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This study was conducted to determine normal rates of growth of different skeletal segments in the thoroughbred horse. Growth of body weight and eight skeletal segments (wither height, hip height, body length, knee to pastern length, hock to pastern length, shoulder to pastern length, width of chest, depth of girth) were monitored in 106 horses (60 colts, 46 fillies) during the period from 14 to 588 d of age. Body weight gains were slightly higher (30 to 40 kg) than previously reported values. Growth in wither height and hip height were similar to previous reports. During the period measured in this study hip height was consistently 2 or 3 cm larger than wither height. Growth patterns for wither height, body length, and shoulder to pastern lengths were similar to one another. Growth of the knee to pastern and hock to pastern segments reached a plateau at approximately 140 d of age, which coincided with the cessation of longitudinal bone growth. These data define skeletal growth patterns in the thoroughbred horse and are useful in determining the relationship between growth and the occurrence of orthopedic diseases in horses.

Summary The highest no effect doses (HNEDs) for the local anaesthetic (LA) effects of procaine, cocaine, bupivacaine and benzocaine were determined using the heat lamp/hoof withdrawal model of Kamerling et al. (1985b) and the abaxial sesamoid block model of local anaesthesia. The heat lamp rapidly (4 or 5 s) increased the temperature of the superficial skin layers of the pastern to about 90°C, at which point the animal sharply withdrew its hoof. Effective LA blockade precluded this response and superficial skin temperatures exceeded 120°C. Thermal stimulus experiments were routinely terminated after 10 s of exposure to prevent undue tissue damage. Following abaxial sesamoid block with bupivacaine, the HNED for that drug was about 0.25 mg/site. Increasing the dose to 2 mg/site apparently produced complete and prolonged LA blockade. Analogous work showed that the HNED for procaine was about 2.5 mg/site. Similarly, the dose response curve for procaine was parallel with that of bupivacaine but was shifted 10‐fold to the right The duration of the LA response following procaine injection was less than for bupivacaine with the statistically significant response following 40 mg/site injection lasting less than 45 min. Cocaine was less potent than procaine, showing a shallower dose response curve. The HNED for cocaine was less than 5 mg/site, although at this dose the duration of action was extremely short (<7.5 min). Benzocaine had no significant LA action when a dose of 800 mg was applied topically as a 5% preparation. These results show that the HNEDs for bupivacaine and procaine are remarkably low, that cocaine is somewhat less potent as a LA than might be expected, and that 5% topical benzocaine has no significant pharmacology. The small doses of bupivacaine and procaine producing effective local anaesthesia suggests that developing plasma thresholds for these agents is likely to be very challenging.

Effects of high dietary levels of energy, protein and Ca and deficient levels of Ca on skeletal growth and development in the equine were studied in two experiments. The weanlings were fed grain-based diets. In Exp. 1, Group 1 (Ctl) received all nutrients at NRC recommended levels for growth; Group 2 (HE) received 150% of their digestible energy (DE) requirement; Group 3 (LC) received 150% of DE and 35% of Ca requirements. In Exp. 2, Group 1 (Ctl) again received all nutrients at NRC recommended levels for growth; Group 2 (HEP) received 150% of DE and 275% of CP requirements; Group 3 (HEPC) received 150% of DE, 275% of CP and 500% of Ca requirements. In addition, all groups had access to pasture. The HE treatment resulted in greater (P less than .10) increases in BW and total cortical width. However, LC weanlings had lower (P less than .10) gains in third metacarpal length and radiographic bone density. Cumulative increases in BW and wither height were greater (P less than .10) for the HEP and HEPC weanlings than for the Ctl weanlings. Increases in third metatarsal length also were greater (P less than .10) for HEP weanlings than for Ctl weanlings. Higher planes of nutrition increased body weight gains and growth rate of several long bones. However, skeletal development (e.g., cortical area) may be compromised by a high rate of growth.

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