Sabbioni A.(2,3), Superchi P.(2), Bonomi A.(2), Summer A.(2), Boidi G.(2)
(1) Research supported by Italian MURST (local founds for research). Paper presented at the 50th EAAP Congress, Zurich, 22-26 August, 1999.(2) Istituto di Zootecnica, Alimentazione e Nutrizione. Facoltà di Medicina Veterinaria. Università di Parma (Italy). Il piano, l’esecuzione delle indagini e le conclusioni spettano in parti uguali agli Autori (A.Bonomi).
(3) Corresponding Author: sabbioni@unipr.it
The assessment of a growth model is of particular importance in animal production, because of its practical implications (possibility of verifying the adherence of a feeding schedule or a rearing system to a reference condition, as it is calculated by a regression equation). In aviculture, growth curves were calculated for turkeys (Emmans, 1989), ducks (Salomon et al., 1987), quails (Ricklefs, 1979), chickens (Antony et al., 1991) and ostriches (du Preez et al., 1992; Cilliers et al., 1995). For all species, regression equation parameters were calculated on an intensive reared sample. Yet, for ostriches, data were collected on animals in their natural environment (South Africa, Namibia, Zimbabwe). In Italy ostrich breeding started about 10 years ago and is becoming more and more consistent, thus representing the most important ostrich producer in Europe. The number of herds is about 2200, almost all concentrated in the North. Actually, the majority of farmers are "breeders" and not "growers", because ostrich slaughtering was permitted only since 1998. Animals were initially imported from Africa and a low number from EU. Because of the strongly different conditions between the Countries of origin and Northern Italy, it is necessary to verify and to adapt the growth equations reported in bibliography.
The purpose of the present investigation was to study the growth, from birth to maturity, of intensively reared ostriches in Northern Italy, as affected by breed and sex.
Animal husbandry.
Data were collected from 151 ostriches (Struthio camelus), of which 63 African Blacks (30 males, 33 females) and 88 Blue Necks (48 males, 40 females), reared in two commercial herds of the Province of Alessandria (North-West Italy). Eggs were produced by 12 females mated to six males (three families/herd with a male:female ratio = 1:2) and were artificially incubated. Hatches have taken place from May to September and in correspondence of 15 of them, a mean of 10 chickens were randomly selected. Mean (± s.d.) birth weight was kg 0.937 ± 0.082.
At the age of one day they were vent sexed and marked by microchip insertion in the hatching muscle (m. complexus) in the rear part of the neck. Chicks were reared on a concrete floor chicken house from one day to two months (hot season) or four months (cold season) of age, at a temperature not below 28°C during the first 10 days and not below 20°C in the successive period, with access to an external paddock only during the hot season. At that age, ostriches were moved to bigger camps on cement, with night close shelter until four months (hot season) or six months (cold season). From that age and until maturity they were moved to pastures with open shelters.
Chicks were fed until four months a commercial concentrate to appetite and from four months to maturity a commercial concentrate plus fresh lucerne or lucerne hay to appetite. Proximate analysis of concentrates is summarised in table 1.
Birds were individually weighed at about monthly intervals from birth to adults (last weigh recording at 676 days of age).
Statistical analyses
The collected data were analysed by the Statistical Analysis Systems (SAS) NLIN procedure (SAS, 1989), to fit the Gompertz curve in the form of the following equation (Emmans, 1989):
w = c exp [-exp (-d (t-t*))]
where w is the mass (kg) at the day t ; c is the maximum weight (kg) at maturity; d is the rate of growth; t* is the age (days) of the maximum daily weight gain. The analysis was performed separately by breed and sex. Differences among parameters were checked by the "t" method.
The Gompertz equation parameters of Italian ostriches are shown in table 2. The estimated mean (± s.e.) mature weight for African Blacks was 109.1 (± 4.3) kg and 111.0 (± 3.7) kg for Blue Necks (P<0.01) and 109.4 (± 4.2) kg and 110.4 (± 5.7) kg for females and males, respectively (P<0.05). Low CVs were observed (from 3.3% to 3.9%) for all categories, but not for males (CV 5.2%). The estimated growth rates (x 103) were 5.551 (± 0.395), 5.621 (± 0.301), 6.062 (± 0.321) and 5.590 (± 0.447), respectively for African Blacks, Blue Necks, females and males. The corresponding age of maximum growth resulted in 256.6 (± 5.7), 246.3 (± 9.6), 231.0 (± 8.7) and 256.9 (± 13.4) days, respectively. Breed and sex accounted for a high significant effect (P<0.01) on this last parameter.
The rearing conditions of ostriches, with reference to environment and feeding, can be considered as standard under Italian conditions. Differences in Summer and Winter housing of young ostriches depend by the low temperatures in the Winter season. The latest hatches (September) give always origin to weaker animals than Spring and Summer hatches. For that reason they are often not performed. In this research only one hatch was performed in September.
The two herds used the same concentrates (table 1), that were formulated, according to standards, from birth to four months and from four months to maturity. The metabolizable energy contents were calculated using chick ME values and they resulted in 12.38 and 7.96 MJ/kg, respectively. The values are in agreement with those reported by Degen et al. (1991) for growing ostriches and by Swart and Kemm (1985) for adults. Intakes were not recorded because of difficulties due to the presence of pasture and lucerne grass or hay supply.
