Effect of Calcium to Phosphorus Ratios in Concentrate on Milk Production in Dairy Cows (ผลของสัดส่วนแคลเซียมต่อฟอสฟอรัสในอาหารข้นต่อผลผลิตน้ำนมในโคนม)

Abstract

This experiment was conducted to investigate the effect of calcium to phosphorus ratios on milk production in dairy cows. Five Holstein Friesian cows were arranged according to a 5x5 Latin square design. The calcium (Ca) to phosphorus (P) (Ca:P) ratio in concentrate were as follows: 1:1, 2 .5:1, 4:1, 5.5:1 and 7:1. Cows were offered urea-treat ed rice straw as roughage source ad libitum. 111e result s of the experiment revealed that total dry matter intake of cows fed Ca:P ratio at 1:1 -7:1 were not significantly different among treatment s (P>0.05). Digestion coefficients of dry matter, organic matter and crude protein of dairy cattle fed Ca:P ratio at 5.5 were significantly lower (P<0.05) than those in dairy cattle fed Ca:P ratio at 1:1, 2.5:1, 4:1 and 7:1. Urine pH were significantly different (P<0.05) and linearly increased (P<0.01) as ratios  of Ca:P was increased . Milk production, 3.5% fat corrected milk (FCM) and milk compositions were not significantly different among treatment s (P>0.05), but milk protein production (3.02, 3.20, 3.14,3.19 and 2.97) were significantly different among treatments (P<0.05). In conclusion, it can be concluded that increase in the ratio of Ca:P from 1:1 to 7:1 had no effect on milk yield , but m ilk protein production and total dry matter intake tend to be decreased if Ca:P ratio in concentrate was greater than 5.5:1.