Degradation of Potassium Hydroxide-Treated ‘Coastal’ Bermudagrass Stems at Two Stages of Maturity
- Roland R. Spencer,
- Danny E. Akin and
- Luanne L. Rigsby
The highly lignified and rigid stem tissue of grasses form a formidable barrier to digestion and physical destruction in the rumen of the animal. Alkali treatment has been shown to increase the digestibility of many feeds. The objective of this research was to compare the effect of potassium hydroxide treatment on the physical structure and on the degradation of specific tissues by rumen microorganisms in ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] stems. Scanning electron microscopy was used to study the relative extent of in vitro cell wall digestion of stems at 6, 24, and 48 h for two stages of maturity. The less mature top stem (TS) was taken from the upper first or second internode while the more mature bottom stem (BS) was taken from the lowest internode above the root. Potassium hydroxide treatment disrupted tissues and caused a swelling of the vascular, sclerenchyma, and epidermal cells. Alkali treatment appeared to break down the bonding in the intercellular layer allowing this material to be degraded by the rumen microorganisms. Similar material in untreated tissues was resistant to microbial attack. Untreated TS were degraded to a greater extent than untreated BS. This difference occurred in parenchyma tissues, of which more cells gave a positive reaction for lignin with the chlorine-sulfite test in the more mature BS than in TS. Potassium hydroxide treatment increased the disruption of both TS and BS, resulting in a fragile residue, but the TS was more degraded than BS. However, even after alkali treatment and microbial degradation, epidermis, sclerenchyma ring, and disrupted vascular cells were recognizable structures in the residue. The TS was 19% more digestible than the mature BS both before and after alkali treatment. The treated TS and BS's digestibility was increased by 33% over the untreated material.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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