| Abstrakt: |
Weanling, yearling and 2-year-old horses were fed low protein diets supplemented with either urea (U) or soybean meal (SBM) to determine the effect of N source on growth and protein status. Average daily gain (ADG) of the weanlings was greater (P<.05) when they were fed the SBM diet than when they were fed the urea diet (.64 vs.29 kg, respectively). There were no differences (P>.05) in ADG due to diet among the yearling or 2-year-old horses. Height at the withers or croup was not affected by diet in any age group. Concentrations of blood urea N were higher (P<.05) when the 2-year-olds were fed the urea diet than when they were fed the SBM diet (15.0 vs14.0 mg/100 ml, respectively). There were no diet-related differences (P>.05) in blood glucose levels within any age group, but the yearlings had a lower (P<.05) average glucose level than the weanlings. Diet did not affect globulin levels, total protein levels or albumin to globulin (A:G) ratios within any age groups. There were, however, differences between age groups for each of these measures. The globulin and total protein levels in the yearlings (4.16 and 6.41 g/100 ml, respectively) and 2-year-olds (4.40 and 6.70 g/100 ml, respectively) were greater (P<.01) than those in the weanlings (3.47 and 5.72 g/100 ml, respectively). The globulin and total protein levels in the 2-year-olds were greater (P<.05) than those in the yearlings (4.40 and 6.70 vs4.16 and 6.41 g/100 ml, respectively). Weanling horses had higher (P<.01) A:G ratios than yearlings and 2-year-old horses (.66 vs.54 vs.52, respectively). |
