Evaluation Of Nutritional Value And Feeding Effects Of Dehulled Canola Meal In Diets For Growing-Finishing Pigs

The shortage of high-quality feed protein resources seriously restricts the development of animal husbandry in China.It is necessary to research new sources of high-quality feed protein.In this study,the nutritional value of dehulled canola meal was evaluated,and the application effect of different levels of dehulled canola meal in diets for growing-finishing pigs was studied.This study included two experiments.Experiment 1.Evaluation of nutrional value of dehulled canola mealA total of 24 healthy crossbred[Duroc×（Yorkshire×Landrace）]castrated barrows with similar age and an initial body weight of 22.37±0.29 kg were randomly allotted into 3dietary treatments with 8 replicates per treatment.The 3 diets were included N-free diet,soybean meal（SBM）semi-single diet and dehulled canola meal（DCM）semi-single diet,respectively.All diets contained chromic oxide（0.4%）as an indigestible marker.The experiment lasted for 10 d,including 6 d adaptation for experimental diet and followed by 4d of feces and urine collection.At the end of the experiment,all pigs were slaughtered,the digesta of ileum was collected to be analyzed.（1）On the as-fed basis,the contents of gross energy,crude protein,ether extract,crude fiber,calcium and total phosphorus in DCM were 19.35 MJ/kg,48.81%,2.94%,6.78%,0.50%and 1.30%,respectively.The contents of lysine,methionine,threonine and tryptophan were2.78%,1.14%,2.13%and 0.65%,respectively.The contents of total essential amino acids,total non-essential amino acids and total amino acids were 20.34%,25.42%and 45.75%,respectively.（2）On the as-fed basis,except tryptophane,the apparent ileal digestibility of other amino acids in DCM was over 70%,and lysine,methionine,threonine and tryptophane were82.18%,87.23%,71.34%and 64.23%,respectively,while the standardized ileal digestibility of amino acids was over 80%,among which lysine,methionine,threonine and tryptophane were 84.92%,91.77%,82.70%and 112.80%respectively.The standardized ileal digestible contents of lysine,methionine,threonine and tryptophan were 2.36%,1.05%,1.76%and0.73%,respectively.（3）On the as-fed basis,the apparent（true）nitrogen digestibility,apparent（true）nitrogen availability,apparent（true）nitrogen biological value and net protein availability of DCM were 76.75%and 84.78%,57.09%and 68.72%,74.29%and 81.44%,and 57.09%,respectively.The true nitrogen digestibility and availability of DCM were significantly lower than that in SBM（P<0.05）.（4）On the as-fed basis,the apparent total tract digestibility and apparent total tract availability of energy in DCM were 74.86%and 73.86%,respectively.The values of digestible energy（DE）and metabolizable energy（ME）in DCM were 15.17 MJ/kg and 14.96MJ/kg,respectively.In summary,the contents of gross energy,crude protein,crude fiber,digestible energy and metabolizable energy in DCM were 19.35 MJ/kg,48.81%,6.78%,15.17 MJ/kg and14.96 MJ/kg,respectively.The standardized ileal digestibility of amino acids was over 80%,and the standardized ileal digestible contents of lysine,methionine,threonine and tryptophan in DCM were 2.36%,1.05%,1.76%and 0.73%,respectively.However,the digestibility and availability of crude protein in DCM was slightly lower than that of SBM.Experiment 2.Feeding effects of dehulled canola meal in diets for growing-finishing pigsIn order to explore the feeding effects of dehulled canola meal on growing-finishing pigs,a total of 100 pigs[Duroc×（Yorkshire×Landrace）]with an initial body weight of48.73±0.88 kg were randomly assigned to 1 of 5 dietary treatments,with 5 replicates of 4pigs per replicate（2 barrows and 2 gilts）.Diets included a corn-SBM basal diet without dehulled canola meal,and the other 4 groups diets were formulated with dehulled canola meal by iso-nitrogen replacement 25%,50%,75%and 100%of the nitrogen provided by SBM in the basal diet.The experiment lasted for 70 d,including 3 phases.