“Increasing intestinal availability of lysine throughout the transition period improved several indicators of uterine health,” found the team, which included Phil Cardoso, an associate professor of Animal Sciences at the University of Illinois, Urbana-Champaign.
The study was published in the Journal of Dairy Science.
Feeding rumen-protected methionine as an indispensable amino acid source has been shown to improve reproductive performance in dairy cows, but the effect of feeding rumen-protected lysine (RPL) during the peripartum period on reproductive performance is not well explored, according to the paper.
The authors said they looked to determine the effects of feeding RPL prepartum, postpartum, or both on follicular dynamics, uterine health, and mRNA gene expression of the endometrium.
Uterine infection is common in the postpartum period and can have a detrimental effect on ovarian and uterine function, noted the authors.
Improving immune function and reducing the risk of reproductive tract inflammatory diseases could lead to better reproductive outcomes, they said.
"Uterine infections can also be detrimental to ovarian resumption, because inflammation can affect the first dominant follicle (DF) growth and function through neuroendocrine mechanisms of inhibition of hypothalamic GnRH release and pituitary LH secretion.
"Moreover, there is also evidence of direct localized inflammatory mediators, resulting from uterine bacterial contamination after calving, affecting the ovary by suppressing estradiol secretion and decreasing the growth rate of follicles.
"Additionally, chronic inflammation can result in the disruption of uterine regeneration processes in the early postpartum period, which can potentially alter the functional capacity of the uterus and future reproductive efficiency.
"Therefore, ovarian resumption could benefit from modulation of the uterine immune response through nutritional strategies."
However, the effects of feeding RPL on the reproductive tract physiology and immune response are still lacking, reads the paper.
The team added a rumen-protected lysine product to total mixed ration (TMR) at 0.54% for 28 days pre-calving. After calving, the lysine was added at 0.4% for an additional 28 days.
Cows got the lysine additive before or after calving, or both, with an additional control group consuming no supplemental lysine in either time period.
"We found genes involved with producing inflammatory proteins in the uterus were reduced with rumen-protected lysine, especially in cows that consumed the amino acid before and after calving. And genes involved in keeping the uterus clean were more active. Altogether, our results indicate less inflammation in these cows, meaning they can spend less energy defending against infection," Cardoso commented. "It's just more efficient."
Along with characterizing gene expression in the uterus, the team looked for evidence of metritis, a uterine infection affecting 30% of US dairy cows after calving. While the overall inflammation status of the uterus improved with lysine supplementation, the researchers didn't detect a statistical difference in metritis in cows that consumed lysine and those that didn't.
"Metritis is the clinical presentation of uterine inflammation. It requires a larger degree of challenge from the environment to show up. Perhaps our farm does not present real stress in that regard. We did find a difference in the sub-clinical form, also called subclinical endometritis. When we counted the number of inflammatory cells (PMN) in the uterus, cows receiving rumen-protected lysine had a lower number of cells, indicating less inflammation," said the specialist.
No impact on ovulation
The authors said they also tracked the first postpartum follicular growth cycle in the ovaries. Lysine didn't affect time to first ovulation—that averaged 18 days in milk for all groups—nor the follicular diameter at ovulation.
Cardoso, who conducts research and provides outreach programs in the area of dairy nutrition and reproduction, said he was neither surprised nor disappointed that lysine didn't affect ovulation. He added that the health of the uterus right after calving is more important than producers think.
"When you ask farmers how they assess reproductive progress and fertility, the answer is always pregnancy. Usually, farmers are breeding cows around 60 to 70 days after calving, but if it is unsuccessful, it's often because of events like metritis or subclinical endometritis that happen prior to breeding, earlier in the cycle. This research shows rumen-protected lysine can set your cow up for success right after calving so she can achieve a favorable pregnancy later."
The findings on lysine tally with Cardoso's earlier research that evaluated rumen-protected methionine, another limiting amino acid in dairy cows. He showed methionine affected genes related to inflammation and estrogen production, and increased embryo survival.