Ontogenetic Morphological And Histochemical Evaluation Of The Abomasum In Local Lambs And Goat Kids (1–4 Months Of Age): A Comparative Study

Abstract

Background:
The abomasum, known as the true stomach of ruminants, is central to enzymatic digestion and the establishment of mucosal immunity during early postnatal life. Although sheep and goats are critical for food security in developing countries, there is limited comparative evidence on the ontogenetic maturation of their abomasum, particularly in indigenous breeds.

Objective:
This study aimed to evaluate the morphological, histochemical, and morphometric development of the abomasum in local lambs and goat kids between one and four months of age, with emphasis on species-specific differences.

Methods:
A total of 48 abomasal samples (n = 8 per species per age group) were collected post-mortem from the Tikrit municipal abattoir in Iraq. Specimens were fixed in 10% buffered formalin, processed by routine paraffin embedding, and stained with hematoxylin–eosin and Masson’s trichrome. Quantitative morphometric measurements of abomasal layers were obtained from five randomly selected fields per section. Statistical comparisons between species and age groups were performed using ANOVA followed by Tukey’s test, with significance set at p ≤ 0.05.

Results:
Both species exhibited progressive abomasal maturation with age. In lambs, glandular units compacted earlier, and collagen deposition in the lamina propria was evident by three months. Goat kids consistently demonstrated thicker tunica muscularis at all ages, indicating an emphasis on muscular reinforcement. Histochemical analysis confirmed a shift from delicate to dense collagen bundles with age, while lymphocyte and macrophage infiltration reflected early mucosal immune defense. Morphometric analysis showed significant species- and age-related differences across all layers.

Conclusion:
This study provides novel baseline data on abomasal ontogeny in local small ruminants. The divergent developmental patterns between lambs and goat kids highlight adaptive strategies linked to dietary behavior and digestive physiology. These findings have implications for veterinary anatomy, nutrition, and future molecular investigations.