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PROJECT GOALS: The fundamental goal of this experiment station project is to conduct scientifically sound research that answers basic questions yet has immediate applicability to dairy producers and the dairy nutrition support industry. Programmatic focus areas that are of concern to Minnesota dairy producers as well as being of national concern include: 1) the utilization of forages in dairy cow diets, 2) water quality for dairy cattle, and 3) calf and heifer nutrition programs. <P>I. UTILIZATION OF FORAGES IN DAIRY COW DIETS. OBJECTIVES: 1) To evaluate the utilization of grass forages by lactating dairy cows; 2) To compare the lactation performance of dairy cows when fed grass- or legume-based rations. <BR>EXPECTED OUTPUT: Results from this study will be published in a refereed scientific journal and will be utilized by nutritionists, consultants, veterinarians, extension educators and producers to make an economic based decision when choosing legumes or grasses for lactating dairy cow diets. In addition, study results will facilitate further grass forage research needed to define optimal diet characteristics and co-formulation with other feeds, forages and by-products when formulating grass based lactation diets for maximal lactating performance. <P>II. WATER QUALITY FOR DAIRY CATTLE. OBJECTIVES: 1) To determine if water containing arsenic with a concentration greater than 10 ppb, EPA drinking water quality standard, is safe for dairy cattle to drink. 2) To determine the human health risks associated with dairy products produced from dairy cattle consuming water with elevated levels of arsenic. <BR>EXPECTED OUTPUT: Results will address concerns expressed by dairy producers, veterinarians, nutritionists, citizens and government policy makers regarding the effects of arsenic on dairy cattle health and the potential transfer of arsenic to dairy products. Study results will also be utilized by dairy producers, dairy councils, producer groups, animal scientists and vet med professionals, state agencies that regulate dairies, and policy makers at the state or federal level to determine if an arsenic standard should be established for Grade A dairies. In addition, the identification of an appropriate biomarker for arsenic exposure (hair, hooves, blood, or urine) will be useful for future arsenic research.<P> III. CALF AND HEIFER NUTRITION PROGRAMS. OBJECTIVES: To evaluate the effects of feeding organic trace minerals to dairy cows, starting 30 days prior to parturition, on calf 1) health and growth performance 2) colostral immunoglobulin absorption, and 3) intestinal morphology. <BR>EXPECTED OUTPUT: Results from this study will be published in a refereed scientific journal and will be utilized by dairy nutritionists, consultants, veterinarians, extension educators and producers when designing an effective transition cow program. In addition, as this is a relatively unexplored area of research, this study will be utilized to further investigate methods to enhance calf growth and health via trace mineral supplementation.
Non-Technical Summary: I. UTILIZATION OF FORAGES IN DAIRY COW DIETS. Research studies that have compared legumes to grasses in lactating dairy cow diets are limited, and difficult to interpret. Therefore, the objectives of this project are 1) to evaluate the utilization of grass forages by lactating dairy cows; 2) to compare the lactation performance of dairy cows when fed grass- or legume-based rations. A response curve design will be used to compare high-quality alfalfa and orchardgrass hays in diets of lactating dairy cows; hays will be included at 5, 10, 15, 20, or 25% of diet dry matter. Sixty lactating dairy cows will be fed their respective treatment diets ad libitum for 56 days. Results from this study will be utilized to make an economic based decision when choosing legumes or grasses for lactating dairy cow diets. Study results will facilitate further grass forage research needed to define optimal diet characteristics and co-formulation with other feeds, forages and by-products when formulating grass based lactation diets for maximal lactation performance. II. WATER QUALITY FOR DAIRY CATTLE. In the upper Midwest, arsenic in ground water is a widespread, naturally occurring contamination problem that impacts both public and private drinking water wells. Therefore, the objectives of this project are to determine 1) if water containing arsenic with a concentration greater than 10 ppb is safe for dairy cattle to drink. 