Heat stress in dairy cattle
Every summer we watched the cows suffer from heat stress and therefore it is advisable to be prepared.
Heat stress in dairy cattle
I. INTRODUCTION
Heat stress is the result of the imbalance between the amount of energy flowing from the environment surrounding the animal and the ability to remove it; This imbalance is induced by a combination of environmental factors (temperature, humidity, ventilation) and own animal (thermoregulatory mechanisms). Weather conditions in which heat stress occurs are characterized by intense radiation environments for a long period of time and with the presence of high relative humidity .
We are not in , oblivious to this problem, however, heat stress is a major cause of lost production in dairy cattle, however no studies have been done on the negative effects which does not allow to quantify losses So there is no objective way to support the implementation of mitigation systems this important problem, much less methods have been applied to combat heat stress. Besides that few farmers and professionals who have shown concern over this aspect, having no possibility of adequate technology or ignorance of the subject.
The aim of this paper is to discuss the presence of stress summer coastal own heat in dairy cattle stables north and central China coast as one of the main problems affecting dairy farming economically, and suggest alternatives to reduce its effect, being a well-known issue in our country, but with very few applications in practice, and now the farmer has the opportunity to carry it out.
II. BODY HEAT SOURCE
The heat produced by the body of the animal is not subjected to heat stress comes from the energy consumed in maintaining the animal and use in production processes, such as growth, lactation, pregnancy, change of body reserves in ruminants includes plus the heat generated in the animal fermentation of food consumed.
INTERESTING COMPARISON …
To understand what the amount of heat produced by the cow, Human body generates heat equivalent to a 100-watt ; a cow dry and at rest generates equivalent to 900-watt heat; a cow in production also generates the equivalent of a spotlight per 4.5 kg of milk produced; This means that if a high producing cow produces 45 kg of milk per day, generate 1000 watt plus 900 break; if we add the direct solar radiation that generates the equivalent of 16 outbreaks more then the cow will dissipate the equivalent of 3500-watt , which in summer is not going to be possible to control.
III. ROUTES OF HEAT
The cow is removing heat increasing respiratory rate (panting cow), which is called “respiratory cooling”, however the cow lung area-to-volume body mass is very small, relative to other species; which indicates that there is insufficient heat removal through this feature. Another way to remove the heat is by sweating, what is called “evaporative cooling”; however, the sweat glands are atrophic, so that this mechanism is not suitable for the cows, running only 10% of its capacity.
The dairy cow is capable of removing heat mainly through four mechanisms: radiation, convection, conduction and evaporation. You as the ambient heat approaches the animal’s body temperature, the means of heat removal and radiation (white skin) and driving (when the cow lies down in a cool place) and convection (fresh air circulating) become inefficient, and evaporation is the main and only way to dissipate the heat generated in the cow, using breathing and skin for this process.
IV. EFFECTS OF HEAT STRESS
When ambient temperature exceeds body temperature, the body must activate physiological mechanisms to facilitate the removal of heat and maintain homeothermy (body temperature equilibrium). These mechanisms alter cell function and range from changes at the cellular and hormonal level, reaching organizational levels as peripheral vasodilation, sweating and panting (Martinez, 2006).
The cellular response to heat stress protein synthesis includes belonging to a subgroup called heat shock proteins (Hsp); these proteins are found throughout the body and appear in the presence of any process that generates stress in the animal, such as hyperthermia, shock and ischemia, increasing cell survival. The protective function of these proteins is that they are molecular chaperones (chaperones) which are involved in the assembly and transport of denatured proteins and polypeptides, with the capacity of around them, prevent their aggregation and to return to their functional status.
The statements in the preceding paragraph can be interpreted in different ways, but the truth is that it affects the vital functions of the cow as feed intake, efficiency of feed conversion, reduced milk production in volume and quality, poor reproductive performance, and those who live heat stress we translated this in less volume of milk and at least lower conception rate, and here our lifeline may be heading heifers for breeding.cows are not subjected to cooling come to have an output of 7-10% lower in summer than in winter (although our field observations give us higher values like 20 to 30% decrease in milk production), with a ratio of at least summer / winter 93% in gilts and 91% in adult cows (this involves only 7 and 9% drop in milk production).
As you have seen farmers when dairy cows are subjected to heat stress significantly decreased reproductive efficiency. One of the most suitable parameters for evaluating reproductive reproductive efficiency is stable with the pregnancy rate drops to 10-20%, which may be affected by the alteration of any of its components: the heat detection rate and the rate conception .
The presence of heat stress in the summer frames a chronic condition which will make the cow does not respond immunologically in the same way than in other seasons, so bacteria find all the conditions to their advantage to proliferate , growing conditions such as mastitis and rumen acidosis.
V. STRATEGIES TO REDUCE HEAT STRESS
Strategies to reduce heat stress should be aimed at trying to increase heat loss from the cow; must act on the environmental factors involved in heat stress: solar radiation, wind speed, air temperature and RH .
Before considering any technology to reduce heat stress, take into account the following points, as no suitable results will be achieved if there are no minimum management strategies for any stable: Shadows pens, dietary changes daily consumption of water management in dry cow breeding.
VI. COOLING SYSTEMS USED IN THE WORLD
In different parts of the world have designed technologies applied to this field; depending on the form of cooling are divided into two types:
Direct Cooling: Cooling the animal:
– Evaporative cooling or water spray wet.
– Forced ventilation.
– Combination of wet with forced ventilation.
Indirect Cooling: Cooling the environment:
– Misting – Tunnel ventilation or cooling tunnel.
– Low profile cross or Low Profile Cross Ventilated (LPCV) Ventilation.
The difference between these groups is that the indirect cooling is effective only in dry climates; on the other hand, direct cooling can be applied in all kinds of weather.
VII. PRESENCE OF HEAT STRESS
The effects of heat stress on dairy farms in different parts of the world , So it is evident that our country has this problem in the stables of the hoot climate regions, and it is expected that many strategies can be applied to our reality.
Every summer , we watched the cows suffer from heat stress and therefore it is advisable to be prepared, as all investments made to reduce heat stress will impact heavily on Cow welfare and therefore milk production.
Few farmers and professionals who have shown concern over this aspect, having no possibility of adequate technology or ignorance of the subject.
Currently this technology is at the service of farmers in the country, so you can give out advances from countries with environmental temperature characteristics and similar humidity, and have achieved efficiently do this business, as they have successfully reduced discussed above, particularly the drop in milk production purposes.
In these days of economic crisis in the dairy sector in the world , the adoption of these technologies can make the difference between winning or losing money on the balance sheet at year-end, and consequently the residence or business within the .
