The effect of dietary energy and protein level on feather, skin and nodule growth of the ostrich (Struthio camelus).

Accurate diet formulations are required to fulfil the nutrient requirements of birds in order to achieve optimal production. Knowing how the skin, nodule and feather production characteristics vary with diets of different nutrient densities will help in least-cost modelling. Feather growth and nodule development are factors that were previously neglected in ostrich diet formulation, both of which are essential for the development of a predictive production model. In this trial, 120 birds were placed in 15 pens. Varying energy regimes (high, medium and low) and accompanying protein and amino acid profile levels (level 1-5) were assigned ad libitum to each pen. A randomly selected bird from each pen was slaughtered at 1, 35, 63, 103, 159, 168 and 244 days of age. During the slaughter, each bird was weighed, stunned, exsanguinated, defeathered and eviscerated. Feathers from four regions of the skin were plucked and weighed. The shaft diameter of the wing feathers was measured. The nodule size of the tanned skin was measured for each slaughter age. The data were transformed to natural logarithms and regressed against the total feather weight and the total featherless empty body protein weight to set up allometric growth equations. A prediction equation to determine nodule size of the live bird was proposed. Feed cost optimisation is paramount, and results from this study will aid in setting up least-cost optimisation (simulation) formulation models.

The effect of varying dietary nutrient densities on the relative growth of ostrich body components.

The influence of varying dietary protein and energy levels on the relative growth of body components of ostriches was evaluated over a 244-day growth period. One hundred twenty 1-day-old ostrich chicks were randomly assigned to 15 pens. Three varying energy regimes (high, medium and low) and five protein levels (1-5) were supplied ad libitum to each pen. A randomly selected bird from each pen was slaughtered at 1, 35, 63, 103, 159, 168 and 244 days of age. Each bird was weighed, stunned, exsanguinated, defeathered and eviscerated. Individual body components were dissected and weighed at every slaughter age. Proximate analysis was performed on these components, which were ground with the remainder of the carcass, excluding gut content, but including blood and feathers. Based on the analysis of ostrich feathers and the known mass of the feathers, the protein mass contribution of the feathers was deducted from the protein accretion of the bird. All the data were transformed to natural logarithms and regressed against the featherless body protein growth. Intercepts and slopes were compared to determine differences in growth rate ascribed to nutrient densities. Neither dietary energy nor dietary protein level had a significant effect on the relative growth of the measured components in this study. Allometric coefficients were established, which could be helpful to improve the accuracy of simulation modelling attempts for ostrich nutrition.

Soluble and insoluble fibers in ostrich nutrition: influences on growth performance and blood biochemical indices during different ages.

This experiment was undertaken to evaluate the effects of different levels of soluble and insoluble fibers on growth performance and blood indices in ostrich at the age of 1 to 6 months. Thirty 30-day-old ostriches (males and females) were randomly assigned to five treatments with six replicates. There were five dietary treatments consisted of (1) basal diet; (2 and 3) diets containing 2 and 4% more soluble fibers (SF) than basal diet, and (4 and 5) diets containing 2 and 4% more insoluble fibers (ISF) than the basal diet. The dietary treatments had no significant influence on growth performance of ostriches. By increasing the levels of SF and ISF, the concentration of blood glucose (P < 0.0001) and high-density lipoprotein (HDL, P = 0.0046) increased, while the plasma concentration of triglyceride (P < 0.0001) and very-low-density lipoprotein (VLDL, P = 0.0006) decreased. The plasma enzyme activity of alanine aminotransferase (ALT) decreased in ostriches fed diet containing 4% more SF as compared with control (P < 0.0006). Body weight gain (BWG) at the starter phase (3-4 months) was higher than the pre-starter (1-2 months) and grower (5-6 months) phases (P < 0.0001). The highest concentration of blood glucose was observed at 2 months of age while the lowest magnitude was found at 4 months of age (P < 0.0001). The plasma cholesterol concentration increased at 4 months and decreased at 6 months as compared with 2 months (P < 0.0001). The concentration of HDL and LDL at 4 months of age was higher than two other ages (P < 0.0001). The blood concentration of triglyceride (P < 0.0001), VLDL (P < 0.0001), and ALT (P = 0.0005) decreased as ostriches grew up. It could be concluded that increasing the levels of soluble and insoluble fibers in the diet up to 4% more than previous recommendation may not have negative effects on growth performances and blood indices in ostrich.

