Matching nutrient requirements with nutrient supply is essential for maximizing feed efficiency in dairy farming systems. To accomplish this, feeding a consistent and homogeneous ration is critical. In Summer 2015, the variation of the composition of total mixed rations (TMR) was monitored on 7 dairy farms in Franklin County, Virginia.
The assessment consisted of a qualitative description of the mixing and feeding systems, and measuring the nutritional composition of the TMR immediately after delivery. For this, 5 samples were collected and stored independently until analysis. All samples were analyzed using wet chemistry procedures for dry matter (DM), ash, crude protein (CP), and neutral detergent fiber (NDF) concentrations. In addition to chemical composition, the physical characteristics of the TMR were evaluated using the Penn State separator box.
Mixing and feeding systems varied. Mixing systems included reel (5 farms), chain belt (1 farm), and vertical (1 farm) mixers. All mixers had mounted scales, but only 2 of the 7 farms calibrated them periodically (once and twice per year). Mixer overload did not occur in any of the 7 farms. In 6 of the 7 farms, mixing occurred while loading feed ingredients. Mixing time per batch ranged from as little as 6 minutes to as much as 37 minutes. Mixed feed was delivered to feed bunks through conveyors in 5 of the 7 farms, whereas in the other 2 farms feed was delivered to feed bunks directly from the mixer.
In general terms, as reflected by the low coefficients of variation (<7%, Table 1), little variation in DM, ash, CP, and NDF was observed throughout the feed bunks. Adequate mixing and feeding management in most, if not all farms, can explain this little variation. However, for most of the farms, a small proportion (average = 4.8%) of large particles was retained in the upper screen of the Penn State separator box. Having too large proportions of small particles could explain the homogeneous composition of the TMR throughout the feed bunk.
In conclusion, little variation on TMR composition was observed on 7 dairy farms in Franklin County. Even though this indicates adequate feeding and mixing management, managers might need to work on increasing particle size of their forages, while maintaining a homogeneous composition of the TMR.
Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.
November 3, 2015