Vle CONG. INTERN. REPROD. ANIM. INSEM. ARTIF., PARIS, 1968, VOL. II

Trends in some biological characters
in an A,I, cattle population
M.R. HEIMAN
"on'" (A TaCoopaicarids il Esraels

The almost exclusive use of Artificial Insemination (A.L.)in
Israel Dairy cattle, the existence of many very large herds with
skilled management, ready to cooperate in modern projects of
science and investigation, an adequate extent of official milk-
recording and the applicance of electronic computors to process
available data, collected through the milk-recording system, made
it possible to study and influence trends in some biological
characters of reproduction and productive performance in cattle.

1. FREQUENCY OF CALVING-DIFFICULTIES (DYSTOCIA) AND CALF-MORTA-
LITY AT AND AFTER PARTURITION (STILLBIRTH) .

Dr. S.W.J. van Dieten's "Stillbirth in bovine cattle" (Utrecht
1963) and his perscnal communications (1964) accelerated our
pending investigations and consequent breeding policy, concerning
frequency of calving difficulties.

Our computed data for calving from 1.10..64 to 1.10.66 dis-
closed: for 42,120 cows (2 or more parturitions): 4,7% Stillbirth
and 1,6% Dystocia y

for 19,476 heifers: 12% Stillbirths and 9,1% Dystocia.
The first year of registration revealed large differences

between Sires, in calvings of their heifer-mates (carrying their
service), D.eX.

Sire No. of calvings of heifers % Stillbirth % Dystocia
A 2 144 7,0% 4,9%
B 105 8.6% 6,6%

e 1 872 12,9% 9,2%
D 192 15,1% 11,4%
E 100 16,0% 11,0%

There were no considerable differences for calving of adult
cows. The resulting breeding policy was, tc use on heifers only
bulls with low Stillbirth rates. Consequently, the results of
the "ON" A.I. Center, revealed in the following year a pronounced
drop of Stillbirth and Dystocia. In 1966/7 calved 5887 milk re-
corded heifers in herds, inseminated by "ON", with a Stillbirth
rate of 5,8%, a reduction by more than one third.

This biological phenomenon, assessed by electronic computor
and adequately applied by A.I. helps to effect a great reduction
in the losses at birth.

2. GESTATION LENGTH

The comprehensive work of Irma Benerjee (Holland 1964) on the
gestation period in cattle stimulated our investigations, which at
present include data, covering 3 years' calvings 64/67.

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