THE GENETIC AND PHENOTYPIC EFFECTS OF DAYS OPEN AND DRY PERIOD 0N 305-DAY3 MILK, FAT AND PROTEIN YIELDS OF GERMAN FRIESIAN COWS '

Hammoud., M. H.; EI-Awady, H. G.; Tawfik, E. S.

doi:10.21608/jappmu.2006.235476

THE GENETIC AND PHENOTYPIC EFFECTS OF DAYS OPEN AND DRY PERIOD 0N 305-DAY3 MILK, FAT AND PROTEIN YIELDS OF GERMAN FRIESIAN COWS '

Document Type : Original Article

Authors

¹ Department of Animal production. Faculty of Agriculture.Alexandria Univeristy. Egypt

² Department of Animal production, Faculty of Agriculture, Kafr El- Sheikh. Tanta Univeristy. Egypt

³ Fachgebiet Internationale Nutztultierzucht und-haltung. Universitat Gh Kassel. Germany

10.21608/jappmu.2006.235476

Abstract

Data relevant to 9092 Friesian cows from 21 herds located in Germany over a
period of 18 years from 1979 to 1996 were used to estimate the genetic and
phenotypic effects of days open and dry period on SOS-days milk. fat and protein
yields during the ﬁrst three lactations. The effects of herd. season and year of calving
and parity were investigated. Least squares analysis of variance showed a highly
signiﬁcant inﬂuence of all factors on 305-days milk. fat and protein yields. Partial linear
and quadratic regression coefﬁcients apparently showed an average increase of 3.28.
0.128 and 0.108. kg for SOS-days milk. fat and protein yields. for each additional day
open. and 1.72. 0.061 and 0.057, kg of SOS-days milk, fat and protein yields. for each
additional day dry. Multiple-trait maximum Likelihood was used to estimate variances
and covariance. Hentabilities for ﬁrst. second. third and all lactations were 0.34. 0.25.
0.24 and 0.24 for SOS-days milk. 0.30. 0.24. 0.2? and 0.31 tor fat yield, 0.29. 0.25. .
0.22 and 0.33 for protein yield. respectively. Heritability for each of days open and dry
period were low and ranged from 0.04 to 0.09. Genetic correlations between different
traits in all lactations were positive and ranged from 0.32 to 0.87. Phenotypic
correlations ranged from 0.19 to 0.92. A days open period of 60-90 and dry period of
60 days were suggested as optimum intervals for attaining maximum milk. fat and
protein yields for Friesian cows in Germany.