Poultry, Volume 2, Issue 4 (December 2023) – 6 articles

The establishment of commercial infectious laryngotracheitis virus (ILTV) live-modified vaccines has relied on serial passaging in chicken embryo (CEO) and tissue culture (TCO) for attenuation. The objective of this study was to attenuate and adapt a virulent CEO-related ILTV field strain (6340) in immortalized cells (LMH), primary chicken embryo kidney cells (CEK), chicken embryo liver cells (CEL), and chicken embryo fibroblasts (CEF). CEFs were refractory to parent ILTV, LMH cells produced low virus yields (~2.5 log₁₀ TCID₅₀ per mL), while CEK and CEL cells produced higher viral titers (≥log₁₀ 6.0 TCID₅₀ per mL). After 52 passages in CELs, the cytopathic effect (CPE) was observed not only in hepatocytes but also in CEL fibroblasts. Once CPE was evident in CEL fibroblasts, 20 further passages in CEFs with viral titers reaching yields of ~4.4–5.5 log₁₀ TCID₅₀ per mL were performed. The attenuation of CEF-adapted viruses was evaluated after intra-tracheal and conjunctival inoculation in 28-day-old broilers by assessing clinical signs at five days post-inoculation (DPI). Virus CEL cells passages 80, 90, and 100, and CEF passages 10 and 20 were significantly attenuated compared to the parental strain. This is the first report of the attenuation of a virulent field CEO-related ILTV strain (RFLP Group V) in CEF cells—a cell type from a different embryonic germ layer (mesoderm) than ILTV target cells—the respiratory epithelium (endoderm). This finding underscores the potential use of CEF adaptation for the development of a live-attenuated ILTV vaccine. Full article

Vitamin A, a critical micronutrient, plays a vital role in maintaining poultry health and maximizing productivity. This comprehensive review paper conducts a thorough analysis of the consequences of vitamin A deficiency in domestic fowl. It delves into the physiological functions of vitamin A and investigates how hypovitaminosis A impacts growth, immune function, reproduction, and overall poultry performance. Additionally, the review explores effective strategies for preventing and managing vitamin A deficiency, such as dietary adjustments and supplementation, while addressing the specific requirements for vitamin A intake. The implementation of these strategies holds immense importance in optimizing poultry management practices and achieving peak performance in poultry production. A profound understanding of the prevalence and factors contributing to clinical and subclinical vitamin A deficiency in domestic fowl is essential for ensuring the efficiency of poultry farming operations. Recognizing the pivotal role of vitamin A and applying the appropriate measures empowers poultry farmers to enhance the health outcomes and overall performance of their flocks. Full article

This study aimed to determine the effects of dietary energy and body-weight (BW) restriction on layer pullets’ growth, uniformity, and feed efficiency. Two experiments were conducted using a precision feeding (PF) system (Experiment 1) and a conventional feeding (CON) system (Experiment 2). Experiment 1 consisted of a 2 × 4 factorial arrangement (eight treatments) with two feed allocation (FA) levels: meal every visit (MEV) or restricted to the lower boundary of Lohmann Brown-Lite pullets; and three dietary metabolizable energy (ME) levels: Low, Standard (Std), and High (2600, 2800, and 3000 kcal/kg, respectively); the fourth treatment enabled birds to choose from the three diets (Choice). Experiment 2 consisted of a 2 × 3 factorial arrangement (six treatments): two FA levels (ad libitum or restricted) and three dietary ME levels (Low, Std, and High). In each experiment, BW, coefficient of variation (CV), average daily feed intake (ADFI), average daily metabolizable energy intake (MEI), and feed conversion ratio (FCR) were recorded. Diet ADFI preferences and feeding motivation were determined only in the PF experiment. ANOVA was conducted on each experiment with the two main effects as fixed factors (FA and dietary ME), and age or period as the sources of variation. Differences were reported at p ≤ 0.05. MEV (PF experiment) and ad libitum-fed (CON experiment) pullets had greater BW compared to restricted-fed pullets (p < 0.05). The lowest CV was observed in the restricted-fed pullets from the PF experiment (p < 0.05). ADFI was greater in pullets fed the Low ME diet in the PF experiment compared to all the other groups, and the lower the dietary ME, the greater the ADFI in the CON experiment (p < 0.05). Choice-feeding pullets preferred feed with greater ME content in the PF experiment (p < 0.05). The lower the dietary ME, the greater the FCR in the CON experiment (p < 0.05). Restricted-fed pullets had greater daily visits, and lower daily meals, meal size, and successful visits to the PF system (p < 0.05). In conclusion, the results of this trial indicated that lower dietary ME increased FCR and ADFI, whereas feed restriction decreased BW and increased feeding motivation. Future steps after this trial will include examining the effects of dietary energy and feed restriction on carcass composition and sexual maturation. Full article