Extensive human presence and regular gentle handling improve growth, survival and immune competence in ostrich chicks.

A total of 416 day-old ostrich chicks were randomly allocated to one of the three different husbandry practices for 3 months after hatch; HP1 (extensive human presence with gentle human voice, visual and gentle physical stimuli), HP2 (similar to HP1 but without physical stimuli) and S (human presence limited to supply of feed and water). Chick weight (kg) was measured at 6 and 12 weeks of age, while mortalities were recorded daily to calculate the survival rate. Finally, chicks' antibody responses to vaccination against Newcastle disease (NCD) was measured using the Hemagglutination-Inhibition (HI) test at 20 weeks of age. While HP1 chicks were heavier and survived better to 6 weeks of age than HP2 and S chicks (p < .05), no difference was observed thereafter (p > .05). Furthermore, HP1 chicks had an improved immune competence, as illustrated by their lower percentage of positive HI titers, compared to HP2 and S chicks (p < .05). Hence, integrating extensive human presence with positive human-chick interactions may assist in alleviating challenges related to chick rearing in the ostrich industry.

Ontogenetic scaling of pelvic limb muscles, tendons and locomotor economy in the ostrich (Struthio camelus).

In rapidly growing animals there are numerous selective pressures and developmental constraints underpinning the ontogenetic development of muscle-tendon morphology and mechanical properties. Muscle force generating capacity, tendon stiffness, elastic energy storage capacity and efficiency were calculated from muscle and tendon morphological parameters and in vitro tendon mechanical properties obtained from a growth series of ostrich cadavers. Ontogenetic scaling relationships were established using reduced major axis regression analysis. Ostrich pelvic limb muscle mass and cross-sectional area broadly scaled with positive allometry, indicating maintained or relatively greater capacity for maximum isometric force generation in larger animals. The length of distal limb tendons was found to scale with positive allometry in several tendons associated with antigravity support and elastic energy storage during locomotion. Distal limb tendon stiffness scaled with negative allometry with respect to body mass, with tendons being relatively more compliant in larger birds. Tendon material properties also appeared to be size-dependent, suggesting that the relative increased compliance of tendons in larger ostriches is due in part to compensatory distortions in tendon material properties during maturation and development, not simply from ontogenetic changes in tendon geometry. Our results suggest that the previously reported increase in locomotor economy through ontogeny in the ostrich is due to greater potential for elastic energy storage with increasing body size. In fact, the rate of this increase may be somewhat greater than the conservative predictions of previous studies, thus illustrating the biological importance of elastic tendon structures in adult ostriches.

Influences of dietary crude protein and stocking density on growth performance and body measurements of ostrich chicks.

Thirty-six African Black ostrich chicks were used to investigate the effects of dietary crude protein (CP) levels (180, 210 and 240 g/kg), stocking density (4.5 and 3 m2/bird) and their interactions. A factorial arrangement was used to examine the impact of treatments on growth performance and body measurements of ostrich chicks during 2 to 10 weeks of the age. Results indicated that factors studied did not change growth performance traits. The highest value of protein efficiency ratio was observed in ostrich chicks fed diet contained 240 g/kg diet. Birds fed diet contained 240 g CP /kg diet and kept at stocking density of 3 m2 per bird had numerically the highest protein efficiency ratio. Shank girth and tibiotarsus length decreased with increasing dietary CP level. Stocking density did not change values of body measurements, except tibiotarsus length at 6 weeks of age, which increased in birds kept at the lower density than the higher. Body height at 10 weeks of age was significantly affected by the interactions between dietary CP and stocking density. In conclusion, results affirmed that ostrich chicks can grow on diets containing low levels of CP (180-210 g/kg). Our results provide a comprehensive set of morphometric data for ostrich chicks as affected by the factors studied.

