Ph.D. Candidate and Graduate Research Assistant, jing.gao@uga.edu
Department of Animal and Dairy Science
(Editor’s note: This section is part of our effort to highlight our brilliant dairy science students at the University of Georgia to show case their achievement in dairy research)
I am originally from Wuhan, China, where I completed both my B.S. and M.S. degrees at Huazhong Agricultural University. My passion for animal science began when I was a young girl. I have always loved being around animals and knew I wanted to dedicate my career to working with them. However, it was during my M.S. program that I truly discovered my calling for the dairy industry. I had the opportunity to conduct a research internship at the University of Georgia (UGA) Dairy Research Center in Tifton, Georgia, under the supervision of Dr. Sha Tao. This experience was transformative. For the first time, I was fully engaged in dairy research and working closely with dairy cows. That experience ignited my passion for dairy science and ultimately led me to pursue a Ph.D. in Animal and Dairy Science at the UGA. I am incredibly grateful for this opportunity. Even though my original start date was pushed back from Fall 2020 to Spring 2022 due to the global pandemic, I remained committed to my goal. My advisor Dr Tao continued to encourage me throughout this period, and I am now in my fifth year at UGA.
My PhD dissertation research focuses on evaluating different management strategies at dry-off, including milking frequency, the administration of non-steroidal anti-inflammatory drugs (NSAIDs), and advancing vaccination schedules, and their effects on immunity, inflammation, and subsequent lactation performance and animal health. I am particularly proud that most of my studies have been conducted on commercial dairy farms across Georgia. I am deeply grateful for the trust and support these producers have extended to our research team, which has made this work possible.
Below, I have summarized the four primary directions of my Ph.D. research:
Characterizing Systemic and Mammary Inflammation Around Dry-Off
The objective of this foundational research was to characterize the inflammatory response that occurs when a cow transitions from lactation to the dry period. Dry-off is one of the most challenging events in a cow’s life, involving udder engorgement caused by abrupt cessation of milking, dietary shifts from an energy-dense lactation ration to a lower-energy dry cow diet, social regrouping and dry cow vaccination. These factors are stressful for dairy cows and are associated with both systemic (body-wide) and mammary (udder-specific) inflammation. In our study, we monitored healthy Holstein cows transitioning from late lactation to dry period and collected blood and mammary secretions and performed mammary biopsies to measure key inflammatory markers like haptoglobin and pro-inflammatory cytokines. We found that cows experienced a significant spike in these markers immediately following dry-off, indicating upregulated systemic and mammary inflammation. This study provided important baseline data showing that inflammation at dry-off is not just a minor issue. Instead, it represents a systemic physiological challenge that could influence immunity and the cow’s ability to successfully transition into the next lactation. These findings also raised important follow-up questions: What are the primary divers of systemic inflammation around dry-off, and what are the consequences of this inflammatory response for the subsequent lactation performance and animal health? To address these questions, we developed the following projects to evaluate management strategies aimed at mitigating systemic inflammation at dry-off.
Advancing Vaccination Schedules Prior to Dry-Off
The aim of this project was to evaluate whether advancing the timing of dry cow vaccination could reduce the systemic inflammation around dry-off. On many farms, vaccines are administered on or close to the day of dry-off, which coincides with the peak of udder pressure and social stress. This overlap of stressors may contribute to the systemic inflammation observed around dry-off. Therefore, advancing the vaccination schedule could potentially minizine the inflammatory burden during this critical period. To test this hypothesis, we conducted a trial on a commercial dairy farm in Georgia, enrolling total 328 Holstein cows. Of these, 174 in the control group followed the farm’ standard protocol and were vaccinated 2 days before dry-off, while 154 cows were vaccinated earlier on 11 days before dry-off. We found that early vaccination group shifted their inflammatory response to late lactation. As a result, these cows had lower systemic inflammation during the early dry period. More importantly, this strategy increased milk production by 1.9 kg/d in the subsequent lactation in multiparous cows. While no significant difference in milk yield was observed between the two groups in primiparous cows, the overall animal health was not negatively affected. This research suggests a practical and cost-free management adjustment for dairy producers. By simply advancing the vaccination schedule prior to dry-off, producers may help cows transition more smoothly from late lactation to the dry period and improve subsequent lactation performance in multiparous cows without compromising animal health.
