Tropical animal health and production最新文献

Newcastle disease (ND) is a highly contagious disease with the potential to cause massive losses in the global poultry industry. This study evaluated the efficacy of three commercial live ND vaccines based on genotypes I and II (enterotropic) on mortality and viral shedding in specific pathogen-free (SPF) chickens challenged with circulating virulent Newcastle disease virus (vNDV) of genotype VII. Forty one-day-old SPF chickens were randomly divided into four experimental groups (n = 10) and vaccinated (one dose ≥ 10⁶ EID50) with one of three enterotropic ND vaccines (E1, E2, or E3) or received phosphate-buffered saline (PBS) as the control on the 8th day of age. At 28 days of age, the chicks were intramuscularly challenged with genotype VII (GVII) vNDV. Blood samples were collected before the challenge (at 28 days of age) and at 7 and 14 days post-challenge (dpc) to measure serum antibody titers against NDV using the hemagglutination inhibition (HI) test. Cloacal and oropharyngeal swabs were taken on the 3rd, 5th, 7th, and 10th dpc to evaluate viral shedding. The vaccinated groups showed significantly higher antibody titers and protection rates compared with controls (P < 0.05). At 28 days of age, the E2 group had a higher antibody titer compared to E3 (P < 0.05); however, no significant difference was noted between the vaccinated groups at 35 and 42 days of age. All vaccinated chickens showed significantly higher protection in the challenge test compared to the control group; where the E2 group acknowledges the complete protection (70%, 100%, 60%, and 0% for E1, E2, E3, and control, respectively). The E2 group also had the lowest number of shedder birds compared to the E1 and E3 groups (0% vs. 30% and 40%, respectively; P < 0.05). This study shows that some commercially mismatched enterotropic ND vaccines not only provide high levels of protection against genotype VII of vNDV but also effectively control viral shedding in infected chickens.

Castration is common in beef cattle for reproductive and management purposes, but it causes pain and stress, raising welfare concerns. The adoption of perioperative anesthesia and analgesia remains uneven in tropical low- and middle-income settings, where infrastructure, costs, and weak enforcement limit its application. This study aimed to evaluate the effects of different analgesic protocols on physiological stress markers and growth performance in beef calves raised under tropical conditions in Colombia. Forty-two intact Blanco Orejinegro (BON) calves were randomly assigned to three protocols: spermatic cord block with lidocaine plus tolfenamic acid (T1), low epidural anesthesia with lidocaine plus tolfenamic acid (T2), or tolfenamic acid alone (T3). All calves underwent closed surgical castration. Physiological and welfare indicators were assessed through pulse rate variability (PRV), hematological parameters, serum haptoglobin and cortisol concentrations, and infrared thermography (IRT) of the scrotal area at defined intervals, whereas growth performance was evaluated by average daily gain (ADG). Statistical analyses included ANOVA and nonparametric tests when assumptions were violated, with multiple comparisons corrected via Tukey's test or Dunn's test. No significant differences were found among the protocols for the PRV, hematological parameters, cortisol, haptoglobin, IRT, or ADG. In contrast, significant temporal effects were observed, with cortisol decreasing at 48 h, haptoglobin peaking at 48-72 h, and IRT values increasing between 24 and 48 h postcastration. These results indicate that the time after castration, rather than the analgesic protocol, was the primary driver of physiological responses.