Major shifts in gut microbiota during development and its relationship to growth in ostriches.

The development of gut microbiota during ontogeny is emerging as an important process influencing physiology, immunity and fitness in vertebrates. However, knowledge of how bacteria colonize the juvenile gut, how this is influenced by changes in the diversity of gut bacteria and to what extent this influences host fitness, particularly in nonmodel organisms, is lacking. Here we used 16S rRNA gene sequencing to describe the successional development of the faecal microbiome in ostriches (Struthio camelus, n = 66, repeatedly sampled) over the first 3 months of life and its relationship to growth. We found a gradual increase in microbial diversity with age that involved multiple colonization and extinction events and a major taxonomic shift in bacteria that coincided with the cessation of yolk absorption. Comparisons with the microbiota of adults (n = 5) revealed that the chicks became more similar in their microbial diversity and composition to adults as they aged. There was a five-fold difference in juvenile growth during development, and growth during the first week of age was strongly positively correlated with the abundance of the genus Bacteroides and negatively correlated with Akkermansia. After the first week, the abundances of six phylogenetically diverse families (Peptococcaceae, S24-7, Verrucomicrobiae, Anaeroplasmataceae, Streptococcaceae, Methanobacteriaceae) were associated with subsequent reductions in chick growth in an age-specific and transient manner. These results have broad implications for our understanding of the development of gut microbiota and its associations with animal growth.

Feather and skin development of ostriches Struthio camelus.

Information on feather and skin growth is important for the development of mathematical optimisation nutritional models for ostriches. Ostriches (n = 65) were subjected to a four-stage formulated growth diet programme (pre-starter, starter, grower and finisher), with declining protein and energy content. Nine birds were weighed, stunned, exsanguinated, defeathered, skinned and eviscerated at 1, 54, 84, 104, 115, 132 and 287 days of age. Feathers from four pre-selected locations on the body were harvested and weighed. The wet skin weight, wet unstretched skin size and wet unstretched crown size were measured at each slaughter stage. The live weight, feather and skin yields of the birds increased with age at slaughter, as did feather shaft diameter. Prediction models were developed to estimate the yield of the skin in terms of live weight and of empty body protein weight to aid in diet formulation. The allometry of feather growth was determined from total feather weight, as the maturation rates of the feathers differ from that of the ostrich body. Results from this study will aid in setting up a mathematical optimisation nutritional model for ostriches.

Morphology of the extraocular muscles (m. bulbi) in the pre-hatchling and post-hatchling african black ostriches (struthio camelus domesticus L., 1758) (Aves: Struthioniformes).

The aim of the study was to describe the morphology and the development of the extraocular muscles (EOMs) in the pre-hatchling and post-hatchling African black ostrich. The study involved 50 birds aged between 28 days and 3 years. The EOMs were analyzed morphologically with respect to the location and length of the straight and oblique muscles and the third eyelid muscles, the length and breadth of their tendons as well as the distance and shape of the muscle tendon insertions at the corneal limbus. A histological and histometric analysis were also carried out. The greatest increase in the length of the EOMs was noted in groups III-V. A marked increase in the length of the tendons of the dorsal straight muscle was found in groups II and III, in the tendons of the nasal straight muscle in groups IV and V, in the tendons of the dorsal oblique muscle in groups III to V and in the tendons of the ventral oblique muscle in groups IV and V. There was a significant increase in the breadth of the dorsal straight and ventral oblique muscle tendons in groups IV and V and the tendons of the pyramidal muscle in groups III and V. The distance of the distal insertion of the tendon at the corneal limbus increased steadily with age in all the examined groups. The number of fascicles and muscle fibres, their diameter and length in all the studied EOMs were different in the different groups.

