Master of Science

The growing importance of grassland and all its products is becoming more evident. A grassland economy is the backbone of the sheep, dairy cattle, and beef cattle industries. Grassland farming makes for a more permanent type of agriculture. An increased acreage in sod crops results in less erosion, better soil structure and drainage, and higher organic matter. Soil productivity can be maintained or improved under grassland farming practices. A general appreciation of the value of pasture as a source of livestock feed, improvements in strains of grasses and legumes, and better knowledge of fertilizer usage have encouraged the increase in acreage of highly productive pastures. Well managed pastures are highly productive and supply nutritious herbage high in minerals and protein. The Northern Virginia Pasture Research Station at Middleburg, Virginia has experiments under way to measure quantity of production and the nutritional value of pasture herbage when grazed by dairy and beef cattle (1 and 2). These experiments are designed to measure the value of species, mixtures, methods of rotational grazing, and continuous grazing of one mixture as compared with grazing different mixtures in a rotational sequence. Data are being obtained on carrying capacity, livestock gains, carcass characteristics, palatability, and rate of milk production. This study was undertaken to gain supplementary information on the established grazing experiments at Middleburg. It was postulated that data on animal behavior would help interpret the animal responses observed. This report gives data on animal grazing frequency; however, data on other aspects of animal behavior were obtained. / Master of Science

Master of Science

Master of Science

Two feeding trials were conducted to study the effects of source of concentrate and level of concentrate and roughage on milk composition; changes in certain blood and rumen constituents; and efficiency of conversion of feed protein to milk protein. Trial A (63 days) employed two groups of six cows each. The following rations were fed: 1) Control consisting of 1 lb. concentrate per 3.5 lb. milk, 40 lb. corn silage. and orchardgrass hay, ad libitum; 2) Low-roughage composed of 5 lb. orchardgrass hay, 10 lb. corn silage, and concentrates ad libitum. Trial B (70 days) employed two groups (four each) of late and three of early lactation. A control ration similar to that fed in trial A, except 48 instead of 40 lb. of corn silage, and a low-roughage ration of only 2 lb. hay and concentrates ad libitum, were fed to two groups in each stage of lactation. The remaining early lactation group received a ration comparable to the control except the corn in the concentrate was replaced by lactose. The twelve early lactation cows were subjected to a balance study at the end of the feeding trial. Intake of concentrates and milk yields on the low-roughage rations were higher in trial A than trial B. Percent milk fat and the acetate/propionate ratio of rumen fluid were decreased by low-roughage; while rumen propionate was increased. No significant differences in milk protein were observed. Milk SNF and lactose-mineral were increased on low-roughage in trial B. Feeding only 2 lb. hay daily resulted in bloat and diarrhea; while blood glucose and gamma globulin were increased. Lactose increased rumen butyrate and tended to increase milk fat percentages above the controls. Digestibilities of all dry matter components, except crude fiber, were higher on low-roughage. Cows on low-roughage digested a larger proportion of the dietary protein, but were loss efficient in the conversion of digested protein to milk protein. / M.S.

Twenty first-calf heifers and 24 cows in their second or greater lactation were randomly assigned to 4 dietary treatments from day 15 to day 61 postpartum. Mixed diets consisted of corn silage, alfalfa haylage, orchard grass hay, and a pelleted concentrate. Concentrates were control (C), C + additional corn (H), C + 4% calcium stearate (S), or C + 4% tallow (T). C, S, and T contained 50:50 forage and concentrate dry matter and H contained 40:60. / Master of Science