（1）At the stage of 50～80 kg,increasing the inclusion level of DCM in the diets tended to decrease（linear,P=0.058）the average daily gain（ADG）of pigs,the ADG of 75%and100%replacement groups were significantly lower（P<0.05）than that of 25%replacement group.At the stage of 80～105 kg,a trend for the decreased（linear,P=0.086）of ADG was observed with the increasing inclusion of DCM,the ADG of 100%replacement group was significantly lower（P<0.05）than the control group;as DCM supplemented increased,average daily feed intake（ADFI）decreased（quadratic,P=0.030）,the ADFI of 75%replacement group was significantly lower（P<0.05）than that of the control group and 100%replacement group;the ratio of F/G increased（quadratic,P=0.032）as DCM inclusion increased,the ratio of F/G of 50%and 75%replacement groups were significantly lower（P<0.05）than that of 100%replacment group.At the stage of 105～130 kg,no linear or quadratic effects on the ADG,ADFI and the ratio of F/G were observed as DCM inclusion increased,however,the ADG of 100%replacement group was significantly lower（P<0.05）than that of 25%replacement group.At the stage of 50～130 kg,a linear decrease（P=0.009）in ADG was observed as DCM inclusion increased,the ADG of 75%replacement group was significantly lower（P<0.05）than that of 25%replacement group and the ADG of 100%replacement group was significantly lower（P<0.05）than that of the control group and 25%replacement group;a linear increase tendency（P=0.076）in the ratio of F/G was observed,F/G in 100%replacement group was significantly higher（P<0.05）than that of 25%replacement group.（2）Increasing inclusion level of DCM in the diets decreased（linear,P=0.045）carcass weight and tended to decrease（linear,P=0.073）average backfat thicknesses,the carcass weight of 100%replacement group was significantly lower（P<0.05）than that of 50%replacement group,the average backfat thicknesses of 75%replacement group was significantly lower（P<0.05）than that of control group.Additionally,no linear or quadratic effects on loin eye area were observed,however,the loin eye area of 25%and 75%replacement groups were significantly lower（P<0.05）than that of 50%replacement group.（3）Increasing inclusion level of DCM in the diets,there was a tendency for a linear decrease（P=0.055）on the value of a_45min^* in longissimus muscle;there were no linear or quadratic effects on the value of b_24h^* in longissimus muscle,however,the value of b_24h^* in longissimus muscle of 25%replacement group was higher（P<0.05）than that of other four groups.（4）Increasing inclusion level of DCM in the diets increased the apparent total tract digestibility（ATTD）of organic matter（OM）,crude protein（CP）,ether extract（EE）and gross energy（GE）（linear,P=0.023,P=0.005,P<0.001 and P=0.008,respectively）.In terms of the ATTD of OM,the 75%and 100%replacement groups were significantly higher（P<0.05）than that of 25%and 50%replacement groups,respectively.In terms of the ATTD of CP,EE and GE,the 75%and 100%replacement groups were significantly higher（P<0.05）than that of other three groups.（5）Increasing inclusion level of DCM in the diets,there were no linear or quadratic effects on serum biochemical indexes and the concentrations of triidothyronine（T₃）and thyoxine（T₄）in serum（P>0.10）,however,decreased（linear,P=0.053）the serum concentrations of malondialdehyde（MDA）.（6）Increasing inclusion level of DCM in the diets tended to decreased（linear,P=0.001）the pH value of ileum chyme,the pH value of ileum chyme of 75%and 100%replacement groups were significantly lower（P<0.05）than that of the control group,the 25%and 50%replacement groups,respectively.There were no linear or quadratic effects on concentrations of acetic acid,propionic acid,butyric acid and total volatile fatty acids of cecum cheyme or colon（P>0.10）.In summary,the replacement of SBM with DCM by different iso-nitrogen rates in the diets for growing-finishing pigs had no significant effect on the concentrations of serum biochemical indexes,hormone indexes,antioxidant indexes and volatile fatty acids in hind-gut digesta.However,with the inclusion of DCM increased in the diets,the ADG at the stage of 50～80 kg,80～105 kg and in overall（50～130 kg）was decreased linearly and the ratio of F/G in overall was tended to increase linealy.Additionally,the ATTD of OM,CP,EE and GE increased linearly.In conclusion,the contents of CP,DE and ME in DCM were 48.81%,15.17 MJ/kg and14.96 MJ/kg,respectively,and the standardized digestible contents of lysine,methionine,threonine and tryptophan were 2.36%,1.05%,1.76%and 0.73%,respectively.Increasing the inclusion level of DCM in the diets of growing-finishing pigs had no significant effect on the pork quality,serum indexes and volatile fatty acids concentration in hind-gut;however,the ATTD of OM,CP,EE and GE was increased linearly,the ADG in overall（50～130 kg）was decreased linearly and the ratio of F/G in overall was tended to increase linearly.These results indicated that the iso-nitrogen replacement of 75%SBM by DCM in the diets for growing-finishing pigs is more appropriate,based on the optimal ADG,ADFI and F/G in overall and the economic cost.