Evaluation of mineral status in smallholder Dairy farms in Githunguri and Kinangop, divisions of central, Kenya.
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A study to investigate the levels of some macro and micro minerals in soils, feeds and in blood of dairy cows was conducted in two milk producing divisions (Githunguri and Kinangop) in Central Kenya. Serum Vitamin B12 was compared within lactating cows. The survey was conducted in 8 farms, 5 within Kinangop (a predominantly open grazing system) and 3 within Githunguri (primarily a stall feeding production system). Soil, forage and blood samples were collected during the long dry season (December-April), wet season (May to July) and short dry season (August-September). Twentyfour composite soil samples, 108 composite feed samples and 248 blood samplesfrom 36 lactating cows of different parities and stage of lactation were collected. Soil and feed samples were analyzed for calcium (Ca), magnesium (Mg),phosphorus (P), copper (Cu) and cobalt (Co). Serum was analyzed for the sameminerals except cobalt for which vitamin B12 was assayed. Higher(P<O.Ol) soil mineral levels were found in Githunguri than in Kinangop. Season of the year had significant effect (P<0.05) on soil Ca and Cu but no effect (P>0.05) on Mg, P and Co content. The eight farms differed in the levels of soil Ca, Mg, Cu and Co but did not differ (P>O.05) in P. Soil Ca, Mg and P were sufficient for ruminant feeds in Githunguri when compared to critical levels of 400.8, 121, and 17ppm respectively. Phosphorus was however deficient in two farms in Kinangop. Copper was deficient «10 ppm) in both regions while Co was below critical level of 0.10 ppm in one farm (0.07ppm). Thirty percent of forages analysed were deficient in Ca «0.28%),33% had Mg level below the critical 0.20% level while 26% were deficient in P «0.25%). Most of the forages (97%) were low in Cu «10 ppm) while Co was apparently adequate (>0.10 ppm) in all feeds sampled. No consistent correlations were observed between soil and feed mineral content. Most animals in Githunguri had higher (P<O.Ol) serum minerals and Vit B12 than those in Kinangop. Season of the year affected only serum Mg and Cu. Serum Ca was deficient «8mg%) in one farm, while Cu was below critical level of 80 micrograms percent (ug%) in 3 farms under grazing system. Subnormal «300 picograms per millilitre-pg/ml) levels of vitamin B12 which is a manifestation of inadequate cobalt intake was observed in 4 farms under grazing management. This might be as a result of inadequate mineral intake a consequence of suboptimal dry matter intake (DMI). Cows in Githunguri had fewer services (2vs3) per conception, shorter service period (63vs120 days) and calving interval (12vs15 months) when compared to those in Kinangop. It was concluded that soils and common feeds in the two regions were sufficient in the minerals studied. Results from blood analysis however indicated that intervention at the animal level to increase mineral ingestion and thus serum mineral levels especially in Kinangop is necessary. The poor reproductive performance observed in grazing animals may be as a result of suboptimal copper and cobalt intake. To reduce this deficiency, effective animal feeding management practices especially mineral supplementation is recommended.