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Animal Science

Protected from the heat

Protein activated prematurely reduces poultry mortality from variations in the environment temperature

The Brazilian poultry sector has invested heavily in infrastructure, modernization and new handling techniques over the last few years, to increase the volume of production and to meet domestic and foreign demand. The success of these measures can be corroborated by the fact that, last year, poultry took second place in the ranking of farm exports, behind only commodities like soya (beans, bran and oil), and ahead of traditional products like coffee.

The large volume marketed is the main factor for the sector’s profit, and there should therefore be minimal losses so as not to cause negative impacts for the process. In this regard, the farmers need to get round one of the problems that still torments them: the chicken mortality from temperature variations, which affects 1 million birds a month, out of an estimated production of 300 million in the same period.

To try to turn this scenario round, Marcos Macari, a professor at the School of Agrarian and Veterinarian Sciences of the São Paulo State University (Unesp), in Jaboticabal, and the university’s pro-rector for research, stimulated in embryos and recently hatched chickens the production of a heat shock protein (hsp 70), also called a stress protein. The intention was to protect the birds from harsh variations in temperature, when they reached an adult age.

The results obtained have now been passed on to the breeders during congresses for the sector, and they show that the premature activation of this mechanism makes it possible for the birds to better adapt to heat, during the process of growth. “Our studies show that it is possible to put the bird under stress, in both high temperatures and cold, in such a way that it expresses this protein more”, explains Macari, the coordinator of the thematic project Role of Heat Shock Protein in Developing Heat Tolerance in Poultry, financed by FAPESP.

A scholar and a specialist in poultry raising, Macari stresses that there is one myth that involves poultry breeding that has to eliminated for once and for all. “We have to get rid of the myth that chicken meat has hormones, this is untrue, but it is something spread about not only by laymen but even by doctors”, he says. Macari explains that the quick growth of the birds is due to genetic improvement, caused by the selection process. This improvement couples two situations: the expression of the genes for growth, and voracity, which is the capacity for eating a lot.

Tolerance to heat
In the experiments carried out in the thematic project, both the eggs and the recently hatched chicks were put in the normal temperature for incubation, at 37.5 degrees, and alsoat 36.5 and 38.5 degrees. “In the case of the embryo, to our surprise, the birds that were incubated at lower temperatures proved to be more tolerant to high temperatures as adults, and they grew more. We were expecting the opposite, because the data in the literature show that if a chick is exposed up to five days after hatching to an intense heat and if it can stand this heat, it manages to be more tolerant of high environmental temperatures as an adult”, says Macari.

In the experiments carried out straight after the birds hatched, the higher temperature proved to be more effective in the organism’s adaptation response. Macari nevertheless claims that, technically, this procedure is more complicated, because the poultry houses have to be kept closed for three weeks at a high temperature. From the point of view of the industry, it is easier to work with embryos, because it is simpler to raise or to lower the temperature of an industrial incubator – which incubate about 1 million eggs – than to do this with 1 million chickens or chicks. “This is the reason why today research in the poultry breeding area is focused, to a large extent, on manipulating the embryos”.

“We proposed the project, because the chicken, when it is born, is like a baby, very sensitive to cold, and when it grows, it is very sensitive to heat. And the rate of growth of the birds is very fast”, says the professor. Due to the genetic characteristics of chicken today, a chick that weighs on average 45 grams on hatching will be weighing 2 to 2.5 kilos in 42 to 45 days at the most. As Brazil is a country where climatic conditions are not severe, during the initial stage of the poultry raising system, not many problems are met. When the temperature gets very cold, as it usually happens in the south, the breeders use heater to keep the birds warm. But heat ends up causing more problems and losses.

