Methionine Key To Transition?

It has long been known that supplementing methionine in early lactation diets can boost both milk protein yield and percent. But new studies suggest properly supplemented transition cow diets
might also 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, dairy
nutritionist, 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 can improve dry matter intake, milk yield and milk protein yield. “Cows with methionine supplementation had less fatty liver,” says Dan Luchini, nutritionist, Adisseo. “But it’s 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, Luchini says.

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 5 grams per cow per day pre-calving and 10 grams per cow per day post-calving could be beneficial, Luchini says.

Methionine also might be important to embryo development and growth. Research with lambs suggests low methionine levels in dams can result in offspring with lower blood pressure and improved 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.

“The small difference we produced in circulating methionine produced a substantial difference in expression of genes in the embryo,” he adds. “Methionine supplementation seemed to change gene expression in a way that may lead to improved pregnancy outcomes and improved physiology of offspring,” Wiltbank says.

“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.