Levels of Naturally Occurring Thiocynate and Keeping Quality of Cow Milk under Different Rearing Systems in Selected Areas of Tanzania

Abstract

Milk from a total of 80 smallholder farms was studied in Coastal and Kilimanjaro regions. Feed samples from the respective farms were analysed for cynogenics (glucosinalate) contents. The potential keping quality of milk was taken as time required for pH to change from 6.7 to 6.5. Results showed that cyanogenic content in different forage feeds was low (0.016 - 1.7 mg/kg) compared to concentrate mixtures (2.66 - 3.06 mg/kg). The mean ± standard deviation of thiocyanate (SCN) found in milk from traditional cattle grazing natural pastures was 3.49 ± 1.28 and zero grazed smallholder dairy cattle in Kilimanjaro was 4.57 ± 1.96 mg/kg.  The milk from the Coastal region had SCN level of 7.13 ± 2.86 in the traditional cattle and 5.70 ± 2.35 mg/I in the small-holder dairy cattle and the differences were significant (p<0.05). Total bacteria plate count of the raw milk within 3 hours from milking was an average of 895,888 c.f.u/ml, (range 24,000-3.8 million). SCN content of milk from Ayrshire, Holsten Friesian and Crossbred  cows  fed  the  same diet at  Magadu  Farm  were 4.14,  3.37 and 3.78 mg/kg with a  shelf life of milk of 8.0, 3.5 and  8.0  hours  respectively at 24-28°C. SCN content of milk from Aryshire cows from Magadu, SUA farm and LITI farm was 4.42, 4.88 and 3.18 mg/kg respectively. The corresponding shelf life of 8, 13 and 9 hours was not significantly (p>0.05) related to SCN levels. It is concluded that, there was slight relationship between concentration of cyanogenics in animal feeds and SCN excreted in raw milk: but the latter did not influence the bacteriological quality or its shelf life