The effects of calcium and phosphorus supplementation on the performance of Scottish Blackface hill ewes, with particular reference to the premature loss of permanent incisor teeth

Abstract

SUMMARYA subclinical calcium or phosphorus dietary deficiency on many hill pastures and a relationship between this and the premature loss of permanent incisor teeth are postulated. The effects of small individual supplements of calcium (12 g calcium carbonate suspended in water) or phosphorus (13 g monosodium phosphate in solution) supplied three times a week between mid-February and the end of May to Scottish Blackface ewes which grazed reseeded pasture in April and May were compared with those of no mineral supplement and with those of no mineral supplementon hill pastures throughout.Neither supplement had any significant effect on the number or weights of lambs born or reared on reseeded pastures. Both resulted in significantly greater ewe live-weight gain during the treatment period, in a significant improvement in the firmness and permanence of the incisor teeth, and in significantly higher serum Ca levels during lactation. All effects increased with advancing age.The use of hill pastures during late pregnancy and early lactation without any mineral supplement could result in significantly poorer ewe live-weight gain during the treatment period depending on season. This was also associated with significantly lighter single lambs at 6 weeks and with slower deterioration of the incisor teeth.It is suggested that minerals lost from the body during lactation on reseeded pastures are not replaced during the autumn recovery period on hill pastures and that a gradual depletion occurs throughout life, leading possibly to demineralization of the alveolar bone and premature loss of the incisor teeth. It is suggested that this is indicative of a higher mineral requirement for maintenance of the permanent dentition than is necessary for normal acceptable growth andreproductive performance. Mineral content of hill herbage may therefore be too low to supply requirements at the levels of OM intake normal on hill pastures.