Recent advances in the comprehension of the association between the metabolism and inflammatory state of cows have fomented scientists around the world to investigate the role of body tissues, nutrition and management on performance and health of dairy cows. Therefore, the first Animal Health symposia presented at the 2021 ADSA annual meeting brought into discussion the role of adipose tissue in transition dairy cows as an integrator of metabolic and inflammatory cues in health and disease. Presented by worldwide specialists, the symposia enlightened attendees with the most current knowledge regarding the energy and lipid physiology of dairy cows.
Insulin resistance was the first topic depicted during the event. The presenter went through an overview of hormone function, methods to quantify, and limitations of the techniques used for evaluation. Thereafter, data were presented to demonstrated how body condition score is related to insulin resistance and how glucose metabolism plays an important role in the adaptation of transition dairy cows. Over conditioned animals have larger adipocytes, with greater basal and stimulated lipolytic activity that differs in extension depending on the adipose tissue depot (omental vs. subcutaneous). As a result of accumulated fat, cows experience a higher abundance of pro-inflammatory cytokines which are an indicator for infiltration of macrophages. Deepen into the endocrinology of the fatty acids, the next presenter demonstrated that the involvement of adipose tissue in metabolism is not limited to energy storage. The fat mobilization modulates the steroid system that is related to the regulation of different physiological processes such as reproduction and immunology, and it seems to have greater importance for cows with a higher body condition score.
There are many metabolic and inflammatory markers that can be explored in order to better understand the adaption of cows during the transition period. Proteomics is one of the promising tools that is revealing numerous proteins related to the inflammatory pathways and its integration with adipose tissue. Although proteomics is a snapshot of a specific time and tissue, it allows the researchers to track and describe markers, therefore, improving their understanding of inflammation and novel proteins related to the adaptation of periparturient cows. It is well known that a certain degree of lipid mobilization is necessary and will help cows supporting milk production during the onset of lactation when they are on a negative energy balance status. However, cows with intense and protracted lipolysis during the first month of lactation experience increased oxidative stress and, consequently, activation of inflammatory responses.
Therefore, strategies that improve the antioxidant defenses and the function of the adipose tissue such as the use of fatty acid supplementation in the diet are promising and must be the focus of future research. Translating the recent findings of the research into the daily herd management operations is fundamental for the improvement of performance and health of dairy cows. Thus, maximizing dry matter intake early postpartum, providing cow comfort and a feeding program that aims to minimize changes in fat deposition pre- and excessive mobilization post-partum are still key factors to consider. More recently, the use of ultrasound to identify backfat thickness (BFT) seems to be a great opportunity to improve the evaluation of the transition program on farms once experiments have demonstrated increased BFT in cows fed with high energy diets during the prepartum period.
Leoni F. Martins is from Brazil, and he is a research assistant at Penn State University under the mentorship of Dr. Hristov. He has a strong background in ruminant nutrition, and he is currently working on how precision feeding affects performance and enteric gases emissions of dairy cows.