REPRODUCTION AND PRODUCTION STRATEGIES FOR HIGH YIELDING DAIRY COWS*
J. Makulska, A. Stygar, Ł. Smagieł, A. Węglarz
The relationship between the length of days open and days dry periods and milk performance in first three and first five complete lactations of high yielding Polish Holstein-Friesian var. Black-and-White cows was studied. The following classes of the mentioned periods were distinguished: days open — I — <115 days, II — 115–195 days , III — > 195 days and days dry — I — < 30 days, II — 30–60 days, III — > 60 days. The highest yields of milk, fat, protein, FCM and VCM were found in open period longer than 195 days and dry period shorter than 30 days. Milk performance in dry period longer than 30 days was similar. The lengthening of days open resulted in the extension of the lactation even to 484 days - on the average. Often the highest yields per lactation were accompanied by the lowest yields per day of lactation. Higher number of lactations was associated with lower yield of milk, fat and protein per lactation. The obtained results suggest that the lengthening of open period positively affects milk performance of high yielding dairy cows. The shortening of dry period to less than 30 days can be advantageous only in case of the best cows.
Key words: DAYS OPEN, DAYS DRY, LACTATION LENGTH, MILK PERFORMANCE, HIGH YIELDING COWS, HOLSTEIN-FRIESIAN