Spring and fall are pointed out by Macari as being the seasons when the highest mortality rates are recorded with Brazil’s table birds. The low rainfall, coupled with very hot days and cold nights, causes a heart shock in the birds, in particular if they are more than 30 days old and in the final stage of growth. During the summer, in spite of the heat, the rain contributes towards keeping the air more humid, and as in this period the sky is always more cloudy, there is also a lower incidence of sunlight on the earth. “The project had as its starting point a study of the physiological and molecular mechanisms, to see if we could improve the chicken’s tolerance to heat”, the professor says. “Based mainly on cells studies, our premise was that when a cell is put under stress, it produces more hsp 70 protein to protect itself from the stressful conditions”, he explains.

All the proteins present in the cells have a three-dimensional structure, but in stress situations they may lose the original configuration. The role of the hsp 70 is to prevent the other proteins present in the cells from losing this configuration. It is present in all cells, but it is more expressed in tissues with greater sensitivity to stress, like the heart and the brain. That is why these tissues, as besides the liver and the lungs, were chosen to study the expression of this protein.

Change in eating habits
In Macari’s assessment, poultry breeding today plays a considerable social role in Brazil, for the fact that it is a protein accessible to the low income population. A kilo of whole chicken costs the end consumer around R$ 1.50. According to the professor, Brazilian chicken is cheap as a result of the large volume producedand of the low labor cost. Not to mention that the country is a great producer of corn and soya, which is the basis for the birds’ food. “This makes Brazilian chicken the tastiest in the world. British chicken tastes of fish, because there they add fishmeal to the feed”, the professor comments.

The competitive price has resulted in a substantial increase in demand over the last decade. The 13.6 kilos per inhabitant consumed in 1990 reached 30.8 kilos last year. This growth in consumption has come with changes in the eating habits of the Brazilians, who have started to buy chicken in parts, preferably semi-prepared. The feet and the head until a few years ago were part of the “whole chicken” package, and quite frequently ended up in the garbage. Now they have found new markets. China is the main purchaser of the Brazilian chicken’s feet, which have a high added value after boning. The skin, once processed, is transformed into straps for watches and other products.

Immediate application
The thematic project, which started four years ago, has already resulted in three dissertations for masters’ degrees and three for doctorates. It is forecast to be concluded in March next year. The group involved in the study worked with 12 focuses in the course of the experiments, such as embryonic stress and post-hatching, pre and post hatching hormonal variations, and the effects of these hormonal processes on the bird’s growth, amongst others. All the results have now been written up and are being published in Brazilian and international magazines. According to Macari, poultry breeding does not wait around for the publication to come out in a magazine to spread out the technological innovations. “What I produce, I communicate at congresses, and application in the field comes straight afterwards”, he says. For this reason, he has no way of knowing if the results of his research are already being applied by some industry.

“The production system is handled in very particular manner in each company, and there is no single standard in the country for breeding one company may keep secrets that it does not communicate because the system is very competitive”, he explains. “If I handle the embryo in a way that means a gain in weight for the newly-born, at the end of the process I will have a profit”. And he gives an example with figures: each additional 10 grams in a chick will mean 100 grams at the end of the system for production. For a poultry farm that produces 1 million chickens a month, this gain in the weight of the embryo means a substantial net profit.

In the project, Macari can also count on international partners who are collaborating in the studies, like Eddy Decuypere, from the Catholic University of Leuven, in Belgium, and Frank Edens, from the North Carolina State University. Decuypere, has been working on the project since the beginning, is carrying out part of the research in Belgium. Edens joined the team whenthe work was already under way. In Brazil, the research is also receiving the collaboration of Professor Jesus Ferro, also from Unesp in Jaboticabal, of Professor Luís Lehmann Coutinho, from the Luiz de Queiroz College of Agriculture (Esalq) of the University of São Paulo in (USP), in Piracicaba; and of Elizabete Gonzales, from Unesp’s Faculty of Veterinary Medicine and Zootechny in Botucatu.

They used three lineages of chicken in the research: the American Cobb 500, the most used commercially, the Ross, of British origin, and the bare neck chicken[RJS7], which is more tolerant to heat, because of its genetic characteristics. The system for incubation worked with from 120 to 1,000 eggs, and with from 1,000 to 1,200 chickens in each of the 12 experiments carried out in the project.

