Summary
Rambouillet ewes at Purdue University have averaged 2.32 lambs born and 1.96 lambs raised yearly over a four-year period. This was accomplished through an accelerated lambing program in which the ewes produced a lamb crop every eight months or a total of six crops in four years.
During this period the average 120 day weight of the lambs has increased 39 per cent and the average ewe production index, which combines lamb weights and ewe fleece weights, has increased 21.4 per cent. The percentage of lambs raised, the birth weight of the lambs and the fleece weight of the ewes have not been reduced by this acceleration of the reproductive cycle.
Lambs were born in January, September and May. The productivity of the ewes was greatest in January and the lowest in September with May being intermediate between these two seasons.
Nine ewes completed the full cycle of six lamb crops in four years. They showed an increase of 47 per cent in the 120 day weight of the lambs, a 27 per cent increase in the ewe production index and a 55 per cent increase in the percentage of lambs raised during this period. These ewes averaged 2.30 lambs born and 2.06 lambs raised yearly. There was a slight advantage in terms of percentage of lambs raised, lamb weights at 120 days and ewe production index for the
This study demonstrates that the reproductive efficiency of Rambouillet ewes can be increased over a period of years by accelerating their reproductive cycles.
This has been accomplished on a natural selection basis without the use of exogenous hormones and has resulted in more pounds of lambs marketed per ewe yearly. The procedures followed in this study offer possibilities to those interested in increasing the productivity of ewes.
Introduction
The purebred Rambouillet flock of sheep at Purdue University has been kept on an accelerated lambing program for a four-year period from 1964 to 1968. During this period they have produced a lamb crop every eight months without the use of exogenous hormones to promote or synchronize estrus. This flock lambed in September of 1964, May of 1965, January of 1966, September of 1966, May of 1967 and January of 1968. Thus they have produced six crops of lambs in a four-year period, an increase of 50 per cent over the normal once-a-year lambing.
Procedure
The May and September lamb crops were born on pasture, but the January lambs needed the normal care and attention necessary during the colder season of the year. The flock was maintained under normal management conditions with the ewes receiving additional energy feeds dur-
January lambing over the May lambing and both were better than the September lambing. ing the last month of gestation and the first
1/ Appreciation is expressed to James A. Osborn, shepherd, Gary Coots and James Brown for their assistance in conducting this study.
Cooperative Extension Service, PURDUE UNIVERSITY, Lafayette, Indiana
Four-Year Summary of Accelerated Lambing Program
J. B. Outhouse Department of Animal Sciences