Ostrich nutrition in young and breeding birds: what a 1991 review found

Why ostrich nutrition lagged behind other poultry species#

By 1991, ostriches had been farmed for plumes, and later hides and meat, for well over a century, yet the paper notes that published nutrition and management information remained scarce compared with what existed on physiology, ecology and artificial incubation. Du Preez set out to summarise what little was known and to fill gaps with theoretical predictions for growing and breeding birds, while naming research priorities to put ostrich farming on firmer scientific footing.

The approach taken reflects an industry still working out basic numbers. Rather than running new feeding trials, the paper draws on growth curve studies, carcass composition data and a modelling method originally built for turkeys, adapting it to ostriches because direct experimental data did not yet exist. This is explicitly presented as a stopgap: hypotheses to be tested, not settled answers.

The paper sits within a wider set of proceedings addressing nutrition across livestock species, and other papers from the same era can be found in the RAAN Conference Proceedings collection.

Growth curves and carcass data behind the calculations#

Du Preez, Jarvis, Capatos and De Kock had earlier studied the growth of ostriches from three regions of Southern Africa, an area covering most of the world's ostrich population at the time, and found significant differences in growth rate between birds from different regions and between sexes. Degen and colleagues separately described a growth curve for ostriches of mixed sexes that closely resembled the Namibian growth pattern reported by du Preez and colleagues.

To estimate amino acid requirements, the paper used carcass analysis from birds ranging from birth to maturity. Sacrificed birds were defeathered, had the intestinal tract contents removed, and were analysed for moisture, ash, protein and lipid, with dry, lipid-free samples further analysed for amino acids. Because no replicate samples existed at each age or body size, the paper could not establish variation in protein, lipid and ash composition, and the data were not sufficient to describe how protein mass increases with growth mathematically.

Body protein build-up was taken as the central quantity in working out amino acid requirements, using a method set out by Emmans for turkeys. Coefficients of 0.73 and 0.63 were used to convert dietary lysine and sulphur-containing amino acids respectively into body amino acid, values borrowed from poultry research by Fisher and Emmans because no ostrich-specific figures were available. The paper is explicit that any mismatch between predicted and measured ostrich requirements would point to these borrowed coefficients needing revision.

Comparing predicted lysine needs with early feeding trials#

Two existing feeding studies gave the paper something to check its predictions against. Swart and Kemm examined protein needs of ostriches weighing between 60 and 110 kg, with lysine making up 5% of protein in the experimental diets; the highest daily gain of 235 g occurred when birds consumed about 2.2 kg per day of a 14% protein diet, equivalent to 15.2 g of lysine per day. Gandini and colleagues, working with chicks between 1 and 9.5 kg, found the best feed conversion on a 20% protein diet, with a calculated mean lysine intake of 2.73 g per bird per day and average mass gain of 163 g per day on 275 g of diet.

Du Preez judged the lysine figure from the Gandini trial broadly consistent with the paper's own predictions for young growing birds, but flagged the 15.2 g figure from the Swart and Kemm trial as unusually high, suggesting a possible amino acid imbalance in that diet rather than a true requirement. The paper is careful to add that lysine has not actually been demonstrated to be an essential amino acid for ostriches in the way it has for poultry, an important caveat given how much of the modelling assumes it behaves similarly.

This is where the review's evidence is thinnest: predictions built from a single mature carcass and poultry-derived coefficients are being tested against two small trials rather than a body of replicated experiments. We would treat the lysine and amino acid estimates in this paper as reasoned starting points for diet formulation rather than confirmed requirements, given the author's own acknowledgement that confidence intervals could not be calculated from a single-bird analysis.

Feeding, housing and environment for young chicks#

Newly hatched chicks lack an egg tooth and must work their way out of a strong shell using their legs and a third phalange, surviving up to six or more days without food or water on yolk reserves. The paper recommends that food and water be made easily accessible so chicks can learn to find them early, and that warmth similar to recommendations for poultry chicks be provided for about four weeks after hatching.

Floor area and stocking density recommendations are borrowed cautiously from broiler poultry research, with the paper noting that the ideal maximum mass gain density for broilers in environmentally controlled houses is around 30 kg live mass per square metre, with roughly half that in convection-ventilated housing. Du Preez stresses these broiler figures should not be applied directly to ostriches given the species' sensitive temperament, even after domestication.

