Genetic Analysis For Linear Type Traits Of Holstein Cattle In Wuhan

The objective of this study were to estimate phenotypic and genetic parameters for 25 linear type traits and the relationships between some conformation traits and milk production traits by applying single trait and multiple traits animal models through MTDFREML with REML algorithm in Holstein dairy cattle,to provide some valuable information about genetic improvement of type traits of Holstein dairy cattle herd in Wuhan.This study included linear type data from 971 daughters of 58 sires collected from 2006 to 2007,andmilk production data consisted of 18000 records of 971 cows from 2001 to 2007 derived from Wuhu farm in Wuhan.Based on the genetic analysis of linear type traits of Wuhan Holstein cattle,the main conclusions were as follows:1.The conformation traits of Holstein dairy cattle population were not very ideal in Wuhan.The results of analysis of variance indicated that housing types,year,lactation number(parity),stage of lactation at classification were important sources of variation for linear type traits.The average scores of 23 linear type traits ranged from 3.39(fore teat placement) to 7.72(body size),and the standard deviations varied from 1.14(rump width) to 2.40(rear legs rear view).Heritability of linear type traits ranged from 0.03 (bone quality) to 0.37(rump width).Mean for final score was 79.17,and standard deviation was 2.67.Heritability estimate for final score was 0.16.Phenotypic correlations between linear type traits and final score ranged from -0.20(rear legs rear view) to 0.41 (median suspensory).Genetic correlations between linear type traits and final score ranged from -0.49(rear legs side view) to 0.83(heel depth).Environmental correlations between linear type traits and final score ranged from -0.16(rear legs side view) to 0.36 (median suspensory).Phenotypic correlations among capacity traits ranged from -0.17 (stature and front end) to 0.38(body size and body depth).Genetic correlations among capacity ranged from -0.26(stature and front end) to 0.71(body size and front end). Phenotypic correlations among udder traits were low,ranged from -0.15(teat length and udder depth) to 0.33(fore teat placement and rear teat placement).Genetic correlations among udder traits were high,ranged from -0.67(fore udder attachment and median suspensory) to 0.99(fore teat placement and rear teat placement).Genetic correlation between udder depth and fore udder attachment(0.97) was large.Genetic correlations between udder depth and udder height was -0.049,and that between median suspensory and fore udder attachment was -0.67. 2.Locomotion score was affected by lactation number and housing types.There was an increasing tendency in locomotion score with the increase of lactation number. Locomotion score of tie-stall dairy cow was higher than that of free-stall dairy cow. Lactation number and the stage of lactation affected the body condition score. Locomotion score had a low heritability(0.09),the heritability of body condition score was 0.19.There was an obvious negative correlation between locomotion score and body condition score,the phenotypic,genetic,environmental correlations were -0.43,-0.78, -0.38,respectively.3.Milk production traits(305d milk yield,305d fat,305d protein) had moderate heritability that ranged from 0.21 to 0.24.There were significant positive genetic correlations among 305d milk yield,305d fat(0.77) and 305d protein(0.89).Positive genetic correlations were found among rear udder width,305d milk yield,305d fat,305d protein(0.44～0.89).Rear udder height and 305d milk yield(0.27),305d fat(0.16) had positive genetic correlations,but it displayed a negative genetic correlation to 305d protein(-0.32).There was no sign of correlation between fore attachment and milk production traits.Positive genetic correlation between median suspensory and 305d milk yield(0.79),slightly genetic correlations between median suspensory and 305d fat or 305d protein were estimated.The genetic correlation between udder depth and 305d milk yield was -0.20.The genetic and phenotypic correlation estimates between final score and 305d milk yield,305d fat,305d protein were positive and moderate,and the phenotypic correlations value were 0.12,0.15,0.15,genetic correlations were 0.29,0.35, 0.25,environmental correlations were 0.14,0.11,0.14,respectively.