Effects of Supplementing Different Doses of Glycerol on Apparent Digestibility of Nutrients,Rumen Internal Environment,and Volatile Fatty Acids Absorption in Non-Pregnant Ewes
This study was conducted to investigate the effects of supplementing different doses of glycerol on the apparent digestibility,rumen fermentation parameters,expression of genes related to volatile fatty acids(VFA)absorption in rumen epithelium,and rumen morphological structure in non-pregnant ewes.Forty health-y adult ewes of similar age and weight were randomly assigned to one of four groups:control,test group Ⅰ,test group Ⅱ,and test group Ⅲ,each group consisted of 10 replicates with one animal per replicate.The con-trol group was fed a basic diet.In addition to the basic diet,the test groups were drenched daily with 1％,7％,or 12％glycerol(dry matter basis,calculated based on an estimated daily dry matter intake of approximately 1.3 kg per ewe in each group,equating to glycerol drench volumes of 10,70 and 120 mL,respectively;puri-ty:99.88％;calorific value:18.1 MJ/kg).A pre-feeding period of 14 days was followed by a main feeding period of 60 days.The results showed as follows:1)the neutral detergent fiber(NDF),acid detergent fiber(ADF),and ash apparent digestibility in test group Ⅱ were significantly higher than those in the control group(P＜0.05),and the NDF and ADF apparent digestibility in test group Ⅱ were also significantly higher than those in test group Ⅰ(P＜0.05),with no significant difference between the other groups(P＞0.05).2)In test group Ⅰ,the ruminal fluid pH was significantly lower than that in the control group and test group Ⅱ(P＜0.05).Compared with the control group,the total volatile fatty acids(TVFA)content in the rumen was sig-nificantly higher in test group Ⅰ and test group Ⅲ(P＜0.01),and significantly higher in test group Ⅱ(P＜0.05).The contents of acetate and propionate in the control group were significantly different from those in test group Ⅰ and test group Ⅲ(P＜0.01),and significantly different from test group Ⅱ(P＜0.05).The butyrate content,the proportions of various VFAs,and the acetate to propionate ratio showed no significant differences among the groups(P＞0.05).3)With the increase in glycerol feeding,the expression of down-regulating ade-noma carrier(DRA),Na+/H+exchanger 3(NHE3)and proton-pumping ATPase(vH+ATPase)in the ru-men epithelium increased first and then decreased.However,the expression of monocarboxylate transporter 1(MCTT),monocarboxylate transporter 4(MCT4)and sodium/potassium ATPase(Na+/K+ATPase)in the ruminal epithelium gradually decreased.There was no significant difference in the relative expression of Na+/H+exchanger 1(NHE1)and Na+/H+exchanger 2(NHE2)among the groups(P＞0.05).4)The rumen papillae morphology was good in the control group,test groups Ⅰ and Ⅱ,but the keratin layer in test groupⅢ was damaged.Compared with the control group,the papillae width in all test groups was significantly lower(P＜0.01),and the height was significantly higher(P＜0.05).The thickness of the keratin and granular layers in test groups Ⅱ and Ⅲ was significantly lower than that in the control group and test group Ⅰ(P＜0.05).In conclusion,daily gavage of glycerol can improve nutrient apparent digestibility,improve rumen fermentation environment,promote the growth of stratum corneum of the rumen epithelium and granular layer,and promote the expression of some genes related to VFA absorption in rumen epithelium.Under the conditions of this ex-periment,7％gavage of glycerol is more effective.[Chinese Journal of Animal Nutrition,2024,36(4):2541-2550]
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维普
