How to manage heat stress in livestock

Erastus Ngaruka - Climate change is a long term change in climatic and weather patterns. Such change is observed in temperature and rainfall patterns amongst others.

It is being evidently reported that the earth temperature is on an increase and that rainfall activities have become unpredictable in many parts of the world, and Namibia is evidently experiencing the adverse effects of climate change.

The agricultural output is primarily driven by climatic events, and these have adverse effects on both food and water availability in agroecosystems, thus hampering sustainable crop and livestock productivity, as well as farmers’ livelihoods.

The climate change effects can be direct or indirect. Livestock productivity is directly reliant on rangeland productivity which in turn is determined by soil moisture availability and environmental temperature. The management aspects as secondary determinants of agricultural output, should therefore aim at mitigating or enhancing farmers’ adaptation to climate change events.

Climate change has been characterised by increases in environmental temperature, hence the extreme heat waves being experienced in most parts of Namibia at times over the past couple of months, and figures of more than 40°C were recorded especially in the southern regions. The direct impact of this on livestock is heat stress which negatively affects their wellbeing and performance.

HEAT STRESS AND FEED INTAKE

When an animal is eating, the digestive processes generate heat and increases the body temperature. For example, the normal body temperatures of cattle, sheep and goats are 38.5°C, 39°C and 39.5°C respectively.

When the body temperature increases beyond the normal, the animals physiological functioning is affected and could be detrimental or life threatening in extreme cases. These ruminant animals (cattle, goat, and sheep) under normal circumstances will prefer to graze/forage during cooler hours of the day (early morning, late afternoon, or night) to avoid heat stress. They would only rest during the hot hours of the day to ruminate or re-chew the food they have eaten, breaking them into smaller pieces to enhance digestion further.

Grazing during the hot hours will mean too much heat will be exerted on the animal, from the sunlight and from the internal digestive processes rendering it to heat stress. This means the animal’s physical activities such as walking, and feed intake will have to be reduced in order to maintain normal or optimal body temperature, and this in turn compromises the animal’s nutrition and health status, and the overall performance. These will be experienced as nutrient deficiencies, poor growth rate and body condition, reduced milk yield, and poor reproduction amongst others.

HEAT STRESS AND REPRODUCTION

High temperature also affects livestock reproduction. The heat stress forces animals to reduce their exhaustive physical activities which also includes mating.

The female animal’s reproductive system as well as the sperm production process in male animals can be adversely affected by high temperature. Heat stress is said to depress the release of reproductive hormones such as the oestrogen and progesterone, compromising the consequent processes of oocyte (female egg cell) growth, oestrus (heat) cycle, conception, embryo development, and foetus growth amongst others. I

n male animals, high temperature negatively affects the process of sperm production, leading to temporal infertility.

PREVENTING HEAT STRESS IN LIVESTOCK

Although animals have the ability to adapt to environmental conditions and management regimes, the hot environments will compromise their potential physiological functioning and overall performance to some degree. It is therefore advisable to minimize the exposure of your animals to extreme high temperatures.

The most available mechanism is when the animals themselves laze in the shade under the tress when they are out in the veld. It is critical to provide shade in the kraals by having trees or use of shade nets or other appropriate shading structures.

This is very important especially for the young (calves, kids, lambs) animals that spend a lot of time or in some cases, a whole day in the kraal without any shelter.

In hot environments or when animals forage during the hot hours of the day, the water demand or intake increases. Thus, animals should have daily access to clean, cool and sufficient water. Water has a direct role of quenching the thirst and in digestion, and is importantly used as a coolant by animals through the sweating mechanism.

During the current drought, farmers would be relocating their animals to “greener pasture”. On that, it is important that the animals be transported during the cooler hours of the day, and to have stop-overs along the way for them to rest or even drink water especially when trekking. The transporting vehicle should also be well covered to provide sufficient shade and ventilation at the same time. It is also advisable to execute routine husbandry practices such as vaccination or branding during the cooler hours or early morning.

Lastly, if animals have to adapt to new environments, they will have a lot to change in response, e.g. food preference, foraging time, respiration rate, and water intake amongst others.

With that in mind a farmer should as well adjust the management regime to respond to the animals’ demand or requirements.

*Erastus Ngaruka is a Technical Officer for Livestock at Agribank.