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Two trials were designed to study the relationships of dietary fiber (ADF) and protein level and source to fecal consistency in lactating cattle. In Experiment 1, 30 cows (12 multiparous, 18 primiparous) were randomly assigned to one of six total mixed diet treatments through four 21 d periods. For Experiment 2, six primiparous cows were used in two 6 x 6 Latin squares to evaluate water consumption, apparent digestibilities of DM, AOF, NOF, and starch, and to quantitate whole corn kernel passage. Total mixed diets for both trials were formulated to contain 17% (LF) or 25% AOF (HF) with CP levels of: 15% (S15) and 22% (S22) with soybean meal (SBM) supplementation, or 22% (G22) with combination of 50% corn gluten meal (eGM) and 50% SBM. Two forage sources were evaluated: corn silage (e) and alfalfa/corn silage (Ae) (50:50 on OM basis). Fecal consistency was evaluated using a 4 point scale (l-most fluid to 4-least fluid). Experiment 1 demonstrated that lower dietary fiber reduced fecal pH (LF=6.65, HF=7.11) and fecal score (LF=2.18, HF=2.41), but increased fecal DM (LF=16.1%, HF=13.2%). Supplementing SBM (S22) decreased fecal DM (S22=14.1%, G22=15.5%) and fecal score (S22=2.01, G22=2.48). Forage source affected fecal DM (C=14%,AC=15.3%), but not pH or score. HF=13.2%). Supplementing SBM (S22) decreased fecal DM (S22=14.1%, G22=15.5%) and fecal score (S22=2.01, G22=2.48). Forage source affected fecal DM (C=14%,AC=15.3%), but not pH or score. Results of Experiment 2 support major conclusions of Experiment 1. High supplementation of SBM increased daily water consumption (S22=80.2 kg, G22=74.5 kg), and reduced fecal score (S22=1.9, G22=2.4). Forage source affected apparent corn kernel (C=21.1% ,AC=33.9%) and starch (C=96%, AC=93%) digestibilities. High protein diets resulted in greater apparent DM digestibility (S15=68.2%, S22=71.8%, G22=71%). In prediction of fecal score from dietary components and animal parameters, dietary DM percent and 4% fat corrected milk (r²=.09, Experiment 1), and DM intake (r²=.12, Experiment 2) were variables most related to fecal score. Dietary effects on fecal consistency were primarily due to ADF level and type of protein supplement. Accurate prediction of fecal consistency score from the dietary and animal parameters identified was not possible. Further study is suggested to evaluate different protein sources, the contribution of water consumption, and to clarify interactions of protein, forage source and fiber level in relation to fecal consistency. / Master of Science

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

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

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.

One hundred and eight Holstein dairy heifers were divided into two weight blocks based on beginning body weight (E = < 182 kg, light, > 270 kg, heavy). Heifers within weight blocks were randomly assigned to one of five treatments. Treatments consisted of three levels of NDF (35%, 45%, 55%) at 100% ofNRC TDN recommendation, and three levels of TDN (85%, 100%, 115 of NRC) at 45% NDF for light heifers. For heavy heifers, treatments consisted of three levels of NDF (40%, 50%, 60%) at 100% NRC TDN, and three treatments with similar levels of TDN at 50% NDF. Heifers were fed total mixed rations of corn silage, alfalfa haylage, ground orchardgrass hay, soybean meal, high moisture corn and a mineral mix formulated for 0.68 kg ADG. Mean gains (kg/d) were 1.07 and .96 for the light and heavy blocks, respectively. DMI as a percent of BWT differed across NDF levels for light heifers (3r'= 2.96, 2.56, 2.57, 2.57, and 2.87 % of BWT for the low, med., high NDF, and low, high TDN treatments, respectively). Heavy heifer DMI% did not differ (.Â¥= 2.45, 2.40, 2.24, 2.15, and 2.42 % ofBWT for low, med., and high NDF, and low, high TDN treatments, respectively). Equations to predict DMI were developed using intake information from this and a previous study. Backward stepwise regression was utilized to generate a simplified model. Model selected was: DMI (kg/d) = -5.9781 + (2.2120E-05 * BWTSQ) - (5.5527 * GAIN) + (2.7837 * GAINSQ) + (0.4668 * NDF) + (5.3930 * NDFSQ) + (0.03285 * DM) + 1 (7.7859E-03 * BWT * GAIN);11 = 514, rz = .67. / Master of Science

Three experiments were conducted to determine the relationship of milk fat secretion to concentration and ratio of rumen fermentation products, blood metabolic parameters, ration characteristics, and certain enzymic activity involved in fatty acid synthesis. In Experiment I, 21 cows in mid-lactation were randomized according to milk production to (1) roughage ration (~22% CF) restricted to NRC; (2) concentrate ration (~12% CF) ad libitum; or (3) concentrate ration (~12% CF) restricted to NRC and fed for 30 days. Ad libitum concentrate showed higher dry matter intake (DMI), body weight (BW), milk production than restricted concentrate. The opposite was true for fat test. Concentrate rations (ad libitum and restricted) when compared to roughage showed higher values for DMI, BW, milk production, serum glucose, molar proportion propionate and valerate and lower values for fat test and molar proportion acetate. In Experiment II, 24 cows 180 d. post parturition, were assigned to four rations based on anticipated parturition. Rations were: (1) roughage ad libitum (~20% CF); (2) concentrate ad libitum (~10% CF); (3) concentrate restricted (~10% CF) to NRC; and (4) normal ration (~14% CF) ad libitum. Cows on ad libitum and restricted concentrate consumed less dry matter, acid detergent fiber, neutral detergent fiber and crude protein than control cows (roughage and normal). Cows fed control rations gained more weight than concentrate fed cows. No difference was found for milk production. Milk protein was higher for control cows. Concentrate cows had lower fat test than control cows. Cows on all rations decreased fat test up to week three or four but by week eight or nine, concentrate fed cows had decreased to their lowest fat test. Energy restriction improved milk fat secretion compared to ad libitum intake after the eighth week. Molar proportion VFA favored propionate for concentrate cows and was similar for restricted and ad libitum concentrate. Total ruminal VFA concentration was higher for ad libitum concentrate cows and those cows showed slightly higher glucose and smaller blood acetate compared to control. Twelve cows in mid-lactation were fed the rations of Experiment II to determine the effect of available energy intake on activity of key enzymes of fatty acid synthesis. Activity of 6-phosphogluconate dehydrogenase was not different among rations. Mammary tissue showed from five to six times higher activity than adipose tissue. Fat tissue activity tended to be higher for concentrate rations compared to roughage. No differences among rations were found for glucose 6-phosphate dehydrogenase nor isocitrate dehydrogenase. Mammary tissue was 21 to 28 times more active than adipose tissue for latter enzyme. Fatty acid synthetase showed no difference in activity due to rations, but mammary tissue was seven to ten times more active than adipose tissue. / Ph. D.

no abstract provided by author / Master of Science