Alkali treated bagasse shows promise as a drought ration for cattle

Why a sugar mill waste product needed a chemical boost#

Sugar milling in Queensland and northern New South Wales produced large volumes of bagasse, the fibrous residue left once cane has been crushed for juice. The paper reports that in 1986, 307,000 ha of cane was planted, yielding 3.2 x 10^6 tonnes of sugar and 693,000 tonnes of molasses, alongside roughly 7.4 x 10^6 tonnes of bagasse carrying about 50% moisture. Most of this residue was burnt inside mill boilers to raise steam for the factories themselves, but the authors note that a portion of it, somewhere between 5 and 10%, went unused each season and was simply burnt off or dumped.

The obstacle to using that surplus as stockfeed was its make-up: hundreds of grams per kilogram of cellulose and hemicellulose, with a sizeable lignin fraction and very little protein. Earlier work by Beames had explored mixing untreated bagasse with molasses as a fattening ration, but the fibre portion only reached around 30% digestibility in laboratory testing, which limited how much of that mix could actually consist of roughage. The authors wanted to find out whether sodium hydroxide treatment, which had already lifted digestibility in other poor-quality roughages, could make bagasse genuinely useful as cattle feed, and then to establish whether the treated material could be handled, stored and sold on a commercial scale.

From a research mixer to on-farm metabolism cages#

The project moved through several stages. Laboratory work first sprayed fresh bagasse with alkali solution at a range of strengths on a dry fibre basis, mixing it either by hand or through a small roller mill, then measuring digestibility with the established Tilley and Terry laboratory technique. Digestibility climbed and cell wall content dropped as the strength of alkali applied increased, with the higher test strengths producing values in the 50 to 55% range.

The treatment was then scaled up in a horizontal mixer to produce what the authors term treated alkali bagasse, combined afterwards with molasses and urea to make a basal ration referred to as TAB/M. Three separate cattle trials followed, each using Brahman-cross animals at Queensland research sites. The first allocated thirty-five steers across seven dietary treatments over an 84 day period, with organic matter digestibility also measured in a smaller group of steers held in metabolism cages. A second trial compared protein supplements, including untreated and chemically protected cottonseed meal, in twelve steers over 78 days. A third used forty-eight heifers split across six treatments over 84 days, with blood sampling used to check for any ill effects from the unusually high sodium content of the diet.

Weight gains and feed efficiency on alkali treated bagasse diets#

Cattle given the basal TAB/M ration on its own, with or without extra molasses or urea, tended to hold their weight steady or lose only a little over the feeding period. Adding a chemically protected casein supplement produced genuine live weight gains, which the authors attributed to amino acids bypassing the rumen and being absorbed further along the digestive tract, since feed intake barely changed between that treatment and the plain urea diet. A mixed meal combining several protein sources performed better still, supporting higher intake and stronger gains than casein on its own.

In the third trial, the strongest daily gains recorded were 0.71 kg/d in heifers on a richer bagasse-to-molasses mix given a protein supplement, closely followed by 0.69 kg/d in a group whose ration included a portion of grain. Elsewhere the paper states that cottonseed meal supplementation supported daily weight gains as high as seven-tenths of a kilogram. Cattle fed the treated bagasse diet with the mixed protein supplement also converted feed into live weight more efficiently than animals on a comparison diet of Rhodes grass chaff with similar digestibility, needing noticeably less organic matter per kilogram of gain.

Checking the diet did not harm cattle health#

Because sodium hydroxide treatment pushes dietary sodium well above typical levels, the researchers tracked a panel of blood markers covering kidney, liver and muscle function across the heifer trial. Most of these markers stayed within what the paper describes as the normal range throughout the feeding period. One marker linked to muscle function, creatine phosphokinase, came out higher than normal in animals given bagasse treated with the stronger alkali dose tested, compared with those on the lower dose, although it eased somewhat by the later blood sampling point.

