Response of growing rabbits in growth performance and carcass composition to balanced dietary protein.
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Date
2023
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Abstract
The broad objective of the study was to measure growth performance and carcass composition
of growing rabbits as influenced by the dietary protein levels. A 56-day feeding trial was
conducted to measure the response of two rabbit breeds in growth performance and carcass
composition to balanced dietary protein. A total of 72 sexed rabbits at the weaning age of 5-6
weeks were weighed upon arrival at the farm and randomly distributed singly to 72 grower
cages of 61 x 60 x 58 cm. The breeds used were New Zealand White (NZW) and Californian
(CAL) rabbits with equal numbers of males and females per breed. A representative sample of
8 New Zealand White rabbits was slaughtered before the beginning of the feeding experiment
to estimate the initial carcass composition of the remaining NZW rabbits used in the response
experiment. All the remaining rabbits were subjected to the experimental dietary protein
treatments that were a result of blending low and high protein basal diets to produce four
additional intermediate diets that resulted in a total of six experimental diets (126, 143, 161,
178, 196, 213g/kg). The trial was divided into two periods, from 1-28d and from 29-56d,
respectively. Feed intake, body weight gain, and carcass composition were measured. At the
end of the feeding trial, 48 rabbits (24 from each breed with equal numbers of males and
females within each breed) were sampled for carcass analysis. These were analysed for
moisture, ash, lipid, and protein content. Standard methods were used to determine the
chemical composition of the rabbit carcasses.
Appropriate regression models, including exponential, quadratic, and linear, were fitted to the
data where relevant. The model with the best statistical fit was selected. Daily feed intake and
final body weights were significantly influenced by the dietary protein levels (P < 0.05).
Dietary protein did not influence feed conversion efficiency (FCE), (P > 0.05). The highest
feed intakes, body weight gain, and consequently FCE’s were observed in the NZW breed. The
NZW male rabbits exhibited highest feed intake and body weight gain while NZW female
rabbits had the highest FCE. Significant interactions were detected in feed intake and body
weight of the two breeds (P < 0.05). Female rabbits of the two breeds showed a significant
interaction in feed intake and final body weight to the dietary protein levels.
Moisture, ash, lipid, and protein in the carcass were not affected by the dietary protein content
(P > 0.05). No significant (breed x sex) or (protein x breed x sex) interactions were observed
in the carcass composition parameters. CAL rabbits had higher ash, lipid and protein and lower
moisture contents than the NZW rabbits. Fat content was increased as the dietary protein
content was reduced (P > 0.05). As a result, both males and females of the NZW breed had
highest lipid contents on the lowest dietary protein level. CAL females and males had higher
protein contents than NZW female and male rabbits, respectively. Carcass and pelt weights
exhibited a significant response to the dietary protein levels (P < 0.05). Significant interactions
in carcass and pelt weights were observed (P < 0.05).
Considerable variation within treatments in all responses measured in this study meant that the
responses to dietary protein could not be accurately described. Solutions to this problem would
be to use more rabbits per treatment, to sample more rabbits per treatment, and to check on the
accuracy of the laboratory analyses. Widening the range of dietary protein levels may result in
a greater difference in the response of the rabbits to protein, thereby describing this response
more accurately.
Description
Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.