Each video and podcast contains highlights of ruminant research sponsored by Adisseo and presented during the 2023 American Dairy Science Association (ADSA) Annual Meeting.
Highlights include what was researched and why, a brief summary of the findings, the conclusions drawn, and insights on how best to apply the results.
Researchers from the Universidade Federal do Parana, Curitiba, PR, Brazil, evaluated the effect of RPM supplementation in a low-starch diet, with or without an extra source of sugar, on the productive performance of mid-lactation dairy cows fed with isoproteic diets. Cows either were fed the control diet or the control diet supplemented with methionine, sugar, or both.
The trial results suggest that despite the basal diet being supplemented with enough Smartamine M to closely meet the recommended grams of metabolizable Met:ME ratio, the total energy of the diet may have not been sufficient to elicit a milk volume response with the added methionine coming from Smartamine M. Although total milk protein was not increased, it is noteworthy that milk protein percent increased with added methionine.
The added sugar did elicit a milk volume response, therefore, supporting the assessment that the basal diet was energy limiting. In agreement with previous reports (Boderick et al., 2008) adding sugar did not lower the milk urea nitrogen (MUN).
Before adding Smartamine M to diets that are known to be deficient in methionine, the end user needs to assure that the basal diet carries enough ME to capture the benefits of the additional methionine.
Features: Jorge Carneiro, Ph.D. student at the Universidade Federal do Paraná, Curitiba, Brazil.
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.
Researchers from Cornell University investigated the effects of feeding RPM and calcium salts of fatty acids enriched with or without eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA; i.e., n3FA) in transition cows.
Supplying methionine to dairy cows has been observed to improve milk fat production. Additionally, supplying dietary fatty acids is known to alter the fatty acid profile of milk. The research, therefore, focused on the fatty acid composition of milk from cows fed RPM and calcium salts enriched in omega-3 fatty acids.
Offering RPM and enriched calcium salts improved the fatty acid profile of milk. EPA and DHA are known to have beneficial effects on metabolism in both animals and humans. Thus, producing milk with higher EPA and DHA can have health benefits for consumers.
The same group from Cornell University also looked into the effects of feeding RPM and calcium salts enriched in omega-3 fatty acids (n3FA) on plasma and liver phosphatidylcholine and phosphatidylethanolamine concentrations of transition cows.
Feeding methionine during the transition period has been observed to have beneficial effects on liver metabolism. n3FA have also been documented to alter metabolism. However, no previous work has investigated the effects of supplying both n3FA and methionine during the transition period.
A randomized complete block study with 75 multiparous cows was used. Cows were assigned to one of four treatments: 1) Methionine (Met) deficient with calcium salts (CS) not enriched in n3FA 2) Methionine adequate with -n3FA, 3) -Met with CS enriched in n3FA or 4) +Met with +n3FA from wk -3 prior to expected calving through wk 4 of lactation.
The results from this trial underscore the importance of feeding EPA and DHA along with a RPM source to high-producing dairy cows during the transition period.
Even though there are not known requirements for polyunsaturated fatty acids for dairy cows, feeding them in conjunction with RPM resulted in changes in phosphatidylcholine and phosphatidylethanolamine in plasma and liver, reinforcing the beneficial effects reported previously on DMI, milk production and composition, and liver health.
Features: Tanya France, Ph.D. student at Cornell University, 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 Virginia Tech assessed molecular changes in the livers of cows supplemented with methionine during solely a subclinical mastitis challenge. The trial was designed to determine the metabolic response of cows fed Smartamine M and that had been infected by infusing Streptococcus uberis in the rear right quarter of the mammary gland. Thirty-two multiparous Holstein cows were enrolled in the randomized complete block design and assigned to either a basal diet or a basal diet supplemented with RPM.
The results of this work demonstrate how methionine affects metabolic pathways that impact antioxidant-related genes and, therefore, provide meaningful insights that help to explain the better health and higher milk production of cows after calving. Methionine is not an antibacterial drug, but rather a required nutrient with functional properties.
Feeding methionine during the transition period is becoming a common practice in commercial herds. Cows fed Smartamine M during this period have shown increased DMI and milk production, have experienced lower incidence of post-calving metabolic disorders and have had higher plasma antioxidant status.
Features: Dr. Johan Osorio, Assistant Professor, One Health, Virginia Tech, USA..
Researchers from the University of Lavras, Lavras, Minas Gerais, Brazil, evaluated the effect of supplementation with RPM on the plasma AA profile of lactating grazing cows.
Only a limited number of research trials have been conducted feeding RPM in in growing systems with tropical grasses in South America during the summer season. The grasses contain high levels of crude protein, up to 25%, depending on growth stage and nitrogen supply. To our knowledge, this is the first report of plasma AA concentrations in lactating cows fed Smartamine M on pasture systems.
The results of this work underscore the importance of the methionine’s metabolic elasticity. The trial takeaways are:
The reported plasma concentration of methionine is relatively high in pasture-fed Girolando cows.
The cows fed Smartamine M had numerically higher plasma methionine concentrations, however, the concentrations were not statistically higher than for cows not supplemented with Smartamine M.
Cows fed the basal diet had relatively high plasma methionine concentrations, yet when supplemented with Smartamine M they responded with higher milk protein.
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Researchers at the University of Wisconsin – Madison investigated the systemic transcriptional response to elevated peripheral serotonin in lactating cows using a cross-over design. Among its many functions in the body, serotonin plays a role in energy metabolism. 5-hydroxytryptophan (5-HTP) is the precursor to serotonin, and infusing 5-HTP has been documented to increase peripheral serotonin concentrations in lactating dairy cows.
Eight multiparous cows were intravenously infused with saline or the serotonin precursor 5-HTP. Adipose tissue (WAT), liver, and mammary were biopsied. Extracted RNA was sequenced, mapped to the cattle reference genome, and analyzed for differentially expressed genes.
In conclusion, lactating cows with elevated peripheral serotonin developed a systemic response, altering the expression of genes in energy metabolic pathways, including reduced lipid synthesis in WAT, reduced cholesterol synthesis in the liver, and increased lipid trafficking in the mammary tissue. Together, these changes may function to shift energy partitioning toward milk synthesis. In particular, changes across the three tissues indicated a systemic change in lipid metabolism, suggesting a shift in energy partitioning toward milk rather than storage in adipose tissue.
Researchers at the the University of Wisconsin – Madison evaluated the long-term effects of in-utero heat stress on subsequent heifer performance and greenhouse gas emissions. A total of 38 heifers were subjected to heat stress or artificial cooling in-utero and were enrolled in a 63-day study at 18-20 months old.
Despite previously reported reductions in growth and feed intake of in-utero heat-stress heifers during the pre-weaning phase, it does not seem to have long-term effects on growth, feed efficiency, or methane emissions later in in the lives of heifers.
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 4×4 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.
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 4×4 Latin square with four 28-d periods and 4 treatments arranged as a 2×2 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 Virginia Tech evaluated the impact of some mTOR signaling AAs on de novo milk fatty acid production. Diets were designed to meet the requirements at the predicted dry matter intake (DMI) for the cows in the trial. However, due to the lower-than-expected DMI, the intake of essential AAs was lower than expected and prevented the cows from responding to the added AA.
While the results of this trial do not support the hypothesis, there was a tendency for an increase in milk fat concentration and production from the cows supplemented with isoleucine and leucine. This highlights the potential for the branched chain AA to impact the cow’s energy corrected milk (ECM) production outcome.
