Effects of the interaction between type and production on two measures of functional herd life were examined for Canadian Holsteins. Data were records of survival through first lactation for 1,153,706 cows and number of lactations initiated (maximum of five lactations) for 705,930 cows. Survival data were regressed on ETA for type traits of the sire of each cow after the cows were assigned to groups with low, medium, or high production. Survival through first lactation was analyzed with a threshold model. Factors in the model included herd-year-season; age at calving; month of calving; interaction of registry status, change in herd size, and season; fat and protein production; and linear regressions of sire ETA for type within each production class. Numbers of lactations were analyzed with a linear model that also included month of last calving. Overall conformation and udder traits had the largest effects on survival through first lactation. Effects on number of lactations for feet and leg traits were about the same as for udder traits. Interactions were significant. Type traits were relatively unimportant for herd life of low producing cows. Few differences were observed in the relationships between herd life and type for medium versus high producing cows, indicating no need to increase the emphasis on type in response to current trends for greater production.

Economic values for beef production traits from a herd level bioeconomic model. Can. J. Anim. Sci. 78: 29-45. A bioeconomic model of an integrated Canadian beef production system was developed to derive economic values for genetic improvement of multiple traits. The breeding objective was assumed to be profit maximization of the integrated enterprise. Sixteen input traits were identified as potentially influencing returns and costs in the system. These were mature size, direct and maternal calving ease (in heifers and cows separately), cow fertility, calf survival, cow survival, peak milk yield, residual post-weaning growth rate, residual feed intake in growing animals, residual feed intake in mature animals, residual slaughter weight and dressing percentage at constant backfat thickness, marbling and lean percentage. Most traits were defined to be functionally independent of each other. Thus, traits related to mature size were redefined as residual traits after accounting for the nonlinear relationships among mature size, growth and feed intake traits following mammalian size scaling rules. The base model, which incorporates average returns and costs under production and marketing systems typical of eastern Canada, is described. Economic values in the base model suggest that calf survival, fertility, residual feed intake, and dressing percentage are of primary economic importance in a purebreeding system. These traits also ranked highly in dam lines and (with the exception of fertility) in sire lines in terminal crossbreeding systems.

Koots, K. R. and Gibson, J. P. 1998. Effects of production and marketing circumstances on economic values for beef production traits. Can. J. Anim. Sci. 78: 47-55. The effect of altering production and marketing circumstances on economic values is quantified for a complete beef production system. Absolute and relative economic values were found to vary substantially with large, but realistic fluctuations in prices and costs. In addition, several examples of different management and different genotypes gave markedly different economic values than in the base situation. Also investigated were the effects of rescaling the enterprise to accommodate three alternative limitations; fixed feed available from pasture, fixed dollars available for feed or fixed amount of beef produced. The effects of rescaling were highly dependent on whether or not fixed costs were accounted for. When fixed costs were ignored (corresponding to a small positive profit) the economic value for mature size decreased while that for fertility increased, but other traits were largely unaffected by rescaling. Overall, production circumstances that reduced survival and fertility yielded the largest changes to economic values.

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