THE CORRELATIONS BETWEEN MILK YIELD OF GOATS AND SOME MILK NUTRIENT CONTENT DURING A 3- AND 5-MONTH LACTATION AND A FULL LACTATION

A total of 203 White Improved goats from a farm in Roznow (Kujawsko-Pomorskie province) were investigated in 2007 -2009. The study attempted to simplify the current goat milk recording scheme and make it more accurate by shortening of the evaluation time and finding opti - mum lactation months for recording. In order to reach this aim, coefficients of phenotypic correlation were calculated using the multiple regression method between the yield and basic composition of milk over a 90- and/or 150-day lactation and the same traits for a full lactation taking into account the lactation number. The lactation length in White Improved goats varied according to the lactation from 228 days (1st lactation) to 303 days (3rd lactation), with the daily milk yield from1.90 kg to 2.60 kg. and the fat content of 3.10 -3.30% and protein content of 2.80 -2.90%. High and significant coeffi - cients of phenotypic correlation between milk yield and composition over the 90- and 150-day lac - tation and the same traits over a whole lactation prove that every variant of the shortened recording may serve as a basis for the evaluation of goats before the lactation ends. Slightly higher coefficients of correlation (mostly above 0.900) found for the 5-month compared to the 3-month recording show that the evaluation encompassing four control milkings over a whole lactation is more accurate. How - ever, the 3-month recording during summer months is economically more beneficial. Shortening the frequency of control milkings followed by the reduction of costs will enable a greater number of goat herds to be recorded, which is of considerable importance to the efficiency of the breeding programme.