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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #117617
Title: EFFECT OF MONENSIN ON THE PERFORMANCE AND NITROGEN UTILIZATION OF LACTATINGDAIRY COWS CONSUMING FRESH FORAGE

Author
item RUIZ, R - CORNELL UNIVERSITY
item ALBRECHT, G - CORNELL UNIVERSITY
item TEDESCHI, L - CORNELL UNIVERSITY
item JARVIS, G - CORNELL UNIVERSITY
item Russell, James
item FOX, D - CORNELL UNIVERSITY

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2001
Publication Date: 10/1/2001
Citation: RUIZ, R., ALBRECHT, G.L., TEDESCHI, L.O., JARVIS, G.N., RUSSELL, J.B., FOX, D.G. EFFECT OF MONENSIN ON THE PERFORMANCE AND NITROGEN UTILIZATION OF LACTATINGDAIRY COWS CONSUMING FRESH FORAGE. JOURNAL OF DAIRY SCIENCE. 2001.

Interpretive Summary: Monensin has been used as a feed additive in beef cattle for more than 20 years, and in these cases it has improved the efficiency of feed utilization. The FDA is currently evaluating monensin use in dairy cattle rations. Previous work indicated that monensin could decrease wasteful protein degradation in the rumen, but lactation trials with dairy cattle consuming fresh forage and grain supplements were lacking. Results indicated that monensin decreased ruminal ammonia concentrations, improved nitrogen digestibility and increased milk production. If monensin is approved by the FDA for use in dairy cattle, it could provide a means of improving the efficiency of milk production. The Cornell Net Carbohydrate Protein System (CNCPS) is a computer model that predicts the milk production and weight gain of cattle from dietary ingredients. Results indicated that the CNCPS gave accurate predictions of milk production when cattle were fed fresh forage and grain supplements even if monensin was added to the ration. The CNCPS allows farmers to design more efficient rations for dairy cattle.

Technical Abstract: We conducted a lactation trial to evaluate the effects of monensin on amino acid sparing. Thirty Holstein cows in mid lactation (8 fitted with ruminal fistulas) were gradually introduced to a fresh forage diet. A concentrate mix based on corn meal was fed prior to the a.m. and p.m. milking times 0730 and 1730 h, then the fresh forage was fed at 0830 and 1830 h. Fifteen ncows each were allocated to a control (no monensin) and a treatment group receiving 350 mg/cow/d of monensin in the p.m. concentrate feeding. A 7d fecal and urine collection period and a 3d rumen sampling period were conducted with the 8-ruminally fistulated cows. After the lactation study was concluded, the fistulated cows were fed forage re-growth and a 3d rumen sampling period was repeated. Monensin increased milk production by 1.85 kg. Milk fat and protein concentrations decreased and milk fat and protein yields increased but the effects were non-significant. Monensin did not significantly affect DMI. Ruminal ammonia and the acetate to propionate ratio decreased with the addition of monensin in both fed forages. Monensin decreased fecal N output, and increased the apparent N digestibility by 5.4 %. Because of the decrease in ruminal ammonia and increase in apparent N digestibility, it seemed that monensin was sparing amino acids. The precision of the Cornell Net Carbohydrate and Protein System (CNCPS) in predicting performance was high (r2 = 0.76), and the bias was low (over-prediction of 3.6 %). These results indicate that the CNCPS can be used for dairy cows consuming fresh forage and gives realistic predictions of performance.