The aim of this study was to evaluate the effects of concentrate supplementation on the performance and ingestive behaviour of lambs grazing tropical grasslands of Panicum maximum cv. IZ-5 and its effect on pasture characteristics. Different levels of daily supplementation with concentrate were compared: no supplementation; or supplemented at 1.5% and 2.5% of lamb liveweight. The grazing simulation technique was used for qualitative assessment of the pasture every 28 days. Herbage mass, pasture growth rate, sward height as well as botanical and morphological composition of the pasture were evaluated. Average daily gain, gain per hectare and ingestive behaviour were measured on the lambs. The forage supply was 4% of green leaves (4 kg dry matter per 100 kg of liveweight) in all treatments. Six 3–4-month-old Texel and Corriedale lambs were used per paddock. The design was a randomised block design with three replications. Concentrate supplementation had a direct effect on pasture structure, especially height (significant interaction treatment vs period – P = 0.0373). In the treatment without supplementation, the animals grazed for a longer period than the others. Idle time was higher in the treatment with the highest level of supplementation, and rumination time was similar among the treatments. Supplementation with 2.5% significantly increased the average daily gain (0.143 g vs 0.026 g for no supplementation) and gain per hectare (30 kg vs 258 kg for no supplementation vs supplementation at 2.5% of lamb liveweight, respectively). The results show the potential increase in production and productivity with the use of concentrate supplementation at 2.5% lamb bodyweight. Notwithstanding the increase in production, supplementation with concentrate provided a strong negative impact on pasture structure and behaviour of animals that should be considered when using concentrate supplementation for finishing lambs in tropical regions.

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This study examined tropical pasture contamination dynamics under different feeding systems for finishing lambs. The experiment aimed to evaluate the vertical distribution of gastrointestinal helminth infective larvae (L3) in erect grass subjected to grazing and to assess the parasite load and its impact on lamb performance in three production systems. Three treatments based on Aruana grass (Panicum maximum cv. IZ-5) were as follows: T1, grass only; T2, grass with 1.5% of body weight (BW) nutrient concentrate supplementation; and T3, grass with 2.5% BW concentrate supplementation. The randomized block design had three replicates of three treatments, with six lambs per replicate. L3 were recovered from three pasture strata (upper, middle, and bottom), each representing one third of the sward height, and correlated with microclimatic data. Significant differences (P < 0.05) were observed among treatments in the L3 recovery. Despite different grass heights between treatments and microclimates within the sward, the L3 concentration generally did not differ significantly among the three strata within a treatment (P > 0.05). Pasture microclimate did not correlate with larval recovery. At the end of the experiment, the animal fecal egg count was similar among treatments (P > 0.05). The results indicated that different lamb feeding systems in a tropical erect grassland caused differences in grass height but did not affect the distribution of infective larvae among strata. Larvae were found from the base to the top of the grass sward.

RESUMOAvaliaram-se os efeitos dos tipos de suplementação sobre o desempenho produtivo e o comportamento ingestivo diurno de cordeiros mestiços Santa Inês mantidos em pastagem de capim-aruana (Panicum maximum cv. Aruana) sobressemeado com aveia branca (Avena sativa L.) e azevém (Lolium multiflorum Lam.), em um delineamento inteiramente ao acaso, com três tratamentos e três repetições. Os cordeiros foram distribuídos aleatoriamente em três sistemas alimentares, com seis animais cada, sendo: PASTcordeiros mantidos exclusivamente a pasto; SIL -cordeiros mantidos em pastagem recebendo suplementação (1,0% do peso vivo) com silagem de milho; CONC -cordeiros mantidos em pastagem recebendo suplementação (1,0% do peso vivo) com concentrado. Os cordeiros suplementados com concentrado apresentaram ganho de peso médio diário 37,5% superior aos mantidos em pastagem, mas não diferiram da suplementação com silagem de milho. O tempo de pastejo foi superior para os animais não suplementados quando comparados aos animais suplementados. Cordeiros mantidos a pasto e suplementados com silagem de milho ou concentrado ganham mais peso do que os cordeiros não suplementados.Palavras-chave: aruana, ganho médio diário, silagem de milho, tempo de pastejo, tempo total de alimentação ABSTRACT