Prospects of compensatory growth for sheep production systems

The dry (lean) season imposes a natural feed restriction in grazing animals that must be compensated for during the wet (lush) season. The nutrition physiological backgrounds governing the changes during growth retardation and higher gain during compensation are obscure. Immature male lambs were used to determine the effects of feed quality restriction, i.e. feeding grass straw, on the pattern of feed intake, feed efficiency and growth, and changes in the physiological state of the animals. During restriction and following realimentation, the grass straw intake of the restricted animals was significantly higher than of their controls. Maintaining gut capacity was the main reason of ingesting more low quality feed. The delay in growth during the restriction period was fully compensated after realimentation with a significantly lower total feed consumption, while the carcass of the realimented animals was leaner than of the controls. Higher grass straw intake, lower maintenance requirements, an increased feed efficiency and changes in the composition of gain were mechanisms supporting compensatory growth. During the dry season with limited amounts of good quality feed available, imposing feed quality restriction is a useful strategy. During the following recovery period, animals compensate through increased feed intake and a more efficient use of the nutrients. Modelling the implementation of a strategy of compensatory growth indicated the possibility of a reduction of the total concentrate input by 40% per animal compared to an intensive system. Compared to an extensive system, only 35% of the rangelands is required, thereby reducing the grazing pressure on the rangelands and allowing regeneration of the vegetation species.