co-EDTA were used as markers. Urea supplementation improved N retention but did not affect DM, ADF and energy digestibilities. The extent and efficiency of rumen fermentations were low, with a high methane production. Supplementation did not significantly affect the partition of digestion of DM and N along the gastro-intestinal tract. ADF digestion in the large intestine was increased by urea supplementation. Mean retention time of food along the gastro-intestinal tract was similar among treatments. / M.S.

Ph. D.

Thirty primiparous Holstein cows in mid lactation (106± 24 d) were randomly assigned to one of six diets in an incomplete block design. Each cow received two of six diets. Cows received the first diet for 32 d, then were offered a different diet for 32 d. received two of six diets. There were 5 observations per diet per period for a total of ten observations per treatment. Diets were 12% CP soybean meal (LSB), 20% CP soybean meal (HSB), 20% CP fishmeal (FM), 20% CP corn gluten meal (CG), 20% CP CG:SB, and 20% CP FM:SB. All diets were > 75% TDN and ~ 16% acid detergent fiber. Milk yield was not different between treatments. Milk fat percent, milk lactose percent, and fat corrected milk yield were higher in cows on CG (3.13%, 5.30%, 23 kg) in contrast to cows receiving FM (2.11%, 5.00%, 20.5 kg). Milk protein percent was not different, but milk protein yield was different across treatments. Rumen ammonia concentrations differed significantly with HSB (13.5 mg/dl) higher than LSB (7.33 mg/dl), indicating the increase in ruminally degraded protein. Plasma urea concentrations reflected rumen ammonia concentrations with HSB (16.2 mg/dl) higher than LSB (6.4 mg/dl). Results suggest that protein source can affect milk composition in cows fed low fiber diets. / Master of Science

Forty-two high producing Holstein cows were paired by body condition and mature equivalent milk production and fed either a high or low energy complete ration ad libitum during the last 16-20 weeks of lactation. Cows fed the high energy ration ate more feed, produced more milk and gained more body condition than cows fed the low energy ration. Cows were fed to maintain condition during the dry period. During weeks 3-15 of the next lactation, half the cows in each condition group (fat or thin) were fed a mixed ration with soybean meal (SBM) as the major protein source. The remaining cows were fed a ration with dried brewers grains (DBG) as the main protein source. / Master of Science

Twenty Holsteins, ten pregnant heifers and ten pregnant cows (third or greater pregnancy) were subdivided and fed either a low calcium (Ca) or Ca-supplemented ration for four weeks prepartum to determine the influence of age and prepartum Ca intake on hormonal control of peripartum Ca homeostasis. Jugular blood samples were taken on a fixed schedule from 21 days prepartum through 21 days postpartum for parathyroid hormone (PTH), calcitonin (CT), Ca, magnesium (Mg), and phosphorus (P) analysis. Heifers and cows receiving the high Ca ration prepartum tended to have higher prepartum serum Ca. Cows fed the high Ca ration prepartum (hi-Ca cows) exhibited severe hypocalcemia (6.1 mg/dl) at parturition and remained hypocalcemic for three days. Serum PTH concentration increased prepartum (-5 to -3 days) and at parturition, followed by an increase in CT, in all groups except high-Ca cows. Circulating CT was lower in high-Ca cows throughout the experiment. Serum concentrations of PTH and Mg increased from 7 to 21 days in all except high-Ca cows. Feed intake corrected for metabolic bodyweight was similar for both dietary treatments and ages. Milk production was greater for the first week in cows fed low Ca prepartum. There was no correlation between hypocalcemia and increased milk Ca concentration. In conclusion, heifers were able to achieve calcium homeostasis despite the high Ca ration, while high-Ca cows exhibited subclinical milk fever. / M.S.

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. / M.S.

