The productive potential of a Cynodon dactylon var.dactylon pasture managed under continuous stocking with wethers was evaluated. The effect of three (3, 6 or 9kg of dry matter (DM) 100kg-1 of body weight (BW)) green leaf allowances (GLAL) on pasture attributes and animal performance of two genetic groups (Texel × Ile de France and Lacaune × Texel × Ile de France) was tested. Experiment was carried out through a 53 days period with 18 wethers of each genetic group randomly distributed in nine pasture plots (three pasture plots per treatment). Actual GLAL were near to those planned for each treatment (i.e. 3.2, 6.7 e 9.5% of BW). Forage mass (mean of 3474kg of DM ha-1) and the content of DM, neutral detergent fibre and crude protein of samples taken through grazing simulation (mean of 49.4, 76.1 and 12.9%, respectively) were not affected by treatments. The green leaf growth rate increased (P<0.05) from 12.1 to 20.5kg of DM ha-1day-1 and stocking rate decreased (P<0.05) from 1178 to 609kg of BW ha-1 when GLAL increased from 3.2 to 9.5% of BW. Animal production per area was in average negative (mean BW gain of -551g ha-1day-1), highly variable (variation coefficient of 280%) and not affected by treatments. Individual animal performance was affected by interaction between treatments and animal breed (P<0.05). Daily BW gain by Lacaune-crossed wethers was positive (34g day-1) and higher (P<0.05) for the highest allowance, null for the lowest allowance and negative (-62g day-1) for the intermediary allowance treatment. Differently, the daily BW gain by Texel × Ile de France wethers was negative and similar for all treatments (mean of -18g day-1). Independently of animal breeding, the daily grazing time was similar for the lowest and highest forage allowance treatments whereas it was lower for the intermediary level of forage allowance (P<0.05). In conclusion, the Cynodon dactylon var. dactylon pasture showed a low productive potential, mainly when the GLAL was similar or lower than 6% of animal BW. However, results also indicate that pasture structure and animal breed interact with forage allowance to determine animal performance.
Cynodon dactylon var. dactylon; ingestive bahaviour; intake; live weight gain; tropical grass; growth rate
