Reproductive activity in beef heifers following post-weaning feeding on spear grass hay alone or with supplements

Abstract

A group of 24 heifers was weaned, divided into three groups of eight and pen-fed during the dry season in north Queensland (Lat. 18¦S). One group, which received poor quality native pasture hay only, lost body weight. Another group, which received in addition a small portion of legume hay in the diet, gained body weight slowly. The third group received a further addition of legume hay plus cereal grain and gained body weight more rapidly. During the following wet season all animals were allowed to graze and the occurrence of oestrus was noted. Only two heifers in the poorly fed group exhibited oestrus. Six heifers in each of the other groups exhibited oestrus, but those that were better fed exhibited oestrus cycles for a longer period. Following this grazing period, all animals were slaughtered and analysed for the major chemical components.It was concluded that only small improvements in nutrition need be made during the tropical dry season to increase protein and energy intake sufficiently to support body weight gain. During subsequent grazing marked changes in oestrous activity can result from such improvements. The onset of oestrous appeared closely related to body fat content.