Congenital anomalies in sheep and goats in Iran over ten years

Iran ranks among the world's leading producers of small ruminants, with over 53 million sheep and 25 million goats. Despite this prominence, congenital defects in these animals remain under-documented, presenting a major gap in veterinary epidemiology and herd health management. This study represents the first nationwide effort to systematically classify and analyze congenital anomalies in Iranian sheep and goats.

Over 10 years (2014-2024), cases of congenital anomalies were recorded across all 31 provinces of Iran. Data were collected through farm-level clinical evaluations and necropsies. Cases were categorized into 10 anatomical classifications based on internationally recognized veterinary criteria. Statistical analysis, including Chi-square and Poisson regression tests, assessed interspecies differences and incidence patterns.

A total of 7038 congenital disorder cases were documented in sheep and goats across Iran during the 10-year study period, with 3578 cases (50.84 %) observed in sheep and 3460 cases (49.16 %) in goats, reflecting a nearly equal distribution of anomalies between the two species. Craniofacial anomalies were the most prevalent, comprising 2796 cases (39.53 %), followed by reproductive (1509 cases, 21.24 %) and digestive system defects (831 cases, 11.57 %). Other observed categories included locomotor system (11.2 %), eye and attached structures (4.09 %), urinary system (1.86 %), cardiovascular (1.7 %), fetal diseases (3.71 %), skin defects (1.92 %), and total body malformations (3.18 %). Notably, no cases of entropion were recorded in goats during the entire study period. The Chi-square test showed that the types of congenital disorders differed significantly between sheep and goats (p < 0.001), indicating species-specific predispositions. but the Poisson regression analysis found no significant difference in the overall number of cases between the two species (p = 0.16), a finding confirmed by the negative binomial model (p = 0.18), meaning that while sheep and goats tend to develop different kinds of defects, they are affected by them in similar overall numbers.

This study provides the first large-scale, structured account of congenital anomalies in small ruminants in Iran, identifying major categories and their relative frequencies. Craniofacial and reproductive anomalies were the most frequent. The data offer a valuable model for countries with similar livestock systems, particularly in arid and semi-arid regions. This foundational dataset is expected to catalyze further research into the genetic, infectious, and environmental drivers of congenital defects and support targeted breeding, prevention, and diagnostic strategies throughout the region.