Untreated and formaldehyde-treated urea as nitrogen sources for lactating dairy cows

Authors

• Jouko Setälä Department of Animal Husbandry, University of Helsinki, 00710 Helsinki 71, Finland
• Liisa Syrjälä-Qvist Department of Animal Husbandry, University of Helsinki, 00710 Helsinki 71, Finland

DOI: https://doi.org/10.23986/afsci.72088

Abstract

An experiment was performed with 22 Friesian cows, using a double reversal design with two treatments and one similar sequence for the two groups. The lengths of the standardization period, adaptation periods, test period and post-test period were 4, 1, 8 and 4 weeks, respectively. During the standardization and post-test periods the cows received pre-wilted grass silage ad libitum and a small amount of field-dried baled hay. In the test period hay was given ad libitum and the amount of grass silage was restricted. A concentrate mixture (barley, oats, minerals) was given daily to each cow at the rate of 0.3 kg/kg 4 % milk. During the standardization and post-test periods the mixture contained one percent of untreated urea and during the test period 2.5 % of untreated or treated urea. The urea had been treated with 1.5 % formaldehyde on a weight basis. The concentrate mixture was fed individually to each cow, but group feeding was used for the roughage. Among the cows producing more than 15 kg of 4 % milk a day, those receiving formaldehyde-treated urea had a significantly (P< 0.01) higher milk yield, and the fat content of their milk was significantly (P< 0.05) lower than the group receiving untreated urea. Among the cows producing less than 15kg of 4 % milk/day, the group given treated urea had a significantly (P<0.05) higher milk fat content. No significant differences were found between the groups in the protein content of the milk. Formaldehyde was found in five milk samples (total 55) taken from the formaldehyde-urea group during the test period. The formaldehyde content of these samples varied from 0.2 to 0.3 mg/kg milk.