The expression of the enriched gene CYP1A1/GSTM decreases with age, and studies have found that these two genes are related to rumen toxin clearance [50], indicating that the probability of gastrointestinal diseases increases in 6-year-old Tibetan sheep, while the immunity of 4-month-old Tibetan sheep is improved through breast milk due to incomplete weaning (lactation + grazing). Here, GSTM2 is linked to gastrointestinal disease.