effect of forage on rumen development and performance of newborn balouchi lambs

. an experiment was conducted by incorporating 35 newborn balouchi lambs to study the effects of different type and levels of forage in starter diets on rumen development characteristics and performance. the 5 experimental treatments were included; starter diet without forage (control) and starter diet containing two levels (7.5 and 15%) of alfalfa hay and wheat straw. inclusion of forages increased abrasive value (p=0.001), average particle size (p=0.006), pendf (p=0.0002), bun (p<0.001) and stomach weight (p=0.002) and capacity (p<0.001) and decreased bhba (p<0.001), dry matter intake and bad feed efficiency (p<0.001) in starter period. inclusion of forage resulted to decrease of keratinized layer and increased muscular layer thickness. thinnest keratinized and thickest muscular layers were observed in treatment 3. the rumen weight were higher in treatment 5 (15% wheat straw) and were lower in animals that fed control diet. inclusions of forage don't affect dmi, fcr, glucose and bun concentrations in growing period. however, lambs that fed by 15% wheat straw had lower dmi. carcass characteristics and internal organs weight don’t affect by treatments. this tendency observed in intestine and rumen weight and their capacity. in conclusion it seem that the concentration of volatile fatty acids (vfas) in rumen (feeding concentrate feeds) is premier factor in rumen development, although forage roles in physical development and maintain of stable condition in rumen wasn't negligible.