Over the past two decades, there has been a marked shift in herd size distribution among dairy farms in the U.S.; farms with fewer than 100 cows accounted for 49% of the country’s milk cows in 1992, but just 17% of milk cows in 2012. In contrast, farms with at least 1,000 cows accounted for 49% of all milk cows in 2012, an increase from 10% in 1992. As overall herd size increases, dairy farms are also becoming more reliant on the hiring of non-family labor. However, greater reliance on employees has raised new challenges for training and compliance of critical farm protocols, including milking cows. Improper milking can impact the health of dairy cattle, particularly with respect to mastitis. Bovine mastitis is one of the most important diseases of dairy cattle in the United States and continues to cause major economic losses to the dairy industry, due to decreased farm productivity and quality of dairy foods. Crucially, the capacity of farms to train and educate personnel may play a key role in mastitis control and milking efficiency. However, many farms have not adapted management strategies to address changes in the employee training and education landscape. This ‘cultural lag’ in the dairy industry has warranted further study of the labor culture on dairy farms, and to find the means to assess employee performance and success of employee training, as measured by the milking efficiency. Therefore, the hypothesis of Chapter 2 was that employee and management factors affect milking efficiency of cows as measured by the proportion of cows within a herd with delayed milk ejection. Results of this study showed that herd size and mean stimulation time during pre-milking preparation was a significant factor in the proportion of cows with delayed milk ejection. While past research indicates that stimulation time is important for proper milk ejection, it is a novel concept that stimulation time has the possibility of overriding many other factors that may play a role. However, this did not fully explain the employee factors that could potentially affect milking efficiency. To further investigate this relationship, Chapter 3 hypothesized that employee and management factors had an effect on the mean stimulation time during the pre-milking protocol. The results of that study showed that increasing lag time during the pre-milking routine was positively associated with increasing mean stimulation time. However, herd size and the number of passes during the pre-milking routine was negatively associated with mean stimulation time. These results suggest that employees who were expected to complete more tasks in a shorter amount of time were less likely to properly stimulate teats before milking, which as determined in Chapter 2, then leads to greater frequency of delayed milk ejection.In addition to delayed milk ejection, overmilking of cows (the time period when milking units are attached to teats with no milk flowing) is a critical measure of milking efficiency. Overmilking not only increases the amount of time that cows are unable to rest and eat, but also exposes teats to high vacuum levels and subsequently, increases the risk of mastitis. Chapter 4 hypothesized that there were employee and management factors that are associated with median overmilking time in a herd. The results of this study found that herds with a shorter duration of daily milking periods had a greater proportion of overmilked cows. These results suggested that farm owners or operators who milk cows on farms that do not attain the full daily capacity of the milking equipment, may be making subjective decisions to milk cows inefficiently from overmilking. In summary, milking efficiency in dairy cattle is impacted by several herd level variables, especially those related to herd size. Milking protocols and employee behaviors that are associated with herd size of the farm play a role that impacts a herd’s milking efficiency. Whether a farm is considered to be large or small they can be prone to inefficiencies that could impact milking performance.
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