Nutritional Composition and In Vitro Ruminal Digestibility of Crabgrass (Digitaria sanguinalis (L.) Scop.) in Monoculture or Interseeded with Cowpea (Vigna unguiculata (L.) Walp) and Lablab (Lablab purpureus (L.) Sweet)

Simple Summary A major challenge for livestock producers in a cool-season grass system is the seasonality of forage production, and in particular, the quantity and quality gap that usually occurs during the summer. Crabgrass is a warm-season annual crop with better forage quality than most other common summer annual grasses and can potentially be mixed with summer annual legumes. In this study, we evaluated on field plots the effect of intercropping two summer legumes (cowpea and lablab) with crabgrass on forage yield, nutritional composition, and fiber digestibility. We determined the degradability of the neutral detergent fiber under in vitro conditions using rumen fluid from lactating dairy cows. The results of this study showed that mixing crabgrass with cowpea and lablab partially mitigated the biomass yield drag from the legume monocultures while increasing crude protein concentration and fiber digestibility compared to the monoculture of crabgrass. Under the conditions of this study, the biggest impact of intercropping legumes was observed on the first of three harvests, which suggests that the evaluated legumes might not be an ideal complement for a multi-cut grass like crabgrass. The objective of this study was to evaluate the effects of interseeding crabgrass (CG) with two annual summer legumes on forage nutritional composition, dry matter (DM) yield, and in vitro fiber digestibility. The study was conducted as a randomized complete block design with four replicates per treatment. Plots were randomly assigned to one of six forage mix treatments. Crabgrass, cowpea (CWP), and lablab (LL) were planted in monoculture or in mixtures, resulting in six treatments. Throughout the growing season (three cuts), CG had the highest biomass yield, followed by the CG grown in mixtures with CWP and LL, whereas the two annual legume monocultures had the lowest yield. Cowpea and LL planted in monocultures had the highest concentration of CP and fiber digestibility, while the CG monoculture had the lowest. Furthermore, growing CG in a mixture with CWP and LL boosted the CP concentration and fiber digestibility to intermediate levels to those observed between both legume monocultures and CG. Regardless of treatment, the highest forage quality and yield was observed in the first harvest, with a drastic decline in the following harvests. In conclusion, the benefits of mixing crabgrass with legumes might be less than expected and should be carefully evaluated by livestock producers, especially when considering the effects of DM yield, forage quality, and pasture seeding costs.

Automated summary

A study evaluated the effects of intercropping crabgrass with two annual summer legumes on forage yield, nutritional composition, and fiber digestibility. Mixing crabgrass with cowpea and lablab partially mitigated biomass yield drag and increased crude protein concentration and fiber digestibility compared to monoculture of crabgrass. However, the benefits of mixing crabgrass with legumes might be less than expected, especially considering the effects of dry matter yield, forage quality, and pasture seeding costs.