Comparative feed efficiency of Holstein and Jersey cows

Feed efficiency measures, gross energy (solids-corrected milk/estimated energy intake), N (milk N/N intake) utilization, and apparent digestibilities of ration dry matter and N were calculated for 34 daughters of 21 Holstein and 29 daughters of 18 Jersey sires in first and second trimesters of lactation. Cows were studied in N balance trials and were fed ad libitum corn silage-based, complete rations formulated to meet average nutrient requirements. The objective was to determine whether these breeds differ in rates of converting dietary protein or energy to milk protein or milk energy. Holstein and Jersey did not differ for digestibility of ration dry matter in either trimester of lactation. They also converted dietary protein to milk protein at similar rates. Energy efficiencies of Holstein and Jersey did not differ in first trimester, but Holstein exceeded Jersey in second trimester. Because intake of dry matter by Jersey increased about 4% from first to second trimester (opposite of Holstein) and N balance was higher than for Holstein, Jersey cows may have been repleting more adipose tissue. We suggest no comparative advantage for Jersey in spite of higher ratios of milk to body weight and feed intake less than Holstein.