title: Relationship between the magnitude of the inbreeding coefficient and milk traits in Holstein and Jersey dairy bull semen used in Brazil.
abstract: Artificial  insemination has been used to improve production in Brazilian dairy cattle;  however, this can lead to problems due to increased inbreeding. To evaluate the  effect of the magnitude of inbreeding coefficients on predicted transmitting  abilities (PTAs) for milk traits of Holstein and Jersey breeds, data on 392  Holstein and 92 Jersey sires used in Brazil were tabulated. The second-degree  polynomial equations and points of maximum or minimal response were estimated  to establish the regression equation of the variables as a function of the  inbreeding coefficients. The mean inbreeding coefficient of the Holstein bulls  was 5.10%; this did not significantly affect the PTA for percent milk fat,  protein percentage and protein (P = 0.479, 0.058 and 0.087, respectively).  However, the PTAs for milk yield and fat decreased significantly after  reaching inbreeding coefficients of 6.43 (P = 0.034) and 5.75 (P = 0.007),  respectively. The mean inbreeding coefficient of Jersey bulls was 6.45%; the  PTAs for milk yield, fat and protein, in pounds, decreased significantly after  reaching inbreeding coefficients of 15.04, 9.83 and 12.82% (P < 0.001, P =  0.002, and P = 0.001, respectively). The linear regression was only significant  for fat and protein percentages in the Jersey breed (P = 0.002 and P = 0.005,  respectively). The PTAs of Holstein sires were more affected by smaller  magnitudes of inbreeding coefficients than those of Jersey sires. It is  necessary to monitor the inbreeding coefficients of sires used for artificial  insemination in breeding schemes in Brazil, since the low genetic variability  of the available sires may lead to reduced production.
authors.affiliation: Instituto Federal de Educação, Ciência e Tecnologia Catarinense, Campus Araquari, Araquari, SC, Brasil.
authors.forename: M P
authors.initials: MP
authors.lastname: Soares
authors.forename: L G
authors.initials: LG
authors.lastname: Gaya
authors.forename: L H
authors.initials: LH
authors.lastname: Lorentz
authors.forename: F
authors.initials: F
authors.lastname: Batistel
authors.forename: G A
authors.initials: GA
authors.lastname: Rovadoscki
authors.forename: E
authors.initials: E
authors.lastname: Ticiani
authors.forename: V
authors.initials: V
authors.lastname: Zabot
authors.forename: Q
authors.initials: Q
authors.lastname: Di Domenico
authors.forename: A P
authors.initials: AP
authors.lastname: Madureira
authors.forename: S F N
authors.initials: SF
authors.lastname: Pértile
mesh_terms: D000818:Animals; D001938:Brazil; D001947:Breeding / Q000379:methods*; D002417:Cattle / Q000235:genetics* / Q000502:physiology; D003611:Dairy Products; D003612:Dairying; D005260:Female; D014644:Genetic Variation; D007178:Inbreeding; D007315:Insemination, Artificial / Q000662:veterinary; D007774:Lactation / Q000235:genetics; D008892:Milk / Q000502:physiology*; D010641:Phenotype; D012661:Semen