Six Angus steers were used in a series of three metabolism trials to study the effect of energy concentration on nitrogen metabolism and digestibility. The experimental design consisted of two randomly selected 3 x 3 Latin squares. Three fattening rations were ted which contained 1133, 1164 and 1222 kcal. digestible energy per lb. feed and 12.18, 12.51 and 12.29% crude protein, respectively. The rations were composed of 10% grass hay, shelled corn, corn cobs and cottonseed meal. An attempt was made to equalize calcium and phosphorus contents. Vitamins A and D were added at the rate or 30,000 I.U. and 3750 I.U. per steer per day, respectively. Energy concentration was varied by changing the proportions of shelled corn and corn cobs. Digestible and metabolizable energy and TDN were all significantly increased with each increase in energy concentration. Digestible energy concentration of feed had no significant effect on nitrogen retention. Biological value waa higher for the medium energy ration than for the low or high energy rations. The quadratic effect was significant (P < .05). The apparent digestibilities of crude protein and ether extract were not influenced by energy concentration. Digestibility of' dry matter, organic matter and NPE significantly increased and digestibility of crude fiber significantly decreased with each increase in energy concentration. / Master of Science

The objective of this study was to examine the use of technical indicators, in an econometric context, as guides in making pricing decisions relative to feeder cattle production. Technical indicators were developed for both the short and long term. Short term indicators were designed to capture divergence/convergence between the Relative Strength Index and the futures price stream to form the Price Linked to Divergence index. A long term indicator using an average difference in price over a longer period was developed to form the Price Linked to Trend index. These indicators were used in the econometric models which in conjunction with cash production costs formed a hold/price/sell decision framework. Analysis was conducted on fall-to-spring, spring-to-fall, and fall-to-fall production programs. Results for the three production programs in both the in and out-of-sample environments showed that on average a futures price in the top half of the futures price range was captured. This resulted in average improvement in returns through hedging for every program. / Master of Science

The effects of quantity of dietary starch and type of dietary protein on hindgut fermentation were evaluated. Thirty-two Holstein bull calves were fed diets containing variable amounts of orchardgrass hay and a grain mixture. The amount of starch and types of protein were: [L1] low starch, soybean meal (SBM); [L2] low starch, fishmeal plus dried brewers' grains (FBG); [Hl] high starch and SBM; [H2] high starch, FBG. The percentages of acid detergent fiber (ADF) and crude protein were: [L1] 19.2%, 15.1%; [L2] 18.0%, 15.6%; [H1] 9.5%, 14.9%; [H2] 9.6%, 15.4%. After calves were fed the diets for 17 days, they were slaughtered to obtain their intestinal tracts. Ileal, cecal, and colonic digesta and feces of calves fed Hl and H2 versus Ll and L2 contained less water and ADF. Concentration of nitrogen in digesta and feces did not differ. Ileal, cecal, and colonic digesta from calves fed H1 and H2 had significantly greater numbers of viable anaerobic bacteria and lower pH._ Cecal digesta from calves fed high fiber diets (L1 and L2) had lower total VFA, propionate, and buytrate concentrations than calves fed high starch diets. Colonic and cecal digesta of calves fed diets H1 and H2 contained less ammonia. Acetate and propionate flux across cecal epithelium ro vrtro was faster for diets H1 and H2. Results indicate that high dietary starch stimulated anaerobic bacterial growth and fermentation in the hindgut, and enhanced acetate and propionate flux across the cecal epithelium. Acetate and propionate transport across the cecal wall probably is not due solely to passive diffusion, but it may involve a carrier. Replacement of SBM by FBG also altered cecal fermentation to a lesser extent. Calves fed H2 had significantly greater numbers of viable anaerobic bacteria in cecal and ileal digesta and 2 to 10 times the number of bacteria associated with cecal epithelium than calves fed the other diets. Butyrate cecal concentration and production was significantly increased when calves were fed diets containing FBG. Cecal VFA production may account for approximately 3 to 5% of digestible energy intake. / Ph. D. / incomplete_metadata