Responses Of Carcass Traits And Meat Quality To Dietary Fiber Level In Different Breeds Of Pigs

With the increase of population and the rapid development of animal husbandry,the conflict between human and animals for food has become more and more serious.Meanwhile,unconventional feed resources in China are rich,but they are not effectively used because of the high fiber content.Bran is one of the important unconventional feed resources in China.The rational usage of bran will help to alleviate the pressure of grain competition between human and animals,and will reduce the cost of feeding.In addition,pork is one of the major sources of meat.As people pay more and more attention to the relationship between nutrition and health,consumers have higher requirements on pork quality.It is of great significance to improve pork quality based on nutrition.Erhualian pig,one of Chinese domestic pig breeds in the Taihu Lake region,is well known for its high prolificacy,superior meat quality and strong adaptability to harsh environments.Large White pig is one of the main imported lean meat pig breeds in China,which is large in size,fast in growth but not able to bear rough feeding and poor in meat quality.In this experiment,bran was used as the whole fiber source to replace the basic diet to evaluate the response of carcass traits,meat quality and subcutaneous fatty acid content in different breeds of pigs.Our results will provide a reference for improving pork quality by scientific and rational utilization of dietary fiber in pig production.Twenty-four Erhualian barrows(Er-HL,approximately 40 kg),24 large Large White barrows(L-LW,the same physiological stage as the Er-HL,approximately 65 kg)as well as 24 small Large White barrows(S-LW,the same body weight as the Er-HL)were selected.There were 72 pigs in 3 groups with 24 pigs in each group.The 24 pigs were randomly divided into 4 treatment groups(6 replicates for each treatment),the control group(CON)was fed the basal diet,and the 3 experimental groups were fed 7%,14%and 21%bran replaced control diet group(BRC),respectively.The pigs in each treatment were housed in different pens,equipped with Osborne Testing Stations System(OTSS)and water-saving stainless steel water dispenser to allow the pigs ad libitum access to water and pelleted food during the whole trial..All the experimental pigs were slaughtered after 28 days of the trial period.The results of carcass traits and meat quality traits were as follows:1.Response of carcass traits and meat quality traits to dietary wheat bran levels in different breeds of pigsThe results of carcass traits and meat quality traits were shown as follows:(1)Compared with L-LW and S-LW,Er-HL got lower(P<0.01)live weight before slaughter,hot carcass weight,and dressing percentage as well as thicker(P<0.01)backfat thicknesses.Increased dietary fiber levels significantly reduced the hot carcass weight and dressing percentage of pigs(P<0.05).(2)With the increase of dietary fiber level,the backfat thickness of Er-HL decreased significantly,the live weight before slaughter,hot carcass weight of L-LW remarkably decreased,the dressing percentage of S-LW decreased as the increase of fiber level(P<0.05).(3)Compared with L-LW and S-LW,the Er-HL had higher values of Redness(a*),Intramuscular Fat content(IMF),Saturated Fatty Acids(SFA)(including C14:0,C16:0,C18:0)and Monounsaturated Fatty Acids(MUFA)(including C18:1,C20:1)of subcutaneous fat,lower shear force,drip loss and Polyunsaturated Fatty Acids(PUFA)(including C18:2n-6,C18:3n-3,C20:4n-6)of subcutaneous fat(P<0.05).In comparison with the 7%BRC group,the 14%BRC group increased the content of C18:3n-3 of subcutaneous fat(P<0.05).(4)As dietary fiber levels increased,there was an increase in pH45 min of Er-HL(P<0.05).The a24 h of Er-HL in the 7%BRC group was higher than that of those in other groups(P<0.05).With the increase of fiber level,the content of C20:4n-6 in Er-HL subcutaneous fat decreased significantly(P<0.05),the content of C20:4n-6 in L-LW subcutaneous fat increased at first and then decreased in the end(P<0.01).The subcutaneous fatty acid content of S-LW was not affected with the increase of dietary fiber level.2.Response of glycolysis and muscle fiber types to dietary wheat bran levels in Er-HL pigsAs shown in experiment 1,we found that the increased dietary fiber level significantly affected the pH45 min and a*value of the Longissimus Dorsi(LD)of Er-HL.Glycolysis and muscle fiber types are important physiological factors,which affect the pH value and a*value of muscle.Therefore,we hypothesized that the effect of dietary fiber levels on meat quality of Er-HL(pH value and a*value)may be regulated by glycolysis and muscle fiber types.The results were shown as follows:(1)There was no difference in lactate,glycogen content,glycolytic potential(GP)or the mRNA levels of PFKM,PKM and HK2 among the 4 diet groups of Er-HL.(2)There was an upregulated tendency on the mRNA expression level of MyHC I in 7%BRC group compared with the other 3 groups(P=0.05)and Er-HL fed with 7%BRC diet exhibited significantly lower expression levels of MyHC Ⅱb than those fed the CON,14%BRC and 21%BRC diets(P<0.05).Moreover,compared to Er-HL pigs fed with CON diet,the protein level of MyHC Ⅱx was significantly downregulated in the other 3 groups(P<0.01),(3)The addition of bran fiber in the diet did also affect protein levels of MyHC Ⅱb and MyHC Ⅱx of Er-HL.Compared with the CON group,the protein expression level of MyHC Ⅱb was significantly decreased in the 7%BRC group,and the MyHC Ⅱb protein level in 7%BRC group was also significantly different from the 14%BRC group and 21%BRC group(P<0.01).Moreover,compared to Er-HL pigs fed with CON diet,the protein level of MyHC Ⅱx was significantly downregulated in 7%BRC,14%BRC and 21%BRC groups(P<0.01).In conclusion,we found that(1)The breed of pig influenced most of the carcass traits and meat quality traits more than the diet did,and pork quality of Er-HL was superior to that of LW.(2)The fiber level did not affect the carcass weights,while it significantly reduced the backfat thickness of Er-HL.However,the increase of dietary fiber level had a negative effect on the carcass quality of LW pigs.With the increase of dietary fiber level,the content of C20:4n-6 in Er-HL subcutaneous fat decreased significantly,the content of C20:4n-6 in L-LW subcutaneous fat increased at first and then decreased in the end,while the subcutaneous fatty acid content of S-LW was not affected by the increase of dietary fiber level.(3)The redness and pH values of the LD in Er-HL were improved in the 7%BRC group,which was possibly associated with the regulation of fiber type conversion by the alteration of dietary fiber level.