الفهرس 
Material and methodsOnly 14 pages are availabe for public view
 |  | from | 104 |  |  |
| | | from | 104 | | |
Abstract
Milk production reccrds of the Friesian herd,
located at Sakha Expe]C-:.i.>~:.talStation, Animal
Production Research Ins~itute, Ministry of Agricu1-
ture were used. These records included data tor
imported cowa from the Netherlands between 1960 and
1961, in addition to ’:~heir descendents up till
1979.
First and second l~~tation records (1794 and 1389
records, respectively) oGtained through the period
from 1l)bU to 11)7Y Wl\8 une u to inveat1gate the nongenetic
factors that 1.r..1: __..•e• nced 305-day mUle production
and to evaluate phenot;:;i-c, envirDDDl8ntal aDd genetic
trends of change in -:’~ .’_ ;:05-day milk yield. The least
squares procedures were :ollowed •.
Results obtained are sl,..;::.r.;;,eriZed as fol101J8:
Non-genetic factors:
’lhe overall mean
29.67 months. It ShOWf
the age at first calving was
on-signi:ficant effect on
305-day milk yield.
Autumncalvers recorded the highest milk prod..u.c’tion
compared with calvers of the other seasons of
the yea:r. The differences due to season of oalving
in 305-day milk yield were non-significant.
Year or calving c:”:’;itituted U considerable
highly significant (P 0.01) source of variation
in 305-day milk product i”’ll of either the III or the
2-nd lactations.
Trends of change:
~oDltive phenotypic change was observed in )05-d~
milk yield of both tbe III and 2nd lactations. The
average annual phenotypic change ranged between 22.C17
and 44.05 Kg.
Bnvironmental change in J05-day milk yield of
either the 1-st or the 2.-rU laotation was indioated to
- ~4
be positive. The averu.L. amount of this change, obtained
by the 2 methods used, ranged between 45.09 and
65.75 Kg per year.
Genetic change in the 305-day milk yield of the
1ll and 2Ee, lactatiorj.~ was found to have a negatiTe
diroct ion. The overage annual genetlo ohange, oaloulated
by the three methods of analysis used, ranged between
_ 1.03 and _ 36.17Kg. The average genetic change per
generation ranged betw$en - 31.25 and - 49.68 Kg.