Practical Application of Balanced Diets - Where Rations do not Result in Expected Dairy Herd Performance

Ration Balancing

Testing forages and balancing rations are the foundation upon which nutritionists build sound, nutritionally-complete feeding programs. As we learn more about rumen fermentation, use of nutrients within the mammary gland, liver, and other tissues, and the interactions between the rumen environment and cow’s metabolism, specifications for nutrients used when formulating rations have changed and become more sophisticated. To take advantage of these advances, more complicated ration balancing models are utilized which often require more nutrient composition data to be entered for each feedstuff. Often we use “book values” which may or may not describe the nutrient composition of the feedstuff actually being fed. These inadequacies and gaps in our knowledge of rumen fermentation and nutrient metabolism can lead to performance which may not meet expectations.

From a practical standpoint when rations do not perform as well as expected, the most common problem is not the ration formulation, but rather, the interpretation and feeding of the ration and the amount and composition of the ration actually consumed by the cows. Thus, highlighting the statement describing the four different rations which are fed to cows or heifers (Table 1). When troubleshooting performance problems, these areas often offer at least a partial explanation. Table 2 illustrates the various areas that should be evaluated when formulated rations are not performing as expected.

Resolving Nutritional Problems

Often the formulated ration (and the nutritionist who formulated the ration) gets blamed when cows do not milk as well as expected or health issues arise in the herd. The formulated ration can be the problem but other management-related factors can contribute to the problem. Often, changes in management practices are needed to resolve the problem in addition to formulation changes or refinements. Most nutritional problems are often a combination of several factors that have changed which result in a decrease in milk production, growth or health problems. Some of the areas that should be investigated to resolve some of the common problems seen in dairy herds can be seen in the article entitled Areas to Evaluate when Troubleshooting and Resolving Nutritional Problems in Dairy Herds.

Trace Mineral Nutrition

Proper mineral and vitamin nutrition impacts milk production, growth, reproductive performance, and the health of cattle. From a health standpoint, proper mineral and vitamin nutrition can help prevent several common metabolic disorders, such as retained placenta and clinical and subclinical milk fever, and improve the immunity of cattle to fight off diseases, such as mastitis. Also, proper mineral and vitamin nutrition can help improve immunity from vaccines administered to prevent various diseases.

Minerals and vitamins need to be provided in adequate amounts in forms which are readily absorbed (bioavailable). The amount of minerals provided by forages, concentrates or grains, mineral sources, and water need to be taken into account when evaluating the mineral adequacy of diets for growing heifers and lactating and dry cows. Forages and concentrate mixes should be analyzed via wet chemistry methods to determine their mineral content and the results used to assess whether the proper amount of each mineral is provided. Often we forget that cattle need a certain amount of each nutrient, not concentrations of a nutrient. The mineral content of water needs to be taken into account when evaluating the adequacy or excesses of a trace mineral and vitamin program.

Interactions with other minerals

Various minerals have been shown to interfere with the absorption or metabolism of other trace minerals (Figure 1). Table 4 lists some of the common mineral interactions which can decrease the effective absorption of copper and selenium and result in health-related problems in dairy and beef herds. Higher concentrations of iron, sulfur, zinc or molybdenum can be found in not only forages (Table 5) but also water sources and mineral sources, such as dicalcium phosphate (Table 5). For example, some sources of dicalcium phosphate contain higher concentrations of iron than other sources. To counter these interactions often organic sources of copper or selenium are added to the diet

Table 5. Selected mineral concentration in alfalfa haylage and dicalcium phosphate.

Implementing a Close-up Dry Cow Program

Properly-implemented close-up dry cow programs have been shown to improve production (+/- 2000 lbs milk) and health of cows after calving. Several additives, such as anionic salts and other B vitamins (i.e., ruminally protected choline), have been shown to minimize health problems when added to diets 3 weeks prior to calving. Implementing close-up dry cow programs with our smaller herd sizes has presented some challenges and problems. These difficulties may include (1) providing facilities that provide adequate cow comfort, bunk space, and hygiene for both groups of dry cows; (2) mixing and storing another grain mix specially formulated for the forages being fed which can be fed out within a reasonable time frame; and (3) small numbers of cows in this group makes mixing small batches of TMR, especially those incorporating long hay, a challenge. In these situations, one group of dry cows with 50 to 60 day dry periods may be the best even though cows are fed expensive additives for a longer timeframe.

Communication...

Establishing true communication lines between you, the farmer’s other consultants, the farmer, and his/her staff are critical when designing and implementing feeding programs that work. Communication needs to flow to and from all parties which are involved in the feeding program. Often the greatest misunderstandings could have been avoided or quickly corrected if communication lines have been established and all parties truly communicate, with one another. To accomplish these objectives, both sides need to listen to each others’ needs and concerns raised.

Author: Donna Amaral-Phillips