Naked oats poultry feed: what early trials found for layers, broilers

Why naked oats drew attention from the poultry industry#

Naked oats, botanically Avena nuda, had been through Australian breeding programs for years without matching the yield of ordinary hulled oats once the hull was removed. The paper explains that only recently had breeders selected lines that came close to matching conventional oats on a dry matter basis, work referenced to Barr and colleagues from 1988 and to Barr's 1990 report. One line, called Terra 11-1, was described as close to commercial release.

The appeal to feed formulators was straightforward. Naked oats tend to run high in oil and in crude protein, and unlike most other cereal grains, as their crude protein rises so do their essential amino acids, in direct proportion. For the poultry industry specifically, the oil fraction was of particular interest because it is rich in linoleic acid, a fatty acid linked to larger egg size, and the grain's metabolizable energy value looked attractive for broiler rations.

Set against that promise was a known problem. Like hulled oats, naked oats were expected to carry a reasonably high content of beta glucans, gums that can interfere with digestion and have been linked in earlier work by Cave and Burrows and by Maurice and colleagues to depressed broiler growth when naked oats made up too much of the diet. The paper set out to characterise a range of naked oat cultivars chemically and then test their performance in both broiler and layer diets, including attempts to work around the beta glucan problem with pelleting and added enzymes.

How the naked oats poultry feed trials were run#

The work combined laboratory analysis with feeding trials. Nitrogen and ether extract of grain and diet samples were measured using standard Association of Official Analytical Chemists methods, amino acids were analysed by Degussa Corporation in Germany, and metabolizable energy was assessed in adult cockerels using a rapid assay method from Farrell's own earlier work, and in growing chickens by total collection of excreta over four to five days.

Three broiler experiments were run, all confined to the starter phase of growth, housed in electrically heated brooders or small wire-mesh cages with continuous light and free access to feed and water. Diets were formulated by least-cost computer program to meet Standing Committee on Agriculture specifications. The first experiment compared a wheat-only diet against naked oats included at 200, 400, 600 and 840 grams per kilogram, fed as mash to male broiler chicks from 10 to 22 days old. The second repeated some of these diets in both mash and pelleted form. The third added a beta-glucanase enzyme or an enzyme cocktail to diets with 600 and 840 grams of naked oats per kilogram.

Two layer experiments followed. The first, at Armidale, let bantamised hybrid layers self-select between whole naked oats and either a low-protein or high-protein concentrate package, compared against a commercial 17 percent crude protein layer diet. The second, run at Parafield in South Australia between July and October 1990 using Tegel White ST hens aged 30 weeks, compared a commercial layer diet against naked oats included at 50 or 75 percent in mash or pelleted form, plus a diet with oat groats at 75 percent, pelleted.

Chemical composition and amino acid patterns#

Across experimental cultivars, crude protein content ranged from 9.8 to 18.1 percent of dry matter and oil content from 3.1 to 11.8 percent. The soon-to-be-released Terra 11-1 cultivar averaged 14.3 percent crude protein across sites in South Australia and Western Australia, and averaged 9.2 percent oil, ranging from 7.4 to 11.6 percent.

Amino acid profiles were worked out for seven cultivars spanning 13.0 to 18.6 percent crude protein, and the paper reports a linear relationship between crude protein and both lysine and threonine content, meaning these amino acids could be predicted reliably just from knowing the protein level of a given batch of naked oats. The authors contrast this with many other cereal grains, where, citing Johnson and colleagues from 1970, several essential amino acids actually fall as a proportion of crude protein when protein content rises.

Digestibility measurements told a more nuanced story. Fat digestibility and resulting metabolizable energy values were consistently lower in young chicks aged 7 to 20 days than in adult cockerels, a difference confirmed statistically by a paired t-test. This pattern, the paper suggests, reflects an improving ability of birds to digest the oil fraction of naked oats as they mature, alongside other possible factors such as the capacity of older birds to ferment non-starch polysaccharides, a point also raised in work by Annison from 1990.

Broiler performance: pelleting and enzymes make the difference#

In the first broiler experiment, increasing the inclusion of naked oats depressed growth and worsened feed conversion ratio, largely because feed intake fell as naked oat content rose in the mash diets. The second experiment showed that pelleting improved matters substantially; among the diets tested, only the pelleted naked oat diet at 30 percent matched the performance of birds on the wheat-based control.

The third experiment added enzymes to pelleted diets containing 600 and 840 grams of naked oats per kilogram. This improved both growth and feed conversion ratio significantly, to the point where performance on the 840 gram per kilogram naked oat diet equalled that of the wheat-based diet, particularly when the enzyme cocktail was used rather than beta-glucanase alone. The enzymes barely changed outcomes on the wheat-based diet itself, though feed conversion ratio improved slightly with the enzyme cocktail.

Metabolizable energy measurements on these same diets, taken across chicks aged 4 to 8 days, chicks aged 8 to 12 days, and adult cockerels, showed that enzyme addition lifted the energy value of naked oat diets by almost 2 MJ per kilogram in broiler chicks at both ages tested. On the wheat-based diet, improvement from enzyme addition only showed up in chicks aged 4 to 8 days. In adult cockerels, enzyme effects on naked oat diets were small, and on the wheat-based diet the enzyme cocktail actually reduced metabolizable energy compared to no enzyme at all, an unexpected result the paper notes without fully explaining.

