Dr. Glen Broderick's Contributions to Protein and Amino Acid Nutrition of the Dairy Cow

Abstract Text: Dr. Broderick’s interest in amino acid (AA) nutrition of the dairy cow started as early as the 1970’s stemming from his M.S. and Ph.D. studies at the University of Wisconsin under the supervision of the late Dr. Larry Satter. In these early experiments, Dr. Broderick demonstrated that abomasal infusion of casein plus Met in cows fed a 16% crude protein diet increased milk protein content and yield. In his thesis work, Dr. Broderick utilized the concept that an essential AA will not accumulate in plasma, if it is limiting, but will start to accumulate once demands for it in the tissues are met. Using this approach, he concluded that Met, Val, and Lys were most likely limiting AA for milk production in dairy cows. Dr. Broderick’s interest in Met continued throughout his career resulting in a number of key publications on production responses to rumen-protected Met (RPMet) products. These experiments demonstrated that, under some circumstances, supplemental RPMet may alleviate the negative impact of decreased dietary protein on milk production and composition with the additional benefit of drastically reducing N excretion in urine and manure. His protein and AA research branched into investigating sources of rumen-undegraded protein (RUP) for the high-producing dairy cow. Early experiments in this challenging area showed increased milk production with roasted soybeans compared with solvent-extracted soybean meal. By comparing forages in the basal diet, it was concluded that resistant protein sources may have a greater value with diets containing alfalfa silage than corn silage-based diets. Working at the US Dairy Forage Research Center, Dr. Broderick’s research was focused exclusively on the nutritional aspects of feeding forages, specifically alfalfa, to dairy cows. A series of studies were conducted to assess the feeding value of alfalfa silage vs. hay, with or without preservatives, and the benefit of protein supplementation of alfalfa silage-based diets. This work confirmed that alfalfa silage-based diets may benefit from RUP supplementation and identified the effectiveness of various protein feeds as RUP sources supplying limiting AA postruminally. Other forages, including tanniferous plants, were also investigated as dairy feeds. Research on urea vs. true protein sources established maximum urea supplementation levels. Studies on the interaction of fat and RUP challenged the concept that fat-supplemented diets would benefit from RUP supplementation. These numerous contributions have made Dr. Broderick one of the world’s foremost experts in protein nutrition of the dairy cow.

Keywords: Glen Broderick, amino acid, dairy cow