Growth Performance, Mineral Digestibility, and Blood Characteristics of Ostriches Receiving Drinking Water Supplemented with Varying Levels of Chelated Trace Mineral Complex.

The effects of water supplementation of chelated trace minerals (CTM, which is named Bonzaplex designed with chelate compounds technology) on growth performance, apparent total tract digestibility (ATTD) of minerals, and some blood metabolites, TM, and antioxidant enzyme values in African ostriches were investigated from 8 to 12 months of age. A total of 20 8-month-old ostriches (five birds in five replicate pens) was randomly allocated into one of the following four treatments: (1) control (basal diet + tap water), (2) low CTM (basal diet +100 mg/bird/day CTM powder in tap water), (3) medium CTM (basal diet +1 g/bird/day CTM powder in tap water), and (4) high CTM (basal diet +2 g/bird/day CTM powder in tap water). Compared with control, medium CTM improved (P < 0.05) daily weight gain and ATTD of phosphorous, zinc, and copper in 12-month-old ostriches. Furthermore, the feed conversion ratio was lower, and ATTD of magnesium was higher in the medium- and high-CTM groups than that in the control group (P < 0.05). At the end of the trial, ostriches receiving high-CTM treatment exhibited the lower (P < 0.05) serum triglyceride and very low-density lipoprotein cholesterol concentrations and higher copper levels compared to those of the control treatment. Supplementation of higher amounts of CTM (medium and high CTM) also increased the activity of serum superoxide dismutase (P < 0.05). No differences were detected for other blood parameters including glucose, total protein, albumin, cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, iron, magnesium, and glutathione peroxidase values. In conclusion, supplementation of CTM at the level of 1 g/bird/day to the drinking water can be recommended for improving growth performance, mineral absorption, and antioxidant status of ostriches fed diets containing the recommended levels of inorganic TM.

The effect of dietary energy and protein levels on body weight, size, and microflora of ostrich chicks.

The aim of this study was to evaluate the effect of different dietary energy and protein supplements on performance, weekly body sizes or body frame size, and microbiota of ostrich chicks during 2-9 weeks of age. Two metabolic energy levels of 2400 and 2600 kcal/kg live weight and three protein levels of 20, 22, and 24% were used. A total of 36 ostrich chickens (Struthio camelus) of the blue and black African breed were used. Body weight, 12 body measurements (i.e., circumference of the head, neck, breast, abdomen, thigh, body height, length of tail, list the other 5 here) and excretion of microbial population (Escherichia coli, Coliforms bacteria, and Lactobacillus bacteria) were measured. Mean body weight in each week of the experiment was generally the lowest when chicks were offered 2600 kcal/kg dietary energy and 24% protein. Of the 12 body measurements, the breast, abdomen, and thigh circumference and also body length were greater at the lower energy (2400 kcal/kg) and higher protein (24%) levels. Total Aerobic bacteria excretion was generally lower in response to the diet containing the higher level of energy. We conclude that ostrich chickens during 2-9 weeks of age can grow on diets that contain lower energy levels.

Developmental morphology study on the stomach of African ostrich chicks.

