Influence of different growing stages of whole-plant soybeans on their nutrient content and silage quality for cattle

ABSTRACT

The objective of this study was to determine the effects of growing stage (GS) on morphological and chemical composition of whole-plant soybean (WPS), and fermentative profile and chemical composition of whole-plant soybean silage (SS). This study was divided into two trials conducted in a complete randomised block design. The first trial evaluated the effect of GS from R1 to R8 (59–135 d after sowing) on morphological and chemical composition of WPS and its botanical components. The second trial determined the effects of GS from R3 (71 d after sowing) to R7 (124 d after sowing) on dry matter (DM) losses, fermentative profile, chemical composition and aerobic stability of SS. The proportion of leaves in WPS was reduced, while stem and pod proportions were increased as the GS progressed. Ensiling WPS at R6 and R7 decreased the contents of acetic acid, lactic acid and branched-chain fatty acids, and ethanol, and increased the contents of propionic acid and NH₃-N. However, silage butyric acid concentrations in R6 and R7 were relatively high (18.1 and 19.9 g/kg DM, respectively). Butyric acid and buffering capacity varied according to GS with the lowest values observed in silages derived from GS R3, R5 and R7, and the highest values observed in silages made from GS R5. Later GS resulted in greater contents of DM, crude protein and ether extract, and lower contents of acid detergent fibre and non-fibre carbohydrate in SS. The high fat of SS produced from later GS limits high inclusion levels in ruminant diets. Morphological components impacted chemical composition of SS, whereas the R7 stage improved fermentative profile and resulted in an SS with greater in situ degradability of DM and neutral detergent fibre.

KEYWORDS:

• Harvesting stage
• legume forage
• morphological characterisation
• soybean silage

Acknowledgements

The authors acknowledge members of Dairy Cattle Research Laboratory of University of São Paulo for support during the experiment. This study was financed in part by the Coordination of Improvement of Higher Level Personnel (CAPES, Brasília, Brazil) - Finance Code 001. The authors thank the National Council for Scientific and Technological Development (CNPq, Brasília, Brazil) under Grant #425762/2018-1, and São Paulo Research Foundation (FAPESP, São Paulo, Brazil) under Grant #2016/23132-8 for awarding scholarships for the first author.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was partially funded by the Coordination of Improvement of Higher Level Personnel (CAPES, Brasília, Brazil) - Finance Code 001. National Council for Scientific and Technological Development (CNPq, Brasília, Brazil) – Protocol 425762/2018-1.