Effects of fresh forage quality on feed intake and live weight gain of red deer in spring

Changes in voluntary feed intake (VFI) and average daily gain (ADG) of 10to 12-month-old male red deer (Cervus elaphus) in response to a range of pasture morphological development stages of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture in spring were investigated. An intake study in November 2000 tested responses to pastures spelled for 6, 8 or 10 weeks in a combined indoor/outdoor comparison over two weeks. This was followed by a 5 week grazing study which compared 3, 5 or 7 week spelling periods during November and December in 2001. Pasture spelled for 6, 8 or 10 weeks had acid detergent fibre concentrations of 216, 229 and 252 g/kg DM (P<0.001) and seed head proportions of 145, 364 and 539 g/kg DM (P<0.001) respectively. As spelling interval increased from 6 to 10 weeks ADG declined (P=0.003) from 394 g/day to 361 g/day and 221 g/day. VFI also declined from 2.40, to 2.23 and 1.64 kg DM/day (P=0.016), and digestibility declined from 786 to 764 and 734 g/kg DM (P=0.002). The grazing study comparing 3, 5 or 7 week spelling provided a different response to spelling interval as seed head production was similar regardless of spelling interval. During the course of the grazing study voluntary feed intake increased from 1.93 kg DM/day to 2.69 kg DM/day (P=0.004), while the digestibility of the forage declined from 719 to 687 g/kg DM (P=0.013). The energy lost during digestion increased by 4.9% for every 10% increase in seed head offered (P=0.011). The coefficient of conversion of digestible energy to metabolisable energy declined from 0.86 to 0.56 as the diet offered increased from 0% to 60% seed head.