Importance of foot and leg structure for beef cattle in forage-based production systems: characterizing foot and leg scores for Montana Angus cattle
Sitz, Taylre Elizebeth
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The objectives of this study were to increase the amount of phenotypic data available for enhancing the foot and claw EPDs of Montana sires and evaluate factors that could impact foot angle and claw set scores. Specifically, this study evaluated the interaction of sex and age on claw set and foot angle scores of front or hind legs. Researchers used the American Angus Association (AAA) Foot Scoring Guidelines to subjectively analyze claw set and foot angle on a series of Montana Angus herds, scoring a total of 4,723 cattle: 1,475 yearling bulls, 992 yearling heifers, 1,044 two- and three-year-old cows, and 1,212 cows that were four years and older. The AAA Foot Scoring Guidelines require breeders to score the combined "worst foot" for both the claw set and foot angle traits on a hard, flat surface. Yearling bulls had a 0.12 and 0.20 greater mean foot angle and claw set score compared to yearling heifers (P < 0.01). The proportion of scores that differed from 5 (ideal foot score) were greater (P < 0.01) for front feet as compared with hind feet, with 61.5 and 74.5% of the scores not equal to 5 being front feet issues for yearling heifers and bulls, respectively. Foot angle scores increased linearly (P < 0.01) with advancing cow age, ranging from 5.15 to 5.80 for heifers versus cows 4 years and older, respectively. Likewise, claw set scores increased quadratically (P < 0.01) as a function of cow age. The location of the "worst foot" also changed quadratically with age (P < 0.01) with the majority of problem feet in 2/3 year old cows and cows 4 years and older being hind feet issues (70.5 and 77.1% respectively). The proportion of foot angle and claw set scores not equal to 5 also increased quadratically with age (P < 0.01) with heifers having the lowest proportion of scores not equal to 5 (15.8 and 31.7%, respectively) compared to 4 yr and older cows (66.0 and 68.0%, respectively). In analysis of progeny of sire lines, the range between the progeny of the sire line with the greatest foot angle score and that of the least was 0.60 for foot angle. Likewise, for claw set, a similar range 0.57 was observed. Sire lines did have an effect on progeny claw set (P < 0.05) and foot angle scores (P < 0.05), as well as variation of progeny foot scores. In summary, progress is being made by utilizing the AAA foot scoring guidelines, as well as foot angle and claw set EPDs. Additional improvements may be possible with continued model refinement and improvements with scoring guidelines specific to age and sex effects.