Seasonal effects on milk yield and milk composition in dairy cows
2001
Oresnik, A. (Ljubljana Univ. (Slovenia). Biotechnical Fac., Zootechnical Dept.)
Slovenian dairies purchase in period from May to August larger quantities of milk than in other months of the year. In summer months purchased milk contains lower fat and protein concentrations. These regularities are well known also in other countries. It is concluded that direct and indirect seasonal effects alter milk yield and composition. Out of milk yield and milk composition analyses of 398 Black and White cows reared on one large farm malnutrition (to low amounts of structural fiber and to high amounts of crude protein consumed per cow) was connected with low milk fat and protein content. These failures and to fast transition from pasture to winter feeding regime caused a deficient milk persistency in autumn months. On an other farm (428 Black and White cows) average milk yield of cows that calved in summer months (July-September) was for 919 kg (15,2 %) lower than of cows that calved in autumn months (Oktober-Dezember). The highest average milk yield in the lactation attained cows that calved in November (7195 kg) and the lowest cows that calved in June (5652 kg). With higher amounts of maize silage feed in summer months, reduction of dry matter intake on the pasture and with prolonged periode of transition from pasture to winter feeding regime in the year 2000 on a farm (215 Black and White cows) an optimal milk persistency in autumn period was obtained. After the same quantities of concentrates feed per kg of milk (0,23 kg) in comparison to 1999 average milk yield on the farm increased for 1020 kg (15,1 %) of milk per cow.
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