Data were collected from a 1,000 cow commercial dairy unit during three different time periods to determine the interrelationships between teat shape, teat erosion, mastitis (as measured by the California Mastitis Test and somatic cell counts), and milk production. Results showed no relationship between teat shape or teat end erosion and milk or fat production. The relationship between teat end erosion and mastitis appeared to be masked by the high level of teat erosion. There was an indication that cows with flat and cone shaped teat ends were prone to higher California Mastitis Test scores than cows with pointed, round, or disk shaped teat ends. Pointed teat ends showed the highest amount of erosion and cone and flat teat ends showed the least amount of erosion. There was a high correlation between the California Mastitis Test and somatic cell counts. Teat end erosion and California Mastitis Test scores decreased and milk production increased when a change in milking equipment and milking technique occurred and teat dipping was instigated.

Twenty three cows with an average of 2.7 lactations were used to measure the effects of different protein sources (soybean meal, soybeans, and heat-treated soybean) and supplementation with niacin on milk production, milk components (protein, fat, somatic cell counts), 4% fat corrected milk, solid corrected milk, dry matter intake, body weight changes, and rumen volatile fatty acids (acetate, propionate, butyrate). Diets affected performance of cows. The results indicate, in general, that feeding heat-treated soybean and soybean meal to lactating dairy cows in early lactation resulted in greater milk production, milk protein, dry matter intake and less loss of body weight than these parameters in cows fed soybean. Cows fed heat-treated soybeans had greater protein percentage in the milk and milk protein yield than cows fed soybean meal; however, there was tendency for higher fat tests early in lactation when cows were fed soybean. Also the results indicated that niacin supplementation improved milk production and dry matter intake, but did not influence milk composition.

The study was conducted using nine Holstein heifers with weights ranging from 700 to 990 pounds (lb). The design was a 3 X 3 Latin Square. The three rations consisted of 26.5 lb of corn silage supplemented with 3 ounces of sodium bicarbonate, 26.5 lb of corn silage, and 26.5 lb of soybean and milo haylage per head per day. The rations were offered on a rotational basis for three experimental periods consisting of three weeks each. Blood samples were taken at weekly intervals during each period; plasma concentrations of glucose, ammonia, beta-hydroxybutyrate and volatile fatty acids were determined. There was no significant dietary effect on the mean group concentrations of the measured blood parameters. Also, there was no dietary effect on the performance of the animals. The correlations relative to diets showed some variations. The correlations varied in value and relationship. Mean values observed for some of the blood parameters measured indicated that the animals received adequate nutrients.

Previous studies of dairy cattle have indicated that heifers and cows in hot, cold and moderate weather had different patterns of sexual activities. The purpose of this study was to compare distribution of sexual activities within estrus of dairy cattle. Three groups of lactating cows in hot, cold and moderate weather and a group of heifers in cold weather were observed. Estrus for each individual was divided into 12 equal periods. Sexual activities for 3 and 6 hours before and after estrus were also observed. The numbers of mounts and distribution of total sexual activities was analyzed. Mounts received per animal per period for all four groups were significantly different. Heifers had significantly more mounts than cows with 5.8 mounts per animal per period. Cows in hot weather had significantly less mounts than other groups with 1.2 mounts per animal per group. Cows in cold and moderate weather had similar numbers of mounts with 2.9 and 2.4 mounts per animal per period, respectively. This was significantly fewer mounts than were received by heifers but a significantly higher number of mounts than received by cows in hot weather. There was much individual variation; however, the distribution of mounts and activities per period did not significantly differ across groups. There were trends for cows in hot weather to have rest periods within estrus where less mounting occurred. Secondary sexual activities before and after standing estrus were less intense than during estrus. Secondary sexual activities were greater in the three hours before and after estrus compared to the three to six hours before and after estrus.

A study of the reproductive performance of 179 dairy cows during the period from December 1978 through March 1984 was conducted at the Western Kentucky University Farm, Bowling Green, Kentucky. The climatic data showed seasonal variation in temperature as follows: winter 3.10C, spring 15.7°C, summer 23.8°C, and fall 12.0°C. The seasonal humidity was similar for winter (81.2%), spring (83.4%), and fall (85.3%); but for summer it was considerably higher (89.4%). The conception rate varied through all the months but was lowest during the summer months. Seasonal data for conception rate were obtained and the results were as follows: winter 54.1%, spring 46.4%, summer 15.6% and fall 39.0%. Low fertility during summer months was associated with high air temperatures and high relative humidities. The coefficient of correlation for temperature vs. conception was low (-0.15) because there was low fertility in some winter months and in some summer months. The coefficient of correlation for humidity vs. conception was high (-0.65), and the coefficient of determination was 42%. A completely randomized design and analysis were used, resulting in significant differences among seasonal fertility rates but no significant differences among months within seasons. Significant differences were found for the following comparisons: winter vs. spring, summer, and fall; spring vs. winter, summer, and fall; and summer vs. spring, fall, and winter. The total services involved were 546, and the total conceptions obtained were 155--resulting in a service per conception ratio of 3.52. The average number of days open was 177 (79 cows). The average number of days in the calving interval was 457 (63 cows).

