EDUCATION and TRAINING

B.S. in Animal Science, Oklahoma State University
M.S. in Animal Science, Oklahoma State University
Ph.D. in Animal Nutrition, Oklahoma State University

RESEARCH INTERESTS

Economic losses associated with the detrimental effects of heat stress on poultry production are at times substantial. Producers as well as consumers are affected in that return on investments for the producer is severely curtailed while the consumer is faced with elevated prices. The economic implications of this problem are great because of its geographically widespread nature. Environmental factors beyond the control of producers in both the more developed countries as well as those with emerging economies impose hardships that I hope can be alleviated by some of my research efforts. My goal is to engage in relevant, high impact research which will help to set the stage for further investigation, and in time, lead to answers which could prove to be valuable tools in the hands of producers world-wide as they attempt to combat the effects of a declining food supply.

My research is focused on examination of physiological and nutritional factors involved with the growth and survival of heat stressed poultry and to examine the interaction between nutrients, other additives and environment in this type of bird population. Using these findings, I attempt to develop management and nutrition-based tools to augment poultry production during heat stress. Exposure to high ambient temperatures and high relative humidity causes altered respiration or other physiological aberrations that generally result in reduced growth and decreased efficiency of production. A portion of this growth reduction may be directly attributed to decreased nutrient intake. In the past, nutrient requirements have been estimated based on bird performance in near ideal growing conditions. With decreased feed consumption being a reality under elevated temperature conditions, the challenge is to include environmental considerations in the nutrient requirement determination process while continuing to formulate balanced rations that will support efficient and profitable production.

My research has been directed towards the following areas:

Use of Electrolytes During Heat Stress

The hypothalamus is considered to play a central role in behavioral homeostatic mechanisms including control of body temperature. The concept of a hypothalamic set point at which a thermoregulatory defense against heat is initiated and its relationship with electrolytes have been investigated. The relationship between electrolyte consumption, thermoregulation and survival was one focus of my research . My studies determined that the excretion of potassium ions increased during heat exposure and that replenishing the bird’s body with this electrolyte had
beneficial effects. In addition, other common electrolytes (sodium and chloride) also proved beneficial when added to drinking water during heat exposure. These benefits were in the forms of improved weight gain, feed efficiency, and survival, as well as decreased body temperature.

Mineral Biological Availability in Broilers During Heat Stress

Mineral availability is a major concern and is influenced by a number of factors. Although they play very important roles in growth and maintenance of tissues, minerals that are generally adequate or only slightly deficient in practical diets have traditionally been overlooked in some areas of research. Requirements for some of these minerals vary because of biological availability in practical diets. Although it has become an accepted practice to increase mineral supplementation during periods of stress, very little research has been conducted to determine requirements and availability during these times. Many stressors change the profile of hormones that affect the biological processes of growth and reproduction. At the same time, tissue procurement of minerals may be impaired by the presence of stressors. Changes in immune competence may be the result of changes in availability of the growth-limiting nutrients for structural or metabolic functions in the cells of the immune system. Research has demonstrated that excretion of several minerals increase substantially when birds are exposed to periods of elevated temperatures. In light of this relationship, I identified evaluation of mineral biological availability under heat stress conditions as an area of research to pursue. We demonstrated that the proteinated form of manganese had greater biological availability than some salt forms. We also demonstrated that feeding heat stressed birds diets high in zinc from a zinc-polyamino acid source improved the birds’ ability to mount an immune response.

Lighting Regimen, Acclimation and Thermotolerance in Broilers

Small but significant changes in broiler livability have been realized by manipulating photoperiod. These results when combined with decreased incidences of leg disorders attributed to the use of a restricted light schedule have furthered an interest in lighting programs other than the generally accepted 23 hour light: 1 hour dark photoschedule. Most studies however have been conducted without regard for the possible influence of ambient temperature changes. I therefore designed experiments to evaluate possible growth responses to different lighting regimen in heat stressed broilers. It was determined that heat stressed birds reared on either a typical 23 hour light: 1 hour dark or a reduced light period (16 hour light: 8 hour dark) exhibited similar growth performance but reduced body temperature. This lack of a photoperiod effect on body weight gain, feed consumption and chilled carcass weight is important. It strengthened the current interest in the use of restricted lighting patterns because birds were not adversely affected.

