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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #124406
Title: EFFECT OF A RUMINAL NITROGEN (N) DEFICIENCY IN DAIRY COWS: EVALUATION OF THE CORNELL NET CARBOHYDRATE PROTEIN SYSTEM RUMINAL NITROGEN ADJUSTMENT

Author
item RUIZ, R - CORNELL UNIVERSITY
item TEDESCHI, L - CORNELL UNIVERSITY
item MARINI, J - CORNELL UNIVERSITY
item FOX, D - CORNELL UNIVERSITY
item PELL, A - CORNELL UNIVERSITY
item JARVIS, G - CORNELL UNIVERSITY
item Russell, James

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2002
Publication Date: 11/1/2002
Citation: RUIZ, R., TEDESCHI, L.O., MARINI, J.C., FOX, D.G., PELL, A.N., JARVIS, G., RUSSELL, J.B. EFFECT OF A RUMINAL NITROGEN (N) DEFICIENCY IN DAIRY COWS: EVALUATION OF THE CORNELL NET CARBOHYDRATE PROTEIN SYSTEM RUMINAL NITROGEN ADJUSTMENT. JOURNAL OF DAIRY SCIENCE. 2002.

Interpretive Summary: 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, but the effect of ruminal nitrogen deficiency was not accommodated. The CNCPS has been modified to include equations for a nitrogen deficiency and these changes have been validated with an in vivo feeding trial. The CNCPS allows farmers to design more efficient rations for dairy cattle.

Technical Abstract: Twenty-four multiparous and fifteen first lactation Holstein cows averaging 263 days in milk and weighing 614 kg were fed diets adequate or deficient in ruminal nitrogen (N), based on predictions of the Cornell Net Carbohydrate and Protein System (CNCPS). After adjustment to a low CP TMR (11 % CP), the cows were allocated to 13 blocks based on milk production, body condition score, and body weight. Within each block, cows were randomly assigned to one of the 3 treatment (TRT) diets (8, 10 and 13 % CP for TRT 1, 2, and 3, respectively). All diets contained the same proportion of high moisture corn, chopped grass hay, and minerals, with urea substituted for corn silage as needed to reach the 3 CP levels. The TRT diets then were fed for 4 weeks. Milk production was significantly affected by TRT; 15.5, 18.8, and 21.7 kg milk for TRT diets 1, 2, and 3 respectively. DMI was 17.6, 20.0, and 21.2 kg for TRT diets 1, 2, and 3, respectively. CNCPS predictions (with and without the N adjustment for ruminal N deficiency) of metabolizable protein (MP) allowable milk production were compared to observed milk production. Using individual weekly cow data from all 3 TRT, the CNCPS accounted for 72 and 68% of the variation in MP allowable milk without and with the N deficiency adjustment, respectively. The overall mean bias without the N adjustment was 3.3 kg of milk (over prediction model bias of 14.6 %, P < 0.001), and the N adjustment reduced the model over-prediction bias to 0.01 kg of milk (P = 0.96).