| Popis: |
Summary. Growth, carcass and meat characteristics, market suitability and economic return were compared in surgically spayed (SS), immunologically spayed (IS) and entire (E) heifers. Spaying had no effect on daily weight gains of heifers up to 8 weeks following spaying. Between spaying at 15 months of age, and slaughter at 30 months of age, growth was greater for E heifers (0.36 kg/day) than for SS heifers (0.32 kg/day) (P0.05). Other carcass attributes (meat and fat colour, texture and marbling) were similar for the 3 treatments. Subcutaneous rump fat depth (P8 site) was similar for the 3 groups (E, 20 mm; SS, 21 mm; IS, 19 mm) and the percentages of carcasses that had rump fat depths between 6 and 22 mm were: E, 72%; SS, 66%; IS, 83% (P>0.05). All other carcasses had fat depths greater than 22 mm. Warner-Bratzler initial yield and peak force values of striploin (Longissimus dorsi) samples were lower (P0.05) from E and SS heifers. Direct costs of the spaying treatments (SS, $2.50 per head; IS, 4 vaccinations at $5.50 each) increased the difference relative to E heifers to $29.50 (SS) and $41 (IS) per head. |
