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Comparison of D-Alanine and Diaminopimelic Acid as Bacterial Markers in Young Calves^1,2,3,

University of New Hampshire⁵, Durham 03824

Abstract

D-alanine (DAL) and diaminopimelic acid (DAP) were compared as markers to estimate proportion of bacterial N in total N reaching the abomasum of young calves. Sixteen Holstein bull calves fed complete pelleted starter or unpelleted starter plus hay and weaned at 4 or 8 wk of age were fitted with ruminal and abomasal cannulas and sampled twice weekly from 2 to 11 wk of age. Isolated ruminal bacterial cells contained more DAL than DAP at all weeks and averaged 7.0 and 5.4 mg N/g N, respectively. Weekly mean marker concentrations were highly correlated (.89) in ruminal bacteria, except at 3 wk of age. Concentration of DAL in abomasal digesta was greater than that of DAP at all weeks and averaged 5.2 and 2.4 mg N/g N, respectively. Weekly mean DAL correlated with DAP .61 in abomasal digesta and correlated .57 and .89 with starter intake, respectively. The proportion of bacterial N in total abomasal N was greater at all weeks when estimated by DAL than by DAP and averaged 77% and 46%, respectively. Estimates by DAL exceeded 100% in several cases and reflected large variation in analytical estimates. Estimates by DAL and DAP correlated .33 and .92 with starter intake. D-alanine was not an acceptable bacterial marker in this study.

¹ The authors thank S. Safford and C. Bozak for assistance in sample preparation, analysis and animal care.

² Scientific contribution no. 1502 from the New Hampshire Agric. Exp. Sta.

³ Supported in part by a grant from Agway Inc., Syracuse, NY.

⁴ Dept. of Anim. Sci., Univ. of Tennessee, Knoxville, TN.

⁵ Dept. of Anim. and Nutr. Sci., NH Agric. Exp. Sta.