In vivo digestibility of different types of forages using sheep as a model of ruminants

Abstract

Digestibility of a forage is very important as it contributes to the energy and protein values and intakepotential of the feed in ruminant production systems. The silages used in this digestibility trial present therange of variation encountered in practice of forages used within Finland: early cut grass (EG), late cutgrass (LG), red clover (Trifolium pratense, RC) and whole-crop barley (Hordeum vulgare, WCB). Grasssilages were a mixture of timothy (Phleum pretense) and meadow fescue (Festuca pratensis). EG, LG,RC and WCB were cut on 13 June (2006), 3 July (2006), 29 June (2006) and 2 August (2006),respectively. Grass and clover silages were wilted for 1 day and all silages were ensiled with AIV 2, andensiled in round bales. Four rams (Dorset and Finnsheep × Texel crossbred) were used to estimatedigestibility in a 4 × 4 Latin square experiment with four 3-week experimental periods. The totaldigestibility was determined using total collection method by measuring daily forage intake and theamount of faeces excreted over the last 7 days of each period.All silages were well preserved and had relatively high DM concentration, within 395 - 566 g/kg.The ash concentration in EG, LG, RC and WCB was 88, 70, 97 and 62 g/kg DM. The respective CPconcentrations were 180, 113, 163, 71 g/kg DM and NDF concentrations were 509, 623, 385and 548 (g/kgDM).The organic matter digestibility for EG, LG, RC and WCB was 0.751, 0.608, 0.645 and 0.618.There was a 20 day difference in the cutting dates of EG and LG resulting in 0.008 unit decrease inorganic matter digestibility per day. Neutral detergent fibre digestibility was highest for early cut grasssilage (0.74). and lowest for red clover (0.50) and whole-crop barley (0.51).Forages vary greatly in their digestibility depending on species and maturity as shown by theresults of the current study. The great variation emphasizes the importance of accurate routine digestibilityanalysis and need to analyze farm silages for ration formulation.