By Ananda Wickramasinghe
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In 2017, over 5000 young pregnant cows (heifers) imported from Australia and
New Zealand, were sold to some farmers. They were assured that a cow would
yield 20 litres/day. Within a few months, the farmers’ expectations started to shatter when the cows failed to
produce the promised milk yields. Currently, farmers are facing financial ruin
as a consequence of several grave issues with the cows they purchased: Poor
milk yields, very low conception rate, abortions, stillbirths, high mortality
rates, and unrecognised diseas
Some
of the imported cows.
This article is an attempt to examine the reasons for the poor performance
of imported cows under local conditions.
The dairy cow is a biological milk-producing plant which converts nutrients,
derived from a variety of dietary constituents, into a nutritious product. The
quantity and quality of milk governed by factors such as cow’s genetic makeup, quality of feed,
management practices and surrounding environmental conditions.
The imported cows were a cross-bred between Holston Friesian (HF) and
Jersey. The high milk producing capability of HF and Jersey’s ability to tolerate high-temperature
conditions could be the reasons the authorities selected such a cross-breed.
Since past information of the animals was not divulged, it is not possible to
state much about the history of these heifers.
Assuming that the heifers have the required genetic potential to produce
higher milk quantities, let’s examine
whether factors such as poor quality of feed, bad management practices or
unfavourable environmental conditions caused these disturbing issues.
Quality of feed
Some authorities have alleged that farmers fed cows with a poor quality feed
which triggered the issues with the animals. According to the farmers, at the
start animals were fed with a recommended feed mixture. However, once they
noticed the cows were not economical some started to feed them with locally
available fodder.
The digestibility rate of high fibrous grass such as matured ‘Gini’ is quite
low and it can generate a high level of body heat during the digestion process.
Such a situation can adversely affect the milk production capabilities of a
cow.
If the poor quality feed is the cause, one has to query how government-owned
National Livestock Board (NLDB) farms failed to obtain expected milk yields
from imported cows. Those farms are managed by experienced managers and
veterinary surgeons.
According to the Auditor General’s 2018
report, the average milk yield per cow in 2016, at three upcountry NLDB farms
were around 11-15 litres/day. At Ridiyagama NLDB farm this was about 11
litres/per cow/day.
Impact of local environmental condition on imported heifers
Globally, many studies have been conducted on environmental stress on
cattle. Although Sri Lanka has collected climatic data for over a century it is
rather unfortunate that no attempt was made to use this information in animal
sciences.
Climatic factors such as ambient temperature, relative humidity (R/H), wind,
rainfall, and radiant temperature can negatively affect the cows’ performances. The influence of
environmental impact on animals is complex and it is not possible to isolate a
single factor to explain the stress on an animal. We have to recognise what cow
senses is a combination of all surrounding environmental factors.
Environmental stresses in cattle could result in loss of appetite, cessation
of feeding, lethargy, increase respiration and heart rates, immobility, aimless
wandering, staggering, flow of saliva outside the mouth, open mouth breath, and
the collapse of the animal, non-responsiveness, and seizures. Further, these
conditions can cause reduction of milk yield, reduce weight gain, shorter
gestations, abortions, calves with reduced body weight, reduction of the
quality of colostrum (mother’s first
milk after the calf is born), development of unproductive udders, sick and weak
calves, higher mortalities among calves and drop in conception rate.
Our farmers too noticed such symptoms among their animals. Let’s examine whether these issues initiated
due to unfavourable environmental conditions.
Comfort (Thermo Neutral) zone
During the milk-producing process, higher amounts of internal heat are
generated, especially among high yielding cows. When environmental conditions
are favourable, the animal has the ability to dissipate this heat without using
her stored energy. The temperature range that the animal doesn’t have to expend stored energy to
maintain normal body temperature is called its comfort zone or thermo neutral
zone. For healthy cattle, this temperature is between -15 and 22 degrees
Celsius.
When the cow is exposed to conditions beyond the comfort zone, it starts to
utilize stored energy to dissipate its own internal body heat. At this stage,
the cow reduces its feed intake followed by a reduction in milk yield.
Prone to diseases
Due to environmental stress, the animals’ immune
system can also be weakened and become very susceptible to various bacterial,
viral and physiological diseases.
Impact on the
development of udders
During pregnancy, the cow utilises her stored energy to form the mammary
glands. When environmental conditions are not favourable, the stored energy is
utilised to overcome the stresses. Eventually, this will negatively affect the
morphology of her mammary glands. In such situations, udders can become dried,
underdeveloped and unproductive.
