Protein for finishing cattle

Crude protein requirements are influenced by certain factors:

Rate of gain

Large frame size

Aggressive implants programs

Extensive grain processing

Meeting protein requirements does little unless energy requirements are also met. One strives for an ideal protein to energy ratio. As energy intake increases in the diet, rate of gain increases, which requires an increase in the protein to energy ratio in the diet. Using these ratios, the CP requirement of cattle can be calculated for varying rates of gain. From Table 1, one can observe that protein requirements are a function of energy density and rate of gain.

Table1. Crude protein requirements of cattle ( % of DM)

Diet composition

 

Average daily gain (lb)

R%

Conc%

 

.5

1.0

2.0

3.0

4.0

     

--------------( protein % of DM) --------------

100

0

 

7.5

8.2

9

9.5

9.8

80

20

 

7.9

8.7

9.6

10.1

10.4

60

40

 

8.3

9.1

10.1

10.7

11.1

40

60

 

8.7

9.6

10.7

11.3

11.7

20

80

 

9.2

10.1

11.3

11.9

12.4

0

100

 

9.6

10.6

11.9

12.6

13.0

Receiving cattle

Upon arrival at the feedlot, some nutritionists believe that calves require higher CP levels. However, when calves arrive at the feedlot, their feed (energy) intake is often

Low ( 2<% of BW) and if higher levels of CP are fed, the protein will be used for energy,

This is inefficient and releases more nitrogen to the environment.

For receiving diets, it is important to provide adequate CP but do not exceed 13 % CP.

The source of CP in receiving diets has been found to be more important. Addition of UIP to receiving diets improved average daily gain as compared to cottonseed meal or urea. Addition of UIP to receiving diets should be added at 7% UIP.

Finishing Cattle

CP requirements decrease with time on feed. It has been shown that 7.1 % CP in diet had lower gains during the 56 days, but parallel gains occurred after the 56 days as compared to those fed 11.4 and 13. % CP. When fed more CP than needed Plasma Urea N increases in with time on feed to levels greater than 10 mg/ dl, which indicates protein wastage.

If we calculate MP for the diet, supplemental protein is not required for cattle weighing 900 lb and fed diets containing 50 % shelled corn and 50 % corn silage. With small frame cattle, CP concentration in the diet can be reduced to as low as 8.6 % ( 5.8 % DIP and 2.8 % UIP). With large frame cattle CP concentration should not be released as soon or as low of CP level. In general, once cattle on full feed of a high concentrate diet and weigh about 75 % of weight at projected choice grade, dietary CP levels can be reduced . Others suggest that reducing dietary CP below 10 % CP is inappropriate.

Recommendations for finishing diet

 

CP in diet

Arrival in feedlot ( feed intake < 2 % of BW)

no more than 13 %

On full-feed of grain

no more than 13 % 7 % DIP

On full-feed for 60 days, weigh 75 % estimated
weight at choice grade

CP of diet reduced to 10%
Maintain 5.5 % DIP