Z. Brand

The effect of dietary energy and protein levels on production in breeding female ostriches

1. In a study spanning two breeding seasons, we assessed the effect of different dietary energy and protein levels on body mass, body condition, and egg production of female ostriches. 2. During the first breeding season, groups were given diets with energy concentrations of 8·5, 9·5 and 10·5 MJ/kg dry mass (DM) metabolisable energy (ME) and protein concentrations of 135, 150 and 165 g/kg. In the second breeding season, groups were given diets with ME of 7·5, 8·5 and 9·5 MJ/kg and protein contents of 105, 120 and 135 g/kg. 3. Body mass of birds on diets of 7·5 and 8·5 MJ/kg ME decreased significantly in the course of the breeding season compared with birds fed on diets with higher energy contents and body measurements decreased, suggesting a loss of body condition. 4. Females fed on diets containing only 7·5 MJ/kg ME produced significantly fewer eggs at significantly longer intervals, resulting in fewer chicks hatched. 5. There was no significant difference in egg mass, initial chick mass, chick survival to one month of age and body mass of chicks at one month. 6. Dietary protein concentrations had no effect on egg production, egg mass, hatchability, initial chick mass, chick survival or chick mass at one month old. 7. The female ostriches regained their original body mass during the 4-month rest period between breeding seasons, but significant differences in some parameters during the second breeding season suggest that they may not have fully recovered their body condition. 8. A dietary energy content of 7·5 MJ/kg proved to have an adverse effect on egg production by breeding female ostriches, and it may be concluded from this study that a diet containing 8·5 MJ ME/kg DM and 105 g/kg protein should be regarded as the minimum that can be used for breeding female ostriches without compromising egg production.

The development of ratite production through continued research

This paper summarises research on farmed ratites and their industries over the past 100 years. Commercial ratite products include meat, skins, feathers and oil. Research on ratites has attempted to enhance the quantity and quality of these products by focusing on the disciplines of breeding and genetics, reproduction and incubation, assisted reproduction, nutrition and animal welfare. Advances in these disciplines are discussed, and directions for future research are provided.

Genetic relationships between water loss and shell deaths in ostrich eggs, assessed as traits of the female

The ostrich industry suffers from a high rate of embryonic mortality during artificial incubation of eggs. Data from 34285 eggs were used to derive 969 female-year records for evaporative water loss (WL), treated as a trait of the female. Heritability was significant for WL at a level of 0.40–0.41 (both after 21 and 35 days of incubation). WL at 21 and 35 days was negatively correlated on the genetic level with chick weight at hatching (–0.84 and –0.81, respectively). Shell deaths did not exhibit high levels of genetic variation (0.06), but were affected by the permanent environment of the female (0.33). Shell deaths were correlated with WL on a genetic level (–0.34 to –0.41), but the estimated genetic correlations were associated with high standard errors and are, therefore, not very robust. Further research is needed to obtain more accurate genetic relationships between traits influencing incubation.

Embryonic development in the ostrich (Struthio camelus) during the first 7 days of artificial incubation

Abstract 1. Early development of ostrich embryos was investigated in relation to time of egg collection and genotype. 2. A total of 321 ostrich eggs were collected during the 2008 and 2009 breeding seasons and the development of the embryo for up to the first 168 h of incubation was described and analysed. A sample of the incubated eggs was weighed and opened daily to investigate developmental changes. 3. In fresh eggs, the blastoderm contained a round, translucent dark area pellucida (AP) in the centre, with a surrounding thin white ring, likely to be the beginning of the area opaca (AO). Fresh eggs were considered infertile if the blastoderm was absent and instead numerous white droplets were present surrounded by vacuoles. 4. The average blastoderm area of a fresh fertile egg was 15.8 mm2, increasing to 143.3 mm2 after 2 d of incubation. By 72 h of incubation the area vasculosa (AV) was discernible in the posterior half of the blastoderm. 5. At 48 h of incubation the blastoderm area in eggs from the South African Black genotype (SAB) × Zimbabwean Blue genotype (ZB) crosses (104.5 ± 18.6 mm2) was lower than the pure SAB (141.0 ± 10.5 mm2), ZB (161.7 ± 13.5 mm2) and ZB × SAB crosses (166.1 ± 14.2 mm2). 6. Embryo length was 5.01 mm after 72 h of incubation and 14.5 mm after 168 h of incubation. At 168 h of incubation AV lengths for both ZB × SAB (53.2 mm) and SAB × ZB crosses (54.1 mm) were longer than in embryos from the pure breeds. 7. Results from this study can be put to practical use when determining whether eggs are infertile or fertile and also in investigating the age of early embryonic mortalities.