Repeated exposure to heat results in a state of acclimatization that is manifested by the bird’s ability to reduce body temperature rise as well as increased survival during subsequent periods of heat exposure. I combined this practice with a daily feed withdrawal regimen. It was determined
that although the acclimation process did not significantly improve survival during subsequent
cyclic high temperature exposure, feed withdrawal prevented excessive body temperature rise and enhanced survival while at the same time causing no significant weight reduction. It was
also determined that environmental heat stress does not reduce blood ionized calcium in hens acclimated to elevated temperatures.

Dietary Fats, Growth and Immune Response

Addition of fat to poultry diets generally results in an increase in energy concentration, improved productivity and improved feed efficiency. Feeding fats to poultry apparently increases digesta retention time and as a result allows for a more complete utilization of other feed components. Other positive attributes of feeding fats may lie in the fatty acid composition and their effects on the immune system and a relationship between essential fatty acids and immune response has been suggested. An energy deficiency during heat stress, caused by reduced feed intake which in turn resulted from the discomfort of dietary heat increment, may be alleviated by manipulating dietary fats. The relationship between essential fatty acids and immune response has been reviewed. The degree of saturation as well as chain length may have an effect on metabolism and conversion to immunoregulatory products. As a result, dietary fatty acid intake may be expected to influence poultry immune response. The interaction between fats and other nutrients is also important. Magnesium and calcium retention were shown to be reduced by fatty acid supplementation and fats have been implicated in the reduction of mineral absorption because of the formation of insoluble soaps when cations come in contact with fatty acids released during digestion. We have examined this relationship between dietary fats and the production performance of broilers grown under heat stress conditions. Our research showed that the humoral immune response of heat stressed birds in the form of higher primary antibody titers (IgM and IgG) was greater for fish oil diets when compared with corn oil. It was also noted that cellular immune response in the form of phagocytic activity of abdominal macrophages was greater for birds fed the fish oil diet and the number of internalized sheep red blood cells per phagocytic macrophage were also greater. The results of our research also indicated that the ash (mineral) content of bone was higher for birds fed fish oil than for those fed corn oil while bird growth was also apparently affected by fat source

Heat Stress, Carcass Yield and Nutrient Content

Examination of the domestic United States broiler meat production consumption pattern indicates an increasing demand for ready-to-cook presorted cut-up parts. With this increase in the proportion of broiler meat being marketed as cut-up parts, periodic examination of the relationship between relative yields of various parts and some production-influencing factors such as heat stress is warranted. If the economic rewards in the form of increased yield of broiler parts are worthwhile, producers are more likely to attempt sustained environmental management. The broiler industry is constantly searching for ways to improve its product in order to meet the
demands of an increasingly discriminating public. Recent federal rulings in the United States relative to the Food Safety and Inspection Service’s nutrition-labeling program dictate that processors must pay attention to the nutritional quality of their products if they are to increase or maintain market share. With the advent of mandatory nutrition labeling of meat products, one obvious concern is the information that is required on the label. If consumers expect a certain level of nutrients in the products they purchase, then producers and processors must respond to these demands and ensure that the desired product reaches the marketplace. With this in mind, I designed experiments to test the effect of cycling high temperature stress on the relative yield of marketable broiler parts. Studies were also conducted in which carcass parts from broilers reared under different growing regimens were examined for their crude protein, ether extract, calcium, phosphorus, sodium, and potassium contents. We found that environmental temperature had an effect on the part yield distribution. We also established that difference exist in the nutrient content of broiler carcass parts. In addition, environmental temperatures were found to influence the nutrient content of some parts.