EFFECT OF INCREASING LEVEL OF BREWER'S GRAIN IN DIET OF RABBITS ON GROWTH AND CARCASS TRAITS

Keywords: Brewer's grain, Rabbits, Growth, Carcass traits

The effect on growth and carcass quality of increasing level of brewer's grain (0, 20 and 30%) in growing rabbit diet was studied. A total of 180 rabbits (5 weeks old, average live body weight of 860 ± 147g) were divided into three experimental groups of 60 rabbits and housed in collective cages (4 rabbits per cage) until slaughter (77 days). Each group was fed ad libitum, either the control diet (B0) or the experimental diet containing 20% (B20) or 30% (B30)of dried brewers grains (DBG). Health status was not affected by the treatment. Also, growth and ingestion performances did not differ significantly between the 3 groups (individual weight gain=29.2 -30.5g /d and feed intake per cage = 379 -390 g /d). Feed conversion was higher (P<0.01) in B20 group compared to the 2 other groups (3.92 vs. 3.65). The incorporation of DBG did not alter the carcass characteristics of the groups. Increasing level of brewer's grain until 30%, in partial substitution to soybean meal and decreasing alfalfa and barley grain rates can be used in rabbit diets without effect on health, growth performance or carcass traits.

INTRODUCTION

In Algeria, the main raw materials which compose industrial rabbit feed are imported, which makes the price of the feed expensive, thus constituting a burden and major constraint for the breeders. Indeed, feed represents about 60% of the production costs of rabbit meat [START_REF] Hannachi-Rabia | La graine de fève sèche (Vicia faba major L) en alimentation cunicole: effets sur les performances de croissance et d'abattage[END_REF].The search for alternative sources of energy, proteins and fibres is the subject of several studies in our laboratory [START_REF] Kadi | Alimentation du lapin de chair : valorisation de sources de fibres disponibles en Algérie[END_REF][START_REF] Guermah | Nutrition du lapin : étude de sources alimentaire alternatives[END_REF][START_REF] Harouz-Cherifi | Utilisation des drêches de brasserie en alimentation du lapin[END_REF][START_REF] Djellal | Valeur nutritive pour le lapin en croissance des feuilles de deux espèces de frêne (Fraxinus angustifolia et Fraxinus excelsior[END_REF]. The brewer's grain is a residue of the beer industry, recovered at the end of the brewing process that barley seeds undergo during the production of beer. According to the Feedipedia database [START_REF] Heuzé | Brewers grains. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO[END_REF], it provides proteins (25.8%), fibres (NDF: 56.3%, ADF: 21.9%, ADL: 5.4%) and even energy (4942 kcal / kgDM), making it an important alternative source for both lactating dairy cows [START_REF] Westendorf | Nutrient content of brewer's grains produced at a commercial brewery: Variation in protein/nitrogen, fiber, carbohydrate, fat, and minerals[END_REF] and growing rabbits [START_REF] Fernandez-Carmona | Prediction of the energy value of rabbit feeds varying widely in fibre content[END_REF][START_REF] Maertens | Feeding value of brewer's grains for fattening rabbits[END_REF]. Especially since rabbits are known for their ability to take advantage of proteins contained in plants and agro-industrial coproducts rich in fibre [START_REF] Gidenne | Dietary fibres in the nutrition of the growing rabbit and recommendations to preserve digestive health: a review[END_REF]. In addition, this agro-industrial co-product, available locally, can also be used as a partial substitute for fibre, protein and energy sources, thus reducing the usual and imported raw materials (alfalfa, soybean meal and barley) used in feeding of rabbits.

In this sense, our study aims to evaluate the effect of incorporating, at increasing rates, locally available brewer's grain into the growing rabbit feed, on growth and carcass traits.

MATERIAL AND METHODS Diets

Fresh brewer's grain was obtained from a local brewery (Algiers). Because of its high water content, it was sun-dried by spreading over a thin layer on a plastic sheet. It was turned twice a day, during 5 days, to improve the drying process. A control diet (B0) was formulated to fit with nutritional requirement of the growing rabbit. Two experimental diets containing 20% (B20) and 30% (B30) of dried brewer's grain (DBG) in partial replacement of soybean meal with decreasing alfalfa and barley rates (Table 1) were prepared. The control and experimental diets were pelleted (4 mm diameter, 9 mm length).

