ANN 121: Applied Animal Nutrition-I (2+1)

INDICATOR METHOD

• It is an indirect method of estimation of digestibility in grazing animals.
• The digestibility of a nutrient is calculated by estimating the concentration of the indicator/marker in feed and faeces and that of the nutrient in the feed and faeces without quantitative collection of total faeces and measuring feed consumption. The formula for estimation of digestibility is given below.

• DM intake of grazing animal can be measured if internal and external indicators are used in the digestion trial.

Exercise

1. The indicator % and the nutrient % in feed and faeces are as follows. Calculate the digestibility of nutrient in the feed.

	Trial 1	Trial 2
% indicator in feed	1.1	1.8
% indicator in faeces	2.45	4.2
% nutrient in feed	20	25
% nutrient in faeces	15	15

2. A grazing animal was fed 2 g of Cr₂O₃ in a capsule per day. Find out the forage intake and its DM digestibility. The data is as follows

	% composition
	DM	Lignin (Internal Indicator)	Cr2O3 (External Indicator)
Forage	20	0.05	-
Faeces	15	0.10	0.1

Answer

Daily dry matter voided in faeces (g/day)

                    Amount of Cr₂O₃ fed daily               2

      = ------------------------------------------- = --------- = 2000 g

                     g of Cr₂O₃ per g of faeces            0.001

                                                                          0.05            15

DM dige.coe.of forage = 100 - { 100 x ----------- x -------- }

                                                                           0.10            20

                                      = 100 -37.5

                                      = 62.5

                                    DM voided

DM intake = ------------------------------- x 100

                        % of DM indigestibility

                      2000

                 = --------- x 100 = 5333 g

                      37.5

                                            5333

Fresh forage intake = ---------- x 100

                                              20

                                 = 26.665 g/day = 26.665 kg/day.

Courtesy: Applied Nutrition for Livestock,Poultry,Pets,Rabbits and Laboratory animals,Second Edition, by D.V.Reddy 2009.