Layer performance under self-selection and fixed inclusion#

In the Armidale self-selection trial, the commercial diet produced a significantly higher overall mean egg production, at 72.9 percent, than the high-protein concentrate treatments H and H2, at 65.3 and 63.6 percent respectively, but was similar to the low-protein concentrate treatment L at 70.7 percent. Peak production reached 87 percent on the control, 91 percent on H, 86 percent on L and 84 percent on H2. Egg weights were consistently heavier on the H and L diets than on the control or H2, which the authors link to the oil and linoleic acid content of naked oats and to lower bodyweights in the H2 group.

Feed intake patterns varied by treatment. Birds on diets H and H2 ate similar amounts of naked oats daily, 53.9 and 53.2 grams, while birds on L ate less, 49.8 grams. Concentrate intake was highest on L. Crude protein intake was significantly higher under the choice-feeding regimes than on the commercial diet, with H birds taking in the most at 22.0 grams per day.

At Parafield, the second layer experiment found that a 75 percent naked oat diet fed as mash produced a marked drop in egg production after week 12, an effect much less pronounced when the same inclusion was pelleted. Mean egg production stayed above 86 percent on the commercial diet and on the 50 percent naked oat diet in both mash and pelleted form, but fell to between 78 and 83 percent on the higher-inclusion diets. Daily egg mass on the commercial diet, at 48.2 grams, was similar to the 50 percent naked oat diets but significantly greater than on the 75 percent naked oat and oat groat diets. Feed efficiency was better on most naked oat and groat diets than the commercial diet, with the notable exception that 50 percent naked oat diets had significantly lower feed efficiency than other naked oat treatments.

Reading the results against earlier work#

The paper's metabolizable energy figures for naked oats, between 14.8 and 15.2 MJ per kilogram for young chickens, came in higher than the 13.31 MJ per kilogram reported earlier by Maurice and colleagues. That earlier study had also found growth depression in broilers above 40 percent naked oat inclusion, which the authors attributed to phytic acid causing a phosphorus deficiency, while feed conversion ratio in that trial stayed unaffected. Cave and Burrows reported a comparable depression in broilers grown from 28 to 48 days on diets with 30 and 60 percent naked oats.

A more detailed study by Cave and colleagues from 1990 found that naked oat mash diets reduced feed intake and weight gain and raised feed conversion ratio in broilers over 28 days. Adding beta-glucanase improved growth in birds aged 8 to 20 days on a 60 percent naked oat diet, but other interventions, including penicillin, EDTA or autoclaving the oats, gave no convincing benefit. That team concluded beta glucans, not phytase, were behind the growth depression, though they could not demonstrate any rise in true metabolizable energy from enzyme addition, a point of contrast with the clearer energy gains reported in the present paper.

On the layer side, the authors note there is little published work on oat groats in layer diets beyond a report by Karunajeewa and Tham on changes in egg fatty acid content with groat inclusion, which did not address production parameters. The authors also flag that their use of an experimental bantamised layer strain may have clouded the Armidale results, since two batches of birds on the identical H concentrate performed quite differently, a gap they attribute to bodyweight differences at point of lay rather than to the diets themselves.

What this means for feeding naked oats in practice#

The authors conclude that naked oats show real promise as a near-complete poultry feed, but with qualifications. For broilers, pelleting plus the right enzyme additions let naked oats replace wheat at very high inclusion rates, up to 840 grams per kilogram, without sacrificing growth or feed conversion. For layers, the picture was more mixed: at inclusion above 50 percent, or oat groats at 75 percent, laying performance suffered whether or not the diet was pelleted, though pelleting clearly helped at the higher naked oat inclusion level compared with mash.

The core tension the authors identify is between the very high energy value of naked oats and their amino acid concentrations, which can lead birds to reduce feed intake and, as a result, take in less of several essential amino acids than intended. They describe this as a solvable formulation challenge rather than a fundamental barrier, and they are careful to say that in commercial practice naked oats would not likely be used as the sole grain source for broilers, even though their pelleted, enzyme-supplemented diets had achieved that in trial conditions.

We would treat these findings as a promising first pass rather than a settled recommendation. The broiler trials were short, confined to the starter phase of growth over periods of a few weeks, and the layer work involved small numbers of birds per treatment at two sites, with one trial acknowledged by the authors to be affected by unexplained batch differences in the bird stock used. The authors themselves call for more extensive production trials before firmer conclusions are drawn, a point this summary endorses given the scale of the experiments described.

This paper was presented within the Recent Advances in Animal Nutrition community, alongside other proceedings gathered in the RAAN Conference Proceedings collection, and sits in the broader Livestock Library research index covering feeding, breeding and management research relevant to Australian producers.

Sources and further reading#

• Trove library search: find a library that holds the paper
• Animal Genetics and Breeding Unit
• Feedipedia animal feed database: an open-access database of animal feeds
• Poultry Hub Australia: poultry science information

Questions#

— The Livestock Library team