ChileanJAR

The extensive mating system used in Magallanes with a stocking rate of 1 ewe/ha and 4% rams was compared with an intensive system of 4 ewes/ha in the scrub country during 3 seasons (1971-73). Adult Corriedale ewes used and changed every season. Bush density was low and slope gentle.
In experiment 1 with a complete randomized desing comparison of extensive system in a 500 ha paddock with intensive system in a 50 ha paddock gave a 15.9% and 6.9% barren ewes respectively, this difference being significant (P < 0.01).
Experiment 2, a 2 x 2 factorial, compared 2% vs. 4% rams in both mating systems. Intensive mating was carried out in 16.6 ha paddocks with a stocking rate of 6 ewes/ha while extensive mating was on 100 ha paddocks and 1 ewes/ha. Intensive mating with 2% or 4% rams showed no significant difference in percentage harren ewes, being 6.2% and 8.6%, respectively. Extensive mating with 2% instead of 4% rams showed no significant difference in percentage barren ewes, being 16.3% and 15.4%. respectively.
Acritical mating population density might exist for sorne breeds of sheep below which rams would not work with maximum efficiency, this being the situation of extensive mating in Magallanes.