New methodology
For the study to be regarded as concluded, according to the coordinator, two pending items need to be cleared up. One is the way of quantifying the protein. The method used up till now is the Western Blot, but the team is developing a new methodology based on the Elisa technique. “It is a very simple and quick technique that makes it possible to work with larger volumes”, Macari explains. “And we also want to know how the bird’s brain behaves in a situation of stress. In particular, how the areas of the hypothalamus react, as this is the bird’s temperature control system”. To reach their findings here, the technique of hybridization in situ is being used, in which the bird is put under stress, the brain is removed immediately, frozen, cut, and then a histochemical reaction (a chemical study of the cells and tissues) is done to identify and to analyze which area is reacting best.

Macari upholds that a knowledge of the physiology, biochemistry and immunology of the birds is fundamental for avoiding the appearance of diseases and, as a consequence, of losses. “In this way, 70% of the problems that appear will be solved in time to avoid losses”. The professor credits part of the success of Brazilian poultry farming to the technical level and understanding of the professionals who work in the sector. “They are very good”, he maintains. “This is due to the education they have had at Brazilian universities, and also to the involvement of private companies in training this personnel”.

In Macari’s assessment, one of the ways of making this scientific knowledge reach the interested parties are books. For this reason, as the director of publications of the Apinco Foundation for Science and Technology (Facta in the Portuguese acronym), an entity connected with the Brazilian Association of the Producers of Table Chicks (Apinco in Portuguese), he dedicates himself, in some cases, to compile valiant works on the theme, even if to do so he has to work with texts from 57 Brazilian specialists, as it happened in the process of editing the book Doença das Aves [Disease in Birds], issued in 2000. For Macari, this work filled a gap of 50 years, because the last Brazilian book on the subject had been issued in 1950, by Professor José Reis, a researcher at the Oswaldo Cruz Institute, at the Biological Institute, and a precursor in publicizing science in Brazil.

At the end of last month, Macari launched the 2nd edition of the book Fisiologia Aviária Aplicada a Frango de Corte [Bird Physiology Applied to the Table Chicken]. Both in the books and in the research work, Macari marries scientific knowledge to the concern with finding alternatives that favor the system for raising chickens. The result of his thematic project with embryos and newly born chickens is a proof that he has succeeded in finding a simple solution for reducing mortality from heat in birds at the stage of growth, without burdening the productive system.

Heated dispute for the world market

The United States dominates the world poultry market, but as each year goes by Brazil has taken a larger share slice of this tough trade. In 2000, the United States held 48% of this market, and Brazil had 17%, according to data from the United States Department of Agriculture (USDA). Last year, the American participation remained stable, at 48%, while the Brazilian share rose to 21%. This growth was the result of winning new markets in Europe, because of the mad cow disease and foot and mouth disease, as well as of the expansion of shipments to Russia, caused by a more aggressive export policy, under the command of two companies, Sadia and Perdigão.

About 80% of Brazil’s production of poultry, nowadays around 600,000 tons a month (nearly 300 million birds) is intended for the domestic market. The rest goes to the Middle East, Europe and Japan. Last year, the country shipped 1,266,000 tons of poultry, both unprocessed and processed, which means growth of 38% over the previous year’s volume. The income brought in reached US$ 1.292 billion, a 60.3% rise over 2000. This year, according to the executive secretary of the Brazilian Association of the Producers of Table Chicks (Apinco), José Carlos Godoy, Brazil has retained its markets and expanded its sales. The figures released by the Secretariat for Foreign Trade (Secex) show that shipments of poultry in the month of February reached 108,743 tons, a volume 20% higher than in the same month of the previous year.

The project
Role of Heat Shock Protein in the Development of Heat Tolerance in Table Chickens (nº 97/09533-7); Modality Thematic project; Coordinator Marcos Macari – School of Agrarian and Veterinary Sciences of the São Paulo State University (Unesp) – Jaboticabal; Investment R$ 205,387.51 and US$ 126,826.33