This study investigates the developmental morphology changes on the proventriculus and gizzard of African ostrich chicks using gross anatomy, and light and transmission electronic microscopy. The body weight; the weight of the proventriculus and gizzard; the thickness of simple tubular glands, muscularis mucosae, compound tubular glands, and muscular layer of the proventriculus; and the thickness of the gizzard glands and muscularis mucosae were measured on postnatal d one, 45, 90, and 334. Under transmission electronic microscopy, the oxynticopeptic cells, mucous cells, and endocrine cells were observed in the proventriculus on postnatal d one, 45, and 90. Our results revealed that the weights of the proventriculus and gizzard (relative to the body weight) both peaked on d 90, respectively, and declined thereafter. The thicknesses of the simple tubular glands, muscularis mucosae, compound tubular glands, muscular layer of the proventriculus, and gizzard glands increased with increasing bird age. However, the thickness of the muscularis mucosae in the gizzard peaked on d 90 and gradually decreased thereafter. The result of transmission electron microscopy revealed that the glands in the submucosa layer of the proventriculus did not differ from other cell types, aside from an increase in cell diameter and an increase in cytoplasmic content. A significant increase in the number of mitochondria and smooth endoplasmic reticulum was noted, as well as an in granules secreted by endocrine cells. Therefore, to improve brood rates of reared African ostrich chicks, feed management ought to be enhanced between postnatal d one and day 90.

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

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.

Effects of exposing ostrich eggs to doses of gamma radiation on hatchability, growth performance, and some blood biochemicals of hatched chicks.

Effects of radiating ostrich eggs before incubation on hatchability, growth performance, and some blood components of ostrich chicks were studied. 72 ostrich eggs were randomly distributed into four groups. The first group was kept without exposure to gamma radiation (control). The 2nd, 3rd, and 4th groups were exposed to 0.8, 1.6, and 3.2 Gy, respectively, of 60Co gamma rays just before incubation. Total bacterial counts (×103 CFU) were significantly increased with the increase in gamma radiation levels before incubation. Feed conversion was lower (P ≤ 0.01) in the control group than those irradiated. Embryonic mortality rate (%), hatchability (%) and chick weight at hatch, body weight, daily body weight gain, feed consumption, and all of hematology parameters studied were insignificantly fluctuated with the doses of gamma rays used. Serum concentrations of total protein, albumen, globulin, glucose, and triiodothyronin of the chicks from eggs of the control and the 1st group were significantly the highest. Chicks of the control group had significantly the lowest values of serum concentrations of uric acid, creatinine, triglyceride, total cholesterol, ALT, and AST when compared with the other groups. In conclusion, radiation of ostrich eggs before incubation with a dose of 0.8 Gy gamma has a stimulative effect upon the metabolism of hatched chicks.

Some novel growth functions and their application with reference to growth in ostrich.

Four novel growth functions, namely, Pareto, extreme value distribution (EVD), Lomolino, and cumulative ß-P distribution (CBP), are derived, and their ability to describe ostrich growth curves is evaluated. The functions were compared with standard growth equations, namely, the monomolecular, Michaelis-Menten (MM), Gompertz, Richards, and generalized MM (gMM). For this purpose, 2 separate comparisons were conducted. In the first, all the functions were fitted to 40 individual growth curves (5 males and 35 females) of ostriches using nonlinear regression. In the second, performance of the functions was assessed when data from 71 individuals were composited (570 data points). This comparison was undertaken using nonlinear mixed models and considering 3 approaches: 1) models with no random effect, 2) random effect incorporated as the intercept, and 3) random effect incorporated into the asymptotic weight parameter (Wf). The results from the first comparison showed that the functions generally gave acceptable values of R2 and residual variance. On the basis of the Akaike information criterion (AIC), CBP gave the best fit, whereas the Gompertz and Lomolino equations were the preferred functions on the basis of corrected AIC (AICc). Bias, accuracy factor, the Durbin-Watson statistic, and the number of runs of sign were used to analyze the residuals. CBP gave the best distribution of residuals but also produced more residual autocorrelation (significant Durbin-Watson statistic). The functions were applied to sample data for a more conventional farm species (2 breeds of cattle) to verify the results of the comparison of fit among functions and their applicability across species. In the second comparison, analysis of mixed models showed that incorporation of a random effect into Wf gave the best fit, resulting in smaller AIC and AIC values compared with those in the other 2 approaches. On the basis of AICc, best fit was achieved with CBP, followed by gMM, Lomolino, and Richards functions, respectively. The exponential, MM, Pareto, and EVD equations produced negative values for initial weight (W0) if left unconstrained. The Gompertz equation, in spite of having a fixed inflection point and therefore being less flexible, gave accurate estimates of both W0 and Wf and an acceptable goodness of fit favored by having fewer parameters than the other sigmoidal functions. Nevertheless, all the sigmoidal functions appeared appropriate in describing the growth trajectory of male and female ostriches to a reasonable level of accuracy.