This study aimed to evaluate the addition of liquid cellulose, produced by Humicola grisea, in 21-day-old broiler chickens’ diets. The treatments comprised control rations of corn and soybean meal and rations to which 500 mL/t and 1000 mL/t of cellulase were added. A total of 180 male broiler chickens were used, distributed in a completely randomized design, with three treatments and six replicates. Broiler chicken performance was monitored during the period from 1 to 21 days old. Significant effects were detected for digestibility only between four and seven days old, when a reduced dry matter nitrogen intake was recorded, and for nitrogen digestibility in the broilers fed cellulase-supplemented rations at a dose of 1000 m/L. Among the analyzed digestive organs, only the biometrics of the large intestine were affected significantly at seven days old. The absolute weights of the liver and pancreas and the activities of amylase, alkaline phosphatase, and transaminases were not affected significantly, indicating that cellulase did not affect the metabolism of these organs. No significant effect was detected in the serum for electrolytes, total protein, or alkaline phosphatase. So, the addition of liquid cellulase produced by Humicola grisea did not affect performance and metabolism in 21-day-old broiler chickens. Full article

The effects of Tagetes erecta flower extract (TFE) and increasing levels of vitamin E (VE) in the diet of Japanese quail breeders on progeny performance and oxidative status were studied. Methods: 480 Japanese quail breeders were distributed in a completely randomized design with five treatments and twelve replications of six females and two males each. A control diet (25 mg/kg VE) and four diets supplemented with TFE (3 g/kg) and VE (25, 100, 175, or 250 mg/kg) were used. Fresh yolk samples and the yolk sac and liver from embryos (11 and 15 days) and chicks (hatch and 3 days) were analysed. Data were subjected to ANOVA, a regression linear model, and contrast tests and the level of significance was set at p < 0.05. Results: TF and VE in the maternal diet improved the amount of alfa-tocopherol and total carotenoid content in the yolk. TFE + VE reduced lipid peroxidation and improved the oxidative status in the fresh yolk, in the embryo and chick yolk, and in the liver. Liver superoxide dismutase activity in hatched chicks increased linearly with the VE level and was not altered by TFE. Maternal diets did not influence progeny performance (1 to 28 days) or the relative expression of superoxide dismutase or glutathione peroxidase genes in the liver of chicks. Conclusions: TFE is an effective antioxidant in fresh eggs and supplementation of 3 g/kg TFE and high levels of VE in quail breeders improves the oxidative status of embryos and newly hatched chicks. Full article

In ovo injection of the Marek’s disease (MD) vaccine (MDV) has been widely practiced in commercial US hatcheries. However, the MDV is very sensitive and may not be compatible with some nutrients when administered together by in ovo injection. When individually administered by in ovo injection, L-Ascorbic acid (L-AA) and 25-hydroxyvitamin D₃ (25OHD₃) have previously exhibited very promising results on the post-hatch physiological and immunological characteristics of broilers subjected to stressful commercial conditions. However, the compatibility of the MDV with these vitamins has not been previously explored. Their compatibility must first be established before their combined administration by in ovo injection can be considered. Therefore, the objective in this study was to determine the compatibility of the MDV with various levels of 25OHD₃ or L-AA. The treatments employed were MDV-alone, MDV in combination with 0.6 (low) or 2.4 (high) μg doses of 25OHD₃, or MDV in combination with 1.2 (low) or 12 (high) mg doses of L-AA. The live and dead ratio of primary chick embryo fibroblast cells infected by the MD virus (CEF-MDV) in each treatment was determined every 30 min for 2 h. The L-AA at both the low and high doses resulted in a 70% death of CEF-MDV within 1 h, but either dose of the 25OHD₃ exhibited only an approximate 5% lower CEF-MDV survival as compared to those in the MDV-alone treatment. Therefore, it is suggested that the two designated doses of 25OHD₃ have the potential to be effectively combined with the MDV for subsequent administration by in ovo injection. Full article