Antibiotics are used as prophylactic agents to promote growth and for treating infections in animals. However, the irrational use of antibiotics in livestock management is a significant cause of the development of antibioticresistant genes in the environment. Each year 2 million people suffer from the infections caused by bacteria which are resistant to antibiotics and 23,000 of these people are estimated to die because of antibiotic resistance. New drugs are continually coming into the market but are at the risk of developing resistance. Thus, there is a need for the development of analytical methods which can be used to monitor these antibiotic concentrations in environmental samples. This research is focused on developing and validating a Solid Phase Extraction (SPE) procedure and liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying tylosin antibiotic in cattle waste. Tylosin was extracted from cattle waste samples using Strata polymeric weak cation cartridges by adding a sodium-EDTA buffer solution and methanol. Chemical analysis of the extracted tylosin was performed using a Varian 212-LC HPLC and Agilent 500 Ion Trap mass spectrometric detector. The concentrations of tylosin in study group animals were compared with respect to the date of sampling and cattle body weight with a control group and results are presented.

Lameness is considered one of the most important health and welfare issues in the dairy industry. Understanding the total cost per case of disease-specific lameness can help producers select better treatment, prevention, and control strategies for their herds. The first objective of our research was to calculate the costs associated with 3 lameness causing hoof diseases: digital dermatitis, sole ulcer, and white line disease. To accomplish this, a survey of hoof health professionals (hoof trimmers and veterinarians) was conducted to identify treatment related expenditures per case. Data from the hoof trimmer responses to the survey and previously published research were incorporated into a farm-level stochastic simulation model to determine the expected costs per case of each disease and the most influential factors associated with disease costs. The cost per case was calculated by disease type, severity (mild or severe), incidence timing (0 to 60 days in milk, 61 to 120 days in milk, 121 to 240 days in milk, or > 240 days in milk), and parity group (primiparous or multiparous). The second objective of our research was to determine the economic value of investing in different lameness prevention strategies. Two prevention strategies were considered: 1) prevention of infectious hoof diseases and 2) prevention of non-infectious hoof diseases. The total expenditures (therapeutics, outside labor, on-farm labor, and prevention costs) and losses (discarded milk, reduced milk production, extended days open, increased risk of culling, increased risk of death, and recurrence losses) associated with each prevention strategy before and after prevention implementation were calculated and compared to find the breakeven investment cost.

Mastitis and milk quality affect every dairy farmer across the globe. Sand bedded freestalls are the industry standard for cow comfort, welfare, and the control of environmental mastitis. Compost bedded packs may be a viable alternative to the sand bedded freestall. Compost bedded packs are maintained at a consistent level of moisture, nutrients, and aeration to favor compost microorganisms. Greater bacteria counts in bedding have traditionally been associated with increased mastitis rates and mastitis pathogens can be found in the pack and on the teats of cattle housed in even well managed compost bedded pack barns. In spite of this, herd SCC often remains low in well managed herds. The relationship between stress and comfort in the housing environment was a primary focus of this research. Cows housed in environments with low stress and high comfort may be better able to defend themselves against pathogens. Establishing changes in immune function in response to housing environment would improve milk quality by contributing to the knowledge of how mastitis-causing pathogens are contracted. An additional goal of this research was to determine the effect of compost bedded pack barns on thermoduric bacteria populations. Due to the increased temperatures associated with composting, thermoduric bacteria capable of surviving pasteurization are of potential concern in compost bedded packs. This research will investigate potential differences in thermoduric bacteria counts between compost bedded packs and sand bedded freestalls.

Precision dairy monitoring technologies can be used to monitor changes in physiology and behavior associated with transition period postpartum diseases and heat stress. Research Objective One was to evaluate how traditional visual examination, body condition, and locomotion with and without blood, milk, and urine variables and precision dairy monitoring technologies determine variable association with hyperketonemia, metritis, mastitis, hypocalcemia and retained placenta,. This was accomplished by monitoring cows 2 weeks before calving to 3 weeks after calving for any postpartum diseases using daily visual examination and automatically detected variables including activity, milk yield, milk components, lying behavior, feeding behavior, rumination time, and reticulorumen temperature. Deviations in reticulorumen temperature, milk production, eating time, lying time, and activity were detected by precision dairy monitoring technologies among cows with postpartum diseases. Research Objective Two was to determine the association between automatically detected variables and heat stress. This objective was accomplished by monitoring cows under natural ventilation, fans, and fans plus sprinklers for variations under each condition. Changes in physiology and behavior as detected by precision dairy monitoring technologies was associated with postpartum diseases and heat stress. Using precision dairy monitoring technologies and visual examinations may aid producers in identifying postpartum disease and heat stress.

Precision dairy technologies (PDT) are becoming more accessible and are therefore becoming more common on commercial dairy farms and in dairy research. Prior to any use of PDT, one should understand the precision, accuracy and bias of the device by a validations studies before interpreting the behavior measurements. Thus, the objective of the first section of my thesis is to validate ruminating, feeding and resting measurements of a behavior monitoring collar used in the second section. Precision dairy technology is used in heat stress studies to compare behavior of cows exposed to different heat stress treatments or abatement strategies. Heat stress is an important issue to research because it negatively affects cow behavior, physiology, and therefore production in lactating dairy cows. The objective of the second section is to assess the ability of a free choice soaker to reduce heat stress measured utilizing PDT and compare use of a free choice to a soaker in addition to one of the two treatments 1) no mandatory soakings, or 2) two mandatory soakings.