Reproduction issues
Under an environmental stress situation, cow’s
expression of heat (estrus) signs and also the duration and intensity of estrus
expression can be dramatically weakened. Without such signs, farmers are unable
to detect estrus signs. This will cause a sharp drop in the success rate of
artificial insemination.
Embryo death and effect
on the fetus
Embryos of the cows are highly vulnerable for heat stresses during the first
17 days of conception. At this phase, a protein that resists heat stress is not
formed. This situation can be fatal to the embryos.
Development of follicles can also be retarded due to heat stress. This could
result in weakening of signals to indicate that she is pregnant. In the absence
of such signals from the embryo, a cow can stop secreting the needed hormones
to maintain the pregnancy. Finally, this can cause the death of embryos.
Calves born under heat stress
Due to environmental stresses, placental development of the cow can be
negatively regulated. The placenta is an organ that develops in the cow’s uterus during pregnancy aiming to
provide oxygen and nutrients to the growing fetus.
Environmentally stressed cows normally have a shorter gestation length and
give birth to lighter calves by about 5 kg. Calves of such cows will have a
reduced efficiency to absorb antibodies (immunoglobulin) from colostrum (first
milk) and could be easily infected with diseases. Malformation, growth
retardation and higher mortality rates can also be observed among those calves.
Stresses due to transportation
Imported cattle were transported from ports in poorly ventilated lorries
that were not designed to carry the live animal. Cattle transport produces
physical and psychological stresses among animals. Stress may result in altered
metabolism, immune competence, and behaviour, as well as failure in
reproduction. Further, it can reduce milk production.
Comparison of Australian
and local climatic conditions
The average R/H and temperature of Victoria province of Australia (the
source of heifers) was compared with a few locations in Sri Lanka such as
Nuwara Eliya, Hambantota, Badulla, Kurunegala, and Vavuniya. It was revealed
that R/H in Victoria is around 60 per cent while in Sri Lanka locations R/H is
around 80 per cent. The temperature in Victoria was higher than that in Nuwara
Eliya from November to March.
The heifers that rose under the Australian low humid environment during
their first 3-4 years were later exposed to high humid tropical Sri Lankan
conditions. Has the impact of environmental changes together with the
transportation stress caused the above-mentioned issues to the imported cows?
Impact of Relative Humidity
on milk yield
It is interesting to observe how cows with European blood perform under
various humid conditions. Daily average milk yield per cow in a farm which this
writer visited at the Californian desert town called Barstow, US is 30
litres/day. Within a year R/H varies from 14-66 per cent and it rains only
about 24 days. The milk yields drop on rainy days due to rising humidity.
An Israel cow produces the highest quantity of milk in the world. In 2017
the average milk yield of a cow was more than 33 litres/day. The humidity in
this zone from March-December is around 45-60 per cent. During summer months
the temperature could go above 300 C.
There are many countries where cows with European blood have been
successfully raised in low humid high-temperature regions. We do not have such
low humid zones in Sri Lanka.
After visiting a farm in Israel or Australia one could easily come to the
conclusion that cows with European blood can be raised in high-temperature
zones. Was this a reason the authorities selected Ridiyagama at Hambantota
district to raise exotic cows without considering the existing high R/H
conditions?
Misting animals as a measure to relieve heat stress has been done at
Ridiyagama. This operation tends to increase the surrounding R/H in humid
areas. Direct wetting of the animal’s body
should be practiced in such zones.
The distribution of imported heifers directly to the farmers was a grave
mistake. These heifers should have been raised in government farms and only
distributed the offspring. Studies found that the calves born under
unfavourable climatic conditions have the ability to better cope with acute
environmental stresses in the future.
The existence of different climatic zones in Sri Lanka has been completely
ignored when imported cows were distributed.
Sri Lanka should introduce a long-term feasible strategy to become
self-sufficient in dairy milk. Improving the genetic potential is just a single
measure that should be implemented with several other essential factors. In
order to achieve this, we should concurrently implement tasks such as
reintroducing higher import tax for powdered milk, improve the local powdered
milk industry, infrastructural developments, assistance to dairy farmers
(loans, grants), development of farmer organizations (cooperatives, etc),
farmer training and research, selection of breeds based on climatic zones,
production of extra professionals such as veterinarian/agriculturists,
grassland development and feed management, dairy marketing, processing and
quality control, and dairy waste management.
(The writer is a former research officer at the
Department of Agriculture, Sri Lanka. Detail report of this article with
references and other resources can be found in his blog: https://outofboxag.wordpress.com/.
He can be reached at
anawicks@gmail.com
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