Experimental design and feeds
The study was carried out at the National PolytechnicInstitute Félix HOUPHOUËT-BOIGNY of Yamoussoukro in Côte d’Ivoire. The district of Yamoussoukro is located between 6°15 and 7°35 North latitude and 4°40 and 5°40 West longitude. The farm was subjected to a natural atmosphere of lighting and ventilation. The average temperature was 27°C with a relative humidity of 81%. Forage of
Stylosanthes guianensis CIAT 184 was harvested at vegetative stage after 5 months of cultivation, then sun dried. A basal mixture containing
Pennisetum purpureum (elephant grass) hay, wheat bran, rice bran, corn grain, soybean meal, cottonseed meal and cane molasses was formulated to cover the nutritional needs of the growing rabbit according to the recommendations of
De Blas and Mateos (2020). Four experimental diets containing an increasing rate of
Stylo incorporation have been formulated by substituting the basal diet with 0, 15, 30 and 45%
Stylo (SH0, SH15, SH30 and SH45, Table 1) without minerals and premix. Minerals and premix were added to all diets at a fixed amount of 2%. The mixtures were then pelleted (4 mm diameter, 9 mm length).
Animals and measurements
Forty-eight (48) local rabbits, weaned at 35 days old (mean body weight: 628 g), were used for this study. They were divided into four batches of 12 rabbits and individually housed in wire cages (70×60×55 cm), for digestibility measurement. The weight and the origin of the litter were taken into account to constitute homogeneous lots. Animals in each batch were randomly assigned to one of the four experimental diets from 35 to 78 days.
During the experiment, the rabbits were given the feeds and water ad libitum. Feed intake was measured daily and growth once a week. In addition, the rabbits’ health was monitored by daily morbidity and mortality control as recommended for feeding experiments in rabbits
(Fernandez-Carmona et al., 2005).
After an adaptation period of 10 days (at 45 days old), 10 rabbits per group were selected for digestibility study, according the European reference method EGRAN (European Group on Rabbit Nutrition) described by
Pérez et al. (1995). The cages were equipped under the floor with a drawer with a grid to collect faeces over a 5 days period. Faeces were collected daily in plastic bags and stored at -20°C until chemical analysis .
Slaughter and carcass characteristics measurement
At the end of the trial, eight rabbits per diet were selected and slaughtered in controlled conditions, according the recommendations of the World Rabbit Science Association (WRSA) described by
Blasco and Ouhayoun (1996). On each rabbit slaughtered, the weights of the full digestive tract, the hot carcass including the head, all the organs of the neck (thymus, trachea, esophagus), the rib cage (lung and heart), organs (liver and kidneys) and abdominal fat, were recorded. Liver, kidneys and perirenal fat were collected and recorded. Dressing percentage was determined by ratioing the weight of hot carcasses to the live weight at slaughter.
Chemical analyses
Samples of
Stylo, feed and animals faeces were analysed according to harmonised European procedures (
EGRAN, 2001). Dry matter was determined in the oven for 24 h at 103°C, crude protein according to the Kjeldahl method (N×6.25) and crude ash in a muffle furnace at 550°C for 8 h. The fibres (NDF, ADF and ADL) were determined according to the sequential procedure of
Van Soest et al. (1991).
Statistical analysis
The analyses were performed with R software
(R Development Core Team, 2021). The data obtained were subjected to one-way ANOVA with the regime as the source of variation. Means were compared using the Tukey test (5%). The linear effect of
Stylo incorporation on nutrient content and dry matter intake of the experimental feeds, as well as on animal growth, was analyzed using REG procedure from RCMDR package. The protein value of
Stylo was determined according to the method described by
Villamide et al. (2001).
