Influences of diet composition on milk protein percentage in mid-lactation Holstein cows
2005
Koga, Y. (Fukuoka-ken. Agricultural Research Center, Chikushino (Japan)) | Yokoyama, M. | Umeda, T. | Kakihara, T.
This study aimed to examine the influences of diet composition on milk protein percentage, by multiple regression and discriminant analyses with winter data (investigative data for Dec-Mar.) from 101 midlactation Holstein cows. The results of multiple regression analysis showed the contribution ratio (R2.) of a multiple regression equation on milk yield was 0.76 (P<0.01). The diet composition that significantly affected milk yield was the DMkg/d (amounts of dry matter fed) and CP (crude protein) contents of the diet, (total relative contribution ratio-95.9%). On the other hand, in the multiple regression equation on milk protein, percentage (R2=0.5O:P<0.O1), the diet composition with highest relative contribution, ratio was a 52.3% DMkg/d, followed by 24.5% EE (ether extracts) contents of the diet and 14.4% TDN (total digestible nutrients) roughage content. Discriminant analysis showed that in mid-lactation Holstein cows of less than 37kg/d 4% FCM (fat-corrected milk), when a diet of less than 3.7% EE content and over-55.5% TDN roughage content was offered, a milk protein percentage of over 3.3% and a SNF percentage of over 8.9%, respectively, could be expected with a 11.1% misdiscriminate ratio.
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