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Managing Water Soluble Carbohydrates and Fibre in Oaten Hay

Jeff Braun1, Mick Faulkner1, Pamela Zwer2 and Glenn McDonald3

1Agrilink Agricultural Consultants Pty Ltd, PO Box 118, Watervale, SA, 5452,, Email:
SA Research and Development Institute, Waite Campus, GPO Box 397, Adelaide, SA, 5001, Email:
University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA, 5064, Email:


The quality of oaten hay for domestic and export markets depends in part on the concentrations of different carbohydrate fractions. High water soluble carbohydrates (WSC) and low acid and neutral detergent fibre (ADF/NDF) are needed for high quality hay. Field trials were undertaken in 2006 and 2007 to determine the influence of management factors on oaten hay quality. The experiments examined the effects of: 1) time of sowing, 2) time of cutting, 3) nitrogen rate and timing, 4) variety and 5) the use of plant growth regulators. Samples were cut at regular intervals prior to and after flowering, dried and analysed by Near Infrared Spectroscopy (NIRS) to determine quality. Time of cutting was found to be crucial to achieve high quality with rapid falls in WSC and increases in both ADF and NDF 5-7 days post anthesis. In both seasons high yields were obtained by early sowing, however this required cutting earlier in the season and increased risk of weather damage. High nitrogen rates increased yields, but also reduced WSC content, leading to lower quality hay. It was also found that applications of nitrogen at GS 31 reduced WSC content and sometimes yield. Significant varietal differences were also observed for the majority of quality parameters giving further support for breeding programs selecting for forage quality. Some plant growth regulator treatments have increased WSC and reduced in ADF/NDF, without losing yield. Hay quality is sensitive to management and this work will lead to guidelines to allow farmers to consistently achieve high quality.

Key Words

Oats, water soluble carbohydrates, fibre, time of sowing, nitrogen, plant growth regulators


The export oaten hay industry in Australia began in the 1980s predominantly exporting product to Japan where it is used as an ad-lib feed for dairy and beef cattle operations. Most of the export hay in Australia is produced in Western Australia (45% of total annual production) and South Australia (45%), with Victoria (8%) and New South Wales (2%) producing the remainder. The Victorian share in this market is expected to increase with many new hay plants beginning operations in the State and farmers looking for alternative ways to manage frost risk and herbicide resistant annual ryegrass (Lolium rigidum).

Australia’s main competitors in the East Asian forage market are United States, Canada and China. North American timothy (Phleum pratense) hay is the strongest competitor with Australian oaten hay in the export market as it can be sold as a direct replacement for oaten hay in rations. This, combined with inherently high quality of timothy hay and the large volume produced in North America that can be sold onto the market, makes it formidable competition for Australian oaten hay. Increasing and maintaining consistent quality of hay is therefore important if the Australian oaten hay industry is to maintain and increase its market share. Currently, consistency is not always achieved: there appears to be a trade off between yield and quality (Stuthman and Marten 1972). Information on the best management practices for achieving high yield and qualityl is limited, but has been explored in a series of experiments over the last two growing seasons (2006-07).


Cultural Conditions

Experiments were sown in 2006 at ‘Mona Vale’, Tarlee, SA and 2007 at ‘Navan’, Riverton, SA. The experiments were grown after an oaten hay crops to minimise weed competition and volunteer contamination of plots. The timing of nitrogen fertiliser application and crop sampling was related to Zadok’s growth stages (GS; Zadoks et al 1974). The sites in both years were sown with a six row cone seeder on 23cm row spacing. Plots were sown to Wintaroo oats at 300 seeds/m2. There were 3 times of sowing (TOS) in each year . In 2006 these were 12 May, 29 May and 16 June and in 2007 they were 11 May, 6 June and 16 June.

All plots were fertilised with 90 kg/ha of triple super phosphate, sown with the seed. Topdressed N was applied as urea, which were applied by hand post emergent and incorporated by rainfall. Plant Growth Regulator (PGR) treatments were applied using a hand boom (XR02 nozzles, 2bar, 100 L/ha) at GS 30 for each time of sowing.

Experimental Design

All experiments were randomised complete block designs with 3 replicates. Plots were 1.37m wide x 11m long. These were divided in half to create sub plots 1.37m wide x 4.8m long.

