Exploiting dietary fibre in equid diets

Abstract

AbstractFour in vivo apparent digestibility trials were carried out over a period of two years using 4 to 6 Welsh cross pony geldings of approximately 300kg LW. In all experiments ponies were individually housed in 10x12 ft loose–boxes with rubber mat flooring. In Experiment 1 three diets were offeredad libitumto 6 ponies in a replicate 3 x 3 Latin squares design. In Experiments 2, 3 & 4, four ponies were offered 1.5 – 1.75 % of LW per day in dry matter (DM) in 4 x 4 Latin square changeover designs. In all experiments periods lasted for 21 days, a 16-day adaptation period followed by a 5-day data collection phase. Diets were fed in two equal meals per day and water was availablead libitum. Dried feed and faecal samples were analysed for DM, ADF, NDF and CP using the methods of the AOAC (1990), GE was determined via bomb calorimetry and non–starch polysaccharides (NSP) were quantified by the method of Englyst and Cummings (1984). Differences between diets were determined by analysis of variance (Genstat 5, 2000). NSP analysis gave detailed information on the individual fibre constituents and allowed the subtle differences between feeds to be identified. The DMI of grass and red clover silages were 0.6 and 1.7 kg/d greater than hay indicating that the low DM content of these two forages does not negatively affect feed intake. The apparent digestibilities of these two feeds were also significantly greater than hay for all parameters measured. In Experiment 2 the combination diets of alfa-beet and hay (AB:H) and sugar beet and hay (SB:H) fed in 60:40 and 70:30 ratios were all significantly more digested at > 50% than the hay only diet at <39% for DM, CP, NDF, ADF, NSP, Ca, P and Mg. The addition of AB to H in the 70:30 diet produced a DE value of 2.89 MJ/kg DM higher than the hay alone only diet and also caused an associative affect which improved the digestibility of CP, arabinose, galactose and uronic acids from the hay portion of the diet. No significant differences were noted between the digestibilities of the proximate constituents for the chopped hay replacer (CHR), CHR and highly digestible fibre (HDF) cubes and CHR and course mix (CM) fed in Experiment 3. When looking at the digestibilities of the individual NSP constituents the CHR : CM diet was generally less digestible than the CHR: HDF diets indicating that HDF cubes are equally well or more digestible than a diet containing conventional course mix. With DE values similar to the CM the HDF feed can be offered as a valuable alternative to concentrates in equid diets. The high fibre forage (HiFi) fed in Experiment 4 was also highly digestible for all constituents measured and showed that a combination of chopped straw and alfalfa makes an excellent fibre feed for horses. The results from the four experiments reported here show that detailed chemical analysis is extremely valuable when choosing complimentary fibre feeds for horses. Moreover all the fibre feeds examined here were more digestible than hay. Feeds like the HDF cubes can be used to replace some or all of the cereal portion of the diet. The associative effects between the alfa-beet and hay and the mineral digestibility from these alternative feeds also suggests that not only is gut health enhanced, but that the supply of nutrients from these feeds makes them ideal choices for stabled horses.