Introduction:
Groups feeding vs. individual feeding of animals has been a controvesial subject among nutritionists for many years. Some believe the psychological effect on animals, being housed individually or in groups influence the results of experiment, some have found that effect to be depended on the ration fed. Individual feeding of animals is important in nutritional and biological research. In addition, individual data have statistical advantages in the number of degree of freedom with an equal number of animals and in identifying individual variation.
Materials and methods:
16 Dalagh lambs with an average age of 3 months and weight of 1 22±2 with 2 treatments and 8 replications were used in a completely randomized design. The treatments include: 1- individual nutrition and 2- group nutrition. The duration of the trial period was 90 days, which included 14 days of habituation. The lambs of treatment one were kept individually in individual stalls and the lambs of treatment two were kept in groups. During the entire experiment, the animals had free access to clean drinking water and the daily feed was completely mixed in two meals (at 8:00 AM and 4:00 PM). The feed conversion factor was calculated by dividing the average daily dry matter intake of each lamb by the average daily weight gain of the same animal. The samples collected from each lamb were mixed and one sample was used for the chemical analysis of feces. Dry matter digestibility was calculated using acid-insoluble ash as an internal marker. Also, blood sampling was done on the last day of the test period and before the morning meal with 12 hours of food restriction, at the rate of 10 cc from the jugular vein and without the use of anticoagulant. To measure the feed consumption activity on the last day, the lambs were observed for 24 hours and the behavior of eating, ruminating, chewing and resting was observed and recorded.

Results and discussion:
Experimental treatments had no significant effect on daily feed consumption, daily weight gain and feed conversion ratio. Also, group and individual feeding could not have a significant effect on the amount of digestibility of dry matter and organic matter, but its amount increased insignificantly in the treatment with individual feeding compared to the treatment with group feeding. The behavior of chewing, resting and ruminating was not affected by the group and individual feeding methods, but the eating behavior was affected by the treatments and its amount increased significantly in group feeding. The reason for this increase can be attributed to the competitiveness of eating and the effort to have better and constant access to food in group feeding than in individual feeding where eating food is not competitive. The experimental treatments had a significant effect on the amount of glucose (P=0.0169), but the amount of cholesterol, triglyceride and urea nitrogen was not affected by group and individual feeding of lambs. The amount of cholesterol in individually fed lambs was insignificantly higher than group fed lambs. Probably, individual animals are involved in metabolic stress compared to group animals, and during the period of stress to meet the high metabolic demand of body tissues, changes in the level of serum lipids, especially cholesterol, are made, and the level of serum cholesterol also changes. Increase. In general, the results showed that group feeding had no significant effect on the performance of lambs compared to individual feeding.

Conclusion:
In general, the results showed that group feeding had no significant effect on the performance of lambs compared to individual feeding.