DISCOLORATION OF YELLOW BODY-FAT IN FAT H EIFERS AS A RESULT OF A CAROTIN-LOW DIET

61 heifers were given a carotin-rich diet of meadow grass and grass co bs. When the grazing period ended the animals, which had an average ag e of 18 months, were divided into 49 experimental animals and 12 contr ols. The controls continued to receive a carotin-rich diet of grass co bs and were slaughtered after 92 and 127 days. The experimental animal s however changed to a carotin-low diet of maize silage and were slaug htered after from 43 to 120 days. The colour of the body fat was deter mined by means of the MINOLTA reflexion values for yellow, red and bri ghtness and also photometrically using the extinction value E. The mea surements were made at three points on the depot fat 1 h and 24 h post mortem with 5 repeats in each case. Extinction value E was found to b e the most suitable when determining the effects influencing the yello w colouring, followed by the yellow value 24 h post mortem. The lenght of time maize silage was given and the age of the animal when changin g over to maize silage had the greatest effect on the yellow colour. A s feeding with maize silage proceeds the yellow colour first declines sharply and then at a slower rate. We can conclude from this pattern a nd the subjectively evaluated yellow colouring that heifers fed grass products need to be fed maize silage for 3-4 months, depending on thei r age (500 or 600 days), before the yellow colour is sufficiently redu ced for the carcasses to avoid price deductions.