Functional anatomy of the lacrimal gland in African black ostrich Struthio camelus domesticus in the embryonic and postnatal period.

The aim of the present study was morphological and histochemical analysis of the lacrimalgland (LG) in African black ostrich Struthio camelus domesticus in the embryonic and postnatalperiod. Studies were conducted on 50 ostriches aged between the 28th day of incubation until7 months old. Tissue sections were stained with haematoxylin and eosin, Azan trichrome,periodic acid-Schiff, Alcian blue pH 2.5, aldehyde fuchsin and Hale's dialysed iron. The LGin ostrich was classified as a tubulo-acinar type. The primordia of the lobes were determinedin the LG structure on the 28th day of incubation, whilst the weakly visible lobes with aciniand tubules were observed on the 40th day of incubation. Morphometric studies of the LGshowed steady growth, characterised by an increase in both length and width. Histometricmeasurements of lobe size showed little difference between the first, second and third agegroups, whilst in the fourth age group a marked increase in size of lobes was observed.The study showed that, apart from morphological changes, during the growth of the LGthe character of acid mucopolysaccharides changed. Sulphated acid mucopolysaccharideswere indicated, particularly with aldehyde fuchsin (AF) staining in the fourth age group.The Hale's dialysed iron (HDI) staining showed a low concentration of carboxylated acidmucopolysaccharides in the first and second age groups and a higher concentration in thethird and fourth age groups. Periodic acid-Schiff staining (PAS)-positive cells were observedin each age group, but only a small number of cells with a weakly PAS-positive reaction weredemonstrated in the first age group.

Morphological studies on the harderian gland in the ostrich (Struthio camelus domesticus) on the embryonic and post-natal period.

The present investigation was performed on 50 ostriches from 28th day of incubation until the 7th month of life. The morphological (morphometric, histological, histometric and histochemical) studies were conducted. Tissue sections were stained with haematoxylin-eosin, methyl green-pyronin Y, periodic acid-Schiff, alcian blue pH 2.5, aldehyde fuchsin and Hale's dialyzed iron studies. The Harderian gland becomes macroscopically visible on the 28th day of incubation. It is situated in the ventronasal angle of the orbit near inter-orbital septum, between medial rectus muscle, pyramidal and ventral oblique muscles. The Harderian gland of ostrich is a tubulo-acinar gland. The acini were composed of tall conical cells which formed a small lumen and were surrounded by myoepithelial cells. These cells had a granular basophilic, vacuolated cytoplasm. Each of the lobes has a system of complex branching ducts - tertiary, secondary and primary. In the III of research group (3rd week of life), the presence of few plasma cells was demonstrated, which were located within acini and tertiary and secondary ducts, whereas the biggest concentration of plasma cells was observed in group IV of research tissue (4th month of life). The dark cells were observed first time in main ducts 72 h after hatching of nestlings (group II). The morphometric and histometric studies showed that the most intensive growth of Harderian gland occurred between the third week and the seventh month of birds' life. The histochemical study indicated the presence of neutral and acidic mucins, glycoproteins and carboxylated acid mucopolysaccharides.

Effects of supplemental boron on growth performance and meat quality in African ostrich chicks.