This result supported the authors' decision to settle on the lower alkali concentration, 5% on dry fibre, for their main feeding programs rather than the higher level tried early on, since the extra digestibility gained from the stronger treatment was judged only marginal. On that basis the paper concludes there were no health problems associated with diets built mainly around the treated bagasse, provided alkali strength was kept at or below that 5% ceiling. We would treat that conclusion as a reasonable pointer rather than a settled finding, given it rests on one trial, one class of cattle, and a modest number of blood draws.

Elsewhere in the catalogue, readers can find separate papers sharing the word bagasse in their titles, such as a 1998 study on sheep intake of sugarcane bagasse supplemented with cottonseed meal, and another 1998 study on sheep intake of sugarcane bagasse supplemented with cottonseed meal and sucrose or a protected fat, alongside a 1988 paper on alkali-treated straw and nitrogen synthesis in cattle. These are listed here only by title and year, without any claim about how their findings relate to this one.

Field trials on commercial feedlots and drought-affected properties#

Beyond the research yards, the paper describes trials run on an operating mill site during an actual crushing season, where a continuous system sprayed raw bagasse moving along a belt with alkali solution before it passed through a rotating drum ahead of storage. The resulting treated bagasse was fed successfully as the roughage portion of grain-based diets in two working feedlots, and bales of the molasses-enriched version were trucked substantial distances to properties further north, with cattle showing no particular preference for bales of differing age or moisture content.

A separate trial supplied a bagasse-based ration containing cottonseed meal to a mob of pregnant, grazing cows during dry conditions, stockpiled on site and fed out daily by hand. Those cows ate considerably more of the treated ration each day than a comparison mob offered whole cottonseed, and farm and advisory staff judged the treated-ration group to be in better condition, with better coat colour and stronger calves, though this was a field observation rather than a controlled scientific comparison.

How well the bales kept in storage#

A central practical question was whether bagasse treated with alkali, prepared at a moisture content of about 40%, could be baled and stored for any length of time without spoiling. Bales made at varying densities were stored for up to six months, some sealed in plastic and others left open to the air in a shed. Moisture in the sealed bales barely shifted, while the unsealed bales dried out gradually over the following months, reaching a moisture content similar to that of ordinary air-dried bagasse at the edges well before the centre caught up.

Acidity measurements showed the bagasse-only bales held a stable, strongly alkaline pH across the full storage period, and the molasses-containing bales stayed in a similarly high range whether sealed or not. That residual alkalinity appears to have restricted microbial growth; bacterial counts in stored bales resembled those found in fresh, freshly cut bagasse rather than material that had begun to spoil, and no mould growth was reported. Some nitrogen was lost from the unsealed molasses-containing bales over time, along with a noticeable ammonia smell in the richer mix, yet digestibility of the roughage fraction itself held steady throughout storage.

Production costs and likely markets for the feed#

The cost of producing both loose and baled versions of the treated bagasse depended heavily on how much material the plant processed, since fixed equipment and capital costs made up a large share of the total. Baling came out cheaper and quicker than pelleting as a packaging method. The researchers identified the sodium hydroxide itself as the single biggest cost driver in the whole process, and noted that searching for a cheaper source of alkali had so far proved unsuccessful. For buyers close to the mill, supplying the product loose rather than baled was expected to work out cheaper, since it avoided the extra handling cost of compression even though the loose material took up far more space per tonne.

The paper points to several possible uses: as the roughage portion of grain-heavy feedlot rations, as a drought feed, for settling newly arrived cattle into a feedlot, or paired with a protein meal for slower weight gain programs. It also flags a possible export market in Japan, while acknowledging that freight costs and buyer acceptance remained unresolved obstacles standing in the way of that trade. The wider body of nutrition research from this conference series sits within the Recent Advances in Animal Nutrition proceedings and the broader RAAN Conference Proceedings collection, both searchable through the Livestock Library research index.

Sources and further reading#

• Trove library search: find a library that holds the paper
• Meat & Livestock Australia: red meat industry research and marketing body
• Integrity Systems (NLIS and LPA): which runs NLIS, LPA and the National Vendor Declaration
• Feedipedia animal feed database: an open-access database of animal feeds

Questions#

— The Livestock Library team