Evaluation Of Nutritional Value Of Sweet Sorghum And Application In Dairy Production

The recent statistics shows that the number of dairy cows has been increased during the period between 2000 to 2015,in Gansu Province.However,the supply of forage grass is far from meeting the optimum needs for the development of the grass-feeding animal husbandry.Gansu Province has harsh weather conditions and poor water resources.Sandy,andsaline-alkali land,hillside land,etc.The land area area is about 667,000 hectares,which seriously restricts the sustainable development of animal husbandry and economy in Gansu due poor sandy soil and salinity problems.Sweet sorghum is a perennial forage which has higher biological yield than corn and other crops.It can be easily grown on barren lands and under drought conditions because it has high water use efficiency and meet the development of water-saving and efficient agriculture in Gansu Province.As atraditional forage of dairy cows,corn forages play a decisive role in dairy cow breeding.However,if sweet sorghum is cultivated for some or all of the safe and efficient replacement of silage corn,It can not only solve the problem of insufficiency in forage of dairy cows,but also save land and increase farmers'economic benefits.This study evaluated the biological characteristics,nutritious ingredients and degradation characteristics in animals of four varieties of sweet sorghum planted on arid irrigated farmland in the Hexi Corridor of Gansu Province.using conventional chemical composition analysis and in vitro simulated fermentation gas production techniques?Monste,Big kahuna,Jackpot 1180,Jackpot 3180?At the same time,the effect of sweet sorghum and corn silage on the milk production and milk quality of dairy cows was comparatively studied through a cow feeding control experiment.Finally,the forage structure and milk quality of 65 dairy factories was investigated in Gansu Province and he application of sweet sorghum for the actual production of dairy cows in Gansu Province was also analyzed.Provide scientific invetigations for the safe and efficient use of forage sweet sorghum for dairy farming industry in Gansu Province,the main findings of this research include as follow:Part I:Nutritional Value and Artificial Rumen Degradation Characteristics of Feeding Sweet Sorghum?1?There was a significant difference in fresh grass yield,stem and leaf ratio and plant height among the four varieties of sweet sorghum?P<0.05?.The similar findings were recorded in the fresh weight per plant of each sweet sorghum variety at different growth stages?branching,jointing,heading?.The fresh grass yield,stem-leaf ratio and plant height were found highly significantly?P<0.001?.Manatees had better agronomic traits in all growth stages,and the 1180was worse.?2?The differences for leaf,stem,whole plant neutral detergent fiber,acid detergent fiber,relative feeding value,crude protein,phenolic substance and soluble sugar content among the four varieties were highly significant?P<0.001?.Soluble sugar production gradually increased with the growth period.Regardless of whether it was at the time of branching,jointing or heading,the soluble sugar content of Big kahuna was significantly higher than that of the other three varieties.?3?The crude protein content of each cultivar decreased significantly with the advancement of the growth period?branching,jointing,heading?.The order of crude protein content in each part of the plant was observed as leaf>whole plant>stem.There was no significant difference in protein production between heading stage,manatee,Big kahuna,and Jackpot 3180,which were extremely significantly higher than the Jackpot 1180?P<0.001?.?4?There was no significant difference in total gas production between the whole plant samples of four varieties during the branching period.The total gas production of the manatee at the jointing stage was the highest recorded as 155 mL,which was significantly higher than that of the Jackpo 3180 and the Jackpot 1180?P<0.05?;The total gas production of the manatee at the heading stage was the highest,the lowest award 3180.The dry matter degradation rate had non significant difference among the four cultivars during the branching and jointing stages,The dry matter degradation rate of manatee,Big kahuna,and jackpot 1180 at the heading stage was significantly higher than that of the jackpot 3180?P<0.05?.Part II:Effect of Sweet Sorghum as a substitution of Corn on Milk Yield and Milk Quality of Dairy Cows?1?The effect on milk yield and quality of dairy cows was analyzed by using different proportions of silage sweet sorghum as a substitute for whole plant corn silage,including the control group:100%silage whole plant corn?SS₀?,test group 1:65%silage whole plant corn+35%silage Sweet sorghum(SS₃₅),trial 2 groups:35%silage whole plant corn+65%silage sweet sorghum(SS₆₅),trial 3 group:100%silage sweet sorghum(SS₁₀₀).The results showed that the four groups of different feeding treatments had no significant effect on the milk yield of dairy cows;the dry matter intake of dairy cows in the whole silage group was significantly higher than that of the sweet sorghum silage group?P<0.05?;the milk protein in the SS₆₅5 group was significantly lower In the SS₀ group?P<0.05?,the somatic cell number in the milk of the test group added with sweet sorghum was significantly lower than that in the control group?P<0.05?,indicating that adding appropriate amount of silage sweet sorghum in the diet can reduce the incidence of mastitis in dairy cows.?2?The addition of silage sweet sorghum in the diet had no significant effect on WBC,HGB,and platelet count?PLT?in dairy cow blood;there was no significant difference in serum aspartate aminotransferase?AST?concentrations between the experimental groups;The group?SS₀?alkaline phosphatase?ALP?was significantly higher than other experimental groups?P<0.05?.Part III:The Utilization and Effect on Milk quality of Sweet Sorghum from Gansuin In dairy farming?1?The forage types of dairy cows in Gansu Province mainly include nine categories:silage corn stalk+wheat straw?QJ+X?;corn stalk?YJ?;silage corn stalk?QJ?;silage whole plant corn+alfalfa hay+dry wheat Straw?QQ+M+X?;Hay?X?;Silage Whole Plant+Wheat Straw?QQ+X?Green feed sweet sorghum+wheat hay?T+X?;green feed sweet sorghum+silage corn stover?T+QJ?;storage sweet sorghum+silage whole plant corn+axillary hay?T+Q+M?.The results show that in the 65 dairy factories of Gansu Province,the ratio of wheat stalks as a roughage feed to dairy cows reached 31%,followed by silage with whole plant corn+wheat straw+alfalfa hay,and there are fewer farmers feeding sweet sorghum with dairy cows i.e 5%.?2?Different forage combinations?9 species?had no significant effect on the milk fat percentage and somatic cell number in milk,which significantly affected the milk protein and milk urea nitrogen content?P<0.001?.The T+Q+M group had significantly higher milk protein contents than other groups.The lactose content in the T+X group was significantly higher than that in the X and QQ+X groups?P<0.05?.?3?The content of C18:3,cis-6 in the polyunsaturated fatty acids in milk from three sweet sorghum groups was higher than that in other groups?P<0.001?,and palmitic acid in milk from T+X group?C16:0?.The contents of myristic acid?C14:0?and stearic acid?C18:0?were the lowest,but the content of polyunsaturated fatty acids was significantly higher than that of other groups?P<0.001?.The results showed that the sweet sorghum cultivars of manatee and Big kahuna have good agronomic traits,nutritional value and ruminal degradation characteristics,They are suitable for planting and feeding livestock.Silage sweet sorghum gradually substitutes for silage whole corn,not affect the milk yield,milk quality and the physiological and biochemical indicators of the dairy cows,and it can also reduce the somatic cell count in milk.Feeding sweet sorghum forage can reduce stearic acid?C18:0?content in milk,but it cannot increase the content of monounsaturated and polyunsaturated fatty acids.It is therefore recommended that forage Sweet sorghum can be used to prepare silage with a certain proportion of alfalfa hay and wheat hay to feedi cows This can have positive effects to increase the content of unsaturated fatty acids in milk,while reducing the content of saturated fatty acids.