Effects of Lactation on Performance of Grazing Beef Cows Wintered with Supplements Containing Soybean Meal, Wheat Middlings, or Soybean Meal-Wheat Middlings Mixtures

Abstract

Eighty-eight spring calving and 58 fall calving Hereford and Hereford × Angus cows were wIntered on dormant native tallgrass range to study the value of wheat middlings (WM) as a source of supplemental CP and energy. Supplements consisted of soybean meal (SBM, 40010 CP), SBM and WM (32% CP), WM and SBM (24% CP), and WM (16% CP). Each supplement was individually fed and provided .36kg CP daily from November 5 to December 9, and .54kg CP from December 10 to May 4 for spring calving cows. Fall calving cows were fed .36kg CP daily from November 29 to December 9 and .54kg from December 10 to March 15. Precalving weight changes for spring calving cows increased linearly (P<.001) witth increasing amounts of supplement. Weamng weights and pregnancy rates were not significantly affected by treatments. Weight and condition changes for lactating, fall calving cows wem similar for all supplement treatments. Calf gains tended to be greater for cows on treatments fed greater amounts of supplements containing WM. Pregnancy rates were similar for all treatments. In a second study, 42 lactating Hereford, Hereford × Angus, and Limousin × Angus beef cows were fed one of three supplements betvlleen Nov 11 and Mar 31. The suppllements were: .57kg/d SBM (.21kg/d CP, SBM1), 11.36kg/d SBM (.54kg CP, SBM2), or 3.45kg/d WM (.54kg CP). Winter cow weight and condition losses were reduced, calf gains were greater, and pregnancy rates were greater for SBM2 and WM compared to SBM1. Performance of cows was similar when fed isonitrogenous amounts of SBM and WM. Hesults suggest that WM is efficiently utilized as a source of supplemental protein and energy by beef cows. However, response in body weight when protein and energy supplements are fed during the winter may be different for nonlactating vs. lactating cows.