Question

1. Oxidation of 1g carbohydrate, fat and protein yields 0.56, 1.07, and 0.42 g metabolic water respectively. Retention of 1g of dietary protein yields 0.16 g metabolic water whereas 0.07g of water is prduced when 1 g of dietary fat and carbohydrate, respectively, are retained as fat.

For a lactating cow consuming 15 kg DM/day and feed contains 76% carbohydrate, 4% fat, and 14% crude protein;

How much metabolic water will the cow produce under the following scenarios:

(i) If 65% of carbohydrate, 70% fat, and 60% crude protein is oxidized?

(ii) If 15% of crude protein, 15% fat, and 12% carbohydrate is retained?

Answer 1

Ans (i) : 991.288 g

	DM basis (%)	Grams oxidised	Grams retained	Water due to oxidation	Water due to retention
CHO	76%	1140 x 0.65 = 741 g	1140 - 741 = 399 g	741 x 0.56 =414.96 g	399 x 0.07 = 27.93 g
Fat	4%	304 x 0.70 = 221.8 g	304 - 221.28 = 82.2 g	221.8 x 1.07 = 237.326 g	82.2 x 0.16 = 13.152 g
Protein	14%	1064 x 0.60 = 638.4 g	1064 - 638.4 = 425.6 g	638.4 x 0.42 = 268.128 g	425.6 x 0.07 = 29.792 g
			Total	920.414 g	70.874 g

Total water produced = 991.288 g

Ans (ii) : 1240.586 g

	DM basis (%)	Grams retained	Grams oxidised	Water due to oxidation	Water due to retention
CHO	76%	1140 x 0.15 = 171 g	1140 - 171 = 969 g	969 x 0.56 = 542.64 g	171 x 0.07 = 11.97 g
Fat	4%	304 x 0.15 = 45.6 g	304 - 45.6 = 258.4 g	258.4 x 1.07 = 276.488 g	45.6 x 0.16 = 7.296 g
Protein	14%	1064 x 0.12 = 127.68 g	1064 - 159.6 = 936.32 g	936.32 x 0.42 = 393.2544 g	159.6 x 0.07 = 8.9376 g
			Total	1212.3824 g	28.2036 g

Total water produced = 1240.586 g