Restricted (Penn State Only)
Fetter, Molly Elizabeth
Graduate Program:
Animal Science
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 06, 2017
Committee Members:
  • Dr. Troy L. Ott, Thesis Advisor
  • Dairy cattle
  • Transition period
  • Periparturient diseases
  • Flaxseed
  • Methane inhibitor
  • Negative energy balance (NEB)
In cattle, the transition period, which encompasses three weeks prior to three weeks after calving, is a critical time in the cow’s life with increased incidence of metabolic and infectious diseases. During this time cows suffer from immunosuppression and negative energy balance. Negative energy balance (NEB) and immunosuppression are related in transition dairy cows and occur due to extreme metabolic stress and changing hormones as the cow transitions from a pregnant to energy-demanding lactating state coupled with decreased dry matter intake. Incidences of periparturient diseases are not only detrimental to the overall health and well-being of the cow, but they can also decrease milk output and reproductive efficiency, causing economic loss to the producer. For these reasons, improved management during the transition period that improves the health and well-being of the cow are paramount for setting the stage for successful reproduction and high milk production. Two approaches were taken to address the challenges of the transition period. The first approach was to feed an omega-3 fatty acid extruded flaxseed supplement and measure effects on transition dairy cow immune function, plasma metabolites, and fatty acid composition of milk fat, plasma, and red blood cells. Polyunsaturated fatty acids (PUFA) decrease expression of pro-inflammatory cytokines promoting an anti-inflammatory state. Further benefits of feeding fats include improved milk production and composition and improved fertility. The second approach was to supplement transition dairy cows with a small molecule methane inhibitor and observe effects on return of ovarian activity. In a recent study, cows that received a methane inhibitor had increased body weight gain compared to cows that received a placebo. It is hypothesized that reducing methane production could make more energy available to the cow for other productive functions. To test this hypothesis, progesterone was measured in defatted milk via enzyme-linked immunoassay (ELISA). Parameters measured were days to evidence of a first corpus luteum (CL), length of first luteal phase, days to evidence of second CL, and interval between luteal phases. Evidence suggests that ovarian activity cannot resume until negative energy balance ceases and cows enter a positive energy balance. Cows that enter positive energy balance and cycle more before first service are more likely to have higher conception and pregnancy rates. These two approaches were taken because NEB and immunosuppression are the primary causes of negative health events in transition dairy cows. Overall, the first approach showed cows receiving the flaxseed supplement had greater ALA in plasma and milk fat, reduced mRNA abundance of TNF and IL6, and reduced neutrophil phagocytosis and ROS. Results indicate that the omega-3 supplement altered the activation status of the immune system and reduced inflammatory responses. This reduction in neutrophil activity may increase energy available to the cow for productive functions, although this speculation needs to be confirmed with further research. The milk fat and plasma exhibited greater ALA the longer the cows were on the diet indicating this supplement can be used to produce milk with higher omega-3 fatty acids, which is an area of increased consumer interest. In the methane inhibitor study, there were no differences observed between treatment groups for any of the reproductive parameters. Results from both studies provide further support for the importance of maintaining proper energy balance during the transition period to support immune function and productive functions in dairy cattle.