Rock phosphates and cattle feeding in Sahel. II. Influence on the Bobra zebu survival rate, milk production and reproduction performances

Abstract

The influence of rock phosphates on survival rate and reproduction performances has been tested in the Senegalese Sahelian zone at Dahra from 1991 to 1994. Four groups of 15 young Gobra heifers each were raised in permanent pastures at the Dahra station and a supplementation program was applied during 8 months each year for 4 years. Group 1 was supplemented continuously with 50 g Taiba rock phosphate, group 2 with 100 g tricalcic phosphate from Lam-Lam mine and group 3 with 65 g bone meal. Group 4 was not supplemented as a control. Mineral intake was daily recorded and animals growth rate measured. Other observations were mortality, calving rate, herd fecundity and milk production. Health status was monitored by monthly clinical examinations. Special attention was paid to fluorosis as it may be a consequence of long lasting phosphates consumption in ruminants. Results emphasized non toxicity of rock phosphates, no fluorosis lesions were observed. Rock phosphates efficiency was clearly demonstrated in mortality reduction (50 to 85% in the groups ingesting Lam-Lam rock phosphate and bone meal respectively). In November, 1994, for groups 1, 2, 3 and 4 respectively, calving rate was 25, 53, 57 and 40%, calving interval 633 j, 654 j, 621 j and 704 j, calve weight 23,5 kg, 26 kg, 23,9 kg and 23,8 kg. Mineral supplementation improved these parameters and significantly (p < 0,01) milk production. Results would recommend, for mineral supplementation in traditional systems, 50 g Taiba phosphate and 100 g Lam-Lam (Thiès) tricalcic phosphate daily intake during dry season (eight to nine months per year).