The impact of practically all the everyday stress factors occurring in the first days of the chick life on the rate of the utilisation of the yolk sac content, on the chicken immune status and on the growth of the animal's body and intestinal masses was investigated. The impact of the stress was investigated during the first five days of chick's life. The chicks were divided into five groups, each comprising 44 birds. The first chick group was exposed to moderate cold (2–3°C below the optimal temperature for the chick age). The second group was exposed to moderate heat (2–3°C above the optimal temperature for the age). The third and fourth group were deprived of feed and drinking water for 12 hours and 24 hour, respectively. The fifth chick group was the control group: the birds in this group had optimal environmental conditions and received feed and drinking water immediately upon entering the trial. Ten chicks were taken every day and weighed. Their blood samples were obtained for the assessment of infectious bursal disease virus antibody titres using ELISA method. After that, the birds were sacrificed, their intestinal masses weighed and the quantity of resorbed yolk measured. The greatest body and intestinal masses were found in the control animals. The body and intestinal masses were the lowest in the group which was denied water and food for 24 hours. The resorption of the yolk sac content was approximately equal in all the chick groups, but the resorption rate varied by days. The highest resorption was observed in the chick groups on the day when feed was denied to them, so that this high resorption could be associated with the bird's body energy requirements. The resorption of the remaining yolk is associated with feed intake: in chicks to which feed is withheld the yolk is resorbed through the yolk sac wall directly into the blood, which increased its usability. When energy requirements are not satisfied, the chick's body probably utilises resorbed antibodies from the yolk remnants, as their glycoprotein composition is suitable for this purpose.

This study describes the introduction and spread of avian influenza A (H5N1) subtype in Croatia. Seventeen isolates were identified during the period from October 2005 to March 2006, all originating from wild birds. The full-length nucleotide sequence analysis of the hemagglutinin (HA) gene of seven representative isolates revealed that three distinct genetic strains involved in the outbreaks, implicating at least three independent introductions of the virus into Croatia during a relatively short period of time. All three genetic strains belonged to clade 2.2 (Qinghai-like viruses) and each strain displayed significant similarity to concurrent H5N1 viruses from other European countries. The dominant strain of the virus was present in all four affected areas and in all three bird species (mute swan, mallard, and black-headed gull), indicating cross-species transmission of the virus. Two other genetic strains were found, together with the dominant strain, only in a marsh at the Adriatic coast during late February and early March 2006, which could be associated with frozen water surfaces in the continental part of Croatia as well as in Eastern Europe in early 2006 and the movement of birds toward warmer areas. This is also the first isolation of highly pathogenic avian influenza virus of H5N1 subtype from apparently healthy black-headed gulls.

The aim of this study was to evaluate the effect of dried Cannabis sativa L. leaves as a phytogenic mixture added to broiler feed on CD4⁺ and CD8⁺ T lymphocyte subpopulations, Newcastle disease virus (NDV) antibody titres, and the presence of E. coli in faecal samples. The study was conducted on 100 male Ross 308 broilers, divided into four groups of 25 broilers, for a 42-day research period. The groups were housed separately in boxes on a litter of softwood shavings and were fed starter mixture from day 1 to day 21 and finisher mixture from day 22 to day 42. Industrial hemp (C. sativa) was grown in the Crkvina area, Croatia (latitude: 45°18′46.8″ N; longitude: 15°31′30″ E). The hemp leaves were manually separated, sun-dried, and ground to a powder. The mixture offered to the control group did not contain cannabis leaves, whereas the three experimental groups received mixtures containing mixed cannabis leaves in a quantity of 10 g/kg, 20 g/kg, or 30 g/kg (E_10, E_20, and E_30, respectively). The mean NDV antibody level was uniform in all study groups until post-vaccination day 14 and increased comparably with time. The percentage of CD4⁺ and CD8⁺ lymphocytes in the peripheral blood subpopulation showed statistically significant differences (p < 0.001) in the E_20 group as compared with the control group and both the E_10 and E_30 groups throughout the study period. As the broiler age increased, the CD4⁺-to-CD8⁺ ratios also increased and were statistically significant (p < 0.0001) on day 42 in all experimental groups as compared to the control group. Comparing the control group with the experimental groups indicated that the bacterial count was lower in broiler groups having received feed with the addition of 20 g/kg and 30 g/kg C. sativa leaves. In conclusion, the C. sativa leaves were found to elicit a favourable immunomodulatory effect on cell-mediated and humoral immune responses in broilers via increased CD4⁺ and CD8⁺ lymphocyte subpopulations and higher CD4⁺:CD8⁺ cell ratios, thus indicating enhanced immune function capacity. In addition, C. sativa leaves may have complementary effects on the broiler post-vaccination immune response, increase broilers’ resistance to infectious diseases, reduce the effect of stress associated with vaccination, and improve broiler health and welfare.

As immune responses to live and inactivated vaccines might differ, temporal responses of broiler chickens to vaccination were examined on the basis of the abundance in the circulating blood of gene transcripts of IFN-α, IFN-γ and IL-2, critical cytokines for immune responses. Blood samples were collected 6, 12 and 24 hours, and 7 and 14 days following vaccination with either live or inactivated Newcastle disease virus, La Sota strain, at 14 days of age, and the abundance of transcripts for each cytokine was assayed by real-time RT-PCR. Physiological saline and vaccine emulsion without viral antigen were administered to control groups for live and inactivated vaccine groups, respectively. The abundance of IFN-γ transcripts was elevated during the early times following vaccination and had reached baseline by the seventh day but the abundance of IFN-α transcripts remained elevated. Transcripts for neither IFN gene were detected in the control birds. The abundance of transcripts for each IFN was not different between the two vaccinated groups at any time. Transcripts for IL-2 were detected only in spleens from chicken embryos that had been inoculated with the live virus. The results show that cells stimulated to produce IFN-α and IFN-γ enter the circulating blood but those stimulated to produce IL-2 do not, or in very low number, and the IFN responses to both vaccines are the same.