Ventilation guidance follows a similar borrowed logic: a general rule of 4 m3 per kg live mass per hour, with feeding space of 4 cm per kg live mass and water space at 20% of that figure. The normal cloacal temperature of adult ostriches is given as 39.3°C, and dim lighting around 5 lux, as used in broiler houses to keep birds docile, is suggested as potentially useful for young ostriches too, though this remains an assumption rather than a tested finding for the species.

Estimating feed intake and water needs#

Using an energy system developed by Emmans, the paper estimates daily feed allowance by combining maintenance heat requirements with the energy cost of protein and lipid gain, converting these into kilojoules using values of 56 MJ per gram of lipid and 50 MJ per gram of protein. Graphs in the paper show expected energy intake and estimated feed allocation across different body weights, though the underlying constants have not been confirmed experimentally for ostriches.

Water requirements measured by Withers found adult ostriches consumed 8 litres per day while eating 5 kg of dry alfalfa daily under experimental conditions, and that withholding water led to a sharp decline in feed intake, cutting it by 84 percent. Degen and colleagues separately reported a water-to-dry-matter feed intake ratio of nearly 2.31.

Du Preez identifies the nutritional value of ostrich feedstuffs as the area where information is most lacking, since energy values of diet ingredients are essential for predicting how much birds will actually eat. Without this basic ingredient data, even well-constructed intake models remain theoretical exercises rather than practical feeding tools.

Breeding season patterns and egg production#

Wild ostriches take three or more years to reach sexual maturity, with males needing four years, though domesticated birds given adequate nutrition can be ready to breed at just over two years of age. Breeding is seasonal, typically starting in winter, and a sample of 26 females across 13 pairs showed a pattern of laying roughly one egg every second day before resting seven days.

Over a 147-day period, three laying peaks emerged at about 49-day intervals, matching field observations of three peaks in 150 days reported elsewhere. From 3822 potential laying days among the 26 females, the paper calculated 940 eggs, which doubles when accounting for the every-second-day laying pattern to 49.2% to allow comparison with poultry; adjusting for the estimated 22 productive females in the flock raised this to 58%. This translates to 36 eggs per female per season across all females, and 42 eggs per female per season among productive females. Private communication cited in the paper described individual females on established farms producing 75 eggs through selection for breaking the laying pause.

Daily nutrient demand for egg production was modelled using a method from King describing a sigmoidal rise in requirements driven by follicle growth, lay rate and clutch size, with the period of follicular growth in ostriches estimated at 16 days, meaning additional nutrient demand might begin 18 days before the first egg and peak eight days beforehand. Tables in the paper give daily amino acid and energy requirements for breeding birds, while noting that increases in bird size of 5 kg have a smaller effect on requirements than changes in egg size or skipped laying days.

Practical handling, hatching success and the gaps that remain#

The paper gives practical guidance for handling adult birds given their capacity for aggression, recommending that anyone entering a pen carry a long forked implement fitted with dark material on the end, fences 2 m high with seven strands of barbless wire, and solid wood loading chutes and catch pens 2.5 m high to prevent injury. Breeding paddocks of a quarter hectare with one male per pair of females are described, alongside a ranch-style alternative using a mating ratio of 3 to 4 females per male.

Hatching success of fertile eggs can reach a figure close to 85%, with eggs cooled to 16°C and set within 2 to 5 days of collection, since longer storage reduces hatching success. Survival to 16 weeks in natural African habitat averaged a poor 36.9% and 43.4% across two seasons, although successful commercial farms reported survival of 90% and more to the same age, a gap the paper attributes largely to management quality.

Du Preez closes by listing unresolved questions: body composition differences by sex and genotype, whether amino acid requirements genuinely differ between maintenance and growth, whether lysine is truly essential for ostriches, and whether coefficients borrowed from poultry hold up under direct testing. The recommendation to slaughter five to ten birds per body size to properly measure variation underlines how preliminary the whole quantitative framework still was at the time of writing. Later industry work, such as quantifying semen and egg traits in an ostrich flock and a review of ostrich leather quality, can be found alongside this one in the Livestock Library research index.

Sources and further reading#

• Trove library search: find a library that holds the paper
• Feedipedia animal feed database: an open-access database of animal feeds
• Poultry Hub Australia: poultry science information
• AgriFutures Australia: which funds chicken meat and other rural industry research

Questions#

— The Livestock Library team