Phosphorus status of lactating dairy cows fed total mixed rations containing 2.24% vs. 0.36% phosphorus
2005
Shore, K.V. | Odongo, N.E. | Mutsvangwa, T. | Widowski, T.M. | Cant, J.P. | Bettger, W.J. | McBride, B.W.
The effect of dietary P content on P balance was evaluated using 14 lactating dairy cows fed a corn silage based total mixed ration (TMR) containing either 0.24% P or 0.36% P. The animals were paired by calving date at dry-off with one cow from each pair randomly assigned to either dietary treatment. All cows were fed a common TMR containing 0.34% P prepartum, and then 0.41% P for 2 wk postpartum. Experimental diets were fed from 3 to 13 wk postpartum. Phosphorus balance was conducted at week 13 postpartum. Cows fed 0.36% P diet consumed more (P < 0.05) P than the 0.24% P diet cows (69.2 vs. 50.9 g d(-1)) and excreted more (P < 0.05) P in the faeces (49.1 vs. 25.7 g d(-1)). Phosphorus digestibility was lower (P < 0.05) for the 0.36% P diet than the 0.24% P diet (29.0 vs. 48.8%). Dry matter intake and milk yield were not (P > 0.05) affected by treatments. These results suggest that short-term P balance in lactating dairy cows can be maintained on a diet supplying 26% below National Research Council 2001 recommendations of P while reducing the amount of P excreted into the environment.
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