Project Details
The use of legumes under innovative grazing methods and strategic nutrients supplementation for cattle in tropical grazing systems
Applicant
Dr.-Ing. Joaquin Castro
Subject Area
Animal Breeding, Animal Nutrition, Animal Husbandry
Term
Funded in 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 424144661
Grasses are a main feed source for ruminants across the world. However, the productivity of grazing animals is commonly limited by a low supply of nitrogen (N), which hinders microbial protein synthesis in the rumen. The N supply under grazing systems can either be increased by incorporating legume species into the sward, by supplementing animals with concentrated N sources, or by a combination of both strategies. Legumes have been successfully incorporated into temperate grazing systems, but their incorporation into tropical systems has been less successful. This is related to the legumes’ susceptibility to trampling as well as to the preferential grazing of livestock for these species, which adds pressure to legumes. Additionally, pasture management strategies, which are adopted from exclusive grass swards based on the vertical defoliation of plants, can cause extreme defoliation of legumes, further limiting the incorporation of legumes into tropical grazing systems. In cases when legumes have been incorporated into the grazing system, an improvement in the nutritional status of animals has become clear, but, because of the preferential grazing by animals evidence of N wastage has been observed, a development opposite to the aim of efficiently using natural resources.Therefore, the aims of this research are i) to evaluate an innovative rotational grazing management based on the horizontal utilization of pastures in mixed legume-grass swards, and ii) to the study the interactions between N supplementation and the forages available in the pasture on the digesta kinetics of grazing cattle.For this, in a first study Zebu bulls will graze on experimental plots of only grasses or mixed legume-grass swards. A rotational scheme based on the horizontal proportion of un-grazed pasture will be compared with a control rotation scheme based on pasture height. The n-alkanes marker method will be used to estimate total intake and the proportion of each species consumed. A second trial with Zebu bulls grazing in sole grass or grass- legume tree pastures and supplemented with organic or inorganic sources of N will evaluate the fractional outflow rate of solid and liquid rumen digesta. This will be done by fitting the bulls with a peristaltic pump to constantly infuse Chromium and Ytterbium –markers for the passage rate - during grazing. Microbial protein synthesis and diet selection will be estimated from the purine derivatives excretion, and the n-alkanes methodology, respectively. The research will produce a better understanding of the plant × animal interactions during grazing of mixed legume-grass swards; it will also provide an improved pasture management strategy for a successful incorporation of legumes into tropical grazing systems. Moreover, important understanding will be generated on the physiological responses of the rumen dynamics of cattle, when grazing on mixed legume-grass swards, as affected by the characteristics of the supplemental N.
DFG Programme
Research Fellowships
International Connection
Australia