title: Genetic and environmental  factors that influence production and quality of milk of Alpine and Saanen  goats.
abstract: Data  from 1279 lactations of 783 Alpine and Saanen goats of the herd of our  university in Minas Gerais, Brazil, were used to study environmental effects on  and to estimate genetic parameters for milk production until 270 days of  lactation (MP270) and for production and percentages of fat (PFAT and %FAT),  protein (PPROT and %PROT), lactose (PLACT and %LACT), and total dry extract  (PEXTR and %EXTR). Environmental effects were estimated by a statistical model  that included contemporary group effect, type of kidding, genetic grouping, and  kidding order. A multi-trait animal model with animal and permanent environment  random effects was used to estimate genetic parameters and the significant  environmental effects (fixed). Contemporary group influenced all traits;  genetic grouping did not influence %LACT; type of kidding did not influence  PFAT, %PROT or %LACT, and kidding order did not influence %FAT or %EXTR.  Heritability and repeatability estimates were, respectively, 0.19 and 0.37  (MP270); 0.10 and 0.20 (PFAT); 0.12 and 0.24 (PPROT); 0.15 and 0.27 (PLACT);  0.13 and 0.24 (PEXTR); 0.21 and 0.34 (%FAT); 0.39 and 0.44 (%PROT); 0.17 and  0.29 (%LACT); 0.31 and 0.47 (%EXTR). Estimates of genetic correlations among  MP270 and production of milk constituents were positive and high, but  correlations between MP270 and %FAT, MP270 and %PROT, MP270 and %ESTR were  moderate and negative. These heritability estimates show that satisfactory  genetic gains can be obtained by selection, especially for milk constituents.
authors.affiliation: Departamento de Zootecnia, Universidade Federal de Viçosa, Viçosa, MG, Brasil. lfbritozootecnia@yahoo.com.br
authors.forename: L F
authors.initials: LF
authors.lastname: Brito
authors.forename: F G
authors.initials: FG
authors.lastname: Silva
authors.forename: A L P
authors.initials: AL
authors.lastname: Melo
authors.forename: G C
authors.initials: GC
authors.lastname: Caetano
authors.forename: R A
authors.initials: RA
authors.lastname: Torres
authors.forename: M T
authors.initials: MT
authors.lastname: Rodrigues
authors.forename: G R O
authors.initials: GR
authors.lastname: Menezes
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D017753:Ecosystem; D004777:Environment; D005260:Female; D006041:Goats / Q000235:genetics*; D040582:Inheritance Patterns / Q000235:genetics; D007774:Lactation / Q000235:genetics*; D008892:Milk / Q000378:metabolism*; D019655:Quantitative Trait, Heritable; D015203:Reproducibility of Results