Toward Precision Feeding Regarding Minerals: What Is the Current Practice in Commercial Dairy Herds in Québec, Canada?

Abstract

Simple SummaryIt has been known for several years that limiting phosphorus in the cow diet mitigates its excretion in manure, hence reducing the environmental phosphorus load after manure spreading. The quantity of phosphorus that could be applied in the field is regulated by law in several countries. This is not the same for trace minerals such as cobalt, copper, manganese, and zinc. Nevertheless, if overfed, these last minerals are excreted in manure in great quantities and could accumulate in the soil after manure spreading, which could lead to detrimental environmental effects. However, formulating cow rations according to the mineral requirements is challenging for nutritionists. The aim of this analysis is to compare dietary phosphorus, cobalt, copper, manganese, and zinc concentrations from 100 commercial Holstein dairy herds with the National Research Council recommendations. Phosphorus is included as a point of comparison, as its overfeeding has been well studied compared with other studied trace minerals. The results indicate that, at the median, phosphorus, cobalt, copper, manganese, and zinc were respectively fed 8%, 405%, 52%, 372%, and 65% over the recommendations. This suggests that most nutritionists are aware that precision feeding regarding phosphorus is important for dairy production sustainability. It also shows that the other studied minerals were fed in excess and that some attempts should be made to reduce the mineral concentrations of diets.This analysis is performed to obtain information on the current situation regarding phosphorus (P), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) concentrations in cow diets of commercial dairy herds in Québec, Canada, and to compare them with National Research Council recommendations. Data are collected on 100 Holstein dairy herds in Québec, Canada, and 4430 cows were involved. Rations are analyzed for selected minerals and cow requirements relative to the recommendations were calculated. Median percentages of mineral recommendations fulfilled by forage were 55%, 196%, 54%, 776%, 181%, and 44% for P, Co, Cu, Fe, Mn, and Zn, respectively. Daily dietary concentrations of P, Cu, Mn, and Zn decreased as lactation progressed, whereas Co and Fe were stable throughout lactation. Phosphorus was the mineral fed the closest to the requirements, cows below 21 days in milk were even underfed by 11%. All studied trace minerals were fed in excess for the majority of cows. Cobalt was fed on average 480% above requirements regardless of the stage of lactation. For Cu, Fe, Mn, and Zn, rations for cows below 21 days in milk were fed 23% (95% confidence interval: 15–32), 930% (849–1019), 281% (251–314), and 35% (22–47) above the recommendations, respectively, and were closer to the requirements than after 21 days in milk. These results show that most nutritionists are aware that precision feeding regarding P is important to minimize detrimental environmental impacts of dairy production. However, some efforts should be made to limit trace mineral overfeeding to ensure environmental resiliency.