. 1997. Effect of trenbolene acetate/estradiol implants and estrus suppression on growth performance and carcass characteristics of beef heifers. Can. J. Anim. Sci. 77: 325-328. The effects of estrus suppression (none, oral melengestrol acetate (0.4 mg d -1 ) or ovariectomy via Willis spay technique) and an anabolic implant (none or Synovex Plus ® ) on growth performance and carcass characteristics were determined using 90 beef heifers of composite breeding in a 2 × 3 factorial experiment conducted in the last 50 d before slaughter. Spaying caused no morbidity or mortality and resulted in average daily gains (1.37 kg d -1 ) comparable to heifers fed melengestrol acetate (1.33 kg d -1 ). Implanting improved (P < 0.05) feed efficiency and increased (P < 0.05) animal gain, ribeye area, carcass weight and yield and reduced (P < 0.05) intramuscular fat deposition but estrus suppression did not. Method of estrus suppression did not influence (P > 0.05) carcass traits. Spaying and implanting represent an effective means of improving returns from heifers, even late in the finishing period.

. 2000. Electronic identification: Applications in beef production and research. Can. J. Anim. Sci. 80: 381-392. Individual identification of beef cattle is not new to the Canadian beef industry, as traceback systems played a pivotal role in the eradication of bovine tuberculosis in the 1940s and 1950s and brucellosis in the 1970s and 1980s. Recent concerns over animal health (e.g., bovine spongiform encephaolopathy), export markets, product consistency, meat quality (e.g., tenderness, marbling) and safety (e.g., Escherichia. coli O157:H7, Salmonella spp.) make reestablishment of a traceback system a logical approach to assuring consumer confidence in Canadian beef. Originally, simple Kurl-lock™ ear tags with a unique number were used to trace individuals back to their herd of origin. Although useful for addressing disease concerns, this system did not lend itself to compiling additional information (e.g., growth performance, animal health, breeding programs, carcass quality) for use in management or marketing decisions. More sophisticated electronic identification systems can readily interface with computers and make information management an even more pivotal component of beef production. Several electronic identification systems (e.g., bar codes, radio frequency identification, read-write systems) are being assessed for their effectiveness for identifying individual cattle under production conditions. In research applications, this technology has the potential for individual animals to become the experimental unit under group housing conditions. By combining electronic identification technology with devices that measure physiological (e.g., temperature, pH, body weight, feed intake) parameters, researchers will be able to collect data in natural production environments that were previously only obtainable under controlled experimental conditions with a limited number of animals. . L'identification individuelle des bovins à viande n'est pas nouvelle au Canada puisque des systèmes de retraçage ont joué un rôle clé dans l'éradication de la tuberculose bovine dans les années quarante et cinquante et dans celle de la brucellose dans les années soixante-dix et quatre-vingts. Devant les préoccupations récentes pour la santé des animaux d'éle-vage, entre autres l'encéphalite spongiforme bovine (ESB), pour les marchés d'exportation, pour la régularité des produits, pour la qualité de la viande, tendreté et persillé notamment, et pour la sécurité (Escherichia coli souche 0157 :H7, Salmonella spp.), le rétablissement d'un système de traçabilité s'impose comme une solution logique pour conserver la confiance du consommateur envers la viande bovine canadienne. Au départ, de simples marques d'oreille Kurl-lock MD portant un numéro exclusif étaient utilisées pour retracer les individus au troupeau d'origine. Bien qu'utile dans les questions de maladie, le système ne se prêtait cependant pas à la compilation des données complémentaires, par exemple performances de croissance, situation vétérinaire, calendrier de mise à la re...

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