Contributions of animal nutrition research to nutritional principles: energetics.
Recognition of the parallels between animal life and flame provided the impetus to view life as combustion. Animal digestion and metabolism experiments revealed principles of nutrient sources of energy, the relation of chemical content to absorbed nutrient value, respiratory quotient, and biological value. Measurements of heat loss by animals revealed dramatic, >30-fold, differences in mass specific biological oxidation, leading to mass exponential descriptions of these metabolic rates, e.g., the Kleiber-Brody Law. More recent animal experiments have explored principles explaining the large mass specific rate variation, leading to principles of visceral organ mass primacy and the importance of ion pumping, proton leak, and membrane lipid composition as drivers of the variation. (+info)
Contribution of research with farm animals to protein metabolism concepts: a historical perspective.
The roles of proteins, carbohydrates, fats, and micronutrients in animal and human nutrition were broadly described during the late 18th and 19th centuries, and knowledge in protein nutrition evolved from work with all species. Although much of the fundamental and theoretical research in protein metabolism during the 20th century was conducted with laboratory animals, basic protein nutrition research in farm animals complemented those efforts and led to the development and use of new investigative methods (particularly in amino acid nutrition) as well as use of animal models in furthering the understanding of human protein metabolism. All these efforts have led to a contemporary hybrid model of protein nutrition and metabolism applicable to both humans and animal species. Now in the 21st century, farm animals are used in fetal and pediatric nutrition research, and data accruing for excess amino acid feeding in research with farm animals provide direction for assessment of pharmacological effects of amino acids when consumed in excessive quantities. Thus, as nutritional science is moving forward into nutrigenomics, nutriproteomics, and metabolomics, farm animal and human nutrition research interactions will likely continue with genetically modified farm animals produced for agricultural reasons (improved function and product quality) or those produced with human genes introduced to generate even better models of human protein metabolism. (+info)
Impact of research with cattle, pigs, and sheep on nutritional concepts: body composition and growth.
Studies with pigs, cattle, and sheep have provided a wealth of information regarding growth and body composition. Most of this information has been obtained using the standard methods for measuring the body composition of meat animals, which consist of dissection and chemical analysis. These methods have been used with meat animals to validate a variety of in vivo techniques that are used in both animal and human body composition studies. Research on the growth and body composition of meat animals has provided important concepts regarding the relation between growth and composition, including chemical maturity, the effects of severe undernutrition, partitioning of nutrients under various physiological conditions, the efficiency of nutrient utilization, and compensatory growth following a period of undernutrition. In addition, several genetic and physiological conditions affecting growth and body composition have been identified in meat animals that serve as important models for both animal and human growth. (+info)
The expression of ovine placental lactogen, StAR and progesterone-associated steroidogenic enzymes in placentae of overnourished growing adolescent ewes.
Overnourishing pregnant adolescent sheep promotes maternal growth but reduces placental mass, lamb birth weight and circulating progesterone. This study aimed to determine whether altered progesterone reflected transcript abundance for StAR (cholesterol transporter) and the steroidogenic enzymes (Cyp11A1, Hsd3b and Cyp17). Circulating and placental expression of ovine placental lactogen (oPL) was also investigated. Adolescent ewes with singleton pregnancies were fed high (H) or moderate (M) nutrient intake diets to restrict or support placental growth. Experiment 1: peripheral progesterone and oPL concentrations were measured in H (n=7) and M (n=6) animals across gestation (days 7-140). Experiment 2: progesterone was measured to mid- (day 81; M: n=11, H: n=13) or late gestation (day 130; M: n=21, H: n=22), placental oPL, StAR and steroidogenic enzymes were measured by qPCR and oPL protein by immunohistochemistry. Experiment 1: in H vs M animals, term placental (P<0.05), total cotyledon (P<0.01) and foetal size (P<0.05) were reduced. Circulating oPL and progesterone were reduced at mid- (P<0.001, P<0.01) and late gestation (P<0.01, P<0.05) and oPL detection was delayed (P<0.01). Experiment 2: placental oPL was not altered by nutrition. In day 81 H animals, progesterone levels were reduced (P<0.001) but not related to placental or foetal size. Moreover, placental steroidogenic enzymes were unaffected. Day 130 progesterone (P<0.001) and Cyp11A1 (P<0.05) were reduced in H animals with intrauterine growth restriction (H+IUGR). Reduced mid-gestation peripheral oPL and progesterone may reflect altered placental differentiation and/or increased hepatic clearance respectively. Restricted placental growth and reduced biosynthesis may account for reduced progesterone in day 130 H+IUGR ewes. (+info)
Metabolic plasticity during mammalian development is directionally dependent on early nutritional status.
Developmental plasticity in response to environmental cues can take the form of polyphenism, as for the discrete morphs of some insects, or of an apparently continuous spectrum of phenotype, as for most mammalian traits. The metabolic phenotype of adult rats, including the propensity to obesity, hyperinsulinemia, and hyperphagia, shows plasticity in response to prenatal nutrition and to neonatal administration of the adipokine leptin. Here, we report that the effects of neonatal leptin on hepatic gene expression and epigenetic status in adulthood are directionally dependent on the animal's nutritional status in utero. These results demonstrate that, during mammalian development, the direction of the response to one cue can be determined by previous exposure to another, suggesting the potential for a discontinuous distribution of environmentally induced phenotypes, analogous to the phenomenon of polyphenism. (+info)
Use of computer simulation to teach a systems approach to metabolism.
Use of a systems approach, as embodied in the computer simulation model of metabolism of a dairy cow, Molly (Baldwin, 2005), is ideal for teaching nutrition. This approach allows the overall complexity of the comprehensive system to be broken down into smaller manageable subunits that are easier to visualize. Quantitative interactions among nutrients supplied and metabolic production processes can be observed over extended time periods. Using Molly, undergraduate animal science students are able to observe detailed effects of changing dietary inputs, altering genetic milk production potential, and exogenously manipulating metabolism on metabolism of the whole cow. This paper demonstrates how Molly is used in the classroom to teach a systems approach to nutrition using example simulations. Three simulation examples demonstrate exercises examining effects of recombinant bovine somatotropin administration, dietary protein, and amino acid supplementation and nitrogen efficiency on milk production and cow metabolism. These and similar examples have been used to teach nutrition, metabolism, and lactation to undergraduate students for the past 20 yr. (+info)
Impacts of animal science research on United States sheep production and predictions for the future.