THOMAS D. CRENSHAW, PH.D.
1675 Observatory Drive
Madison, WI 53706-1284
Principal Research Interest:
Dietary manipulation and cellular regulation of endochondral ossification, renal and skeletal compensation to dietary cation-anion balance; optimization of dietary lysine utilization; baby pig growth and survival.
Endochondral Ossification: The long-range objective is to enhance the productive longevity of swine by reducing the incidence of lameness. Lameness problems cannot be solved simply by adding more Ca and P to the diet.
Current projects involve the study of dietary fatty acid ratios (n-3:n-6 fatty acids) on bone integrity and remodeling. The ratio of dietary fatty acids may alter the precursor pools of long-chain polyunsaturated fatty acids which serve as precursors for prostaglandin synthesis. In connective tissue, prostaglandins serve as important signals regulating the balance between resorption and formation in bone and cartilage. In order to assess the effects of dietary fatty acids on the synthesis and release of Prostaglandins, bone cells will be harvested from animals preconditioned to diets with different fatty acid ratios. Mechanical strains on bone, which induce prostaglandin release, will be used in vivo to confirm responses observed in the in vitro experiments.
Cation-Anion Balance: Diets typically consumed by monogastric animals result in a net acid load that is compensated by renal ammoniagenesis and phosphate excretion (see figure). The ultimate source (bone stores vs. diet) of the phosphate excreted in response to the acidogenic diet is not well established. Depletion of bone phosphate would compromise bone integrity. We are using histomorphometric techniques as well as standard mineral balance techniques to evaluate the effects of acidogenic diets on bone in adult swine.
Renal compensated acidosis results from the consumption of acidogenic diets. The balance of dietary cations and anions presented to the kidneys is influenced by the rates of soft tissue and bone accretion as well as fecal ion excretion. Major compensation occurs by an increase in renal ammonium and monobasic phosphate excretion.
Lysine Utilization: Lysine, the first limiting amino acid in swine diets, is a major economic determinant in production costs. The maximum efficiency of lysine utilization for lean gain occurs at 50 to 60% of the lysine level required for maximum growth. Logistic curve fitting techniques are being used to develop response curves for alternate lysine sources. From predicted based upon a defined set of feed ingredient costs.
Budde, R.A. and T. D. Crenshaw. 2003. Chronic metabolic acid load induced by changes in dietary electrolyte balance increased chloride retention but did not compromise bone in growing swine. J. Anim. Sci. 81:197-208.
Li, Sufen, Xugang Luo, Bin Liu, T. D. Crenshaw, Xia Kuang , Guizhi Shao, Shunxiang Yu. 2004. Use of chemical characteristics to predict relative bioavailability of supplemental organic manganese sources for broilers. J. Anim. Sci. 82:2352-2363.
Choy, V.E., A. Kyparos. A.C. Vailas, T.D. Crenshaw, and D.A. Martinez. 2005. The biphasic response of porcine tendon to recombinant porcine growth hormone. Growth Horm IGF Res. 15:39-46.
Li, S.F, X.G. Luo, L. Lu, T. D. Crenshaw, Y.Q. Bu, B. Liu, X. Kuang , G.Z. Shao, and SX. Yu. 2005. Bioavailability of organic manganese sources in broilers fed high dietary calcium. Anim Feed Sci Tech. 124:703-715.
Crenshaw, T.D. 2006. Arthritis or OCD- Identification & Prevention. Banff Swine Conference. Banff Canada. Adv. Pork Prod. 17:199-208.
Pagano, A.R., K. Yasuda, K. R. Roneker, T.D. Crenshaw, and X. G. Lei. 2007. Supplemental Escherichia coli phytase and strontium enhance bone strength of young pigs fed a phosphorus-adequate diet. J. Nutr. 137:1795-1801.
Patchanee, P., T.D. Crenshaw, and P.B. Bahnson. 2007. Oral sodium chlorate, topical disinfection and younger weaning age reduce Salmonella enterica shedding in pigs. J. Food Protection 70:1798-1803.