Influence of Meteorological Conditions and Temperature-Humidity Index on Fertility, Hatchability and Embryonic Mortality in Kadaknath Chickens

Abstract

The present study was conducted from May 2023 to August 2024 at the Rashtriya Krishi Vikas Yojana (RKVY) backyard poultry farm, Faculty of Veterinary and Animal Sciences, Barkachha, Mirzapur, Uttar Pradesh, India, to assess the influence of meteorological conditions on fertility, hatchability, and embryonic mortality in Kadaknath chickens. A retrospective dataset covering 16 months was analyzed using monthly dry bulb temperature, relative humidity (RH), and temperature–humidity index (THI) data obtained from NASA POWER. Incubation eggs were collected from two Kadaknath layer flocks to minimize flock variation. In the first flock, collection began from the mid-laying phase (30th week onwards), while eggs from the second flock were collected throughout its complete laying cycle. Birds were maintained under a deep-litter system and fed a layer-finisher diet. The dataset comprised 9,437 eggs from 66 hatches. Based on THI, environmental conditions were categorized as comfortable (<75), moderate (75–81), and high (>81). Eggs were candled on day 18 of incubation to determine fertility; infertile eggs and those showing embryonic mortality were removed, while viable fertile eggs were transferred from the setter to the hatcher. Data were analyzed using one-way analysis of variance (ANOVA) in IBM SPSS Statistics, version 22, to compare fertility, hatchability, and embryonic mortality across laying cycles, temperature, RH, THI categories, and seasons. Of the 9,437 eggs set, 1,177 were infertile, 8,260 were fertile, and 2,028 fertile eggs exhibited embryonic mortality. Overall hatchability was 65% on total egg set basis and 76% on fertile egg basis, with mean fertility and embryonic mortality of 86.26% and 24.13%, respectively. Fertility was significantly influenced by THI, with the highest value (91.24%) under comfortable conditions and lower values of approximately 84% under moderate and high THI conditions. In contrast, hatchability and embryonic mortality did not differ significantly among THI categories, indicating comparatively greater resilience of post-fertilization developmental processes to environmental variation. Seasonal analysis revealed significantly lower fertility during summer than winter, whereas hatchability and embryonic mortality remained largely unaffected by season. Regression analysis showed a significant negative association between THI and fertility (Y = 116.473 − 0.386 × THI; R² = 0.144; p = 0.002), indicating an approximate 0.4% reduction in fertility for each one-unit increase in THI. Overall, the findings indicate that thermal stress primarily compromises fertility rather than hatchability in Kadaknath chickens, emphasizing the need for climate-responsive breeding and hatchery management under tropical conditions. Keywords: Fertility; Hatchability; Kadaknath chicken; Relative Humidity; Temperature; Temperature-Humidity-Index (THI)