PATTERN OF HERBAGE GROWTH DURING LACTATION AND LEVEL OF HERBAGE MASS AT LAMBING: THEIR SIGNIFICANCE TO ANIMAL PRODUCTION

Abstract

On most New Zealand sheep farms continuous stocking is practised for the period lambing to weaning. Levels of herbage mass are frequently low both before and after lambing and the high demands of the lactating ewe often results in these low levels being maintained until weaning. Low levels of herbage mass depress herbage growth, herbage intake and animal liveweight gain. A simple simulation model was used to integrate the effects of herbage mass at lambing, pattern of herbage growth during lactation and stocking rate into production functions of animal performance versus stocking rate. These functions demonstrate the necessity at high stocking rates for herbage mass levels to be at least 1000 kg DM/ha at the beginning of lambing if the detrimental effects of prolonged periods of low herbage mass on both herbage and animal production are to be minimised. Keywords: Animal production, herbage growth rates, herbage mass, production functions.