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In situ rumen degradability and intestinal digestibility of rumen-protected choline sources.

M. E. Rodriguez-Prado


In situ rumen degradability and intestinal digestibility of rumen-protected choline sources.
C. Faturi2, F. Francia1, M. E. Rodriguez-Prado*1, S. Calsamiglia1. 1Animal Nutrition and Welfare Service, Univeristat Autonoma de Barcelona Bellaterra, Spain, 2Universidade Federal Rural de la Amazonia Belem, Brazil.

The objective of this study was to determine and compare rumen degradability and in vitro intestinal digestibility of 3 ruminally protected choline (RP-Chol) products. Rumen-protected choline products were CholiGEM (Kemin Animal Nutrition and Health), Product R and Product N and contained 5.75, 3.23 and 2.71% of nitrogen (% DM). Rumen microbial degradability was determined using the in situ nylon bag technique. Samples (2.02 � 0.018 g) of each RP-Chol product was weighed into nylon bags and incubated in the rumen of a Holstein dry cow for 0, 2, 4, 8, 16, 24 and 48 h, in duplicate bags and in 2 consecutive periods. Ruminal degradability was calculated with a simple exponential function (Y = a+b*(1-exp(-ct)), where a was the amount of N disappearing from the bag at 0 h; b was the potentially degradable fraction; and c was the degradation rate. The effective degradability of N (EDN) was calculated as: EDN,% = a+[(b*c)/(c+k)]; where k (10%/h) is the estimated rate of outflow from the rumen, and a, b, and c are the same as described earlier. For the determination of intestinal digestibility, the in vitro 3-step procedure was used. The undegraded residue after 12 h incubation in the rumen was incubated in vitro in HCl pepsin at pH 2.0, 38�C for 1 h, followed by a phosphate-pancreatin buffer at pH 7.0, 38�C for 24 h. Fraction a was 27.6, 0.4 and 24.7%; fraction b was 57.1, 5.8 and 73.6%, and fraction c was 0.032, 0.002 and 0.081 /h for CholiGEM, Product R and Product N, respectively. Effective ruminal microbial degradation was very low in Product R (0.5%), moderate in CholiGEM (41.4%) and relatively high in Product N (57.6%). However, intestinal digestion was low in Product R (12.2%) compared with CholiGEM (98.4%) and Product N (80.9%) resulting in the highest bioavailability for CholiGEM (57.6%), intermediate for Product N (34.3%) and lowest for Product R (12.1%). Determination of the bioavailability of RP products requires the evaluation of rumen degradability and intestinal digestibility.

Keywords: rumen-protected choline, ruminal degradability, intestinal digestibility.