2) the human health risks associated with dairy products produced from dairy cattle consuming water with elevated levels of arsenic. A biological sampling and a residue study will be conducted. Blood, urine, hoof, hair, water, and milk samples for cheese processing will be collected from participating dairy herds. Results will address concerns regarding the effects of arsenic on dairy cattle health and the potential transfer of arsenic to dairy products. In addition, the identification of an appropriate biomarker for arsenic exposure (hair, hooves, blood, or urine) will be useful for future arsenic research. III. CALF AND HEIFER NUTRITION PROGRAMS. A novel approach to improve calf health and growth performance is to provide additional organic trace minerals to the dam during the dry period. Therefore, the objectives of this project are to evaluate the effects of feeding organic trace minerals to dairy cows, starting 30 days prior to parturition, on calf 1) health and growth performance 2) colostral immunoglobulin absorption, and 3) intestinal morphology. Of the offspring, thirty bull calves will be euthanized to measure intestinal villi concentration and length and seventy-five heifer calves will be utilized to obtain performance data for 56 days. Results from this study will be published in a refereed scientific journal and will be utilized by dairy nutritionists, consultants, veterinarians, extension educators and producers when designing an effective transition cow program. In addition, as this is a relatively unexplored area of research, this study will be utilized to further investigate methods to enhance calf growth and health via trace mineral supplementation. <P> Approach: METHODOLOGY: I. UTILIZATION OF FORAGES IN DAIRY COW DIETS. A response curve design will be used to compare high-quality alfalfa and orchardgrass hays in diets of lactating dairy cows. A series of 10 treatment diets will be formulated, 5 each of alfalfa and orchardgrass hays. Hays will be included at 5, 10, 15, 20, or 25% of diet dry matter, resulting in diets ranging from approximately 40 to 65% forage. Cows will be fed their respective treatment diets ad libitum for 56 days. Data collection will include feed intake, milk production, milk composition, body weight, feed ingredient, diet and refusal samples and fecal samples. Current feed and milk prices will be used to determine income over feed costs for all treatments. II. WATER QUALITY FOR DAIRY CATTLE. Dairy herds with confirmed well water arsenic concentration greater than 40 ppb will be invited to participate in the biological sampling phase of the study. Blood, urine, hoof, and hair and water samples will be collected from each herd and analyzed for arsenic. A residue study will also be conducted. Twenty dairy herds ingesting water containing < 10 ppb, > 10 but < 50 ppb, and > 50 ppb arsenic will be identified as low, medium and high arsenic groups, respectively. Water, feed ingredient, milk and urine samples will be collected from each herd and analyzed for arsenic. Approximately 80 pounds of bulk tank milk from each herd in the low and high groups will be processed into cheese. Cheese, whey, and salt will be analyzed for arsenic concentration. Liver and kidney necropsies will be taken from any cow that is slaughtered and analyzed for arsenic concentration. III. CALF AND HEIFER NUTRITION PROGRAMS. One hundred and five Holstein dairy cows will be randomly assigned to one of three trace mineral treatments: 1) control - inorganic trace mineral supplementation; 2) organic trace mineral supplementation; 3) organic trace mineral supplementation with enhanced zinc content. Treatments will be top dressed on the basal diet from thirty days prior to calving until calving. Thirty bull calves (10 from each treatment) will be euthanized to measure intestinal villi concentration and length; twelve bull calves will be euthanized at birth and 18 bull calves will be fed milk replacer for 2 weeks and then euthanized. For calves euthanized at 2 wk of age, a full necropsy will be performed. Seventy-five Holstein calves will be utilized to obtain performance data; growth and feed intake will be recorded from birth to 56 days of age. Milk replacer and starter intake will be recorded daily and body weight will be recorded at birth, day 42 and day 56. EFFORTS: Study results will be published in referred scientific journals. In addition, results will be presented at animal science conferences, scientific meetings, and extension workshops. EVALUTION: Project success will be based on the ability to meet stated study objectives.