Twenty-four cows in a production trial and 8 cows fitted with ruminal and duodenal cannulas were used in 4 x 4 Latin squares to investigate the effects of dietary protein degradability and supplemental fat on rumen, blood, and milk components. Diet dry matter contained 16% CP with two levels of rumen undegradable protein (RUP) obtained by substituting blood meal for soybean meal. Treatments were 29% RUP, 0% added fat; 29% RUP, 2.7% added fat (Calcium soaps of fatty acids); 41% RUP, 0% added fat; and 41% RUP, 2.7% added fat. Dry matter intake was depressed 6.2% by added fat. Plasma urea N (PUN) increased with added fat and 41% RUP, however greater changes were observed due to time of feeding. Milk production increased 7.1% in both breeds and 4% fat corrected milk increased by 8.4% in Jerseys fed added fat. Milk protein yield decreased in Holsteins fed 41% RUP. Milk protein content was reduced 7.1% by added fat and 3.9% by 41% RUP, and milk urea N (g/100g N) was increased by added fat and 41% RUP. Milk urea N followed PUN pattern throughout the day. Added fat reduced content, but not yield, of milk components. Blood meal substitution decreased content and yield of milk protein and casein N. / Master of Science

Data sets from six locations containing 631 dairy heifers and 5409 observations of individual dry matter intake (DMI) were used to develop an equation to predict DMI. Data were contributed by Pennsylvania State University, University of New Hampshire, Purina Mills, Kansas State University, University of Minnesota, and Virginia Tech. Objectives varied by location and trials within locations but all contained DMI (kg/d), BW (kg), age (wk), DM, and CP, and ADF percentages of ration DM. Daily gains (g) were calculated from consecutive BW. Season was expressed as sine wave of Julian day plus 60 d times Ï divided into 180. Average daily temperature, humidity, and wind data were collected from Minnesota and Virginia and analyzed with BW to determine their effect on DMI. Sire PTA milk, protein, and fat of heifers were recorded from all sources to determine the relationship of genetics with DMI. Diet measurements (DM, CP, and ADF percent of ration DM) were analyzed with BW to determine their impact on DMI. Two equations were developed using backwards elimination techniques. The first equation was: DMI = -12.63 + .0587(BW) - .0000264(BW2) - .000 12(BWxDM) - .000477(BWxADF) + .292(DM) - .00103(DM2) - .413(CP) + .01349(CP2) + .181(ADF) - .0025(DMxCP) - .00269(DMxADF) + .00509(CPxADF) with an R2 of .90. Because body weight and diet variables were highly correlated, a smaller model could be created with one diet variable. A smaller model would also be more practical to use if accuracy was not lost. Body weight and ADF were used for second model: DMI = -1.71 + .0429(BW) - .0000246(BW2) - .00023(BWxADF) + .032(ADF) - .00068(ADF2) with an R 2 of .87. Previous DMI prediction equations from Virginia Tech were validated using all data from other locations and had R2 of .90 and .84 with this data set. Body weight raised to the .53 power most accurately described the relationship of DMI and BW. Temperature and DMI had a quadratic relationship. Higher DMI were observed at extreme temperatures between -10 to 27° C. Humidity and temperature x humidity accounted for more variation of OMI than season and other environmental measures, but were not included in the small model due to availability of these measurements and they did not change OMI by .1 kg/SO. Sire PTA milk by groups showed differences among heifer groups although no trends were found. Dry matter percent and CP percent had linear and quadratic relationships with OMI. Maximum OMI plateaued between 75 and 950/0 OM and occurred at extreme percentages for CP between 9 and 27%. Acid detergent fiber percent had a negative linear relationship with OMI between 7 and 45%. / Master of Science

