NUTRITION ▶▶▶
Optimising rumen function could help main- tain milk fat con- tent and produc- tion efficiency of dairy cows under heat stress.
2013). Also, the lack of plasma NEFA, potentially an important precursor for milk fat synthesis under heat stress (Bauman and Griinari, 2001), may contribute to MFD. Other reported negative LPS effects on fatty acid production include: De- crease in activity of lipoprotein lipase (Lopez-Soriano and Williamson, 1994), decrease in expression of lipoprotein li- pase and fatty acid transport protein 1 (Feingold et al., 2009) and suppression of enzymes related to de novo fatty acid synthesis in the mammary tissue (Dong et al., 2011).
Optimising rumen function during heat stress Research to date helps explain how MFD during heat stress relates to depressed rumen health. Given this relationship, optimising rumen function could help maintain milk fat con- tent and production efficiency of dairy cows under heat stress. Heat stress causes physiological and behavioural changes in dairy cows. These changes can lead to suboptimal rumen conditions, resulting in production of fatty acid biohy- drogenation intermediates and LPS that inhibit milk fat syn- thesis in the mammary gland. Today, natural digestive health
30 ▶DAIRY GLOBAL | Volume 6, No. 2, 2019
technologies are available to help optimise rumen conditions through the diet, thereby helping to reduce the negative im- pact of heat stress on milk fat and maintain the production efficiency of high-producing dairy cows.
References are available on request.
Figure 2 - Correlation between rumen lipopolysaccharide (LPS) and milk fat content. Adapted from Zebeli and Ametaj (2009).
4.5 4.0 3.5 3.0
2.5 2.0 1.5
0 2,000 4,000 6,000 8,000 10,000 12,000 Rumen LPS (ng/mL)
Milk fat content (%)
PHOTO: HENK RISWICK
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