Sampling Methods and Analysis

All plots were sampled at the start of flowering on the main stem (GS 61). Plants were cut to ground level from 2 x 50cm of row within each plot. Prior to sampling the plot was observed to determine an even, representative area from which to sample. The two middle rows of the plot were always sampled to avoid any plot edge effects. Following cutting, samples were microwaved (800W) for 2 minutes on high and then placed in a drying oven at 70C for 24 hours. Dried samples were weighed, ground to pass through a 0.5mm screen and analysed using Near Infrared Spectroscopy (NIRS). The NIRS used to analyse samples were located at commercial export hay processors Gilmac (2006 samples) and Balco (2007 samples), both of which undergo quality control measures needed to maintain their quality assurance for fodder testing, as outlined in AFIA Laboratory Methods Manual (2006).

Results and Discussion

Time of Sowing

The earliest time of sowing in both seasons produced significantly higher dry matter yields than treatments that were sown later in the growing season. These results are supported by those of Pendleton and Brown (1961) who found that the highest dry matter yields were obtained by sowing oats early. This concurs with the results found in the long term oaten hay production trials conducted by Agrilink/Gilmac (Faulkner 2006). Hay quality can be increased by delaying sowing (Contreras-Govea and Albrecht 2006; Faulkner 2006) and this was also observed in these experiments. Early sowing of oats tended to increase fibre deposition and reduce water soluble carbohydrate (Figure 2).

Earlier sowing allows the oat plants to grow for a greater period of time, utilising a greater proportion of the in season rainfall, prior to anthesis. This also allows greater overall amounts of photosynthesis and the consequent production of assimilate (WSC) and fibre (ADF/NDF). Objective hay quality grading systems for the export industry in particular are based upon higher WSC and lower ADF/NDF values. Earlier sown oaten hay tends to be the opposite of this and would result in lower quality hay and reduced income for the producer.

Figure 1. The effect of delaying sowing on the total shoot dry matter production (kg/ha) of oats (cv. Wintaroo) cut at GS 61 in 2006 and 2007. Error bars indicate LSD 5%.

Figure 2. The concentrations of Acid Detergent Fibre and Water soluble Carbohydrates in oats (cv Wintaroo) sampled at GS 61 in 2007. Error bars indicate LSD 5%.

Figure 3. The changes in Water Soluble Carbohydrate over time in oats (cv Wintaroo) sown at three dates in 2006. All crops received 100 kg N/ha at sowing.

Figure 4. The changes in Water Soluble Carbohydrate over time in oats (cv Wintaroo) sown at three dates in 2007. All crops received 100 kg N/ha at sowing.

Time of Cutting

The concentrations of water soluble carbohydrates in the shoots were higher in 2007 than in 2006. Time of cutting had a significant effect of the WSC content of the oats in both seasons. Cutting oats after flowering resulted in lower WSC contents as they were being remobilised and deposited as starch in the developing grain. The 2006 season experienced terminal drought conditions during spring, meaning that the peak in WSC content occurred prior to flowering at all times of sowing. It is not always suitable however to cut commercial crops at this stage, as it can lead to curing problems. At the later sowings in 2006, the peak in WSC occurred progressively earlier, due to the later sown oats experiencing greater amounts of water and heat stress during the flowering period. Earlier sown oats were able to maintain photosynthesis and consequently WSC content for a longer period after flowering, as they were maturing under cooler conditions. These results are quite different to the findings of Faulkner (2006) where WSC content peaked considerably later than flowering as a result of cool spring conditions and good soil moisture levels during grain filling. This allowed for continued photosynthesis and storage of WSC during the grain filling process.

In 2007, plants at all sowing dates produced broad peaks in WSC content around flowering, as a result of the mild spring conditions in this season. Despite very low levels of plant available water, the cooler atmospheric temperatures and small rainfall events were enough for the plants to maintain WSC content (matching production and storage of carbohydrate with remobilisation and grain deposition) during the first 10-15 days post flowering. Environmental conditions leading up to sampling appear to strongly influence WSC content in oaten hay. Evidence of this can be seen in Figure 3, where the WSC content of the hay varies considerably between sampling points. Because each data point was the mean of 3 bulked replicates we assume that variation resulting from soil type and nutrition was masked. It is therefore assumed that environmental conditions such as cloud cover and atmospheric temperature leading up to sampling causes most of the variability seen in these graphs.

Figure 5: The changes in Water Soluble Carbohydrate over time in oats (cv Wintaroo) with and without applied nitrogen in 2005 (Faulkner unpublished data).

Nitrogen Management

Figure 6. The effects of time of sowing and nitrogen application on the concentration of Water Soluble Carbohydrate in oats (cv Wintaroo)) in 2007. Error bars indicate LSD 5%.

