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Gal-13 is an antimicrobial peptide isolated from chicken intestine. Ninety chickens were randomly divided into two groups (45 chickens for each group) to determine the effect of oral administration of Gal-13 on the acquired immune response. The chickens in the first group were fed a diet without Gal-13 as the control, and the chickens in the second group were fed the same diet, except that Gal-13 (1 μg/ml) was suspended in drinking water just after hatching. Samples of blood, thymus, bursa of fabricius and spleen were taken at day 1, 4, 7, 10 and 17. The chickens in both groups received infectious bursal disease virus vaccine at day 20, and then sera samples were collected for analysis at 14, 21, 28 and 35 days after vaccination. The results showed: (1) Gal-13 could enhance the content of immunoglobulin (Ig)G at the age of 4 to 10 days (p

Sixty chickens were randomly divided into two groups to determine the effect of oral administration of probiotics on the intestinal mucosal immune response and ultrastructure of cecal tonsils. The first group (control) was fed with a basic diet without antibiotic or probiotics. The second group was fed with the same diet as the control, except they received drinking water with probiotics (4 x 10(9) cfu per chicken and day) from posthatch to day 3 of age. The probiotic preparation was composed of Bacillus subtilis Bs964, Candida utilis BKM-Y74 and Lactobacillus acidophilus LH1F. Intestinal fluid, Peyer's Patch and cecal tonsils were taken at day 1, 4, 7, 10 and 18 after administration of probiotics. The results showed: (i) Compared to the control, probiotics enhanced the content of following items: immunglobulin (Ig)A in the intestinal fluid at day 7 (p0.01), the IgG-forming cells at day 10 (p0.05), IgM-forming cells in the Peyer's Patch at day 7 (p0.05), IgA-forming cells at day 7-10 (p0.05), IgG-forming cells at day 7 (p0.05) and IgM-forming cells in cecal tonsils diffuse area at day 4-7 (p0.05). (ii) T lymphocytes in cecal tonsils were enhanced at day 7 (p0.01) after orally fed with probiotics. (iii) The density of microvilli and length of cecal tonsils increased after probiotics were administrated at day 3. With chicken ageing, the efficiency of probiotics would decrease. These results suggested that probiotics enhance intestinal mucosal immunity of chicken at the early age.

Metabolism and growth trials were conducted to study true digestible methionine (tMet) and lysine (tLys) requirements for growing Lohmann egg-type cockerels and to evaluate the effects of 2 dietary tMet levels and 4 tLys levels in a factorial arrangement on growth, nitrogen balance and serum biochemical indices. In the metabolism trial, 20 caecectomised and anus-stitch-surgery healthy adult male birds were used to determine the true digestibility of Met and Lys. In the growth trial, 30 Lohmann egg-type cockerels were allocated to each of 32 floor pens (total 960 birds). During the 0-6 week starting period, 2 levels of tMet (0.37, 0.42%) and 4 levels of tLys (0.84, 0.92, 1.00, 1.08%) were fed to birds, while during the 7-10 week finishing period tMet levels were 0.29% and 0.33% and tLys levels 0.73%, 0.80%, 0.87% and 0.94%, respectively. The results showed that the survival rate in all treatments was 100% during the whole period, indicating that levels of tMet and tLys in the experiment had no influence on the rate. Considering the average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (FCR), nitrogen retention ratio (N-retention), and serum uric acid (UA) content of all treatments together with Met and Lys digestibility, optimal tMet and tLys levels were 0.42%/1.00% (T7) for the starter diet and 0.33%/0.94% (T8) for the finisher diet. Although serum growth hormone (GH), thyroxine (T4) and triiodothyronine (T3) contents of chicks indicated significant differences among the treatments during the whole period, the relationship between dietary tMet and tLys levels and serum GH, T4 and T3 contents seemed irregular. The results also showed that there were interactions between tMet and tLys, and that this interaction had influenced ADG, ADFI, FCR, N-retention, serum UA and hormone contents significantly during the whole period.

Sixty chickens were randomly divided into two groups (30 chickens in each group) to determine the effect of oral administration of chicken intestinal antimicrobial peptides (CIAMP) on the humoral immune response. Chickens of both groups were fed the same diet. In the treatment group chickens received drinking water supplemented with CIAMP (1 microg/ml) right after hatching. Samples of blood, bursa of Fabricus, spleen and intestine were taken at day 1, 4, 7, 10 and 17 of experiment. CIAMP supplementation enhanced the content of IgG and IgM in serum from day 4-10 and day 10-17, respectively, (p < 0.05), IgM-forming cells in bursa of Fabricus and spleen at the age of 7 days (p < 0.05) and IgG-forming cells in bursa of Fabricus at the age of 4 days (p < 0.05). In addition, CIAMP enhanced the IgA-forming cells in caecal tonsils diffuse area at day 4 (p < 0.05). Furthermore, CIAMP enhanced the antibody response to infectious bursal disease virus vaccine (IBDV) in chickens 21 days following IBDV vaccine administration (p < 0.05). These results suggested that CIAMP could modulate the humoral immune response of chickens and increased the antibody titres of infectious bursal disease virus vaccine.