اثر فصل، مكمل اوره در سيلاژ ذرت و كنسانتره مصرفي بر ميزان اوره خون گاوهاي منطقه گنبد كاووس

Effect of season, urea supplementation in corn silage and source of concentrate on serum urea nitrogen in Gonbad-Kavoos region cows

The objectives of this study were to measure urea nitrogen levels in blood serum (SUN) of lactating cows in Gonbad-kavoos area and relationship between their concentrations with some nutritional and environmental factors. Blood samples were collected in three periods (late summer, late autumn and late winter) from cows of four dairy farms (herd 1, herd 2, herd 3 and herd 4). Samples were taken 2-3 hours after morning feeding. Total mean serum urea nitrogen for all cows was 15.13±0.13 mg/dl. Mean serum urea nitrogen concentrations were significantly higher in herd 2 than in other herds and in herd 3 and 4 than in herd 1(P<0.05), but there was no significant difference between herd 3 and 4 (P>0.05) (respectively 14.39±0.22, 16.11±0.31, 14.70±0.21 and 15.36±0.29 mg/dl for herds 1, 2, 3, and 4). A highly significant difference (P<0.05) observed between the levels of SUN in herds that use urea in their silages and those who not use urea in their silages (respectively 15.41±0.19 and 14.85±0.18). Also, concentrations of SUN were significantly higher in herds that had used of commercial concentrates (herds 2 and 4) than in herds that had mixed their concentrates in farm (herds 1 and 3) (p<0.05) (respectively 15.75±0.22 and 14.54±0.15 mg/dl). Based on this study, serum urea nitrogen concentrations in Gonbad dairy herds were in acceptable status.