Organic matter digestibility of feedstuffs:

1. Organic matter digestibility of feedstuffs: Comparing of in vitro method and a multi enzymatic method to in vivo method K-J Leeuw1*, D. Palic2, F.K. Siebrits3 & H. Muller4 1ARC-Animal Production Institute, Private Bag x2, Irene, 0062, South Africa; 2Institute for Food Technology, BulevarcaraLazara, 1,21000 Novi Sad, Serbia; 3TUT, Dept. of Animal Sciences, P. Bag X680, Pretoria, 0001; 4UNISA, Dept. of Statistics, PO Box 392, UNISA, 0003 *Corresponding author: kleeuw@arc.agric.za Introduction Table 2: Organic matter digestibility regression equations in 21 feedstuff samples for sheep (g OM/kg DM) for in vitro and PME The determination of feedstuff quality can improve formulation strategies aimed at increasing production from ruminant livestock. Organic matter digestibility (OMD) determination is routinely done by in vitro method, with Tilley & Terry (1963) as the benchmark. Many adaptations have been made to this, but its use is restricted by availability of surgically altered sheep from which ruminal fluid can be extracted. The need thus exists to use alternative methods where rumen liquor is no longer required. Material and methods Table 3: Organic matter digestibility regression equations in 38 feedstuff samples for sheep (g OM/kg DM) for in vitro and PME In vivo Castrated adult male Texel sheep housed in metabolism crates designed to separate urine and faecal matter were used. Sheep were adapted for two weeks to the crates, an 11 day diet adaptation period and 10 day measuring period. The materials tested here are single feed ingredients and organic matter digestibility was determined. In vitro A modified Tilley and Terry in vitro method (MT) (Leeuw et al., 2014) was used to determine organic matter digestibility (OMD) of the single feed ingredients. This method requires the keeping of cannulated sheep for providing rumen liquor. Figure 1: Equation for predicting in vivo OMD (g/kg) of feedstuffs using modified Tilley and Terry method Multi enzymatic method A pepsin-acid and multi enzymatic (PME) method (Weisbjerg & Hvelplund, 1993) was used as an alternative to methods where rumen liquor is required, The OMD obtained by PME and MT method were evaluated against OMD data obtained by in vivo. Regression equations presented here were derived using SAS to relate the analytical methods to in vivo digestibility. An initial 17 feedstuff (grasses and grains) samples were analysed, where after a further 21 samples (grasses and grains) were analysed to verify and strengthen the equations derived. Figure 2: Equation for predicting in vivo OMD (g/kg) of feedstuffs using PME method Discussion The R2 values obtained by compilation of the differential regression equations, show that PME and MT derived data can be used to accurately predict in vivo OMD. The PME method can be used as it negates the use of rumen liquor and confidently replacing MT OMD determinations. Results Table 1: Organic matter digestibility regression equations in 17 feedstuff samples for sheep (g OM/kg DM) for in vitro and PME. References Weisbjerg, R & Hvelplund, T., 1993. Estimation of net energy content in feeds for cattle. Report Nº. 3/1993, National Institute of Animal Science, Denmark. Leeuw, K-J., Palić, D., Siebrits, F.K., Muller, H. & Hindle, V. A., 2014, Prediction of in vivo organic matter digestibility of ruminant feeds using in vitro techniques. S. Afr. J. Anim. Sci. (in press). No differences of the mean OMD were observed (tables 1, 2 and 3).