Studies about the calculation of influence of the environmental correction factors on milk and fat production of the Brown Swiss cows bred at Karacabey State Farm by the partial regression coefficient

Alaettin KUTSAL; Gültekin AKTAŞ

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Studies about the calculation of influence of the environmental correction factors on milk and fat production of the Brown Swiss cows bred at Karacabey State Farm by the partial regression coefficient

Alaettin KUTSAL ,Gültekin AKTAŞ

- The objectives of this study were to investigate the effects of age of cow, length of lactation period and calving interval on the milk yield and butterfat production of Brown Swiss cows bred at Karacabey State Farm and to establish correlation factors for these effects.

In a previous paper milk and butterfat records of the same herd were analysed in order to obtain age correction factors based on simple mean values of lactation. This time mean values were estimated for number of lactation and lactation period groups and correction factors were derived for these effects relative to one of the groups in each, with the use partial regression coefficients.

Data were obtained from the milk records of the cows bred in Karacabey State Farm from its establishment (1927) up to the and of 1958-1959 milking season. Taking in to accuunt the fact that correction factors would be calculated common to all cows, each datum to be used in this study should have been influenced by all the factors studied. For this consideration only the records of the cows with lactation periods between 221 and 365 days calving intervals between 305 and 370 days and the records of the ones with first four lectations were included. This 252 lactation records of 80 cows, wich satisfied the above limitations were available for this study. Keywords :