engleski

The concentration of urea in the milk of East-Friesian and Pag island sheep

The aim of the research was to determine the effect of the breed, herd, age and the stage of lactation (0-60th day ; 61st – 150th day and 151st – drying off) on the concentration of urea in sheep milk. The research was conducted between the year 2002 and 2005 on a sample of 78 East Friesian sheep (herds A and B) and 213 Pag island sheep (herds C, D and E). Milk samples were collected every 30 days during the period of lactation. In total, there were 1278 individual milk samples of the evening milking. The concentration of urea in milk was determined by the method of continued measuring. The collected data were statistically analysed by the PROC ANOVA, SAS programme. The average concentration of urea in the milk of the East Friesian sheep was 30.18 mg/100 mL and in the milk of the Pag island sheep 36.56 mg/100 mL respectively. The influence of the breed on the concentration of urea in milk was significant (P<0.001) as was also the influence of the herd (P<0.001) of the analysed breeds. For herds A and B, the average values were 35.19 mg/100 mL and 28.24 mg/100 mL respectively and for herds C, D and E, these were 39.54 mg/100 mL ; 35.18 mg/ 100 mL and 34.04 mg/100 mL. The influence of age on the concentration of urea was not significant for either breed in all the analysed herds. The effect of age was not significant for the concentration of urea in milk in East Friesian sheep (29.84 mg/100 mL in 2004 and 30.82 mg/100 mL in 2005) and in Pag island sheep (37.17 mg/100 mL in 2002 and 35.52 mg/100 mL in 2003). During lactation, the concentration of urea in milk of the East Friesian sheep was balanced, unlike the one in the Pag island sheep, where a significant increase was determined from the beginning (31.28 mg/100 mL) towards the end of lactation (36.67 mg/100 mL). Based on the research results, it can be concluded that the breed, herd and the stage of lactation have a significant influence on the concentration of urea in sheep milk.

sheep milk; urea; breed; stage of lactation and year

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