Estimates of final weights from Italian ostriches are lower than those reported by Cilliers et al. (1995) and greater than those reported by du Preez et al. (1992) for South African ostriches. Because the latest were not be considered as mature weight estimates (Cilliers et al., 1995), actual parameters show that adult ostriches, reared under field conditions of Northern Italy, are about ten kg lighter than those from South Africa. Breed effect was significant (P<0.01) with an advantage of about two kg for Blue Necks in relation to African Blacks. In Italy, Blue Necks are strongly used for crosses with the African Black breed with the objective to improve body size. Sex effect on mature weight is less significant (P<0.05) and, in contrast with previous data by Cilliers et al. (1995), this research has shown a heavier mature weight in males than in females (table 2).
Rearing conditions have strongly affected the growth rates, as compared with previous estimates (Cilliers et al., 1995). Actual data have shown a rate of maturing almost reduced to a half, with differences not significative (P>0.05) between breeds or sexes. Maximum daily weight gains, calculated at t = t* (Emmans, 1989) were 223, 230, 244 and 227 g/day, respectively for African Blacks, Blue Necks, females and males, and occurred at a live weight of 40.1, 40.8, 40.2 and 40.6 kg, respectively. Data reported by Cilliers et al. (1995) have shown a maximum daily weight gain of 382 and 399 g/day, respectively for females and males South African ostriches, at a live weight of 45 and 43.9 kg, respectively.
The age of maximum weight gain was delayed, in the present study, by about two months, due to the different environmental conditions, as compared with previous researches (Cilliers et al., 1995). In particular, females have shown the maximum weight gain 32 days and males 76 days later than those described by Cilliers et al. (1995). Moreover, data from the present study show that females are earlier than males in reaching the mature weight (P<0.01), in contrast with data reported by Cilliers et al. (1995). Also, a significative breed effect (P<0.01) was noted with reference to the age of maximum weight gain.
In conclusion there is the evidence that the growth curves of ostriches are strongly affected by sex and breed under the environmental conditions of Northern Italy (see also graphs 1 and 2). Birds reared in Northern Italy reach their maturity later than those from African herds (Cilliers et al., 1995). Under so different conditions, also nutrient requirements should be studied and validated in relation to managing conditions.
SUMMARY - Growth curves parameters, obtained by the Gompertz equation, were calculated for 151 ostriches (63 African Blacks, 88 Blue Necks ; 78 males, 73 females), reared under typical intensive farm conditions of Northern Italy with ad libitum feeding. Ostriches were weighted at monthly intervals from birth to adults (last weight recording at 676 days of age). Mean (± s.d.) birth weight was kg 0.937 ± 0.082. The estimated mature weights (± s.e.) were 109.1 (± 4.3); 111 (± 3.7); 110.4 (± 5.7) and 109.4 (± 4.2) kg, respectively for African Blacks, Blue Necks, males and females. Maximum daily weight gain occurred at 256.6 (± 5.7); 246.3 (± 9.6); 256.9 (± 13.4) and 231 (± 8.7) days of age and rates of growth (x 103) were 5.551 (± 0.395); 5.621 (± 0.301); 5.590 (± 0.447) and 6.062 (± 0.321), respectively. Mature weight and age of maximum weight gain were significatively influenced by breed (P<0.01) and sex (respectively P<0.05 and P<0.01). Data suggest that environmental conditions of Northern Italy strongly affect the growth parameters of ostriches, compared to those calculated for birds reared in hotter regions.
RIASSUNTO - Curve di crescita di struzzi
(Struthio camelus) provenienti da allevamenti intensivi dell’Italia settentrionale.
Sono state calcolate le curve di crescita, ottenute applicando l’equazione di
Gompertz, relative a 151 struzzi (63 African Black, 88 Blue Neck; 78 maschi,
73 femmine), allevate in allevamenti intensivi dell’Italia settentrionale secondo
tecniche usuali ed alimentati ad libitum. Gli struzzi sono stati pesati ad intervalli
mensili dalla nascita a 676 d di età. Il peso medio alla nascita (± d.s.)
è stato di kg 0,937 ± 0,082. La stima (± e.s.) del peso dei soggetti
adulti è stata di kg 109,1 (± 4,3); 111,0 (± 3,7); 110,4 (± 5,7) e 109,4
(± 4,2), rispettivamente per le razze African Black, Blue Neck, per i maschi
e le femmine. Il massimo incremento ponderale giornaliero è stato raggiunto
all’età di 256,6 (± 5,7); 246,3 (± 9,6); 256,9 (± 13,4) e 231,0 (± 8,7)
giorni, mentre il tasso di crescita (x 103) è stato pari, rispettivamente,
a 5,551 (± 0,395); 5,621 (± 0,301); 5,590 (± 0,447) e 6,062 (± 0,321).
Il peso alla maturità e l’età del massimo incremento ponderale
sono risultati significativamente condizionati dalla razza (P<0,01) e dal
sesso (rispettivamente, P<0,05 e P<0,01). I dati suggeriscono che nelle
condizioni ambientali dell’Italia settentrionale i parametri di crescita degli
struzzi risultano alterati, nei confronti di quelli messi in luce da animali
allevati nel loro ambiente di origine.
REFERENCES