| The pastoral area in southern Qinghai includes Huangnan,Yushu and Guoluo Tibetan-autonomous prefectures.Geographically it is located at the center of the Qinghai-Tibet Plateau and is the source region of Yangtze River and Yellow River.Animal husbandry is the major agricultural sector in this region.However,due to harsh environment and dramatic seasonal variations in grass nutrient content,livestock production efficiency is greatly limited.In cold season,herdsmen do not have forage stored and livestock that completely graze on natural pasture show significant weight loss and in severe scenario die from malnutrition.To make the condition worse,in some areas,overgrazing has been causing grassland degradation,overpopulation of rodents and other ecological hazards such as " black solid patch" in which most forage plants are replaced with noxious weed.In this study,we used 2 types of high altitude adapted oats,hairy-vetch and vetch to develop optimal feeding strategies for Oula-type of Tibetan sheep.The main purpose of the present study was to improve forage yield and enhance sheep meat production performance.1.Evaluating the production performance of different mixture modes of oat,hairy-vetch and vetchThe test was conducted in the Zeku county of Qinghai Province(3300m above sea level),and the materials were Avena sativa(Denmark No.444),Avena sativa(Canada No.2),V.sativa(Ximu333)and Vicia Vilosa(Roth).The results showed that production performance of the Denmark No.444 and Ximu333 was better than Canada No.2 and Ximu333,and the treatment with mixture ratio 15:5 gained the max yield of fresh-grass 2817.2 kg / mu,Dry/Fresh ratio was 29.64;the treatment with mixture ratio17:3 gained the max Stem /Leaf ratio was 1:0.78.2.Evaluating baled-silage forage qualityThe purpose of this experiment was to evaluate the silage quality of oat-vetch and oat-hairy-vetch with different mixture ratio,water content and silage methods.According to the comparative results of forage production performance,we chose the Denmark No.444+Ximu333 and Denmark No.444+hairy-vetch as silage grass raw materials.The test was conducted in the Henan Mongolian Autonomous County(3600m above sea level)of Qinghai Province,and the trial design included different mixture ratio(18:2,17:3,16:4,15:5),water content(40~70%)and different silage methods(whole silage,chopped silage).Quality sensory evaluation results showed that there were 35 treatments with the sensory score in the range of 20 ~16,Quality-Level 1,accounting for 50.0% of the total;18 treatments with a score of 15~10,Quality-Level 2,accounting for 25.7% of the total;15 treatments with a score of 9~5,Quality-Level 3,accounting for 21.4% of the total;2 treatments with a score of 4~0,Quality-Level 4,accounting for2.9% of the total.In all of these 70 treatments,the chopped silage treatment sensory score was higher when the raw material water content in the range of 50~60%.Quality laboratory chemical results showed that from the four indexes: p H value,lactic acid content,crude protein content and AN/TN ratio,h1t2s50,h1t2s55,h1t2s60,h1t2s65,h4t2s50,h4t2s55,h4t2s60,h4t2s65 comprehensive performance were significant higher.Comprehensive sensory evaluation,laboratory chemical evaluation and grass yield,stem/leaf ratio factors in comprehensive comparison,it recommended h4t2s50 treatment as pastoral feeding is more appropriate.3.Evaluating the effects of baled-silage forage feeding on weight and body size of Oula-type of Tibetan sheep.From March to May 2016,Oula-type of Tibetan sheep were fed with Denmark No.444+Ximu333baled-silage forage.The 45 sheep(18 months old)were randomly divided into three groups(n=15),and the feeding test design was divided into three groups: barn feeding,grazing and grazing + feeding.The experimental groups were compared with each other.Compared with the other two groups,the body weight and size of the barn feeding group was significantly higher than that of the other two groups(P<0.01),and the effect of weight gain in feeding stage(31 ~ 60d)was significant(P <0.01)than stage(1~ 30d).The effect of the increase of the size of the sheep was: barn feeding group> feeding+ grazing group>grazing group,and the difference between the barn feeding and the grazing group was significant(P<0.01).The average body height of the feeding group was 80.13 cm,the body length was 84.33 cm,the bust was 106.93 cm,which was 6.94%,10.48% and 9.37% higher than before feeding.4.Evaluating the effects of baled-silage forage feeding on the slaughter performance and meat quality of Oula-type Tibetan sheepAt the end of the feeding test,by comparative analysis of the slaughter performance and meat quality indexes such as slaughter rate,net meat rate,GR value,digestive system weight accounted for live weight ratio,carbohydrate content,crude fat content,protein content and amino acid composition,we found that although the barn feeding group was significantly better than the grazing group and feeding +grazing group in terms of weight gain,there were no significant difference between the rate of slaughter and net meat rate.Feeding+grazing group had a high protein content,low fat content characteristics,and grazing group amino acid content was more abundant,from the taste and flavor was more prominent.Considering the living habits of pastoral areas,the cost of production inputs,and the market value of meat products,we come to the conclusion that the grazing + feeding management mode can be used by the feasible and quantitative artificial feeding,while fully utilizing the value of grassland in cold season in southern Qinghai pastoral area,effectively enhance the value of lamb,reduced the grazing pressure on natural grassland in the critical period of greening,and effectively solve the problem of shortage of seasonal forage in southern Qinghai pastoral area.5.Genetic identification of Oula-type Tibetan sheep populationThis study was designed to investigate the origin and phylogenic relationships of Tibetan sheep breeds in Qinghai Plateau.To determine the relationship and genetic diversity of four distributed geographic ecotype populations(Oula,Tianjun,Ledu and Zhashijia sheep)in Qinghai Plateau,we cloned and analyzed the mt DNA D-loop sequences and Sry(sex-determining region on the Y chromosome)gene sequences of 33 female and 33 male Chinese Tibetan sheep.The haplotype diversity and nucleotide diversity of the four sheep populations were 0.020 ± 0.004 and0.989 ± 0.011 based on D-loop sequences and 0.011 ± 0.004 and 0.331 ± 0.103 based on Sry sequences,respectively.The genetic distance values ranged from 0.008 to 0.047 within the population diagonals and from 0.011 to 0.042 among populations above the diagonals based on D-loop sequences.On the other hand,the genetic distance values ranged from 0.000 to 0.028 within the population diagonals and from 0.000 to 0.033 among populations below the diagonals based on Sry sequences.Our study enriched the previous studies on mitochondrial genetic characteristics of Chinese Tibetan sheep,and provided evidence for the paternal lineages based on Y chromosome information in Qinghai Plateau. |
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