| In order to investigate effects of carbohydrate balance index on physiological index nutrients apparent digestibility,energy metabolism and blood biochemical indexes of heat-stressed goat,and choose a better level of carbohydrate balance index for configuration diet of goat under heat stress,we used a single factor experimental design in the study.According to healthy,small individual difference,weight(25±2)and same batch,twenty five LeZhi black goats were randomly allocated to five treatment groups with different levels of carbohydrate balance index diets contain 0.56(group1),0.76(group2),1.00(group3),1.27(group4)and 1.52(group5)and five repetition per treatment group.The trial was conducted in two phases with a total length of 31 days,a pre test period of 14 days,and a formal period of 17 days,which were conducted in April to May and August to September of2017 respectively.The results showed that there was a significant difference between two trials of THI(P<0.05).The average THI of the first trial was 68.85,and the average THI of the second trial was 79.95.Production performance: Under non-heat stress conditions,there was no obvious change in DMI.The specific conditions were: group 5> group 2> group 1> group 4> group 3;ADG showed no significant change at first rise and then decreased(P >0.05),the change relationship was: group 2> group 1 = group 3> group 4> group 5;the material weight ratio of each group had a significant decrease after first rise(P<0.05),when the CBI was 1.00 reach to minimum.Under heat stress,both DMI and ADG decreased gradually with CBI,but there was no significant difference between the groups(P>0.05);the material weight ratio increased significantly after the first decrease(P<0.05).When the CBI is 0.76,the feed-to-weight ratio is a minimum of 8.02,and when the CBI is 1.52,the feed-to-weight ratio is a maximum of12.37.Under heat stress conditions,compared with non-heat stress conditions,the DMI of all groups increased significantly(P<0.05),which was related to the growth status of goats;ADGs of group 1,2 and 4 groups all increased,5 The groups were similar,and the three groups had decreased;F/G had a significant increase(P<0.05)under heat stress conditions,and the utilization efficiency of feed was not as good as non-heat stress conditions.Apparent digestibility of nutrients: Under non-heat stress conditions,the apparent digestibility of crude protein along with the rise of CBI showed a trend of tortuous decline with significant differences among the groups(P<0.05);neutral detergent fiber and The apparent digestibility of acid-washing fibers showed a significant increase at first and then decreased,reaching the maximum at the CBI of 1.27;the apparent digestibility of calcium decreased significantly with the increase of CBI(P<0.05);apparent digestibility of phosphorus The rate was first decreased and then increased,with the lowest digestibility at 1.00 CBI and the highest at 1.52 CBI.Under heat stress conditions,the apparent digestibility of crude protein,neutral detergent fiber,acid detergent fiber,calcium,and phosphorus all increased first and then decreased with the increase of CBI.The apparent digestibility of crude protein at CBI was 1.00.It reached its maximum while other items were the largest when the CBI was 0.76.Under heat stress conditions,only the apparent digestibility of crude protein and the non-heat stress test,the digestibility of each nutrient in the other groups decreased.Physiological indicators: Under non-heat stress conditions,there was no significant change in respiratory frequency in each group(P>0.05).The relationship of these such as group2> group 3> group 5 > group 1> group4;rectal temperature had increased first Significant reductions(P<0.05)were highest at a CBI of 1.00 and rectal temperatures were lowest at a CBI of 0.56.Under heat stress condition,the respiratory rate of each group did not decrease significantly with the increase of CBI(P>0.05);the rectal temperature of each group had the trend of decreasing first and then increasing,among which group 5>group 1>group2>group 3> group 4.The respiratory frequency in each group under heat stress conditions was significantly higher than that under non-heat stress conditions(P<0.05).The rectal temperature of only diet animals treated with CBI of 0.76 and 1.52 was higher than non-heat stress,and the change was not significant(P>0.05).Energy Metabolism: Under non-heat stress conditions,methane production increased significantly with CBI(P<0.05).Among them,when CBI was 1.52,the methane production was far greater than when CBI was 0.56,0.76,and 1.00,the difference was extremely significant(P<0.01).There was no significant difference in methane emissions between the first three groups(P>0.05);the methane produced per kilogram of dry matter intake also increased significantly with the increase of CBI(P<0.05).Under heat stress conditions,the methane production and the CH4/DMI change rule first decreased and then increased with the increase of CBI,and the lowest was at the CBI of 0.76,but there was no significant difference between the CBI 0.56 and 0.76 groups(P>0.05).).Under the condition of heat stress,the methane production in each group increased significantly(P<0.05),but the CH4/DMI decreased slightly(P>0.05).Under non-heat stress conditions,the digestive energy,metabolic energy,net energy,and total energy maintain a similar pattern of change,that is,changes in feed intake.Under heat stress conditions,the digestive energy,metabolizable energy and net energy gradually decreased with the increase of CBI.The total energy,digestive energy and metabolic energy of heat stress conditions were higher than those of non-heat stress conditions.The net energy was lower in group 5 than non-heat stress.Under non-heat stress conditions,the total conversion energy into digestive energy(DE/GE),total energy into metabolic energy(ME/GE),and total energy into net energy(NE/GE)are not affected by CBI levels.influences.Under heat stress conditions,DE/GE and ME/GE decreased with the increase of CBI,NE/GE increased first and then decreased,and reached the maximum in the second group.In contrast,under the condition of heat stress,the NE/GE of group 3 and group 5 was lower than the non-heat stress condition,and the rest of the indicators were all higher than non-heat stress conditions under heat stress conditions.The efficiency of digestion to metabolisable energy(ME/DE)was maintained at about 83% in both control and heat stress experiments,with only the fifth group being significantly higher than the other groups(P<0.05).Biochemical indexes of blood: On the whole,from the non-heat stress period to the heat stress period,the blood sugar and non-esterified fatty acids of goats will be significantly reduced,while the levels of urea nitrogen,triglyceride,heat shock protein-70,and cortisol will both increase.Under non-heat stress conditions,there was a significant difference in plasma urea nitrogen between groups.Under heat stress conditions,different carbohydrate balance indexes had a significant effect on the above indicators(P<0.05).Glycemia and non-esterifiedfatty acids increased first and then decreased as CBI increased,reaching a maximum when CBI was 0.76.Significantly higher than other groups;urea nitrogen,triglyceride,heat shock protein-70,and cortisol levels decreased first and then increased;only cortisol trough appeared in the diet group with a CBI of 1.00,and the other three indicators were in troughs.Both appeared in the dietary group with a CBI of 0.76.Under the experimental conditions,from the standpoint of production performance and nutrient use efficiency,the CBI of 1.00 under non-heat stress conditions is more suitable for production.In a high temperature and high humidity environment,the CBI of 0.76 is more favorable to production;from environmental protection From an angle of view,diets with lower CBI levels should be used as far as possible under non-heat stress conditions,and CBI of 0.76 under high-temperature and high-humidity conditions can reduce environmental pressure.In summary,the CBI of the summer goat diet is 0.76 better. |
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