Urea in sugarcane-based diets for dairy cows

Alberto Magno Ferreira Santiago,Sebastião De Campos Valadares Filho,André Soares De Oliveira,Stefanie Alvarenga Santos,Iara Furtado Santiago,José Maurício De Souza Campos,Shirley Motta De Souza

doi:10.1590/s1516-35982013000600010

Abstract

We evaluated the effect of adding four levels (0, 4, 8 and 12 g/kg, as fed) of a mixture (9:1) of urea and ammonium sulfate (UAs) to sugarcane on feed intake and digestibility, productive performance and metabolism of nitrogen compounds of dairy cows. Twelve multiparous Holstein cows (12.6±0.5 kg/d of milk, 225±90 days in milk) were distributed in three 4 × 4 Latin squares, receiving diets with the same amount of nitrogen (125 g crude protein/kg of dry matter). Concentrate feed was supplied at a ratio of 1 kg for each 3 kg of milk produced. The sugarcane presented 21.9 oBrix. The level of UAs did not affect intake, total digestibility of diet components, milk production or milk components. Increasing UAs level linearly increased concentration of plasma urea nitrogen (PUN), urinary excretion of nitrogen and contribution of non-urea nitrogen in the urinary excretion and linearly reduced milk production/urinary excretion of nitrogen ratio. In spite of the linear increase of PUN with increased urea, the maximum value observed (14.31 mg/dL) was below the threshold value of 20 mg/dL, above which reproductive function may be compromised. In diets with sugarcane for dairy cows with production below 15 kg/day, the UAs level may be raised from 0 to 12 g/kg natural matter without impairing performance.

Highlights

Sugarcane is characterized as a forage of high yield, with high levels of carbohydrates rapidly fermented in the rumen, but poor in protein, in addition to presenting fibrous components of low extent of rumen degradation, implying limitations in the ingestion of dry matter (Fernandes, 2001).The increase of concentrate in diet is an alternative to circumvent the limitations of dry matter intake imposed by sugarcane, but raises the cost with feeding (Costa et al, 2005)
We evaluated the effect of adding four levels (0, 4, 8 and 12 g/kg, as fed) of a mixture (9:1) of urea and ammonium sulfate (UAs) to sugarcane on feed intake and digestibility, productive performance and metabolism of nitrogen compounds of dairy cows
The experiment was comprised of four 18-day periods, of which the first day was used for acclimatization, and the others for evaluation of intake, digestibility, milk production and composition, excretion of nitrogen compounds and nitrogen balance

Summary

Introduction

The increase of concentrate in diet is an alternative to circumvent the limitations of dry matter intake imposed by sugarcane, but raises the cost with feeding (Costa et al, 2005). In a study comparing the supply of diets containing 1 or 3% urea for Holstein cows and steers, provided orally or via rumen, greater reduction was observed in intake when more elevated levels of urea were supplied through the rumen (Wilson et al, 1975). These effects demonstrated that physiological reactions are involved in the alteration of intake and not sensory characteristics

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Results