Digestible crude protein (DCP) and total digestible nutrient (TDN)

DIGESTIBLE CRUDE PROTEIN (DCP) and TOTAL DIGESTIBLE NUTRIENT (TDN)

Digestible crude protein

  • To find out the digestible crude protein (DCP) content of a feed,multiply the digestibilty coefficient of the crude protein with the crude protein content of the feedstuff.

DCP= Digestibilty Co-efficient x CP

Where, CP represents crude protein content of the feed.

Total Digestible Nutrients

  • It is a measure of apparent digestible energy, but it is expressed in units of weight or per cent rather than energy per se. It is the most widely used expression of energy system in the 20th century. Digestibility coefficients are used to compute the TDN: Digestible ether extract is multiplied by 2.25 since its energy is 2.25 times of carbohydrates.

    TDN = DCP + DCF + DNFE + (DEE x 2.25)

  • Percentage Digestible nutrient is calculated as follows:

Digestible_nutrient

  • Eg. If the digestibility coefficient of protein in soyabean meal is 75 % and the protein content is 45%. The digestible crude protein content of soybean meal is 45 x 75/100 = 33.75 %.

Example calculation of total digestible nutrients (TDN) and DCP

*Factors used to put on a carbohydrate-equvalent basis.
1 kg TDN = 4.4 Mcal DE or 4400 Kcal DE
ME = DE X 82 / 100 (ruminants)
Using the above example, TDN content of a feed = 66.2%
DE content of the feed = 4400 x 66.2 /100 = 2913 Kcal
ME content of the feed = 2913 x 82/100 = 2389 Kcal (ruminants)
Total digestible nutrients (TDN)
  • Total digestible nutrients (TDN), indicates the relative energy value of feed to an animal.
  • Calculation of Total Digestible Nutrients (TDN)
  • TDN (%) = % DCP + % DCF + % DNFE + (% DEE x 2.25).

Nutrients
Percentage value
Digestibe crude potein
4.28 %
Digestible crude fiber
9.55%
Digestible N-free extract
29.90%
Digestile crude fat x 2.25 (1.10 x 2.25)
2.48%
Total
46.21% (TDN)

  • Feeds listed and grouped according to their percentage of TDN for cattle - As fed basis

Group.A. Primarily the pure fats and other high fat feeds, plus certain other feeds of generally high digestibility.

Feed stuffs
TDN value (%)
Hydrolysed animal fat
223.0
Soybean oil
194.0
Corn oil
172.8
Peanut kernels
131.0
Cotton seed
88.0
Soya bean seeds
83.0

Group.B. Mostly low- fiber grains and grain by-products.

Feed stuffs
TDN value (%)
Dried brewers grain
81.0
Corn gluten meal
78.0
Sorghum (Jowar) grain
78.0
Wheat grain
78.0
Corn (Maize) grain
77.0
44% Soyabean meal
75.0
41% solvent extracted cotton seed meal
70.0
Peanut meal
71.0

Group.C.Largely the more fibrous grains and by-products and concentrates.

Feed stuffs
TDN value (%)
Soyabean hulls
70.0
Copra meal
68.0
36% cottonseed meal
67.0
Dried alfalfa leaves
64.0
Rapeseed meal
63.0
Rice bran
63.0
Wheat bran
63.0
Beet molasses
61.0
Wheat middlings
61.0
Sunflower meal
60.0

Group.D. Predominantly the hays, hay meals, straws, hulls corn cobs,corn stover and cane molasses.

Feed stuffs
TDN value (%)
Poultry manure
59.0
Oats hay
56.0
Dehydrated alfalfa meal
55.0
Cow pea hay
53.0
Alfalfa hay
52.0
Millets hay
51.0
Peanut hay
50.0
Oat straw
47.0
Ground corn cobs
45.0
Cotton seed hulls
41.0
Cane molasses
54.0

Exercise

  • Calculate the digestibility coefficients of the nutrients with given data and also calculate the TDN.
    A bullock consumed 10 kg of hay per day. Over the experimental period, the animal excreted 15 kg of wet faeces per day. The per cent chemical composition of hay and faeces were as follows:
Hay Faeces
Moisture
9
70
Crude protein
6.5
1.8
Ether extract
2.5
0.8
Crude fibre
27.5
8.5
Total ash
10.5
18
  • Calculate the DCP and TDN of the feed with given data:
Chemical composition (%) Digestibility (%)
Crude protein
8.6
60
Ether extract
2.5
60
Crude fibre
11.6
50
NFE
42.5
58
DCP = 6.5
Last modified: Wednesday, 4 April 2012, 5:25 AM