| High concentrate diet is a common strategy in intensive beef cattle production.Despite high energy feeding can meet the fattening requirement of beef cattle,the rapid fermentation of carbohydrate would cause rumen metabolic disorder and nutritional metabolic disease like subacute ruminal acidosis(SARA).Some studies showed that the grain treated with organic acid can modulate rumen fermentation and alleviate SARA.However,there are few studies on the effect of treatment of corn of the high-concentrate diet with hydrochloric acid(HA)in beef cattle.In our previous study,we found that treatment of corn with diluted HA helped control beef cattle SARA,while it had no significant improvement on growth performance.This study is based on previous experiment,and the corn was treated with 1% HA to change the starch structure,subsequently neutralized by sodium bicarbonate(SB)to investigate the effects of the HA and SB treatment of corn in high-concentrate diet on ruminal fermentation and bacterial microbiota,inflammatory response and growth performance in beef cattle.Eighteen Simmental × Luxi hybrid steers with an initial body weight(BW)of 318 ± 9.4 kg were selected for this experiment and randomly assigned to 3 groups(n = 6): low-concentrate diet(LCD)group,high-concentrate diet(HCD)group,or HCD based on treated corn(HCDT).The ground corn in the HCD and LCD was steeped in tap water in a 1:1 ratio(wt/wt)for 48 h.The ground corn of the HCDT was steeped in 1% HA in a 1:1 ratio(wt/wt)for 48 h and neutralized with SB in a ratio of 1 : 2.7(wt/wt)after the HA treatment to achieve a pH of 7.The animal experiment lasted for 42 days with an adaption period of 7 days.The cattle were free access to diet and water.The corn samples that steeping in tap water or in 1% HA for 48 h collected to determine the content of RS.At the end of trial,the rumen fluid samples were collected for measuring pH values,short chain fatty acid(SCFA)and lipopolysaccharide(LPS)as well as bacterial composition.The blood samples of each cattle collected at the end of the trial were used to detect the plasma contents of LPS,pro-inflammatory cytokines,and acute phase proteins(APPs).The initial and final BWs were measured for two consecutive days and recorded daily feed intake.The data were used to calculated average daily gain(ADG),average daily dry matter intake(ADMI)and feed : gain ratio(ADMI/ADG).The faces of each cattle were collected on days 36-42 for nutrient digestibility analysis.Total mixed ration samples collected once per 10 days to determine nutrient compositions.The results showed that:(1)Compared with the corn steeped in water,the corn after treated with HA significantly increased the content of RS(P < 0.01).(2)The pH value of the HCD group and HCDT group both significantly higher than the LCD(P < 0.01),however the difference between the HCD groups was not statistically significant(P > 0.05).(3)Compared with the LCD group,the HCD group observed the lower content of acetic acid and iso-butyric acid(P < 0.05),moreover,the content of propionate,butyrate,valerate and iso-valerate had significantly growth(P < 0.05).The concentration of iso-valerate of the HCDT group was significantly lower than the HCD group(P < 0.05),while the other SCFAs did not change significantly.(4)Compared with the HCD group,the LCD group had higher ?-diversity index(P < 0.05).The HCDT group significantly increased the OTU number,microbiota richness and Shannon index,as compared with the HCD group(P < 0.05).(5)At the phylum level,Firmicutes had advantage in abundance in the HCD and HCDT groups.The most abundant bacterial phylum in the LCD group were Bacteroidetes.Compared with the HCD,the HCDT had higher abundance of Bacteroidetes(P < 0.01).(6)At the genus level,Prevotella was the dominant genus in the rumen fluid across the three groups and it had the highest abundance in the LCD group(P < 0.01).The abundance of Unclassified Ruminococcaceae was significantly increased in the HCDT group(P < 0.01),and the contents of Unclassified S24-7 and Unclassified Lachnospiraceae were lower than the HCD group(P < 0.05).Results indicated that HA treatment increased the RS content in corn grain.The HCD treated with HA and neutralized with SB improved the ruminal fermentation and bacterial community as well as decreased the lysis of gram-negative bacteria.(7)The HCD group had higher LPS content in rumen fluid and plasma than the LCD group(P < 0.01).The HCDT group had lower ruminal LPS than the HCD group(P < 0.01),but still significantly higher than the LCD group(P < 0.01).(8)Compared with the LCD group,the HCD group significantly increased the contents of tumor necrosis factor-alpha(TNF-?),interleukin(IL)-6,IL-8 and IL-1?(P < 0.05).The HCDT group had lower concentrations of TNF-? and IL-6(P < 0.05).(9)The concentrations of haptoglobin(Hp),serum amyloid A(SAA),C-reactive protein and LPS binding protein were higher in the HCD group than the LCD group(P < 0.05).Compared with the HCD,feeding the HCDT significantly decreased the levels of Hp and SAA(P < 0.05).Results indicated that the HCDT decreased the LPS concentration in rumen and blood,further alleviated the inflammatory response caused by LPS translocation.(10)Feeding the HCD increased the digestibility of dry matter,organic matter,crude protein and calcium(P < 0.05).(11)Compared with the LCD group,the final BW,ADG and ADMI of the HCD group had significant increase and had lower feed : gain ratio(P < 0.05).(12)The HCDT has no significant effects on nutrient digestibility and growth performance,as compared with the HCD(P > 0.05).Results indicated that the nutrient digestibility and growth performance of the HCDT group had numerically increase,but the difference is not significant.In conclusion,treatment of corn with 1% HA modified the structure of corn starch.The acid-base treatment of corn in the HCD improved the rumen fermentation patterns and bacterial microbiota,helped counter the negative effects of feeding the HCD to beef steers. |
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