p. 178-187

Until 1940, the prevailing view regarding the declining birth of sheep in the highlands compared to what is obtained at sea level, was based on the belief in the existence of sheep "butch" unable to reproduce. Despite this, farmers employing 5 or 7 acclimated males per 100 sheep, long residence with blood from sheep brought for the Colony; while at sea level, this percentage never exceeded 2 or 3 Yet it was extremely difficult to obtain, with imported animals, a higher reproduction ratio to 30% or 40%, particularly the first year of acclimatization, during which the percentage of fertility fell within 20% with the consequent economic loss.