Advancing Vaccination Combined with NSAID Administration at Dry-off
Earlier studies suggested that the systemic inflammation observed around dry-off may arise from multiple factors. Therefore, the goal of this project was to evaluate whether a pharmaceutical approach could further reduce the inflammatory burden during the early dry period. This follow-up study was designed to determine whether combining early vaccination with meloxicam, a non-steroidal anti-inflammatory drug (NSAID), could provide additional benefits. To address this question, we conducted a trial using clinically healthy, high-producing Holstein cows on a commercial dairy farm in Georgia. Cows were blocked by parity, days in milk, and milk yield, and randomly assigned to one of three treatments: standard vaccination on the day of dry-off (n = 56), early vaccination 14 days before dry-off (n = 55), or early vaccination combined with oral meloxicam administration on the day of dry-off and again 3 days later (n = 56). Our results showed that advancing vaccination again shifted the inflammatory response away from the early dry period, resulting in lower systemic inflammation after dry-off without affecting subsequent lactation performance. Administration of meloxicam did not further reduce systemic inflammation or improve subsequent lactation performance in these clinically healthy cows. At the same time, advancing vaccination to 14 d before dry-off was associated with increased risk of milk leakage in multiparous cows, although no increase in clinical mastitis incidence was observed in the subsequent lactation. Overall, this study reinforced an important concept: the timing of vaccination can influence the level of systemic inflammation during the early dry period, whereas pharmaceutical intervention with NSAIDs may have limited benefits in healthy animals.
Reducing Milking Frequency to Improve Udder Health
High milk yield and abrupt cessation of milking are considered as important contributors to the systemic inflammation observed around dry-off. Therefore, the objective of this study was to evaluate whether reducing milking frequency before dry-off could lower milk yield prior to dry-off and mitigate systemic inflammation, and to assess its impact on mammary health and subsequent lactation performance. To address this question, we conducted a large-scale field study on a commercial dairy farm in Georgia. Starting 13 days before dry-off, cows were assigned to one of two treatments based on the last digit of their identification number (even/odd): cows milked three times per day until dry-off (n = 480) or cows milked twice per day until dry-off by skipping the third milking in a day (n = 516). Our results showed that reducing milking frequency successfully decreased milk yield by 10 to 50% before dry-off, with the greatest decline occurring on the first day of the treatment. However, this strategy did not reduce systemic inflammatory markers around dry-off. In addition, reduced milking frequency increased the proportion of culture-positive milk samples in multiparous cows after calving and no treatment effects were observed for subsequent lactation performance. Overall, these findings suggest that although reducing milking frequency can decrease milk yield prior to dry-off, it may not provide clear benefits for inflammation or mammary health. Therefore, the potential advantages and risks of this strategy should be carefully considered when implementing dry-off management practices.
Looking Ahead: A Commitment to the Dairy Industry
In addition to the four dissertation projects highlighted above, my time at UGA has provided many opportunities to broaden my experience and skills in dairy science filed. I have been actively leading and involved in several additional research trials, including heat stress studies, lactating cow feeding trials, and calf feeding trials, which have expanded my understanding of dairy nutrition, management, immunology and physiology across different stages of production. These experiences have strengthened my interest in developing practical solutions that connect fundamental research with real-world challenges in the dairy industry.
Looking forward, my long-term goal is to continue serving the scientific community and the dairy industry as a researcher and educator. I am committed to developing practical, science-based solutions that help producers achieve higher productivity while maintaining the highest standards of animal health and welfare. I believe that by bridge the gap between complex immunology, nutrition and on-farm management, we can build a more resilient and sustainable dairy industry for the future. I am deeply thankful for the journey that brought me to Georgia, and I look forward to the many contributions I hope to make in the years to come.