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By-products of biofuels production such as rapeseed cake and dried distillers' grains with solubles (DDGS) may constitute valuable feedstuffs for livestock. The objectives of the study were to determine the usability of these components in the feeding of growing rabbits and to assess their impact on physiological changes in the gastrointestinal tract of the animals. Sixty-four rabbits were divided into four feeding groups: Control (5% soyabean meal [SBM] in the diet), R (5% rapeseed cake [RSC]), DDGS (5% wheat DDGS), and R/DDGS (2.5% RSC and 2.5% wheat DDGS). The study included a production experiment, a digestibility-balance experiment and physiological assessment of the functioning of animals' gastrointestinal tract (small intestine, caecum and colon). No statistically significant differences were determined in production results of the rabbits. Digestibility of nutrients and energy and nitrogen retention were the highest in the Control and the lowest in Group DDGS. Group DDGS was characterised by the highest relative weight of small intestine and digesta. In turn, Group R was characterised by the highest degree of caecal digesta hydration and bulking and by the highest pH value and the lowest concentration of VFA in caecum. The activity of selected bacterial enzymes released to the caecal environment was similar in all groups; however, the activity of α-arabinopyranosidase was significantly increased in Groups R and DDGS. Worthy of notice is the enhanced enzymatic activity of colonic microbiota in the R/DDGS group which has a positive effect upon increased utilisation of dietary nutrients compared to the DDGS group. The obtained results indicate that SBM from rabbit diets may be successfully replaced by 5% RSC as well as by 2.5% RSC + 2.5% wheat DDGS.

Forty New Zealand White rabbits weaned at 30 d were divided into 2 groups and reared under intensive or extensive production system until slaughter (91 d of age). In the extensive production system, rabbits were housed in free-standing cages on straw litter and fed farm-made feed ad libitum. Control rabbits were raised intensively in wire mesh slatted floor cages, indoors and on a commercial pellet ad libitum. Hot carcass weight was 16,6% lower (P<0.01) in extensive production. The difference of 1 point both in hot and cold dressing percentage in favour of the intensively reared rabbits was not significant (P>0.05). The higher carcass weight of the control rabbits led to heavier primal cuts, including head (P<0.05) and the fore part, intermediate part and hind part of the carcass (P<0.01). However, expressed as % of carcass weight, significantly higher ratio were only found for the head (P<0.01) and edible offal (P<0.05) in intensively produced rabbits. The production systems investigated had no significant (P>0.05) effect on the chemical composition, physicochemical properties and organoleptic characteristics of meat from New Zealand White rabbits.

This study was aimed at determining the possibility of applying rapeseed cake (RC) and wheat distillers dried grains with solubles (DDGS) in diets for HYPLUS meat-type rabbits (n = 64, aged 35–84 days). Control diet (SC) contained 5% of extracted soybean meal. In RC diet, the soybean meal was replaced by RC, in DG diet – by wheat DDGS, whereas in RC–DG diet – by a mixture of RC and wheat DDGS (2.5% each). The study included production analyses, digestibility-balance experiment and physiological assessment of gut response to experimental factors hence data was collected on daily bodyweight gains, feed intake and slaughter performance, nutrients digestibility, nitrogen retention and gut response. The latter included assessment of parameters describing the small intestinal, cecal, and colonic environment of rabbits (e.g. digesta viscosity, ammonia concentration, bacterial enzymes activity, short-chain fatty acid concentration). The highest productivity results were reported for SC group and the lowest ones for DG group. The RC and RC–DG groups were characterised by intermediate productivity. Dressing percentage and contents of carcass elements did not differ among the groups (except for the hind part). Nutrients digestibility and nitrogen retention were the highest in the SC group and the lowest in DG group. The dietary incorporation of DDGS resulted in undesired responses of the gastrointestinal tract including excessively watery digesta in the small intestine, increased concentration of cecal and colonic ammonia, enhanced activity of potentially harmful bacterial β-glucuronidase in cecal digesta, and increased cecal concentration of putrefactive short-chain fatty acids. These negative effects were not due to RC and RC–DG dietary treatments, apart from decreased dry matter concentration in the small intestine in the RC–DG group. In general, the results of our study demonstrated that 5% rape cake can be successfully incorporated into rabbit dietary regimen as a substitute of dietary soybean meal. Considering that the productivity of rabbits fed 2.5% of DDGS (with 2.5% rape cake) and these receiving 5% rape cake was comparable, optional seems also dietary inclusion of up to 2.5% wheat DDGS The higher content of DDGS (5%) in the diet deteriorated most of the growth parameters of rabbits.

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