الفهرس 
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Abstract
The study was conducted at a Strauss Veal Feeds Inc. (North Manchester, IN, USA) finisher barn, which provided facilities, calves, and feed in cooperation with Benha University. The objectives of the present study were:
1) To determine the effect of group size on behavior, health, growth, and welfare of veal calves,
2) To investigate the effect of group size on immune system
3) To evaluate leukocyte gene expression of major pro- and anti-inflammatory cytokines mRNA of veal calves housed in different group size during the finishing period.The first part of the study:
The study was undertaken in spring and summer of 2012 from March 21 to July 21, 2012 on one commercial veal farm. Holstein-Friesian bull calves (n = 168; 44 ± 3 d of age) were assigned randomly to 1 of 3 treatments of group housing with 2, 4, or 8 calves/pen. The pens used for housing were 3 × 1.20 m (2 calves/pen), 3 × 2.40 m (4 calves/pen), and 3 × 4.80 m (8 calves/pen), supplying a total pen space allowance of 1.82 m2 /calf, regardless of pen size. Behavior was recorded from video data throughout the day from 0700 to 1900 h, during a single day each month for 5 mo using scan sampling every 5 min within 30-min observation sessions. On d 0, 1, 5, 14, 42, and 70 after grouping, continuous focal sampling around feeding time (30-min intervals before, during, and after feeding) focused on oral and aggressive behaviors. Plasma cortisol, blood hemoglobin concentrations and differential leukocyte counts were determined.The first part of the study:
mRNA expression of interleukine-1β (IL-1β), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor (TNF)- α, toll-like receptor 4 (TLR4) and tachykinin 1 (TAC1) was determined using real-time RT-PCR in calves blood leukocytes. Health was evaluated monthlyThe obtained results summarized in:In the present study, housing veal calves in large groups (4 or 8 calves/pen) resulted in more conspecific contact, walking, standing, and less objects manipulation, self-licking and less lying when compared with calves housed in small groups (2 calves/pen), although calves were provided with the same housing space.
1) Housing of veal calves in large groups changed how oral needs were manifested; calves housed in groups of 8 had more social contact. So, oral behavior appeared to be directed to pen-mates.
2) The number of calves in a group with the same space (1.82 m2 per head) did not affect growth performance of veal calves.
3) Neither plasma cortisol nor blood hemoglobin were (P ≥ 0.14) affected by group size.
4) Housing of veal calves in groups of 8 was associated with greater percentage of neutrophil, lower percentage of lymphocytes, and greater neutrophil to lymphocyte ratios.
5) In agreement with our hypothesis, we observed that increasing the number of animals per group from 2 to 8 was associated with greater coughing during the first 2 months after grouping
6) In agreement with our anticipation, expression of IL-1β and TAC1 mRNA was up-regulated in peripheral leukocytes of veal calves housed in groups of 8 compared to those kept in groups of 4 or 2.
7) Our results suggest that there is a link between the neurotransmitter SP and cytokines production.
8) These results may have important implication for the assessment of social stress in farm animals and the development of novel science-based variable used to assess animal well-being in livestock production systems. Measuring the expression of some marker genes in leukocytes in addition to use of traditional methods including total leukocyte count and N:L ratio is a good approach for assessment of stress in young calves. Further investigation needed to know how shifting of veal industry from individual to group housing will modulate the innate immunity of calves.
We concluded that:
1- When provided with the identical space allowances, the number of veal calves in a group did not affect production and physiological indicators of welfare and had transient effects on health during the finishing period.
2- Housing of veal calves in groups of 4 and 8 after 6 wk of age had no detrimental effects on growth, and performance, and provided calves with a greater opportunity to interact socially and utilize available space when compared with calves housed in groups of 2. However, calves housed in groups of 2 had the benefits of more eating and drinking, self-grooming, and lying behaviors and less inactive periods.
3- There is immunological evidence of stress from group housing of calves in larger groups even when the space allowance per calf was the same (1.8 m2/head).
4- Housing of veal calves in groups of 8 was associated with neutrophilia, lymphopenia, and greater neutrophil to lymphocyte ratios and greater coughing during the first 2 months after grouping. Therefore, these data suggest that housing of veal calves in larger groups during the finishing period may lead to greater incidence of respiratory disease.