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

Changes in feed intake and live weight gain of 10 to 12 month old male red deer (Cervus elaphus) in response to a range of pasture anatomical development stages of perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture in spring were investigated at the Invermay Agricultural Research Centre, Mosgiel, New Zealand (45° 58' S; 170° 04' E). A standard intake study in November 2000 tested responses to pastures spelled for 6, 8 and 10 weeks in a controlled indoor/outdoor comparison A grazing study over 5 weeks compared 3, 5 and 7 week spelling periods during November and December in 2001. Pasture spelled for 6, 8 or 10 weeks has ADF concentrations of 216, 229 and 252 g/kg DM (P<0.001) and seed head compositions of 145, 364 and 539 g/kg DM (P<0.001) respectively. A decline in live weight gain (P=0.003) of the deer (n=8) from 394 g/d to 361 g/d and 221 g/d was accompanied by a decline in voluntary feed intake from 2.40, to 2.23 and 1.64 kg DM/d (P=0.016) and a decline in digestibility from 786 to 764 and 734 g/kg DM (P=0.002) as spelling interval increased from 6 to 10 weeks. 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 experiment 2 voluntary feed intake increased from 1.93 kg DM/d to 2.69 kg DM/d (P=0.004), even though the digestibility of the forage declined from 719 to 687 g/kg DM (P=0.013). Liveweight gain declined at 2.0 g/d for each additional 1% increase in seed head. The energy lost during digestion increased by 4.9% for every 10% increase in seed head offered (P=0.011). This study demonstrates that while the intake of red deer increases with increasing daylength, declines in feed quality still lead to lower liveweight gains.