| dc.description.abstract | The decline of reproductive efficiency under
heat stress is a drawback for the dairy industry. The
objective of this study is to evaluate whether there is
any relationship between the reproductive performance
in cows and the Temperature Humidity Index (THI) and
to improve the reproductive indices in the imported
cows by using a synchronization protocol followed by
Artificial Insemination (AI). Eight medium scale farms in
Matale, Kandy and Kurunegala districts were selected. A
group of first parity, healthy cows (n=205) were
synchronized using Ov-synch synchronization protocol
using intramuscular hormonal injections (Day 0: 2ml
GnRH, Day 07: 2ml Cloprostinol sodium, Day 09: 2ml
GnRH). Sixteen to eighteen hours after the third
injection, AI was performed. After 35- 45 days,
pregnancy diagnosis was performed using per-rectal
ultrasonic scanning method. On each farm visit the THIs
of the farms were calculated. Pregnancy rate was below
6% in 3 farms in which most of the days THI was beyond
78 causing moderate heat stress and the body
temperature of the cows in those farms were between
102.9 - 104.50
F. Average THI of the farms with a
pregnancy rate beyond 20%, was below78 and none of
them were exceeding the cut off THI for moderate heat
stress zone and the body temperature of the cows was
below 102.50
F.There is a negative effect of high THI and
high body temperature on pregnancy rate among the
imported temperate dairy herds to tropical
environments. Although metabolic heat generation is
sufficient to maintain the body temperature, further
absorption can be continue due to the high
environmental temperature leading to heat stress. Thus
it is essential to implement appropriate measures to
reduce heat stress in order to enhance their reproductive
performances. | |
