Research indicates the supplement does more than boost milk protein.
It has long been known that supplementing methionine in early lactation diets can boost both milk protein yield and percent.
But new studies tantalizingly suggest properly supplemented transition cow diets, before and after calving, might improve cow health, energy balance, embryo development and conception rates.
University studies thus far have been unable to find a definitive link. But this much is known: Cows that have lost body condition and are in negative energy balance at the time of first service are far less likely to conceive than cows who have maintained or are gaining body condition at the time of breeding.
One Wisconsin study field trial of two herds with nearly 1,900 cows showed cows gaining weight at the time of breeding are three times more likely to conceive than cows losing weight, says Milo Wiltbank, a dairy nutritionist with the University of Wisconsin.
Cows losing weight had pregnancy rates of about 25%. Those maintaining weight had pregnancy rates of about 35%. And those gaining weight had pregnancy rates of 75% or more. (This particular study, however, did not look at methionine supplementation.)
Other studies have shown methionine’s ability to improve dry matter intake, milk yield and milk protein yield. “Cows with methionine supplementation had less fatty liver,” says Dan Luchini, a nutritionist with Adisseo. “But it’s complicated, and not just as simple as feeding more methionine.”
Methionine stimulates secretion of very-low density lipoproteins, which in turn transport triglycerides away from the liver and toward effective utilization in the udder. That should result in a faster return to positive energy balance and better liver function, says Luchini.
In addition, methionine is the key precursor of glutathione, one of the most important antioxidants in the cow. During the transition period, a cow’s immune system is typically weakened. With more circulating glutathione, the cow should be better able to ward off infections.
As a result, feeding metabolizable methionine at the rate of 5 grams per cow per day pre-calving and 10 grams/cow/day post calving could be beneficial, believes Luchini.
Methionine also might be key to embryo development. Research with lambs suggests low methionine levels in dams can result in offspring with lower blood pressure and immune function.
Wiltbank and his colleagues compared 570 bovine embryos and found no differences in fertilization or embryo quality based on methionine levels of the donors.
“However, the small difference we produced in circulating methionine produced a substantial difference in expression of genes in the embryo,” he adds.
“A total of 276 genes were expressed differently in embryos from cows supplemented or not supplemented with methionine…,” Wiltbank says. “Thus, methionine supplementation seemed to change gene expression in a way that may lead to improved pregnancy outcomes and improved physiology of offspring.
“Further studies are needed to determine if these gene expression changes lead to changes in embryo development, reduced pregnancy loss and altered physiology of the offspring,” Wiltbank concludes.