Study On The Particle Size Of Feed In Meat Rabbit

Particle size is an important factor affecting the quality of feed processing and animal production.This study investigate the effects of particle size of fiber ingredients and energy ingredient on the feed processing quality,nutrient digestibility,growth performance,health status,digestive tract physiology,slaughtering performance and meat quality of weaned meat rabbits.The aim was to obtain the optimal particle size union of these two types of feed ingredients and to explore the the mechanism of grinding particle size on the health status and growth performance of the meat rabbit,and at the same time provide processing parameters for the rabbit feed production.The experiment adopts a 2×3two-factor design,fiber ingredients（alfalfa,beet pulp,rice husk）and energy ingredient（maize）were the main effects,in which the fiber ingredients is mixed according to the formula and with 2 types of grinding（fine grinding:secondary grinding with1.0-mm and0.6-mm screen;coarse grinding:with a 5.0-mm screen）;energy ingredient with 3 types of grinding（fine grinding with a1.0-mm screen,medium grinding with a 2.5-mm screen and coarse grinding with a 5.0-mm screen）,other materials are grinding with a 2.5-mm screen and formulated into 6 treated diets.This study was divided into two experiments.Exp.1:Effects of particle size on the feed processing quality and nutrient digestibility of meat rabbits.Six isoenergetic and isonitrogenous pelleted diets in a 2×3 factorial arrangement were used with fiber ingredients particle size（fine,coarse）and energy ingredient particle size（fine,medium,coarse）.The processing parameters of feed,such as particle sizes of fiber ingredients and energy ingredient,pulverization ratio and hardness of pelleted diets were determined and digestion experiments were carried out.Sixty"Hycole"meat rabbits（1212.42±92.61 g）at the age of 42 days were randomly divided into 6 treatmens with 10replicates of 1 rabbit per replicate.The experiment lasted for 11 days with 7d adaptation period and 4d continuous feces collection.The results showed as follows:1.The geometric mean particle sizes of fiber ingredients with fine and coarse grinding were 200.18 and 499.55μm,respectively;energy ingredient fine,medium and coarse grinding obtained corn raw material with geometric mean particle sizes of 333.17,357.85,and 514.67μm;the geometric mean particle sizes of the powder before the pelleting of the6 treatment groups were 337.96,350.68,358.41,469.88,501.69,546.10μm,respectively.The geometric mean particle diameter and geometric standard deviation of the fiber ingredients and the energy ingredient increased significantly with the increase of the mesh diameter（P<0.01）.2.The fiber ingredients coarse grinding significantly increased the starch gelatinization degree of pellet feed（P<0.05）,and the energy ingredient fine grinding very significantly increased the starch gelatinization degree（P<0.01）.Both the fiber ingredients and the energy ingredient finely ground significantly decreased the coefficient of variation,powder percentage,pulverization ratio（P<0.01）,very significantly improved hardness of rabbit feed（P<0.01）.The interaction effects on the processing quality of rabbit feed were observed（P<0.01）.The particle size of the fiber ingredients and the energy ingredient had no significant effect on the protein solubility（P>0.05）.Grinding both fiber and energy ingredient finely has the best effect on improving the processing quality of the meat rabbit feed.3.The particle size of the fiber ingredients and the energy ingredient had no significant effect on the apparent digestibility of gross energy（P>0.05）;but the fiber ingredients with fine particle size significantly increased the apparent digestibility of starch（P<0.05）,that with coarse particle size increased the apparent digestibility of crude fiber（CF）（P=0.06）.The energy ingredient with fine and medium particle size very significantly increases the apparent digestibility of starch（P<0.01）,reduces the digestibility of phosphorus（P<0.05）,but that with coarse grinding increased CF digestibility（P<0.05）.Exp.2:Effects of feed particle size on growth