The effect of N fertilizer and polyethylene glycol on chemical composition and digestibility of safflower forage and silage

This study was conducted to determine the effects of nitrogen fertilizer and polyethylene glycol)PEG 6000) application on safflower forage and silage on their chemical composition, ruminal degradability parameters and in vitro gas production. Safflower forage was harvested in June 2010 at budding growth stage with 30 percent dry matter content from research farm of Birjand university agricultural college. Urea was used as forage’s N fertilizer (at rate of 300 kg N/ha) and PEG solution (with concentration of 30g/100 ml, solution 30% w/v) was used as silage’s additive. Chemical composition was determined in both safflower forage and silage but DM ruminal degradability and gas production were determined just in safflower silage. So there was 2 treatments in evaluation of forage chemical composition as: 1- forage fertilized with N, and 2- unfertilized forage, while 4 treatments were available in evaluation of safflower silage as: 1- silage of unfertilized forage and without polyethylene glycol additive, 2- silage of unfertilized forage and with polyethylene glycol additive, 3- silage of fertilized forage and without polyethylene glycol additive and 4- silage of fertilized forage and with polyethylene glycol additive. Forage N fertilizing caused to increase its CP content and took place a suitable fermentation trend in its silage. Also, silages of fertilized forages had higher ruminal and post-ruminal digestibilities. Adding PEG had no effect on digestibility and other determined parameters of experimental silages. The results of this study showed safflower N fertilized forage and its silage was of high nutritional value in ruminant feeding, especially at arid areas with saline soils which this plant is well adapted.