Apparent synthesis of thiamin, riboflavin, vitamin B6 and vitamin B12 in rumen of lactating dairy cows fed 2 concentrations of nitrogen and 2 energy sources

Wednesday, July 23, 2014
Exhibit Hall AB (Kansas City Convention Center)
Valérie Beaudet , Agriculture & Agri-Food Canada, Sherbrooke, QC, Canada
Rachel Gervais , Université Laval, Québec, QC, Canada
P. Yvan Chouinard , Université Laval, Québec, QC, Canada
Pierre Noziere , INRA-URH, Saint Genès Champanelle, France
Benoit Graulet , INRA-URH, Saint Genès Champanelle, France
Michel Doreau , INRA-URH, Saint Genès Champanelle, France
Christiane L Girard , Agriculture & Agri-Food Canada, Sherbrooke, QC, Canada
Abstract Text: Effects of nitrogen supply and energy sources on apparent ruminal synthesis (ARS) and post-ruminal supply of thiamin, riboflavin, vitamin B6, and vitamin B12 were evaluated using 4 lactating Holstein cows distributed in a 4×4 Latin square design with treatments arranged according to a 2×2 factorial. The cows were fitted with cannulas in proximal duodenum. The treatments were 2 concentrations of nitrogen: HIGH: 14% CP, i.e. 110% of the protein requirements and an adequate supply in rumen-degradable protein (RDP), vs. LOW: 11% CP, i.e. 80% of the protein requirements with a shortage in RDP; energy sources were STARCH from barley, corn, and wheat vs. FIBER from soybean hulls and dehydrated beet pulp. Diets were corn silage based, had the same forage: concentrate ratio (60:40, dry matter basis) and were isoenergetic. STARCH resulted in greater (P<0.01) intakes of thiamin (51 vs. 34 ± 2.4 mg/d), riboflavin (1172 vs. 1050 ± 25.8 mg/d) and vitamin B6 (202 vs. 161 ± 3.9 mg/d) as compared with FIBER, whereas nitrogen concentrations had no effect (P≥0.76). Vitamin B12 intake was not affected by treatments (P≥0.43) and averaged 86 ± 2.0 µg/d. Duodenal flow (P=0.34; 35 ± 7.0 mg/d) or ARS (P=0.46; -6 ± 7.6 mg/d) of thiamin were not significantly affected by treatments. STARCH increased duodenal flow of riboflavin (P<0.01; 1546 vs. 1091 ± 92.4 mg/d) and vitamin B6 (P<0.01; 68 vs. 45 ± 4.9 mg/d) but decreased vitamin B12 flow (P<0.01; 3127 vs. 9319 ± 731.1 µg/d) as compared with FIBER. HIGH nitrogen increased riboflavin and vitamin B6 duodenal flows (P=0.02; 1481 vs. 1156 ± 85.5 mg/d and P=0.01; 67 vs. 47 ± 4.6 mg/d, respectively) and ARS (P=0.04; 372 vs. 43 ± 95.2 mg/d and P=0.04; -114 vs. -135 ± 6.3 mg/d, respectively). Nitrogen supply had no effect on vitamin B12 duodenal flows (P=0.64) or the ARS (P=0.63). Energy sources had no effect on ARS of vitamin B6 (P=0.11) but STARCH tended to increase the apparent production of riboflavin (P=0.06; 374 vs. 41 ± 102.3 mg/d). Inversely, FIBER enhanced ARS of vitamin B12 (P<0.01; 9234 vs. 3040 ± 730.3 µg/d, respectively). There was no interaction between treatments (P≥0.09). The apparent ruminal balance was affected by the nitrogen concentration for synthesis of riboflavin and degradation of vitamin B6, and by the energy sources for synthesis of riboflavin and vitamin B12.

Keywords: apparent ruminal synthesis, B vitamins, dairy cow