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
| dc.contributor.advisor | Prof. Berhan Tamir, Dr. Firew Kassa | |
| dc.contributor.advisor | Dr. Gebeyehu Goshu | |
| dc.contributor.author | Dereje, Shibru | |
| dc.date.accessioned | 2020-11-05T09:27:09Z | |
| dc.date.accessioned | 2023-11-08T11:33:05Z | |
| dc.date.available | 2020-11-05T09:27:09Z | |
| dc.date.available | 2023-11-08T11:33:05Z | |
| dc.date.issued | 2020 | |
| dc.description | PhD Thesis | en_US |
| dc.description.abstract | Nutritional and non nutritional factors are the major contributors for variation in milk yield and physicochemical parameters. On the other aspects as milk is nearly perfect food it is also a good growth media for spoilage and pathogenic microorganisms. This study was aimed at analyzing the effects of non-nutritional factors on milk yield and composition, physicochemical and microbial quality. The prevalence of some food borne pathogens in milk and its products was also evaluated in study areas. The study was conducted from, February 2017 to June 2019 in Holeta Agricultural Research Center (HARC) dairy Lab., milk and its product samples were collected from producers and collectors in Bishoftu and Sebeta town’s while pasteurized milk was sampled from shops in Addis Ababa. The study was conducted in three categories where dairy farm recorded data analyis, physicochemical, microbial and food borne pathogenic investigations of milk and milk products samples collected from study sites. Twelve years recorded data of Holstein Friesian crossbred dairy cows were categorized and summarized into parameters of study to see the effects of season, exotic blood level, parity and lactation stages on monthly milk yield and composition from records of HARC dairy farm. Analysis of physicoche mical parameters of one hundred raw milk and twelve pasteurized milk samples collected from st udy areas were conducted using lacto scan in dairy laboratory of HARC. In addition to the retained one half amount of samples used in physicochemical analysis, samples of 40 locally fermented yoghurt and 40 cottage cheese(ayib) summed up to 192 samples were used for investigating microbial quality and food borne pathogens of milk and milk products from Sebeta and Bishoftu areas. The microbial quality and food borne pathogens analysis were done following standard procedures of laboratory in dairy laboratory of HARC. General linear model of SAS was used for statistical analysis of variances. Season significantly affected milk yield, fat and protein content of milk. Higher yield and fat percent composition was recorded in dry season while higher protein percent was recorded during wet season. Genotype significantly affected milk yield where 62.5% and >75% crossbred cows produced significantly higher milk yield than that of 50% crossbred cows. Differences in parity affected milk yield and protein content of milk where higher milk yield and protein content was recorded in parity five. Milk yield and protein content had shown increasing trend as dam parity advances. Mean 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, specif ic gravity and freezing point.The overall result showed that percent composition of raw milk sam ple from Sebeta and Bishoftu area include: lactose (4.91±0.12)%, protein(3.28±0.08)%, fat(3.68 ±0.25)%, solid-not fat(8.93±0.22)%,total solids(12.61±0.41)%, ash(0.74±0.02)%; and lactose(4. 36±0.06)%, Protien(2.90±0.04)%, fat(3.59±0.13)%, solid-not-fat (7.93±0.11)%, total solids(11.5 2±0.20)%, ash (0.66±0.01)% respectively. Significant difference was observed in lactose, protein , and solid not fat, total solid and ash values between the study sites. Raw milk samples from Sebeta area had higher percentage of composition where as physicochemical components of pasteurized milk was significantly lower than that of raw milk and also below the minimum requirement of Ethiopian standard for protein, fat, total solid and specific gravity. Results of raw milk fulfill minimum requirements of standards to be accepted. There was significant variation due to difference in study site for TCC, E. coli, YMC, S.aureus and L.monocytogenes of raw milk samples but no variation in TABC due to differences in study sites on raw milk and milk products . There was also significant difference in S. aureus in cheese, TCC and E. coli in yoghurt due to difference in study site of sampling. Except E.coli, TCC, YMC, S.aureus and L. monocytogenes of raw milk samples were significantly higher in Bishoftu than sebeta milk samples.On the other ha nd, lower count of TABC, TCC, S. aurus and E.coli were found in pasteurized milk. There was high microbial count in milk and milk products of the two sampling site and sources where counts of the respective sites of TABC, TCC, yeast and mould (YMC), E.coli and L. monocytogenes were above Ethiopian quality standards. Given their high count, milk spoilage and health risk is inevitable if these products are consumed untreated. Pasteurized milk had showed less microbial loads, therefore it is one option recommended as solution for reducing the high microbial counts. The high L. monocytogenes in pasteurized milk suggested that the existence of either post process contamination or inefficient pasteurization. Hence, minimizing contamination through proper barn and equipment cleaning, animal health care, facilitating milk cooling systems, strict hygienic practices at farm, collection sites and in dairy processing plants are necessary. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/23040 | |
| dc.language.iso | en | en_US |
| dc.relation.ispartofseries | ;057/06/2020 | |
| dc.subject | Season | en_US |
| dc.subject | parity | en_US |
| dc.subject | genotype | en_US |
| dc.subject | lactation stage | en_US |
| dc.subject | milk composition | en_US |
| dc.subject | Foodborne pathogens | en_US |
| dc.title | 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 | en_US |
| dc.type | Thesis | en_US |