Phosphorus supplementation to natural pasture grazing for beef cows in theWestern Highveld region of South Africa

Simmentaler cows grazing Cymbopogon-Themeda veld in the western Highveld re gion of South Africa (1985/86-1989/90) received three levels of phosphorus (P) supplementation. Dicalcium phosphate content of the supplement was mani pulated to give intakes of 8 (CS), 4 (HS) or 0 (ZS) g P/cow/day during summ er. AU cows received supplemental P (10 g/cow/day) during winter (1986-1989 ). In 1990, supplemental P (10 (CW), 5 (HW) or 0 (ZW) g P/cow/day) was give n in a winter maintenance supplement (protein, energy and minerals). Rainfa ll was above average during the trial period. Reproductive performance was not influenced by P supplementation. Mean livemass of the CS group was grea test (p < 0.01), and that of HS was greater (p < 0.01) than ZS at the end o f summer. Both CS and HS had better (p < 0.01) condition scores than ZS. Bo ne P content was lowest and indicative of deficiency (p < 0.01) in ZS cows (112.6 vs 141.9 and 130.8 mg P/cm(3) hone for CS and HS respectively). Calf performance was not affected (p > 0.05) by P supplementation. Cow mass was affected by winter P supplementation (p < 0.05). Both CW and I-TW displaye d improved (p < 0.01) condition scores and higher (p < 0.01) bone P content than ZW. Fatalities (4) occurred in ZW due to P deficiency (74.5 mg P/cm(3 ) bone), and deficiency symptoms were manifested in the entire group. Both summer and winter veld is deficient in P, which makes continuous supplement ation a recommended practice in this area.