DIGESTIBILITY OF DIETARY NUTRIENTS AND EN ERGY IN THE CZECH WARM-BLOODED HORSE

The objective of the study was to determine digestibility of dietary n utrients in metabolism trials on horses, to establish the relationship of organic matter digestibility to fiber content and to compare organ ic matter digestibility values with the values predicted for ruminants . Metabolism trials were always performed on a group of four horses of the Czech Warm-blooded Horse (weight 565 +/- 50.3 kg, age of 4 to 14 years). Eight feed rations were tested (Tab. I). The horses received f eed twice a day, at 6.00 a.m. and 17.00 p.m. Physical method NIRS (nea r infrared reflectance spectroscopy) was used to predict organic matte r digestibility of feed rations for ruminants. Spectra od samples were measured on InfraAlyzer 450 Technicon apparatus (19 fixed filters of the size 1,445-2,348 nm). Calibration equations (Homolka, Pluharova, 1 993) were derived by means of IDAS-pc program. Tab. I shows the formul ation of feed rations and feed intake in original and absolute dry mat ter in particular metabolism trials. Molasses feed contained these ing redients: oats 26%, wheat bran 32%, rye bran 12%, wheat 20%, mineral s upplement (MKP III) 2%, molasses syrup 8%. Tab. II shows contents of d ietary nutrients and energy. The particular feed rations are arranged according to the increasing fiber content. Tab. III indicates the valu es of dietary nutrient and energy digestibility as obtained in metabol ism trials on horses. Fat zero digestibility for feed ration 8 is due to the low fat content, which probably results in an analytical error of fat determination. Fig. 1 compares organic matter digestibility of the tested feed rations for horses with dietary fiber content. The neg ative effect of fiber content on organic matter digestibility is quite evident. A relationship of organic matter digestibility coefficient t o fiber content (in per cent of absolute dry matter) was calculated by this linear regression equation: y = 87.6 - 0.97 x (r = 0.964; RSD = 2.10). The acquired results of organic matter digestibility from metab olism trials on horses were compared with organic matter digestibility predicted for ruminants (NIRS method). Tab. IV summarizes the results for the particular feed rations. Organic matter digestibility of feed rations determined in metabolism trials on horses was lower in all ca ses than the values predicted for ruminants. The smallest difference w as found in feed rations 1, 2 and 3 containing grains - barley (-2.5%) , molasses feed (-1.8%), wheat bran (-3.1%). On the other hand, the la rgest differences was observed in feed rations 5, 6, 7 and 8 composed of bulk feeds - meadow hay and barley whole plants silage (-4.8%), mea dow hay and alfalfa pellets (-6.0%), meadow hay and corn silage (-6.0% ), ryegrass hay (-6.9%). Out of this distribution, feed ration 4 compo sed of ryegrass hay and oats (-9.7%) stands apart. An average differen ce in digestibility of feed rations for horses and for ruminants made -5.1%.