Non-nutritional Factors Affecting Milk Yield Milk Quality And Prevalence Of Food Borne Pathogens In Milk And Milk Products In Central Highlands Of Oromia Ethiopia

Nutritional and non nutritional factors are the major contributors for variation in milk yield andrnphysicochemical parameters. On the other aspects as milk is nearly perfect food it is also a goodrngrowth media for spoilage and pathogenic microorganisms. This study was aimed at analyzingrnthe effects of non-nutritional factors on milk yield and composition, physicochemical andrnmicrobial quality. The prevalence of some food borne pathogens in milk and its products wasrnalso evaluated in study areas. The study was conducted from, February 2017 to June 2019 inrnHoleta Agricultural Research Center (HARC) dairy Lab., milk and its product samples wererncollected from producers and collectors in Bishoftu and Sebeta town’s while pasteurized milkrnwas sampled from shops in Addis Ababa. The study was conducted in three categories whererndairy farm recorded data analyis, physicochemical, microbial and food borne pathogenicrninvestigations of milk and milk products samples collected from study sites. Twelve yearsrnrecorded data of Holstein Friesian crossbred dairy cows were categorized and summarized intornparameters of study to see the effects of season, exotic blood level, parity and lactation stagesrnon monthly milk yield and composition from records of HARC dairy farm. Analysis of physicochernmical parameters of one hundred raw milk and twelve pasteurized milk samples collected from strnudy areas were conducted using lacto scan in dairy laboratory of HARC. In addition to thernretained one half amount of samples used in physicochemical analysis, samples of 40 locallyrnfermented yoghurt and 40 cottage cheese(ayib) summed up to 192 samples were used forrninvestigating microbial quality and food borne pathogens of milk and milk products from Sebetarnand Bishoftu areas. The microbial quality and food borne pathogens analysis were donernfollowing standard procedures of laboratory in dairy laboratory of HARC. General linear modelrnof SAS was used for statistical analysis of variances. Season significantly affected milk yield, fatrnand protein content of milk. Higher yield and fat percent composition was recorded in dryrnseason while higher protein percent was recorded during wet season. Genotype significantlyrnaffected milk yield where 62.5% and >75% crossbred cows produced significantly higher milkrnyield than that of 50% crossbred cows. Differences in parity affected milk yield and proteinrncontent of milk where higher milk yield and protein content was recorded in parity five. Milkrnyield and protein content had shown increasing trend as dam parity advances.rnMean monthly milk yield, percent of protein and total solid was varied significantly between diffe rent lactation stages where protein and total solid percentage was significantly higher in late ges of lactation. Differences in sample types were affected physical parameters of milk pH, specifrnic gravity and freezing point.The overall result showed that percent composition of raw milk samrnple from Sebeta and Bishoftu area include: lactose (4.91±0.12)%, protein(3.28±0.08)%, fat(3.68rn±0.25)%, solid-not fat(8.93±0.22)%,total solids(12.61±0.41)%, ash(0.74±0.02)%; and lactose(4.rn36±0.06)%, Protien(2.90±0.04)%, fat(3.59±0.13)%, solid-not-fat (7.93±0.11)%, total solids(11.5rn2±0.20)%, ash (0.66±0.01)% respectively. Significant difference was observed in lactose, proteinrn, and solid not fat, total solid and ash values between the study sites. Raw milk samplesrnfrom Sebeta area had higher percentage of composition where as physicochemical componentsrnof pasteurized milk was significantly lower than that of raw milk and also below the minimumrnrequirement of Ethiopian standard for protein, fat, total solid and specific gravity. Results of rawrnmilk fulfill minimum requirements of standards to be accepted. There was significant variationrndue to difference in study site for TCC, E. coli, YMC, S.aureus and L.monocytogenes of raw milkrnsamples but no variation in TABC due to differences in study sites on raw milk and milk productsrn. There was also significant difference in S. aureus in cheese, TCC and E. coli in yoghurt due torndifference in study site of sampling. Except E.coli, TCC, YMC, S.aureus and L. monocytogenes ofrnraw milk samples were significantly higher in Bishoftu than sebeta milk samples.On the other harnnd, lower count of TABC, TCC, S. aurus and E.coli were found in pasteurized milk. There wasrnhigh microbial count in milk and milk products of the two sampling site and sources whererncounts of the respective sites of TABC, TCC, yeast and mould (YMC), E.coli andrnL. monocytogenes were above Ethiopian quality standards. Given their high count, milk spoilagernand health risk is inevitable if these products are consumed untreated. Pasteurized milk hadrnshowed less microbial loads, therefore it is one option recommended as solution for reducing thernhigh microbial counts. The high L. monocytogenes in pasteurized milk suggested that thernexistence of either post process contamination or inefficient pasteurization. Hence, minimizingrncontamination through proper barn and equipment cleaning, animal health care, facilitatingrnmilk cooling systems, strict hygienic practices at farm, collection sites and in dairy processingrnplants are necessary.

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