Effects Of Corn Cob And Rapeseed Meal Mixture For Substituting Alfalfa Hay Meal On Growing Rabbits

The aim of this study was to evaluate the feasibility of corn cob and rapeseed meal used as rabbit feed ingredient at the same time and included two experiments. Firstly, nutritional value of corn cob on growing rabbits was evaluated by chemical analysis and digestion trial. And then we investigated the feeding effect of different levels of containing different levels of corn cob and rapeseed meal that substituted for alfalfa hay meal in the diets on growing rabbits through feeding trial. According to the results, we can get the feasibility of corn cob and rapeseed meal used as rabbit feed ingredient at the same time and the best level of corn cob and rapeseed meal in the diet on growing rabbits.Experiment 1:Chemical composition of corn cob and its nutritional value evaluation on growing rabbitsThe aim of this study was to evaluate the nutritional value of corn cob for growing rabbits by digestion trial. Based on conventional nutrients and amino acids of corn cob, apparent digestible energy and total tract apparent digestibility of energy and nutrients of com cob were determined by total feces collection method and substitution method. Using European reference method for in vivo determination of diet digestibility in rabbits, twenty-four healthy 42-day-old French IRA rabbits randomly divided into two treatments (one basal diet and one experimental diet) according to the principle of similar weight after 4 d (adaptation period for environment) and twelve replicates in each treatment, one rabbit in each replicate. Growing rabbits in two treatments fed control diet and experimental diet (15% corn cob + 85% control diet) respectively. All diets were pellets and diameter was 2.50 mm. Animals were raised in metabolic cages (60 � 60 � 45 cm) in rabbits shed. The temperature was 25.50�2.00?, the relative humidity was 77.00%� 6.77% in rabbits shed and there was natural light and ventilation. The adaptation period lasted 7 d for diets and the collection period 4 d. The results showed as follow:(1) gross energy and content of dry matter, crude protein, ether extract, crude fiber, neutral detergent fiber, acid detergent fiber, acid detergent lignin, ash, calcium and phosphorus were (DM basis) 19.95 MJ/kg,90.13%,7.31%,1.83%,30.51%,75.33%,32.18%,7.71%, 0.19% and 0.37%, and the digestible energy of corn cob was 3.43 MJ/kg. (2) The total tract apparent digestibility of gross energy, dry matter, crude protein, crude fiber, neutral detergent fiber, acid detergent fiber, acid detergent lignin and ash in the corn cob were 22.85%,24.19%,20.98%,24.72%,-0.99%,-62.64%,-21.31% and 49.28%. The results show that corn cob have low content of nutrients except crude fiber, neutral detergent fiber and acid detergent fiber, and the total tract apparent digestibility of nutrients in the corn cob on growing rabbits are low, especially neutral detergent fiber, acid detergent fiber and acid detergent lignin.Experiment 2:Feeding effects of corn cob and rapeseed meal mixture for substituting alfalfa hay meal on growing rabbitsThe aim of this study was to investigate the feeding effect of diets containing different levels of corn cob and rapeseed meal mixture on growing rabbits. This experiment included two experiments (feeding trial and digestion trial) that were carried out at the same time. One hundred and twenty healthy,35-day-old French IRA rabbits that had same genetic background were used and after adaptation period (7 d), these rabbits were randomly divided into four treatments and ten replicates in each treatment, three rabbits in each replicate based on similar body weight and fed different diets which had similar energy, nitrogen and fiber. Group A (control group) fed alfalfa meal based diet, group B, C and D fed experimental diets contained 8%,16% and 24% corn cob and rapeseed meal mixture (equal mixture of corn cob and rapeseed meal) instead of alfalfa hay meal. All diets were pellets and diameter was 2.50 mm. Animals were raised in cages (60 � 60 � 45 cm) in rabbits shed. The temperature was 22.18 � 2.48?, the relative humidity was 72.17%�3.01% and there was natural light and ventilation in rabbits shed. The feeding trial lasted for 28 d and at the first day of it, one rabbit from every replicate was chosen after weighing and raised in metabolic cages (60 � 60 � 45 cm) to carry out digestion trial. The adaptation period lasted for 7 d and the collection period lasted for 4 d. Specific operations were same with experiment 1. The results showed as follow:(1) From 1 to 14 d, ADFI in control group and group C had no significant difference. ADG and ADFI in group B and D were lower (P<0.05) than group A, and FCR was higher (P<0.05) than group A. From 15 to 28 d, ADG and ADFI in group D was Lower (P<0.05) than other groups and FCR in four treatment had no significant difference (P>0.05). At the all experiment, ADG and ADFI in group D was lower (P<0.05) than other groups and FCR was higher (P<0.05) than other groups. (2) Mortality and health risk index in group D were higher than other groups (P<0.05). (3) There was no significant difference (P>0.05) in control group and experimental groups. (4) The total tract apparent digestibility of GE, CF, ADF, ADL, EE and Ash in diets had no significant difference (P>0.05) between these groups. Most treatment total tract apparent digestibility of nutrients trend lower than control group. Group A had the highest (P<0.05) digestibility of DM and digestibility of CP in group A was significant (P<0.05) higher than group B and C. The digestibility of NDF in group A was significant (P<0.05) higher than group B and lower than group D. The digestibility of Ca in group D was significant (P<0.05) lower than other groups, The digestibility of P was significant (P<0.05) lower than other groups. Compared with group A, other groups had significant (P<0.05) lower total tract apparent digestibility of most amino acids in diets. (5)The weight of the small intestine, and caecal of rabbits in group D were significant (P<0.05) higher than group A, B and C, other digestive organ indexes had no significant difference (P>0.05). (6) pH, ammonia nitrogen content and total volatile fatty acids of caecal of growing rabbits at the midterm in group A and D were significant (P<0.05) higher than group B and C, total volatile fatty acid at later stage in group B was significantly higher (P<0.05) than group A, C and D, no significant difference was detected in the other indexes (P<0.05). (7) Immune organs between these groups were no significant difference (P>0.05). IgA level in group B was significant (P<0.05) lower than group C, and IgA level in group D was significant (P<0.05) higher than group A and B. IgG level in group B was significant (P<0.05) lower than other groups and IgG level in group D was significantly higher (P<0.05) than group A and C. IgM level in group A was significant (P<0.05) lower than group B, C and D. And it showed a rising trend along with the increase of the level of mixture of corn cob and rapeseed meal. (8) At the end of this experiment, eviscerated rate and semi-eviscerated rate of rabbits in group B were significant (P<0.05) lower than group A and C and other slaughter traits were no significant (P>0.05) difference, slaughter traits in group D were significant (P<0.05) lower than other groups.In conclusion, the nutrition value of corn cob on growing rabbits was very low, it is practicable to use corn cob and rapeseed meal as rabbit feed ingredient at the same time. Under the conditions of this experiment and recommended amount of equal mixture of corn cob and rapeseed meal in rabbit diets is less than 16%.