Sustainably Optimizing Mineral Nutrition in Lactating Cows The literature on animal nutrition has comprehensively addressed the nutrients that cattle must have for healthy growth, reproduction, and lactation. Considerable research has been conducted to determine the amounts of specific nutrients that must be part of any formula for "economically efficient diets" (Weiss, 2010). Both short-term and long-term metrics must be accounted for when developing adequate feeding diets for livestock. This means that the nutrient quantities must not be excessive, but must contribute to the profitability of the livestock raising or dairy operations while simultaneously seeking to minimize the environmental impact of these activities.

Feeding Diet Trace Minerals for Lactating Cows

Trace minerals -- those required in only minute quantities such as milligram or microgram -- needed by lactating cows have been identified through research. Nine trace minerals are thought to be essential for healthy lactating cows. While it is entirely possible that other minerals beyond the nine core trace minerals may be required in the diets of lactating cows: Chromium (Cr), cobalt (Co), copper (Cu), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se), and zinc (Zn) (Weiss, 2010). Of the nine essential trace minerals, this discussion does not address the role or requirements of iron, molybdenum, and iodine. The following factors help to influence the exclusion of these elements. Iron requirements of cattle are met by basal diets which all contain adequate levels of iron, and iron deficiencies in cattle are not known to be generally observed in cattle (Weiss, 2010). Molybdenum is required co-factor for a number of enzymes, but deficiencies have not been identified as an issue and supplementing molybdenum is not...

Iodine is known to be essential for thyroid hormone synthesis, but the dietary recommendation of 0.3 to 0.45 mg of I/kg of dry matter (DM), as measured in parts per million (ppm), has remained stable for roughly 30 years (Weiss, 2010).
Most Impactful Variables in Dietary Needs of Lactating Cows

To clearly understand the trace mineral requirements of lactating cows, researchers have begun by studying the responses of cows to dry matter feeding diets in order to acquire baseline information about the influence of feed quality and consumption. Linden, et al. (2014) studied the effects of diets of chopped warm-season grass hay (5.5% CP, 67% NDF) for ad libitum (at-will feeding) intake and soybean meal (46% CP) at 450 g/d on Angus-cross cows and heifers. The data show that intake patterns are different between cows and heifers regardless of the similarities of dry matter digestibility, passage rates, and plasma glucose and BHBA concentrations in primiparous heifers. Interestingly, the DMI (% of BW) and digestibility showed no substantive difference between pregnant heifers and pregnant mature cows. However, the DMI (% of BW) for lactating heifers was greater than for lactating multiparous cows. Primiparous heifers were not able to consume sufficient warm-season forage for healthy maintenance, growth, and lactation. This is true even though the DMI (% of BW) was greater for lactating heifers than for lactating cows and non-lactating cows and heifers. Lactation resulted in decreased BW over time in heifers, which can result in a longer postpartum interval and difficulties when rebreeding. The Linden, et al. (2014) study indicates that heifers require additional supplementation to maintain growth, lactation, and reproduction and to maintain a 12-month production cycle…