Translocation from flowering to daughter tillers in perennial ryegrass (Lolium perenne L.)

Abstract

Recent New Zealand cultivars of Lolium perenne often have a high rate of tiller death and replacement in late spring–early summer. A majority of the new tillers are daughter tillers of flowering tillers. Previous research has led to a hypothesis that defoliation may influence the amount of assimilate exported by flowering tillers, and hence the rate of daughter tiller formation. To test this hypothesis, flowering tillers of of nutrition that enabled the dam to gain 100 g/day of conceptus-free liveweight in addition to expected fetal growth) during the mid pregnancy (post-shearing) period (from Day 70 of pregnancy (P70) until P101). At the end of this period ewes were offered either maintenance or a high level of nutrition during late pregnancy (P102–P140). Pregnancy shearing was found to increase lamb birthweight (average birthweight 5.4±0.1 v. 5.1± 0.1 kg) without differentially affecting the birthweight of singles or twins. Dam feeding level post-shearing did not affect the birthweight response to mid pregnancy shearing. Pregnancy shearing treatment had no effect on the summit metabolic rate of twin lambs. However, when results of this study are compiled with those of previous mid to late pregnancy shearing studies under similar conditions, it appears that the birth weight response from pregnancy shearing is greatest where lightweight lambs are born to unshorn (control) ewes.