Use of tritiated water for estimation of dry matter intake in grazing cattle

D. Mohamad Aziz

Abstract

An experiment was conducted on heifers to evaluate the technique using tritiated water for the measurement of dry matter intake. Four Jersey and three LID-J. 15 to 18 months old were used. The animals were stall-fed with Panicum maximum ad libitum and supplemented with concentrate (3 kg/animal/day). Water was given ad libitum. Tritiated water was injected to the animals to measure the water turnover rate. Water intake from the feed was estimated from the difference between water turnover rate and water from concentrate plus water drank. The final value and the value of dry matter content of the grass were then used to calculate the dry matter intake of the animals. The measured value of dry matter intake was calculated from the dry matter content of the grass consumed and the total dry matter intake from the concentrate. The estimated dry matter intake (5.26 kg/animal/day or 2.24% body weight /day) was not significantly different (P'0.1) f rom the measured intake (5.18kg/ animal /day or 2.21% body weight /day) .T he ratio between the former over the latter was 1.01. The dry matter intake of seven dry Sahiwal-Friesian cows grazed on Setaria sphucelata var. Splendida estimated using the same technique was 14.42 kg/animal /day or 4.06% body weight /day. It is concluded that by measuring the water turnover rate. water intake and water content of the feed. the dry matter intake of animals grazing on homogenous pasture can be estimated with high accuracy.

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