Could Cratylia argentea replace Tifton 85 hay on growing and finishing lamb diets in tropical areas?

Legumes shrubs such as Cratylia argentea have an ability to thrive in environments with low water availability and poor soil. On the other hand, forage grasses such as Tifton 85 have a greater demand for inputs to be productive. The objective of this study was to evaluate the performance of growing and finishing Lacaune lambs fed Cratylia argentea hay as an alternative to Tifton 85 (Cynodon spp). Twenty-four Lacaune lambs aged between five and six months (average body weight [BW] 21.50 ± 3.38 kg) were arranged in a split-plot randomized block design. The plots consisted of different Cratylia to Tifton 85 hay proportions (0, 20%, 40%, or 100%, dry matter [DM] basis) as a roughage replacement in the total diet. The subplots represented two evaluation times, entitled "initial period" and "final period", which consisted of the early seven days of total feces and urine collection, and the last seven days of the experiment, respectively. The lambs were blocked by weight with six replicates per treatment. The results show that the level of Tifton 85 replacement for Cratylia hay in the roughage portion of the lamb diet did not influence (P > 0.05) weight gain (WG), dry matter intake or dry matter digestibility; feed conversion, feed efficiency; and the evaluated nitrogen balance variables. The digestibility coefficient of neutral detergent fiber decreased linearly as Tifton 85 replacement for Cratylia level was increased, which probably happened due to the presence of highly lignified material within the Cratylia hay. However, the alternative legume maintained animal performance of Tifton 85. In conclusion, Cratylia hay can be recommended as a potential substitute for Tifton 85 hay, which requires greater inputs for the production. Cratylia may be considered a feeding strategy for livestock production, especially for smallholder livestock systems and regions with unfavorable soil and climate.

Selection of efficient rhizobial symbionts for Cratylia argentea in the cerrado biome / Seleção de rizóbios eficientes na simbiose com Cratylia argentea no bioma cerrado

ABSTRACT: Cratylia argentea is a leguminous shrub native to the cerrado, which has great potential for forage production and recovery of degraded areas. This study aimed to isolate, characterize, and select efficient rhizobial strains in symbiosis with Cratylia argentea . Rhizobacteria were isolated from the nodules of 12-month-old plants and cultivated in pots containing cerrado soil. Twenty-five bacterial strains were obtained, which displayed extensive variability with respect to morphological and symbiotic characteristics. Cratylia argentea seeds were planted in pots containing 5kg of cerrado soil and maintained in the greenhouse. The treatments consisted of 25 rhizobial isolates, two controls (without nitrogen and without inoculation), with or without nitrogen fertilization (5mgN·plant-1·week-1), and four replications. Plants were cultivated for 150 days after planting seeds to evaluate nodule number, nodule dry weight, shoot and root dry weight, shoot and root N content, and relative and symbiotic efficiency. Thirteen isolates improved shoot dry weight (up to 65.8%) and shoot nitrogen concentration (up to 76%) compared with those of control treatments. Two isolates, 4 (CR42) and 22 (CR52), conferred higher symbiotic efficiency values of approximately 20%. Therefore, these two rhizobial isolates displayed the highest potential as beneficial inoculants to optimize the symbiotic efficiency for Cratylia and to increase the incorporation of nutrients and biomass into the productive system in the cerrado.

RESUMO: Cratylia argentea é uma leguminosa arbustiva nativa do cerrado, com alto potencial para produção de forragem e recuperação de áreas degradadas. Este trabalho teve como objetivo isolar, caracterizar e selecionar estirpes de rizóbios eficientes na simbiose com C. argentea . As bactérias foram isoladas de nódulos de plantas com 12 meses de idade, cultivadas em solo de cerrado, em vasos. Foram obtidas 25 estirpes, que apresentaram alta variabilidade em relação às características morfológicas e simbióticas. Sementes de C. argentea foram plantadas em potes contendo 5kg de solo de cerrado, e mantidos em casa de vegetação. Os tratamentos consistiram em 25 isolados, controle (sem N e sem inoculação) e adubação nitrogenada (5mgN·planta-1·semana-1), em quatro repetições. As plantas foram colhidas 150 dias após o plantio para avaliar o número e a massa seca de nódulos, a massa seca e concentração de nitrogênio da parte área e das raízes. Foram calculadas as eficiências relativas e simbióticas. Treze estirpes se destacaram quanto ao acúmulo de massa seca (até 65,8%) e acúmulo de nitrogênio (até 76%), da parte aérea, em relação ao tratamento controle. Dentre estas, as estirpes 4 e 22 apresentaram maiores eficiências simbióticas (em torno de 20%). Portanto, estas estirpes apresentaram potencial para formulação de inoculantes, visando otimizar o processo simbiótico rizóbio- Cratylia e a incorporação de biomassa e nutrientes em sistema produtivos no cerrado.