Response of skin traits to nutrition in Merino sheep differing in estimated breeding value for wool growth

It is unclear how nutritional conditions (below or above maintenance) affect Merino follicle characteristics in sheep with different estimated breeding values (EBVs) for wool production but with similar EBVs for fibre diameter and liveweight. This was addressed in our study. Twenty castrated male Merino sheep were selected from a commercial flock, 10 with high EBVs for wool production (F+) and 10 with low EBVs (F–). The animals were offered a diet providing 1.2 times their metabolisable energy requirement for maintenance (1.2 M) for 4 weeks. After 4 weeks’ acclimatisation, five sheep from each EBV group were offered a diet of providing 0.8 times their metabolisable energy requirement for maintenance (0.8 M), and the other five from each EBV group were offered the 1.8 M diet for 5 weeks. On Day 35, one skin biopsy was taken from a shaved area on the left mid-side of each animal under local anaesthesia (subcutaneous injection of 2 ml 2% (w/v) Lignocaine), using a trephine (1.5 cm diameter). The skin sample was stored in 37% (w/v) buffered formalin (pH = 7) for skin histology analysis. Skin samples were processed by CSIRO (Armidale, NSW). The histology methods were essentially those described by Maddocks and Jackson (1988).