performance,digestive physiology,and slaughter performance of rabbits.Adopts the 2×3 two-factor design described above with 6 treatments.252―Hycole‖meat rabbits at 35 days old with average body weight of（1015.16±14.48g）randomly divided into 6 groups of each 21 replicates,2 rabbits in each replicate.The experimental period lasted for 28d（1-14 days:earlier stage;15-28 days:later stage）.Feed and water were offered ad-libitum during 28 days experimental period.Body weight and feed consumption were recorded to calculate body weight gain and feed conversion.At the end of the experimental period meat and tissue samples were collected from 4 animals per group.The results showed as follows:1.Coarse fiber ingredients increased average daily feed intake（ADFI）in meat rabbits（P<0.05）,but did not affect average daily gain（ADG）and feed/gain（F/G）in meat rabbits.The particle size of energy ingredient had no significant effect on the ADFI,ADG,and F/G of the rabbits in all stage（P>0.05）.The particle size of fiber ingredients and energy ingredient had an interaction effect on F/G of 1-28d（P<0.05）.2.Grinding fiber ingredients coarsely reduced mortality of 1-28d and the health risk of1-14d,1-28d（P<0.05）.The particle size of energy ingredient had no significant effect on the health risk（P>0.05）.The diet with coarse fiber ingredients and medium energy ingredients significantly reduced the morbidity,mortality and health risk index of meat rabbits in the early and the whole period（P<0.05）.3.Fiber ingredients ground coarsely increased the stomach weight（SW/LW）and the value of the villus height to crypt depth（V/C）of ileum（P<0.05）,improved the activity of trypsin of duodenal and jejunal,and the activity of cellulase of cecal chyme in the later stage（P<0.05）.Coarse fiber ingredients reduced the pH of the stomach fundus,the cecum weight（CW/LW）,villus height and V/C of duodenal,and the activity of the pectinase of cecal chyme in the earlier stage（P<0.05）.Energy ingredient ground finely improved villus height and V/C of duodenal（P<0.05）and the activity of trypsin of duodenal and jejunal in the earlier stage（P<0.05）,decreased the activity of trypsin of jejunal,cellulase and hemicellulase of cecal chyme（P<0.01）in the later stage,but improved the activity of the pectinase of cecal chyme（P<0.05）.The particle size of feed had no significant effect on intestinal amylase（P>0.05）.4.The particle size of feed significantly affected the number of cecum microorganism in the earlier stage of rabbits（P<0.05）,but had no significant effect on the number of cecum microorganisms in the later stage（P>0.05）.Fiber ingredients ground coarsely increased the number of bifidobacteria,reduced the content of NH₃-N in the earlier stage（P<0.05）;energy ingredient ground finely increased the number of bifidobacterial in the earlier stage（P<0.05）.The particle size of fiber ingredients and energy ingredient had an interaction effect on the number of chyme bifidobacteria and lactobacillus in rabbit cecum（P<0.05）,the diet with coarse fiber ingredients and fine（or medium）energy ingredient significantly increased the number of bifidobacteria and lactobacillus（P<0.05）.5.Fiber ingredients ground coarsely increased the half eviscerated rate of meat rabbits（P<0.05）;The particle size of energy ingredient had no effect on the slaughter performance（P>0.05）.And the feed particle size had no effect on meat quality（P>0.05）.In onclusion:both the fiber ingredients and the energy ingredint ground finely can effectively improve the processing quality of the feed.Fiber ingredients ground coarsely can increase ADFI,increase the apparent digestibility of CF,promote the development of the stomach,promote growth of beneficial bacteria in the cecal,and reduce the health risk index of meat rabbits.Energy ingredient ground finely or medium can increase the apparent digestibility of starch,improve intestinal morphology,increase the number of bifidobacteria,it is beneficial to the intestinal health of the rabbit.The best combination of particle size of fiber material and energy material is coarse grinding of fiber ingredients（5.0-mm screen）and fine or medium gringding of energy ingredient（1.0-mm or 2.5-mm screen）.