Tammar milk regulates the growth of mouse embryonic lungs in culture. Embryonic lungs were cultured for 86 h in presence of wallaby milk collected at day 20 (A1-E1), day 40 (A2-E2), day 60 (A3-E3), day 80(A4-E4), day 90 (A5-E5), day 100 (A6-E6), day 120 (A7-E7) day 190 (A8-E8), control embryonic lung cultured in media with PBS (A9-E9), media (A10-E10) and in media with BSA (A11-E11). (A1-E1) Embryonic lung treated with day 20 milk showed no change in number of terminal end buds. Embryonic lungs with day 40 (A2-E2), day 60 (A3-E3), day 80 (A4-E4), day 90 (A5-E5) and day 100 (A6-E6) milk showed branching after 48 h. (A7-E7) Embryonic lung cultured with day 120 (A7-E7) and day 190 (A8-E8) milk showed branching after 72 h in culture, but the total volume of lung remained unchanged. Control embryonic lung cultured in media with PBS (A9-E9) and media only (A10-E10) showed delayed branching and no change in lung volume. (A11-E11) Embryonic lung cultured in media with BSA showed no effect on branching. (F) Analysis of branching morphogenesis by counting the number of terminal end buds of tammar milk treated day 20, day 60, day 120 and control embryonic lung. (G) Histological analysis of mouse embryonic lung section stained with H&E after culture with day 20 tammar milk. A small number of terminal end buds were present; (H) day 60 milk – a large number of terminal end buds and well developed branching morphogenesis is evident. (I) day120 milk - fewer terminal end buds and increased mesenchyma, and (J) Control (PBS) - extended branching is present, but the numbers of terminal end buds were less when compared to embryonic lungs treated with day 60 milk (B). Scale bar 250 μm. p values (<0.05) are shown with an asterisk.