Precision Feeding Methods to Increase Nitrogen and Energy Utilization in Lactating Dairy Cows

The environmental and economic costs of overfeeding N to dairy cattle are a challenge in today’s dairy industry. Two studies were conducted to address new opportunities for precision feeding N, which is a strategy where producers strive to feed cows the precise amount of N and amino acids that meet their individual requirements. The objective of the first study was to evaluate the effects of supplementing a rumen protected methionine (RPM) product via automatic milking system (AMS) concentrate on milk protein yield in lactating dairy cows. Fifty-one cows were randomly assigned to control (no RPM) or treatment groups. Milk yield and milk protein yield were similar between control and treatment groups in multiparous cows, but were reduced in primiparous cows fed the RPM. Milk fat percent wasn’t affected by the RPM. These results suggest that feeding RPM via an AMS is promising, but more research is needed. The objective of the second study was to 1) chemically characterize two novel, high protein corn milling coproducts resulting from different processes, and 2) determine the impact of adding one of these products, 50Y, to diets formulated to contain low concentrations of either RDP or RUP. In the first experiment, five samples of each feed were analyzed for chemical composition in a completely randomized design. In the second experiment, utilizing a twice replicated 5×5 Latin square design, 10 multiparous Jersey cows were grouped by milk yield and randomly assigned 1 of 5 treatment diets. Results indicated that the inclusion of 50Y in diets did not affect dry matter intake, milk yield, fat percent, milk fat yield, energy-corrected milk, or concentrations of energy. However, when a diet low in RDP to which 50Y was added was fed, cows increased milk protein percent and N excretion in feces compared to cows fed the low RDP diet. Thus, while there may be negative implications for N excretion, 50Y can be substituted for nonenzymatically browned soybean meal as a source of RUP. Advisor: Paul J. Kononoff