Research On The Growth And Meat Performances Of The Fourth Generation Sheep Of Tianhua Mutton Sheep New Population

Tianhua mutton sheep is a new breed with dual purpose of fine wool and meat bred by Lanzhou University,the Animal Husbandry Extension Station of Tianzhu Tibetan Autonomous County and other organizations,which is suitable for grazing in alpine pasture areas,or half grazing and half housing,and housing.The new breed used South African mutton merino sheep as paternal resource,and Gansu alpine fine wool sheep as maternal resource.The breeding has been progressed to the fourth sheep generation of transverse fixup using 15 years,which showed good adaptability and meat performance.Therefore,131 individuals with pedigree information were selected to test the growth and meat performance of the fourth generation sheep of new group.Of those,50 rams and 51 ewes were born in December 2021,and 15 rams and 15 ewes were born in June 2022.For those born in December,growth and feed intake were measured from birth,and then 15 rams and 15 ewes were randomly selected for slaughter until 12months of age to determine slaughter and meat quality traits.For those born in June,slaughter was conducted until 6 months of age to determine slaughter performance and meat quality,providing basic data for the promotion and variety certification of new breed.The main results of this study are as follows:1.Analysis of growth and development and feed conversion rateThe birth weights of Tianhua mutton sheep for fourth generation sheep of rams and ewes were 4.76±0.8 kg and 4.56±0.82 kg,respectively.Weaning weights at 2months of age were 25.19±4.99 kg and 21.85±3.96 kg,respectively.Weights at 6months of age were 58.62±6.41 kg and 50.17±5.26 kg,respectively.The weights at12 months of age were 83.53±8.78 kg and 71.46±6.45 kg,respectively.The average daily gain were 340.51±80.45 g/d and 286.77±63.04 g/d for rams and ewes before weaning,respectively;315.32±48.51 g/d and 271.20±40.41 g/d for rams and ewes from 2 to 6 months of age,respectively;and 160.91±32.79 g/d and 138.48±22.08 g/d for rams and ewes from 6 to 12 months of age,respectively.The feed to meat ratios of rams and ewes from 2 to 6 months of age were 7.90±2.88 and 7.53±1.85,respectively.The current study indicates that the new breed is characterized by large body size,fast early growth rate and high feed conversion rate.2.Construction of the optimal model for growth fittingIn this paper,three non-linear fitting models were used to analyze the growth curves of fourth generation sheep of Tianhua mutton sheep,including Logistic,Gompertz and Bertallanffy.The results found that Gompertz was the optimal growth model to simulate body weight,and model expressions were Wt=91.804e^{-2.231×exp（-0.249t）}and Wt=77.636e^{-2.217×exp（-0.251t）}for rams and ewes,respectively.Further analysis using the Gompertz model yielded an inflection point of 99.8 d and 98.43 d for rams and ewes respectively,with inflection point weights of 33.77 kg and 28.56 kg and maximum monthly weight gains of 8.42 kg and 7.16 kg,respectively.The construction of the optimal model provided a scientific basis for the feeding management of the new group.3.Analysis of slaughter traitsThe carcass weights of six-month-old rams and ewes were 27.5±4.59 kg and22.32±2.88 kg,respectively,while they were 46.08±6.11 kg and 38.47±4.39 kg for12-month-old rams and ewes,respectively.The slaughter rates of 6-month-old rams and ewes were 51.67±1.84%and 52.10±1.81%,respectively,and 12-month-old rams and ewes were 55.49±2.83%and 56.69±2.30%,respectively.The meat to bone ratio,net meat percentage,net carcass meat percentage,backfat thickness,eye muscle area and GR values for 6-month-old rams and ewes were 3.28±0.15 and 3.98±0.48,36.35±0.75%and 41.94±1.05%,70.90±1.41%and 79.78±1.81%,8.00±1.60 mm and7.40±1.45 mm,14.85±2.14 cm² and 14.65±1.9 cm²,2.27±0.45 cm and 2.27±0.39cm,respectively,while the set of figures for 12-month-old rams and ewes were 4.76±0.60 and 5.78±0.65,45.29±3.71%and 48.68±2.76%,82.50±1.66%and 85.15±1.44%,13.67±3.66 mm and 16.47±3.29 mm,20.43±3.68 cm² and 17.00±2.79 cm²,4.85±0.77 cm and 4.57±0.90 cm.The data showed that Tianhua mutton sheep had high slaughter and net meat rates and showed good meat production performance.4.Analysis of Meat quality traitsData from routine meat trait measurements showed that fourth generation sheep of Tianhua mutton sheep had bright red meat colour,better water retention and high cooking percentage.At the same age,the intramuscular fat（IMF）content of ewes was significantly greater than that of rams,while the muscle fibre diameter of rams was greater than that of ewes and the muscle fibre density was less than that of ewes.A total of 34 fatty acids were detected in longissimus dorsi,including 17 saturated fatty acid（SFA）,10 monounsaturated fatty acids（MUFA）and 7 polyunsaturated fatty acids（PUFA）,of which C18:1N9C was the most abundant,followed by C16:0,C18:0,C18:2N6C and C14,respectively.In terms of SFA content,6-month-old sheep had higher SFA content than 12-month-old sheep,while ewes had higher SFA content than rams at the same month of age;in terms of MUFA content,12-month-old sheep had higher MUFA content than 6-month-old sheep,while rams had higher MUFA content than ewes at the same month of age;in terms of PUFA content,6-month-old sheep had higher PUFA content than 12-month-old sheep,while ewes had higher PUFA content than rams at the same month of age The PUFA content of the ewes was higher than that of the rams at the same age.This study systematically analyzed the growth,slaughter and meat quality traits of the fourth generation sheep of Tianhua mutton sheep,and found that the new group has rapid early growth and development,high meat yield and good meat quality,which provides a scientific basis for the promotion and variety certification of this new breed.