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In vitro evaluation of two additives with different mode of action on rumen protein degradability.

C. Cajarville



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In vitro evaluation of two additives with different mode of action on rumen protein degradability.
A. Alvarado1, A. Britos1, A. P�rez-Ruchel1, F. Gadeyne2, C. Cajarville*1. 1Departamento de Producci�n Animal (IPAV), Facultad de Veterinaria, UdelaR San Jos�, Uruguay, 2Royal Agrifirm Group Apeldoorn, the Netherlands.

This work aimed to evaluate the effects of including 2 additives with differing modes of action to a dairy cow diet on ruminal fermentation and protein degradability. Comparison was made with a diet containing a processed protein source. In a Rusitec system (6 fermentation units) 4 diets were evaluated: C: control (30% corn silage, 30% grass silage, 11.5% soybean meal and 28.5% corn; 17% CP, 30.5% NDF), M: positive control (Mervobest replacing regular soybean meal), Phy (1% DM of a phytogenetic mixture added to C) and ABC (1% DM of Aromabiotic Cattle added to C). A balanced incomplete block design was used, and 4 runs were performed with 3 diets in duplicate incubated at a time. Each run lasted 14d (7d adaptation period plus 7d of sampling). Ten grams of DM was incubated in nylon bags. Inoculum was obtained from 3 rumen fistulated cows fed grass silage ad libitum, 1.5 kg DM/d of corn grain and 1.5 kg DM/d of soybean meal. McDougall artificial saliva was infused at 3%/h. Samples were taken from the fermentation unit at the same time as the bags were changed. Gas production, pH, N-NH3 concentration and disappearance of DM, CP and non-protein compounds (NCP) were determined. Mervobest usage and Phy inclusion decreased N-NH3 concentrations (P < 0.001) and DMd (P = 0.004). The CPd was highest for C, followed by ABC diet, Phy diet and M showed the lowest CPd (P < 0.001). The NCPd was similar between M, Phy and ABC diets, while C diet showed the highest value (P < 0.001). Results indicate that Phy inclusion at 1% decreased in vitro rumen protein degradation similar to Mervobest use and more effectively than ABC.Table 1. In vitro rumen fermentation characteristics and DM, CP, NCP disappearances (d) of the diets1

Gas (mL/d)67870169367548.40.6860.040.849
N-NH3 (mg/dL)8.4a6.8b6.5b8.3a0.54<0.001<0.0010.805
DMd (%)45.0a42.5b42.9b44.4a1.150.0040.3640.777
CPd (%)50.3a41.6d45.4c47.8b1.03<0.0010.0170.473
NCPd (%)40.2a35.9b37.1b36.7b0.66<0.0010.0020.176
1C = control; M = Mervobest; Phy = 1% DM phytogenetic mixture added to C; ABC = 1% DM AromabioticCattle added to C; T = treatment; D = day.

Keywords: Rusitec, nitrogen disappearance, rumen fermentation.