ABSTRACT


Daniel Claro M.1
 
Ewe and lamb mortality rate were measured on Corriedale sheep for Scrub and Tussock Countries in Magallanes, Chile, during 3 consecutive years, 1971 - 1973. Ecological zones were considered as treatments and years as replications.
Ewe mortality rate
For Scrub Country 844 adult ewes were observed, while in Tussock Country 1053adult ewes and 411 2 tooth. Mortality rates were 4.82% in Scrub Country for adultewes, while in Tussock Country 4.79% for adult ewes and 4.14% in 2 tooth. Differencewas non significant.Mortality rate during pregnancy and parturition was significantly higher (P≤ 0.01)than in any other period and similar for both classes of ewes and zones, being3.84% for adult ewes in Scrub Country; 3.93% in adult ewes and 3.65% for 2 toothin Tussock Country.
Lamb mortality rate
768 lambs from adult ewes were controlled in Scrub Country and 693 in TussockCountry. Mortality rates were 17.84% and 19.77% respectively; difference wasnon significan t. A mortality, rate of 27.5 2% was found on 258 lambs from 2 tooth ewesin Tussock Country, being significantly higher than in adult ewes (P≤ 0.01).Mortality rate in twin lambs from adult ewes was 24.7% in Scrub Country and29.4% in Tussock Country, difference being non significant. Over 70% of all deathwere recorded during first 3 days.
In adult ewes birth weight of surviving lambs in Tussock Country with 3.92 Kgwas significantly lower (P ≤ 0.01) than in Scrub Country with 4.32 Kg. In 2 toothit was 3.38 Kg significantly lower than for adult ewes (P ≤ 0.01).Birth weight of lambs dying during first 3 days was 3.5 Kg and similar for adultewes in both zones, while in 2 tooth with 2.81 Kg it was significantly lower(P ≤ 0.01).
Key words:
1Ing. Agr., M. Agr. Sci., Programa Producción Ovina, Estación Experimental La Platina, Instituto de Investigaciones Agropecuarias (INIA), Casilla 5427, Santiago, Chile.