To investigate the effects of boron on growth performance and meat quality, 10-day-old Africa ostrich chicks were randomly divided into 6 groups with 6 replicates in each group. For 80 days, birds in the treatments were fed the same basal diet but given different concentrations of boron-supplemented water. The highest final BW (33.4 ± 0.30 kg), ADFI (376 ± 1.83 g), and ADG (224 ± 1.01 g) appeared in the group receiving 160 mg/L boron (group 4). 160 mg/L boron also decreased drip loss (2.20 ± 0.59), cooking loss (35.3 ± 1.14), and elevated pH value (6.13 ± 0.28) of meat (P < 0.05). Ostrich chicks in the 640 mg/L treatment group (group 6) had the lowest final BW (30.8 ± 1.05 kg) and ADG (208 ± 0.74 g) (P < 0.05). The highest ash (1.35 ± 0.01%) and pH (6.18 ± 0.03) and the lowest protein (20.4 ± 1.74%), drip loss (2.10 ± 0.76%), cooking loss (35.0 ± 0.41%), C18:1 (28.2 ± 0.65%), and C18:3ω3 (2.60 ± 0.51%) appeared in group 6 (P < 0.05) as well. Overall, the optimum concentration of 160 mg/L supplemental boron improved ostrich growth performance and meat quality; however, high concentrations of boron decreased both performance and meat quality.

The effect of dietary energy concentrations on production variables of ostrich chicks (Struthio camelus var. domesticus).

The effects of different dietary energy concentrations on ostrich production variables were examined in two separate trials. The first trial tracked changes in production variables from the pre-starter phase through the starter phase and grower phase. The second trial was based on the finisher phase per se. In both trials, the influence of dietary energy on feed intake, feed conversion ratio (FCR) and growth variables was investigated. Additionally, basic abattoir weights were recorded, and measurements of the feathers and skin were performed. In both trials, three diets with different concentrations of dietary energy were given during each phase where the low-, medium- and high-energy concentrations for each phase were as follows: 13.5, 14.5 and 15.5 MJ ME/kg feed pre-starter; 12.5, 13.5 and 14.5 MJ ME/kg feed starter; 10.5, 11.5 and 12.5 MJ ME/kg feed grower and 9.5, 10.5 and 11.5 MJ ME/kg feed finisher. Feed and water were available ad libitum in both trials. Overall, it was found that the best performance for growth, FCR, skin size and grade, live weight, carcass weight and thigh weight were obtained on the medium-energy diet during the pre-starter, starter and grower phases. During the finisher phase, improved growth rate and tanned skin size was found in birds given the diet with the highest energy concentration (11.5 MJ ME/kg feed). Carcass weight, growth rate and certain feather variables were also significantly influenced by gender.

The growth response of ostrich (Struthio camelus var. domesticus) chicks fed on diets with three different dietary protein and amino acid concentrations.

1. Feeding costs are the largest expense in an ostrich production system, and protein is one of the more expensive components of the diet. This study evaluated the growth response of ostrich chicks on diets containing different concentrations of protein (amino acids). The diets were formulated to contain three concentrations of protein (one diet with 20% less protein than the conventional concentration, L; one diet with the conventional concentration of protein, M and one diet with 20% more protein than the conventional concentration, H) for each of the phase diets. The phase diets were pre-starter, starter, grower and finisher. 2. This study includes the analysis of ostrich body weight (BW) by modelling growth with linear polynomial and non-linear functions for all the data not separated for treatments. In total, 3378 BW recordings of 90 animals were collected weekly from hatch (d 0) to 287 d (41 weeks) of age. 3. Seven non-linear growth models and three linear polynomial models were fitted to the data. The growth functions were compared by using Akaike's information criterion (AIC). For the non-linear models, the Bridges and Janoschek models had the lowest AIC values for the H treatment, while the Richards curve had the lowest value for M and the von Bertalanffy for the L treatment. 4. For the linear polynomial models, the linear polynomial of the third degree had the lowest AIC values for all three treatments, thus making it the most suitable model for the data; therefore, the predictions of this model were used to interpret the growth data. Significant differences were found between treatments for growth data. 5. The results from this study can aid in describing the growth of ostriches subjected to optimum feeding conditions. This information can also be used in research when modelling the nutrient requirements of growing birds.