university wisconsin-madison

Abstract 1: Amino acid supplementation as a potential strategy to mitigate milk fat depression  

Researchers at the University of Wisconsin – Madison also evaluated if they could help promote milk fat synthesis by supplying methionine and leucine during a milk fat depression that was induced by feeding dietary polyunsaturated fatty acids.  Supplying methionine and leucine in the diet has been observed to increase milk fat synthesis via the mechanistic target of rapamycin complex 1 (mTORC1). Both methionine and leucine are essential amino acids (AA) that activate mTORC1.  

The study was conducted as a replicated 4x4 Latin square. All diets included high starch. Factors were fat source: soybean oil  or an 80% palmitate fat supplement; and AA level.  

As expected, supplying soybean oil (linoleic acid) decreased milk fat percentage and yield compared to the control (palmitate fat supplement). While AA supplementation was not able to fully overcome the milk fat depression induced by soybean oil,it increased milk fat content and tended to increase milk fat production under both fat sources, partially mitigating the milk fat depression. The results further underscore the beneficial effects of AA supplementation on increasing milk fat production.  

Abstract 2: Energy source and amino acids independently alter mammary extraction of nutrients  

A separate study at the University of Wisconsin – Madison evaluated if mammary extraction of nutrients for the synthesis of milk components is affected by energy source (glucogenic or ketogenic) and by balanced AA supplementation. Twenty dairy cows were enrolled in a replicated 4x4 Latin square with four 28-d periods and 4 treatments arranged as a 2x2 factorial. Factors were AA level, AA deficient, or AA sufficient, balanced for methionine, lysine, and leucine (branched chain AA); and energy source: glucogenic or ketogenic.  
Overall, energy source did not affect mammary extraction of nutrients, except for fatty acids (FA) that were supplied at a  higher level by the ketogenic diet. On the other hand, balanced AA supplementation increased mammary extraction of AA and FA, in line with the observed response in milk protein and fat production by that treatment. The observed results underscore the benefits of AA balancing on mammary uptake of essential AA, which can support the activation of mTORC1 and, thereby, milk component synthesis.  mTORC1 is a cellular nutrient sensing complex that regulates metabolic processes like protein and fat synthesis.  

AA balancing dairy cow rations has been observed to enhance both milk protein and fat synthesis. Additionally, insulin and glucogenic energy have been observed to stimulate milk protein yields in dairy cows. Both insulin and AA, particularly methionine and leucine, stimulate mTORC1.  

Features: Kathryn Ruh, Ph.D. student at Arriola Apelo Lab, University of Wisconsin-Madison, USA.

Researchers at the University of Wisconsin – Madison examined the beneficial effects of supplemental RPM during transition for dairy cows that were exposed to heat stress.  

Cows were blocked by parity and milk production, and were assigned to either thermoneutral conditions, heat stress induced by electric heat blankets, or heat stress along with the inclusion of RPM in the total mixed ration pre- and post-calving.  

The results underscored the negative impacts of heat stress on immune function and liver function. Supplying methionine to transition  cows under heat stress improved liver function, which can help cows better handle the associated negative metabolic effects.  

Heat stress causes increasing losses for the livestock industry as climate change occurs. Supplemental methionine during the transition period has been adopted on commercial farms due to the beneficial effect of methionine on milk production, immune function, inflammation, and metabolism.  

Features: Anne Gaudagnin, Ph.D. student at the University of Wisconsin-Madison, USA. 

Researchers at the University of Wisconsin – Madison examined the effects on cow-calf performance when heat-stressed transition cows received supplemental RPM.  Fifty-three cows were fed either a control diet or a control diet with Smartamine M beginning six weeks before expected calving. Four weeks pre-calving all methionine cows and half the control cows received an electric heat blanket. The other half of the control cows were left at thermoneutrality. Overall, RPM supplementation to transition cows reverts the negative impact of heat stress on milk protein and calf wither heights.   

The research results underscore the negative effects of heat stress on milk protein production and birth weight of calves. Consistent with previous work using late-lactation cows, methionine supplementation helped to mitigate the negative effects of heat stress on milk protein. Supplemental methionine during the transition period has been increasing on commercial farms due to the beneficial effect of methionine on milk production, health and metabolism as well as on the developing fetus.  

Features: Brittney Davidson, Ph.D. student at the University of Wisconsin-Madison, USA.