• Technical Notes: Survival Analysis of Single and Twin Lambs

      Scrivner, J. H.; Dally, M. R.; Howard, W. E. (Society for Range Management, 1987-03-01)
      We illustrate the use of life tables and survival analysis for evaluating data on livestock losses. The techniques are used to compare the rate of coyote (Canis latrans) predation on single and twin lambs. Based on the number of lambs known to have been killed by predators, the survivorship of single and twin lambs was not significantly different (P>0.05) for any year of the study. Survival functions which can be generated and used to evaluate data on livestock losses include the cumulative proportion of livestock surviving at the end of an interval, probability density, and hazard rate.
    • The Use of Supplement Blocks for Sheep Grazing Dry, Annual Pastures in California

      DePeters, E. J.; Dally, M. R.; Alwash, A. A.; Therkelsen-Tucker, P. (Society for Range Management, 1985-07-01)
      The objective of this study was to evaluate the use of supplement blocks on body weight change, blood parameters, and lambing performance of ewes grazing dry, annual grasses during the summer prior to and during breeding. Two experiments were conducted in successive years to compare performance of unsupplemented control (C) and supplemented (S) Targhee ewes. In the first season, yearling ewes were used while aged ewes (2 or 4 years) were used during the second season. During the first year (1980), supplemented ewes lost less body weight during the dry grazing season than C ewes. However, no lambing performance difference was found between C and S groups. During the second year (1981), supplemented ewes maintained their body weight over the summer while C ewes lost weight. In addition, lambing performance (multiple births) was higher for S than C ewes. Supplementation of ewes with blocks containing molasses, urea, protein, and minerals required little labor input. However, based on lambing performance, it is unlikely that supplementation would be economically profitable under the range conditions utilized in these trials.