Histology of Mammary Gland during Lactating and Non-lactating Phases of Madras Red Sheep with Special Reference to Involution

The histological study was carried out on mammary glands collected from 14 Madras red sheep, 7 in lactating period 7 in non-lactation period. The connective tissue became reduced and lobuloalveolar tissue was predominantly increased during lactating period. The alveoli were laminated, filled with secretion and lined by cuboidal active secretory cells containing lipid droplets and protein granules during active lactation. The alveoli of the non-lactating sheep mammary glands showed the alveolar degeneration. Large empty vacuoles and autophagosomes in the cytoplasm of numerous apoptotic alveolar epithelial cells. Macrophages, mast cells, neutrophils and lymphocytes were found in the interalveolar areas and lumina of alveoli. The occurrence of corpora amylacea located both in the lumen of alveoli (intra-alveolar bodies) and septal connective tissue (Interstitial bodies) was frequent in mammary glands of non-lactating sheep. It was concluded that these regressive changes during non-lactating period form a physical barrier in ductulo-alveolar system for protecting the gland from bacterial infection.