The Effects of Maturity on Range Quality and Animal Performance

The objective of this study was to determine the effects of maturity on the range quality and weight gain of male and female lambs, and the time at which supplementation is needed. The experiment was conducted at TİGEM Altındere Agricultural experiment station. At the start of the grazing season, four 4-m2 areas from 3 different (expected to be heavily grazed) locations of range were excluded from grazing with cages. Dry matter (DM) yield and DM loss due to grazing at different periods of the grazing season were determined from these areas. Forage samples were collected from grazed and ungrazed areas once every two weeks from the 2nd week of May to the 2nd week of August. Parallel to forage sampling, 20 male and female lambs (a total of 40 lambs) grazing on the pasture were weighed once every two weeks to determine daily weight gains. Dry matter yield, chemical composition (DM, OM, ash, CP, NDF, and ADF) and in vitro DM digestibility of range were determined. Dry matter, NDF and ADF concentrations of forages increased (P < 0.01) and crude protein content decreased (P < 0.01), but organic matter and ash concentrations did not change with increasing maturity. The effect of grazing on the parameters mentioned above was not significant, but increasing maturity significantly affected DM digestibility and DM yields (P < 0.01). At the start of the experiment, DM digestibilities for grazed and ungrazed areas were 69.70 and 69.25%; they declined to 42.45 and 43.45% at the 7th sampling, respectively. Dry matter yields for grazed and ungrazed areas were 54.69 and 69.64 for the 1st sampling, 81.88 and 120.54 for the 2nd sampling, 50.55 and 111.74 for the 3rd sampling, 59.10 and 97.13 for the 4th sampling, 32.82 and 78.81 for the 5th sampling, 38.06 and 67.61 for the 6th sampling, and 26.96 and 52.65 kg/da for the 7th sampling, respectively (P < 0.01). Digestible DM yields for grazed and ungrazed areas were 37.82 and 48.12 for the 1st sampling, 51.50 and 78.41 for the 2nd sampling, 28.29 and 58.50 for the 3rd sampling, 30.15 and 48.18 for the 4th sampling, 16.12 and 37.65 for the 5th sampling, 17.76 and 31.56 for the 6th sampling, and 11.96 and 24.10 kg/da for the 7th sampling, respectively (P < 0.01). Both DM and digestible DM yields were also affected by grazing (P < 0.01). Weight gains, determined parallel to forage sampling, during the 2nd, 3rd , and 4th periods were high (228, 263, and 182 g/d for male, and 252, 194, and 184 g/d for female lambs, respectively), but were very low after the 4th period. It is concluded that the range can meet the nutrient requirements of lambs for optimal weight gain during May and June, but lambs require an extra supplementation for optimal weight gain after June under Northern Anatolian conditions.