How lamb production systems can affect the characteristics and sward structure of Tifton 85 pasture?

Aimed at understanding how lamb production systems can affect sward structure in tropical grass pastures, the productive, structural and morphological characteristics of Tifton 85 (Cynodon spp.) pasture were evaluated in four systems: non-weaned and non-supplemented lambs (NW); non-weaned lambs receiving concentrate supplementation in creep feeding (CF); early-weaned lambs not supplemented (W); and early-weaned lambs supplemented with concentrate (WS). The trial lasted 105 days and was set out in a randomized block design with four treatments (systems), three replications (paddocks) and five lambs per replication. In the systems with weaning, lambs were weaned at 46 ± 6 days of age and immediately allocated to the paddocks; in the systems with supplementation, lambs received daily a protein–energy concentrate at 2% body weight (BW) on a dry matter (DM) basis. Continuous stocking management was used and the forage allowance was kept at 12% BW in DM/day in all systems. Changes in the structural and morphological characteristics of pasture were more intense up to 63 days of grazing. Sward height and forage mass were higher in WS compared to NW and CF systems, and forage accumulation rate was also higher in WS compared to the other systems. The mass of leaves and stems were higher in the WS system than in NW. Higher heterogeneity of pasture morphological characteristics was observed when weaning was performed. Forage mass was concentrated up to 20 cm sward height in the systems without weaning, with stem mass concentrated in the 0–10 cm stratum and leaf mass highly exposed to grazing in the 10–20 cm stratum. The systems with weaning presented the greatest dispersion of leaves and stems in all sward strata, which increased when the concentrate supplementation was provided to the lambs. Independent of concentrate supplementation to the lambs, the systems without weaning resulted in a better sward structure, with higher leaf/stem ratio for the animals on Tifton 85 pasture. In addition, supplementation of weaned lambs had a deleterious effect on sward structure.