The effect of nitrogen application on oaten hay dry matter yields have been well documented (Kakol et al., 2003; Loss, 2002; Pendleton and Brown, 1961; Brinkman and Rho, 1984). Their experiments show consistently that dry matter yields of oaten hay increased with increased nitrogen application. These findings are similar to the dry matter yield data obtained in this work in 2006 and 2007.

There has been limited work done on the effect of timing of nitrogen application on the quality of oaten hay however. The results in Figure 6 show that WSC content tends to fall as the rate of N increases. This is a result of the WSCs being used for the reduction of ammonium and also for additional structural material in the formation of proteins within the plant (van Herwaarden et al, 1998).

Later applications of nitrogen to oaten hay have produced inconsistent results for WSC of the hay. The data in Figure 6 shows that there was a trend towards increased WSC (not significant) by applying nitrogen at GS 31 as opposed to applications at sowing, but there was some inconsistency in the data between years. Nitrogen rate/timing experiments conducted on Wintaroo in 2006 suggested that delayed nitrogen applications resulted in lower WSC contents (Table 1), however these differences were not significant at the 5% level. Others from the same year, such as seen in Figure 7, suggest that delayed nitrogen applications can increase WSC content. There appears to be complex interactions between time of sowing and plant available water/nitrogen which require more research work in future for a better understanding of the effects.

Nitrogen Treatment


50N Sowing


50N GS 31


100N Sowing


100N GS 31


LSD 5%


Table 1. The effect of delayed N (kg/ha) on WSC in oats (cv Wintaroo) sampled at GS 61 in 2006

Figure 7: The effect of delayed application of N on Water Soluble Carbohydrates and Acid Detergent Fibre in 8 varieties of oats and two varieties of triticale sampled at GS 61 in 2006.


There is significant genetic variation within oats for the quality of forage produced (Figure 7). The varieties Riel and Brusher tended to have higher WSC and lower ADF compared to the other varieties/variety mixes within the trial. Varieties that tended to produce lower WSC and higher ADF were Kangaroo, Marloo and Wallaroo. This significant variation within oats cultivars is being exploited by the South Australian Research and Development Institutes (SARDI) oat breeding program, which selects for cultivars with better quality parameters.

Figure 8: The influence of growth regulators on the concentration of water soluble carbohydrate (WSC) and acid detergent fibre (ADF) in oats (cv Wintaroo). Error bars indicate LSD 5%.

Plant Growth Regulators (PGRs)

The use of PGRs was trialled during the 2006 and 2007 seasons to determine if 1) High yields can be maintained by preventing lodging and 2) Quality can be improved by altering the deposition of fibre within the stem. The selection of PGRs was based on results of previous work on oats (Le Feuvre, 2004). , Chlormequat and the mix of Chlormequat and Moddus produced significantly higher levels of WSC within the hay as opposed to the Nil control (Figure 8). The mix of Clormequat and Moddus was also able to significantly reduce the percentage of ADF in the hay when compared to the Nil control. The application PGRs such as Chlormequat inhibits the formation of Gibberillic Acid (GA), which causes cell extension and upwards growth. The mode of action of Moddus (trinexapac-ethyl) is less clear. It is thought to work primarily as a competitive inhibitor during GA biosynthesis (Rademacher 2000). Heckman et al (2002) also found that trinexapac-ethyl inhibits mitochondrial electron transport and as a result may also lower respiration rates. Consequently, oats that have these particular PGRs applied to them at GS 30 appear to have their growth retarded for some time. After the effects of the PGRs have worn off however, a period of rapid growth follows, commonly known as “bounce back”. This rapid period of growth appears to catch up any apparent loss of dry matter production, as there have been no significant yield losses associated with PGRs over the two years of trials (results not shown). Plants treated with PGRs tend to have thicker lower stems, leading to better resistance to lodging. It also appears that fibre (ADF and NDF) production is limited following PGR application. Further work is being conducted in this area to quantify the improved quality associated with regulant application. The cost of Moddus (Trinexapac-p-ethyl) is also a factor that may limit the commercial uptake of this technology, as it is currently only registered in sugar cane in Australia.


The quality of oaten hay is heavily influenced by the management strategies imposed on the crop. Production of consistently high quality oaten hay is achievable with a range of practices that promotes the deposition of carbohydrates within the plant. The value of the oaten hay industry to Australian farmers is substantial, therefore the adoption of such management strategies is essential to ensure end user satisfaction and potentially expand export market opportunities.


The analysis of the oaten hay samples were performed using equipment supplied by Gilmac and Balco. Their contribution to the work is gratefully acknowledged.


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