Data from the University of New Hampshire were used to analyze dry matter intake and milk production in Holstein dairy cows. Equations predicting 4% FCM and dry matter intake were derived from this data using ordinary least squares. Days in milk, available nutrients, calving date, and previous period 4% FCM accounted for 90% of the variation in 4% FCM for heifers and 93% of the variation in 4% FCM for cows with previous lactations. Days in milk, acid detergent fiber, calving date, and dry matter intake from the previous 28 day period accounted for 71% of the variation in heifer dry matter intake and 79% of the variation in dry matter intake for the older cows. First period dry matter intake was predicted from first period 4% FCM, cow body weight, and acid detergent fiber of the ration. The lower R² for the first period dry matter intake (41% for heifers and 43% for cows with previous lactations) indicated that dry matter intake for a cow within a lactation was much more predictable than dry matter intake between different cows. Rations were balanced for absolute amounts for simulated lactating cows using NRC requirements and 4% FCM and dry matter intake generated from the prediction equations. Relationships between 4% FCM and nutrient concentrations were determined for heifers and multiparous cows. These recommendations suggest maximum feeding of nutrients to groups producing at least 35 kg of 4% FCM daily. The effect of grouping and individual feeding on 4% FCM were analyzed. Independent variables included nutrient concentration, dry matter intake, groups, calving interval, variability of 305 day milk production within the herd, and level of feeding. Holding dry matter intake and nutrient concentrations constant, increasing the number of groups from one to two increased 4% FCM by 0%-3%, two groups to three groups by 0-2%, and three groups to four groups by 0-1%. Changing from one group to individual feeding increased 4% FCM by 2%-4% and two group to individual feeding increased 4% FCM by 0%-3%. The range of figures was influenced by herd production level, calving interval, and variability of within herd production. High variability of production favored additional groups, while high calving intervals favored individual feeding. To estimate expected change in profitability due to a change in grouping or feeding methods, multiply previous milk revenue by expected percentage change and subtract the increased cost of feeding. Feeding less than the group average for nutrients was not found conducive for increasing profitability. In fact, production response to protein suggested that the low producing groups in multiple group feeding systems should be increased in protein slightly. Individual feeding had the most potential for profitability, although group feeding compared favorably under some circumstances. If cows were grouped, a minimum of two groups was generally preferable. If the high producing group did not satisfy the needs of the high producing cows, or the drop in nutrients between groups was substantial, a three group system would appear more favorable. / Ph. D.

Infection of tall fescue (<i>Festuca arundinacea</> Schreb.) with the endophyte fungus (<i>Acremonium coenophialum</i>, Morgan-Jones and Gam) has been associated with toxicity symptoms observed in cattle. The overall objective was to investigate the influence of endophyte infection on growth and chemical composition of tall fescue and the toxicity of endophyte-infected (EI) tall fescue to cattle. In a greenhouse study with pairs of genetically identical EI and non-infected (NI) ‘Kenhy’ tall fescue clones, concentration of N, Ca, Mg, Al, B, Mn and Zn was higher and K and S was lower in NI, compared to EI tall fescue. Insect resistance was higher in EI, compared to NI. Yield and chemical composition of high and low EI tall fescue were measured at four growth stages (stockpiled, prebloom, bloom and regrowth after harvest at bloom), two sites (Glade Spring and Blackstone) and three rates of N fertilization (0, 40 and 80 kg/ha) in a field study. Tall fescue grown at Glade Spring was higher in N, Mg, Al, Cu, Fe and Mn, compared to Blackstone. Nitrogen fertilization increased N, Mg, Ca, B, Cu, Na, Zn and decreased NDF, ADF, cellulose, P and S concentration in tall fescue. Neutral detergent fiber, ADF, cellulose, lignin, Fe and Na were higher in low, compared to high EI tall fescue. Concentrations of Cu, Na and Zn in stockpiled and Ca, Cu, Na and Zn in bloom-cut tall fescue hay were below dietary requirements for 227-kg steers. A disc meter was also evaluated for use in predicting yield of tall fescue. The meter is useful for non-destructive estimation of yield. Three feeding studies were conducted with steers (6/treatment/year). Diets were orchardgrass/alfalfa hay, spring-cut EI tall fescue hay, spring-cut EI tall fescue silage and fall-cut EI tall fescue silage. Serum prolactin and cholesterol were depressed in steers fed fescue hay and silages, compared to steers fed orchardgrass/alfalfa hay. Differences in mineral composition of hay and silage were reflected in serum minerals in steers. Ergopeptine alkaloids in EI tall fescue may have contributed to the depression of serum prolactin. The spring-cut silage contained the highest concentration of ergopeptine alkaloids, compared to other diets. Steers fed the spring-cut tall fescue silage had the lowest basal and thyrotropin-releasing hormone stimulated prolactin compared to steers fed the other diets. / Ph. D.