Studies On The Adaptation Of Dorset Down Sheep To The Area Of Old Yellow River Course In Northern Henan Province

This paper studied the adaptation of Dorset down,which introducted from New Zealand, rearing at the area of old Yellow River course in northern Henan province by the means of observation,essay and analysis,The goal lies in for this breed provides the basis for extension.Experiment 1:The adaptability of Dorset down sheep on local hot weather condition. Climatic condition of sheep shed,physiological index and serum biochemical traits of Dorset down sheep were measured on June and August.The results shows:(1)Dorset down sheep was in heat stress both on June and August.The results of respiratory rate,rectal temperature and flocci temperature at 15:00 are extreme significant higher than 8:00.(2)The index of rectal temperature contribute most to the measurement of heat stress and the critical point of rectal temperature raising of Dorset down sheep was that THI was about 80-81.(3)There is no significant difference between the results of Dorset down sheep and Small-tail Han sheep on same period.(4)Every physiological indexes of rams about heat stress were lower than ewes,there was no significant difference.(5) According to the stepwise regression analysis,the humidity had a great influence on physiological index than that of high temperature in Xinxiang under the high temperature humidity summer condition.Serum COR concentration of Dorset down on June was 41.33%higher than August and serum COR level of Dorset down was 37.48%higher than Small-tail Han sheep.The concentration different of K⁺,Na⁺,Cl^,Ca²⁺on same period all were no significandy.Experiment 2:The grazing behavior of Dorset down sheep on local pasture.By comparing the feeding mode and growth and development state in different management mode,the eligible management mode of Dorset down sheep was discussed.The results shows:(1)Average intake rate of Dorset down sheep was 38.8±7.2bite/min,which was little lower than Small-tail Han sheep's; average intake(DM)was 97.9 mg/bite;average intake each day was 1.19kg/d,The change of intake rate was wider than Small-tail han sheep on whole day,foraging rate was obviously effected by various pasture condition.(2)The selectivity of Dorset down on forage grass was higher than Small-tail Han sheep,which was highly effect by pasture state.(3)When Dorset down was in grazing mode,average chewing bites each cud was 49.0±8.8 bite/min,average chewing times each cud was 35.3±7.1s,average cud numbers each minute was 1.35,there was no significant difference between Dorset down and Small-tail Han sheep. development,disease incidence of Dorset down sheep in different produce system were investigated, which to study the suitable produce system of Dorset down sheep at the area of old Yellow River course in northern Henan province.The results shows:(1)Growth and development of Dorset down sheep in grazing produce system was better than in confine produce system.(2)Morbidity of Dorset down sheep in grazing produce system were higher than that in confine produce system and Small-tail Han sheep in grazing produce system.6)Partial degeneration of Dorset down sheep offspring was occurred in confine produce system but not occurred in grazing produce system.Experiment 4:The change of melatonin and reproductive hormone levels of sheep in different seasons.The 8 Dorset down sheep and 8 Small-tall Han sheep on diestrus were chose and the levels of blood melatonin and reproductive hormones were tested on April,June,September and November respectively,which to study the secrete regularity of hormones on diestrus during the whole year.The results show that:(1)The serum FSH levels of Dorset down sheep are always lower than Small-tall Han sheep on various months,but the difference was not significant.The highest level occurred on November and the lowest occurred on April.The serum LH levels of Dorset down sheep were similar with Small-tail Han sheep on April on June and significant higher on September and November.(2)The serum E₂ levels of Dorset down sheep were significant higher than Small-tail Han sheep on April,the different on other months were small and not significant. The serum P₄ level of Dorset down was little higher than Small-tall sheep,on the other months Dorset down sheep were significant lower than Small -tail Hart sheep.(3)The apparent circadian and seasonal rhythms of melatonin secretion were existed.The secretion levels on spring and summer were significant higher than fall and winter.The raising scope of Dorset down sheep melatonin level from April to June very bigger than Small-tail Hart sheep,the descend scope from September to November was also bigger than Small-tail Hansheep.(4)Melatonin can influence the sensitivity of hypothalamus and hypophysis to E₂,which can influence the estrus of sheep through MLT-E2-FSH path.The generalized analysis indicated that,Dorset down sheep adapt to the hot weather of the old Yellow river course in northern Henan province.The change of ecological conditions doesn't influence the basic character and overall production level of Dorset down sheep obviously.The comprehensive evaluation "total adaptiveness" achieves good.In the area of old Yellow River course in northern Henan province,Dorset down sheep could display its productive potential in grazing production system.