“The increasing availability of lysine in the gut during the transition improved several indicators of uterine health,”found the team, which included Phil Cardoso, associate professor of animal sciences at the University of Illinois, Urbana-Champaign.
The study was published in Journal of Dairy Science.
Feeding rumen-protected methionine as an essential 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 understood, according to the paper.
The authors said they wanted to determine the effects of feeding RPL before birth, after birth, or both, on follicular dynamics, uterine health and endometrial mRNA gene expression.
Uterine infections are common in the postpartum period and can adversely affect ovarian and uterine function, the authors noted.
Improving immune function and reducing the risk of inflammatory diseases of the reproductive tract could lead to better reproductive outcomes, they said.
“Uterine infections may also adversely affect ovarian resumption because inflammation can impair the growth and function of the first dominant follicle (DF) through neuroendocrine mechanisms of inhibition of hypothalamic GnRH release and pituitary LH secretion.
“In addition, there is also evidence of directly localized inflammatory mediators resulting from bacterial contamination of the uterus after calving that affect the ovaries by suppressing estradiol secretion and reducing the growth rate of follicles.
“In addition, chronic inflammation can lead to disruption of uterine regeneration processes in the early postpartum period, potentially altering uterine function and future reproductive capacity.
“Hence, ovarian resumption could benefit from modulation of the uterine immune response through nutritional strategies.”
However, the effects of feeding RPL on reproductive tract physiology and immune response are still lacking, the study states.
The team added a rumen-protected lysine product to the total mixed ration (TMR) at 0.54% 28 days before calving. After calving, the lysine was added at 0.4% for a further 28 days.
Cows received the lysine supplement before or after calving, or both, with an additional control group receiving no supplemental lysine in either period.
“We found that genes involved in the production of inflammatory proteins in the uterus were reduced by rumen-protected lysine, particularly in cows that consumed the amino acid before and after calving. And genes involved in keeping the uterus clean were more active. Overall, our results indicate less inflammation in these cows, meaning they expend less energy defending themselves against infection.”commented Cardoso. “It’s just more efficient.”
In addition to characterizing gene expression in the uterus, the team looked for evidence of metritis, a uterine infection that affects 30% of US dairy cows after calving. While the general inflammatory state of the uterus improved with lysine supplementation, the researchers found no statistical difference in metritis between cows that consumed lysine and those that did not.
“Metritis is the clinical presentation of uterine inflammation. It requires a greater level of environmental challenge to show itself. Perhaps our farm is not really stressful in that regard. We found a difference in the subclinical form, also called subclinical endometritis. When we counted the number of inflammatory cells (PMN) in the uterus, cows that received rumen-protected lysine had a lower number of cells, indicating less inflammation.”‘ said the specialist.
No influence on ovulation
The authors said they also followed the first postpartum follicular growth cycle in the ovaries. Lysine had no effect on time to first ovulation – which was an average of 18 days in milk for all groups – nor on follicle diameter at the time of ovulation.
Cardoso, who researches dairy nutrition and reproduction and offers educational programs, said he’s neither surprised nor disappointed that lysine doesn’t affect ovulation. He added that uterine health right after calving is more important than producers think.
“If you ask farmers how they assess reproductive progress and fertility, the answer is always pregnancy. Typically, farmers breed cows around 60 to 70 days after calving, but failure to do so is often due to events such as metritis or subclinical endometritis that happen before breeding, earlier in the cycle. This research shows that rumen-protected lysine can set your cow up for success right after calving so she can later achieve a favorable pregnancy.”
The lysine results are consistent with Cardoso’s previous research examining rumen-protected methionine, another limiting amino acid in dairy cows. He showed methionine-affected genes linked to inflammation and estrogen production and increased embryo survival.