RESUMO: O presente estudo testou se a biomassa radicular de misturas compostas por gramíneas é maior do que os seus respectivos monocultivos. Os tratamentos foram monocultivos de Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata e uma mistura delas, cultivadas em um solo rico em nutrientes. A biomassa da raiz foi avaliada uma vez por estação em três profundidades de solo (0-5, 5-10 e 10-20 cm). Os pastos mistos apresentaram a maior biomassa radicular e isso pode ser explicado pela maior concentração de raízes na camada superficial do solo (0-5 cm). Esses achados reforçam a necessidade de práticas permanentes de conservação do solo para não prejudicar os benefícios da biomassa radicular mais abundante encontrada nos pastos mistos.

ABSTRACT: In this study we tested whether the root biomass of mixtures composed by grass species is greater than their respective monocultures. The treatments were monocultures of Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata, and a mixture of them, cultivated in a rich-soil environment. Root biomass was evaluated on a single evaluation per season at three soil depths (0-5, 5-10, and 10-20 cm). Mixed swards presented the greatest root biomass, and this was explained by a greater concentration in the topsoil layer (0-5 cm). These findings reinforce the need for permanent soil conservation practices to not jeopardize the benefits of the more abundant root biomass reported in the mixed swards.

ABSTRACT: This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.

ABSTRACT The objective was to quantify the flow of intestinal nutrients and nitrogen excretion and retention in sheep receiving isoproteic diets. Eight Texel x Lacaune wethers (average body weight = 25±2.5 kg) were fitted with duodenal cannula and housed in metabolic cages. Wethers were assigned to the treatments in a crossover design with two periods of 20 days each, and all feces and urine produced by the wethers were collected. The treatments consisted of two isoproteic (160 g kg−1 of crude protein on dry matter basis) diets composed of red clover (RC) or lucerne (LU; Medicago sativa) silages plus corn silage and concentrate feed. The digestible organic matter and metabolizable energy intake did not differ between treatments. The intestinal non-ammonia N (NAN) flow was 5.9 g day−1 (37%) higher in RC wethers than in those of the LU treatment. This result was a consequence of both an increase in the efficiency of microbial protein synthesis (12.7% higher) and a decrease in ruminal degradable protein (RDP) content (20% lower) of the diet. However, the increase in the intestinal NAN flow was accompanied by a reduction in intestinal digestibility of N, resulting in similar daily N retention between treatments. The reduction of RDP content was probably the main reason for reductions in N urinary excretion in RC wethers compared with those in the LU treatment, showing that RC silage may be a tool for mitigating the impact of N excretion in ovine production systems, without changes in N retention.

RESUMO: Cyclocephala flavipennis Arrow, 1914 (Coleoptera: Melolonthidae), conhecido popularmente como coró-pequeno, é um inseto amplamente disseminado na região sul do Brasil. Embora seja encontrado com frequência em áreas cultivadas com cereais de inverno não é considerado inseto praga, por alimentar-se preferencialmente de palha e restos de plantas. Entretanto, nos anos de 2015 e 2016 foi identificado como causador de danos em pastagens perenes de inverno em Lages, Santa Catarina, Brasil. Os danos foram observados em reboleiras e promoveram redução na massa e profundidade de raízes, resultando em perda de vigor, senescência acelerada da parte aérea e morte de perfilhos de plantas de Festuca arundinacea Schreb. e Dacytilis glomerata L.

ABSTRACT: Cyclocephala flavipennis Arrow, 1914 (Coleoptera: Melolonthidae), popularly known as white grub, is an insect widely disseminated in the South Region of Brazil. Despite the frequent occurrence of this white grub in areas cultivated with winter cereals, it is generally not considered a pest, since it feeds on straw and dead plant material. However, in 2015 and 2016, this insect has been identified as the damage-causing agent in the perennial winter pastures in Lages, Santa Catarina, Brazil. Damage was observed in patches and caused reduction in root depth and mass, resulting in loss of vigor, accelerated senescence in aerial parts, and death of tillers in Festuca arundinacea Schreb. and Dactylis glomerata L. plants.