The relationships of fat thickness and muscle depth with grade yield in pork carcasses

Abstract

Fortin, A. 2004. The relationships of fat thickness and muscle depth with grade yield in pork carcasses. Can. J. Anim. Sci. 84: 297-300. Under the Canadian pork grading system, grade yield, a function of fat thickness and muscle depth, is estimated from a prediction equation derived from a national sample. Data from the 1992 National project (Québec, n = 306; Ontario, n = 306; Alberta, n = 262) are used to examine the relevancy of a national sampling on these relationships. Regional origin did not have an effect (P > 0.05) on the relationship of grade yield with fat thickness whereas it did (P < 0.05) for the relationship with muscle depth.Key words: Canada pork grading, grade yield , fat thickness, muscle depth, sampling Fortin, A. 2004. Lien de l'épaisseur de la couche de gras et de l'épaisseur du muscle avec le rendement des carcasses de porc au classement. Can. J. Anim. Sci. 84: 297-300. Dans le système canadien de classement du porc, la catégorie dépend de l'épais-seur de la couche de gras et de l'épaisseur du muscle. On l'établit au moyen d'une équation prévisionnelle élaborée à partir d'un échantillon national. L'auteur se sert des données de 1992 du projet national (Québec, n = 306; Ontario, n = 306; Alberta, n = 262) pour vérifier la pertinence d'un tel échantillonnage sur la relation entre ces paramètres. La provenance régionale n'a aucune incidence (P > 0,05) sur le lien entre la catégorie et l'épaisseur de la couche de gras, mais elle en a bien une (P < 0,05) sur le lien entre la catégorie et l'épaisseur du muscle.Mots clés: Système canadien de classement du porc, rendement au classement, épaisseur de la couche de gras, épaisseur du muscle, échantillonnage 297In Canada, the overall objective of the pork carcass grading is to identify the true commercial value of a carcass by segregating carcasses on the basis of lean content and carcass weight (Fortin 1989). The Canadian grading system has elements of a classification scheme in that it uses the objective determination of grade yield in the carcass for establishing a carcass grade. It makes use of the negative relationship between fat thickness and carcass lean and the positive relationship between depth of the loin and carcass lean. Under the Canadian grading system, the grade yield of the carcass is estimated from a prediction equation based on fat thickness and muscle depth measured with a light reflectance probe between the 3rd and 4th last ribs, 7 cm off the exposed surface of the split carcass. Until 1996, the Canadian grading system was truly a national system: a unique prediction equation was used, delivery of grading was uniform across Canada and under the responsibility of Agriculture and Agri-Food Canada. With the exception of the 1986 equation (Fortin et al. 1984), the unique prediction equation was derived from national cutouts (Fredeen 1967;Martin et al. 1981; CPC 1994). Carcasses were obtained from all pork-producing regions of Canada to ensure that the prediction equation could be used across the country as there were concerns in the ...