| Hu sheep is a special sheep breed in China which has excellent traits such as early maturity,perennial estrus,more lambing,good lactation performance,fast growth,and strong adaptability.Hu sheep is a first-class national protected breed in China and included in the "National Catalogue of Protection of Animal Genetic Resources".At present,there is a certain gap between China and developed countries for sheep industry including breeding,nutrition and management.Therefore,it is important to develop Hu sheep's collaborative breeding technology and improve the production level in Hu sheep.In this study,we designed a breeding program for genomic selection in Hu sheep,carried out analysis of family identification,35-day-old early weaning experiment,and we also evaluated the effect on the growth of Hu sheep from betaine feeding in Northwest China.Using collaborative breeding technology including breeding,management and nutrition,our findings can provide a certain insight into promoting the development of Hu sheep industry.Details as follows:(1)This study proposed breeding strategy for genomic selection in Hu sheep which includes determining the breeding goals,standardizing the measurement of production performance,establishing reference groups for genomic selection,formulating blood sample collection specifications and selecting appropriate algorithms.(2)The genetic distance was used to identify the pedigree of 30 Hu sheep breeding rams by using 9 microsatellite markers.The results showed that the cumulative exclusion probability of 9 microsatellite loci was 99.6072% when the genotype of the parents was unknown and 99.8808% when the parental genotype was known.The cumulative exclusion probability of the 9 microsatellite loci was 99.9999% when the genotype of the single parent was known and both parents was unknown,and the exclusion probability can meet the requirements of paternity identification and pedigree analysis in genetic breeding.30 rams were divided into 6 families based on the UPGMA cluster map constructed by the Nei's genetic distance.Our study provides a method for identifying Hu sheep family,which has certain application value for the conservation and breeding of Hu sheep.(3)In the 35 days early weaning experiment for Hu sheep,104 Hu sheep lambs(7 days)with the same age and similar body weight were selected and divided into control group and experimental group according to feeding mode.The control group: Lambs and ewes were kept in the same pen,and another 0.5 pen was set for the lambs and only lambs can feed themselves through the lamb channel.The weaning time is 40 days.Experimental group: Lambs and ewes were raised in the same pen but no more lamb feeding pens were set up,a feeding device was installed only for lambs,and the weaning time is 35 days.The lambs were fed at the age of 7 days and raised to the age of 60 days.The lamb growth of the two groups(before and after weaning)was compared.The results showed the weights of the two groups had no significant difference at the age of 7 days,35 days,40 days and 60 days(P>0.05).At the age of 14 days,21 days and 28 days,the weight of the experimental group was significantly higher than that of the control group(P<0.05).The weight gain of lambs in the 7 days to 14 days experimental group was higher than that of the control group,and the weight gain of the lambs in the 35 days to 40 days control group was higher than that of the experimental group(P<0.01).The weight gain of lambs in the experimental group from 21 days to 28 days was higher than that of the control group(P<0.05).However,the difference between the experimental group and the control group was not significant among the age of 14 days to 21 days,the age of 28 days to 35 days,the age of 40 days to 60 days,and the age of 7 days to 60 days(P>0.05).The survival rate of lambs in the experimental group was 92.31%,and 88.89% in the control group.The feeding mode of the experimental group can be used as a 35 days weaning approach for Hu sheep in cold and arid areas,which could improve the early growth and weaning survival rate of lambs.(4)To study the effect of betaine for ruminant on the growth performance of Hu sheep in Northwest China,252 Hu sheep rams were selected for fattening and divided into experimental group and control group.The control group was fed with basic forage,while the experimental group's feed was supplemented with betaine for ruminant at a ratio of 2.5 kg/t.The experiment period lasted 90 days.Both the initial and final weights were recorded.Moreever,3 weight level repetitions(Low = L,Medium = M,High = H)were selected from the control group and the experimental group,and weighed every 30 days.The results showed that the final weights of the experimental group were higher than those of the control group,however,no significant difference(P > 0.05)was observed.The average daily gain(ADG)of the experimental group was higher than that of the control group,and the difference was extremely significant(P <0.01).The feed meat ratio of the experimental group was lower than that of the control group,and the difference was significant(P <0.05).At low,medium,and high weight levels,the final weight of the experimental group was higher than that of the control group,but the difference was not significant(P> 0.05).The ADG of the experimental group L from 0 to 30 days and 30 days to 60 days were higher than that of the control group L(P> 0.05).The ADG of the experimental group was lower than that of the control group from 60 days to 90 days(P> 0.05).The ADG of the experimental group M was significantly higher than that of the control group M from 0 to 30 days(P <0.01).The ADG of the experimental group was higher than that of the control group during 30 days to 60 days(P>0.05).The ADG of the experimental group was slightly lower than that of the control group during 60 days to90 days(P> 0.05).The growth rate of Hu sheep decreased gradually during the fattening period.The betaine for rumination can promote the growth and development for Hu sheep,significantly reduce the feed meat ratio and largely increase ADG.Moreover,this approach showed better effect on the growth performance at medium/low weight levels and during 0 to 60 days fattening stage.In summary,the genomic selection strategy was designed,and the breeding rams were divided into six families based on Nei's genetic distance.The new lactation feeding approach can be used in the early weaning of lambs at 35 days.The betaine for rumination can promote the growth and development of Hu sheep,but the effect is different at different weight levels and fattening stages. |
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