Heritability of embryonic mortalities in ostrich eggs and factors affecting hatching failure of fertile eggs during artificial incubation

The high rate of embryonic mortality during artificial incubation of ostrich eggs is a major concern in the ostrich industry. Data from 48 126 individual egg records were available to derive genetic parameters for embryonic mortalities, modelled as a trait of the individual egg. Embryonic mortality was classified according to stage of death, i.e. early embryonic mortality that occurred before 21 days of incubation (EEM), late embryonic mortality that occurred after 21 days of incubation (LEM) and overall embryonic mortalities (OEM). LEM increased significantly for eggs laid by females >10 years old. Transfer of eggs between incubators during incubation also impaired hatchability. An increase in OEM occurred for eggs freshly set (43%) as well as for eggs stored for more than 6 days (50%). Medium heritability (h2) estimates were derived for all the embryonic death traits and ranged between 0.16 ± 0.02 for LEM and 0.22 ± 0.03 for EEM. The dam permanent environmental effect was low ranging between 0.021 ± 0.005 for LEM and 0.046 ± 0.008 for EEM. Hatchability of fertile ostrich eggs may consequently be improved by removing older females from breeding flocks, setting of eggs between 2 and 6 days after collection, and by refraining to transfer of eggs between incubators during incubation. Moderate h2 estimates indicate that breeding may be used as a tool to enhance chick production in ostriches. This contention is supported by the fact that selected breeding for chick production and liveweight appeared to result in genetic changes in embryonic mortality rates.

Ostrich (Struthio camelus) embryonic development from 7 to 42 days of incubation

ABSTRACT 1. Hatching success of ostrich eggs is poor (50–60% of fertile eggs). The current study was designed to identify the timing of key stages in the development of the ostrich embryo. 2. Growth of both embryo and wing length during 42 d of incubation was comparable and approximately linear, with a more or less weekly doubling in size up to 35 d of incubation. 3. The embryo eye size increased more rapidly than beak length and reached a maximum of ~16.2 mm by 28 d of incubation, whereas beak length increased continuously until hatching at 42 d. 4. Linear regression equations were derived from morphometric measurements of embryos between 7 and 42 d. 5. Information stemming from these results can be used to estimate the age of dead-in-shell embryos in an attempt to identify timing of incubation problems that potentially result in low hatchability of fertile eggs.

Effect of cottonseed oilcake as a protein source on production of breeding ostriches

Abstract South Africa currently produces 70% of the world’s ostrich products. The profit margin of South African producers from the sale of ostrich meat, leather and feathers currently stands at 20%, 65% and 15%, respectively. Local producers want to increase the production of ostrich products but keep production costs as low as possible. Maintaining optimal nutrition of breeding stock is necessary to increase the production of ostrich chicks, thereby decreasing the fixed costs per chick. This research examined the impact on ostrich reproduction of replacing soya oilcake (SOC) as a protein supplement with cheaper cottonseed oilcake (CSOC). Although there are no data available on the impact of CSOC feed on ostrich reproduction, it is well known that gossypol, a naturally occurring toxin in cotton plants, negatively affects male reproduction in other monogastric species and that it may also reduce appetite. Ninety-six breeding ostrich pairs were divided into two groups to compare the effects of diet (CSOC and SOC) during the breeding season on ostrich-breeding parameters. The replacement of SOC with CSOC had no significant effect on the number of total eggs produced (47.8 ± 5.3 versus 48.3 ± 5.1 per breeding pair, respectively) or infertile eggs (31.5 ± 3.9 versus 38.0 ± 5.2, respectively). Also, the number of dead-in-shell chicks did not differ significantly between groups (20.2 ± 3.3 versus 26.8 ± 3.8, respectively). Even though none of these breeding parameters differed, the replacement of SOC with CSOC in the diets of breeding birds led to significantly more chicks hatching per hen from breeding birds fed on the SOC (36.1 ± 4.8) than the CSOC diet (17.2 ± 3.8). Although it would thus seem that feeding breeding ostriches CSOC instead of SOC as a protein supplement will have a detrimental effect on chick production, more data are required to deliver a definitive answer.

Genetic parameters for eggshell traits in ostriches

1. A study was conducted on ∼14000 ostrich eggs to estimate genetic parameters for eggshell traits that could benefit the hatchability of ostrich eggs. Traits measured included the number of pores on the eggshell, the average diameter of these pores, the total area of pores on the eggshell, permeability (pore area/shell thickness) and eggshell thickness. 2. Heritability estimates ranged from 0·16 for total pore area to 0·41 for the natural logarithm of pore count. The heritability estimates for water loss on 21 and 35 d (WL21 and WL35) of incubation were high at 0·23 and 0·24, respectively. 3. On a genetic level, pore count was negatively correlated with average pore diameter (−0·73) and shell thickness (−0·28), whereas it was positively correlated with total pore area (0·58), WL21 (0·24) and WL35 (0·34). The direct and maternal genetic correlations of pore count with total pore area (0·58) and permeability (0·59) were high and significant. Permeability was positively correlated to WL21 and WL35, both on the direct and maternal genetic levels. 4. The estimated genetic parameters indicate that it should be possible to select for the various eggshell traits in ostrich eggs, or for permeability and water loss. However, as a trait with an intermediate optimum, direct selection for permeability and other eggshell traits would not be straightforward, and the possible application of these results to improve hatchability of ostrich eggs in the future needs consideration.