Animals and measurements

A total of 180 rabbits of Algerian white local population, weaned at 35 days(mean live weight = 860 ± 147g),were divided into three groups (n= 60 in each)and placed in collective wire mesh cages (4 rabbits /cage) in flat deck disposition. During the 6 weeks of the experiment, they were fed ad libitum with one of the experimental diets, with a weekly control of live weight, feed intake and a daily control of mortality and morbidity. Fresh drinking water was freely available. At the end of the experiment (77d), 10 rabbits/group were slaughtered, without fasting, in controlled conditions. The weight of skin, full digestive tract, hot and cold carcass, liver, perirenal, inguinal and scapular fat were recorded according to [START_REF] Blasco | Harmonization of criteria and terminology in rabbit meat research. Revised proposal[END_REF].

Chemical Analyses

The following analyses were performed at INRA (Occitanie Toulouse centre, UMR 1388 GenPhySE, France) on feeds and brewers grain according to European harmonized procedures (EGRAN, 2001): dry matter, crude ash, crude protein (N x 6.25, Dumas method, Leco), gross energy (Parr adiabatic calorimeter) and fibres fractions (NDF, ADF, ADL) according to the Van Soest sequential method.

Statistical Analysis

Data were subjected to ANOVA, using R software (V.2.15.02), to evaluate the effects of the diet on growth performance and slaughter parameters. Significant differences between treatments were determined using Duncan's test. Chi-square test was used to compare mortality and morbidity between the groups.

RESULTS AND DISCUSSION

Brewer's grains composition and experimental feeds

According to its composition (Table 1), brewer's grain is a suitably fibrous, energetic and protein feedstuff and a valuable by-product in diets for rabbits [START_REF] Maertens | Feeding value of brewer's grains for fattening rabbits[END_REF][START_REF] Guermah | Nutritive value of brewers' grain and maize silage for fattening rabbits[END_REF], Harouz-Cherifi et al., 2018a,b).

Growth performances

The health status evaluated by the health risk index (HRi=morbidity+mortality) was similar in the3groups. In total 25 rabbits died out of 180 animals (8, 9 and 8 rabbits in B0, B20 and B30 group respectively, no antibiotic treatment used during the trial). The mortality and morbidity occurred during the first and second weeks of fattening, which could be related to weaning stress. During the whole fattening period, growth performance and feed intake were not affected by the level of DBG (Table 2), contrary to feed conversion ratios which were significantly different among the 3 groups. Daily weight gain obtained here (30g/d) was higher than obtained by [START_REF] Lounaouci-Ouyed | Field beans and brewer's grains as protein source for growing rabbits in Algeria: first results on growth and carcass quality[END_REF], 27g/d), Hannachi-Rabia et al. (2016, 25.4g/d) and Mouhous et al. (2017, 25.7g/d) with rabbits of same population and same housing mode (4 rabbits /cage).

Table 2: Growth, feed intake and feed conversion ratio of rabbits in the dietary groups.

Slaughter traits

The incorporation of increasing level of DBG did not impair slaughter traits (Table 3). The dressing out percentage (59 -60%) was similar to the values that reported by Kadi et al. (2011, 59%) but lower than that reported by Lounaouci-Ouyed et al. (2008, 67%) and Kadi et al. (2016, 65%) with the same rabbit population. Therefore, the increase in the level of incorporation of DBG did not affect the carcass characteristics. The weights of skin, digestive tract, liver and perirenal fat seem acceptable and corroborate the recommendations of [START_REF] Ouhayoun | La composition corporelle du Lapin. Facteurs de variation[END_REF].

CONCLUSION

Increasing incorporation level of brewer's grain (0, 20 and 30%), in partial substitution to soybean meal and decreasing alfalfa and barley grain rates, in diet of rabbits, resulted in same performances compared to control feed, without affecting health status, growth and slaughter traits. It is confirmed that brewer's grain can be considered as an alternative raw material in rabbits' diets.

Table 1 :

 1 Ingredients and chemical composition of diets and of brewer's grain

	Ingredients (%)	B0	B20	B30	Brewer's grain
	Brewer's grain	-	20	30
	Wheat bran	31	31	31
	Barley	20	15	12.5
	Soybean meal	12	6	3
	Local dried alfalfa	35	26	21.5
	Minerals	1	1	1
	Vitamin/premix	1	1	1
	Chemical composition, g/kg DM
	Dry matter, g/kg	867	870	869	901
	Crude ash	105.4	122.0	105.4	54
	Crude protein	155.0	142.0	145.7	204
	NDF	280.0	327.0	344.6	602
	ADF	147.0	149.0	159.6	213
	ADL	34.0	36.0	38.9	43
	Gross energy, MJ/kg	15.8	15.7	15.9	19.9

Table 3 :

 3 Slaughter traits of rabbits in the dietary groups

	B0	B20	B30	SEM	P