Effect of nongenetic factors on milk compositional aspects and bacteriological quality in Tunisian Maghrebi dromedaries (Camelus dromedarius) reared under a traditional pastoral management system

Abstract

This study was planned to evaluate the impact of nongenetic factors on physicochemical composition and microbial quality of milk from Maghrebi camels kept under traditional system in oasis areas of Tunisia. Milksamples from 69 animals were collected from lactating Negga over winter and summer. Animals belonging to private flocks were between 5 and 17.5 years of age, with parity numbers ranging from first to sixth. Samples were analyzed for basic composition and microbiological features according to standard methods. No significant association (P > 0.05) between physical characteristics and nongenetic factors has been observed. The maximum contents of total solids, protein, casein, and fat content were observed during winter. The third lactation was characterized with the highest content of total solids, protein, casein, and lactose; while the highest fat content was recorded in the second lactation. The highest levels of Ca, P, and K were recorded in the winter (P<0.01) whereas Na showed an opposite pattern (P<0.01). All major minerals were higher in milk from multiparous than primiparous camels, with maximum concentrations at the fourth lactation. The uppermost levels of mineral concentrations and chemical constituent were recorded in the age class of 7≤ age ≤ 9 years. The microbial analysis of raw milk which is affected by season, parity, and age showed higher overall contamination levels in all studied bacterial counts. The highest levels were observed in winter, among the multiparous and oldest Negga. The results highlighted the complete absence of the two dangerous pathogens Salmonella and CSR in all analyzed samples.