Short communication: Field study to investigate the associations between herd-level risk factors for milk fat depression and bulk tank milk fat percent in dairy herds feeding monensin

Abstract

Fat is the most variable milk component, and maintaining milk fat continues to be a challenge on commercial dairy farms. Our objectives were to establish associations between herd-level risk factors for milk fat depression and bulk tank milk fat content in commercial dairy herds feeding monensin. Seventy-nine Holstein commercial dairy herds in the northeast and Upper Midwest United States were enrolled in an observational study. Data were collected on herd characteristics, total mixed ration (TMR) samples, all component silage samples, and bulk tank milk samples. The unconditional univariable association of each explanatory variable and bulk tank milk fat percentage was evaluated using simple linear regression and multivariable regression models. Milk fat content of trans-10 C18:1 had an exponentially negative relationship to herd milk fat percentage. In general, milk fat content of fatty acids synthesized de novo in the mammary gland were positively related to herd milk fat, and the content of several trans-C18:1 fatty acids, which would be products of alternate pathways of ruminal biohydrogenation, were negatively related to herd milk fat. Variables related to TMR composition did not have univariable relationships with herd milk fat percentage. Herds that had >49.8% of the TMR particles on the middle screen of the Penn State particle separator had higher milk fat percentage than those with ≤49.8%, and herds with >54.0% of TMR particles in the bottom pan had lower milk fat percentage than herds with ≤54.0%. Dietary content of monounsaturated fatty acids (C16:1 and C18:1) had negative relationships with herd milk fat percentage; however, no single diet component accounted for more than 11% of the variation in herd-level milk fat percentage. Univariable monensin dose was not associated with herd milk fat percentage. The relative lack of significant univariate relationships with herd-level milk fat suggests many factors contribute to milk fat content, and herds experiencing low milk fat will need to examine many potential risk factors when working to troubleshoot this challenge.

Does the dry cow treatment with monensin controlled release capsule affect Parmigiano Reggiano cheese production?

“…In our study, DIM of the experimental groups were not controlled; therefore, it is possible that at least some of the difference in FA profile of cheese between the groups could be due to the presence of a higher percentage of fresh cows in the treated group. Existing literature, however, supports the theory that monensin influences FA concentration in milk by altering ruminal microbiota (Bell et al, 2006;McCarthy et al, 2018). Odongo et al (2007) showed an increased concentration of long-chain PUFA and total MUFA in milk by 9 and 5%, respectively, in a group fed TMR + 24 mg of monensin premix per kilogram of DM compared with a control group.…”

Meta-analysis of the relationship between milk trans-10 C18:1, milk fatty acids <16 C, and milk fat production

“…Milk fat production is highly variable between herds and cows within a herd due to differences in genetics, season, production level, and other factors. In a recent field study of 79 herds in the upper midwest and northeast regions of the United States, McCarthy et al (2018) reported milk fat percentage averaged 3.43, but ranged from 2.70 to 4.30; milk fat trans-10 C18:1 averaged 1.06% of milk fatty acids (FA), but ranged from 0.37 to 4.91; and FA <16 C that are de novo synthesized in the mammary gland averaged 22.5% of FA, but ranged from 17.8 to 26.1. They reported an exponential relationship between milk fat concentration and trans-10 C18:1, which is an intermediate of the alternate biohydrogenation pathway associated with BH-MFD.…”

The Milk Fat-to-Protein Ratio as Indicator for Ruminal pH Parameters in Dairy Cows: A Meta-Analysis

“…Besides factors involved in this study like overall diet composition, further factors will have an influence. Among more detailed nutritional factors is, e.g., starch degradability, which has a direct effect on rumen pH and milk fat as a consequence [31]. As mentioned above, the presence of unsaturated fatty acids in the diet is also considered a nutritional factor of relevance.…”