No abstract

Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and diurnal variation in OC, Pyd, and Dpd in eight adult geldings and seven weanling colts. Blood and urine were collected at regular intervals over 24 h. Serum OC and cortisol, and urinary Pyd and Dpd were analyzed. Mean 24-h concentrations of cortisol and all three markers were higher (P<.003) in weanlings than adults. Significant 24-h variation was observed in adult gelding OC, Pyd, and Dpd concentrations (P< .02). Adult OC concentrations were highest between 2400 and 0900; Pyd and Dpd peaked between 0200 and 0800. Similar patterns of bone turnover were observed in weanling values, but they were not significant (P>.17) owing to greater variability between individuals. Cortisol secretion varied (P<.001) over 24 h in both adults and weanlings and, thus, did not seem to be responsible for greater variability in markers of bone turnover between weanlings. These data demonstrate that diurnal rhythms exist for serum OC and urinary Pyd and Dpd in adult horses, as reported in humans, and that sample timing is an important consideration in future equine studies using these markers.

Our objective was to determine the relative importance of the macronutrient components of colostrum in the stimulation of vital organ protein synthesis in neonatal pigs. We studied colostrum-deprived newborn pigs within 4-6 h after birth (unfed) and three groups fed for 24 h mature milk, colostrum, or a formula containing a macronutrient composition comparable to that of colostrum. We measured protein synthesis in vivo using a flooding dose of 3H-phenylalanine. The fractional rates of protein synthesis (Ks) in the brain, heart, lung, kidney and spleen were significantly higher in all fed groups than in the unfed newborns. Among the three fed groups, brain and heart protein synthesis rates were greater in colostrum-fed than in either milk- or formula-fed pigs. Kidney and spleen protein synthesis rates in colostrum- and formula-fed pigs were not significantly different, but both were higher than in milk-fed pigs. The stimulation of kidney protein synthesis in response to feeding was primarily a consequence of greater protein synthetic efficiency; however, protein synthetic capacity in the heart, lung and spleen was generally greater in colostrum- and formula-fed pigs than in unfed newborns. Our results suggest that the predominant stimulus for vital organ protein synthesis in colostrum-fed neonatal pigs is nutrient intake. However, there was a specific stimulation of both brain and heart protein synthesis in colostrum-fed pigs that cannot be attributed to macronutrients.

This project was undertaken to compare growth, meat quality, and diet digestibility when pigs were fed cafeteria food waste (FW) or a corn/soybean meal (CSM) diet. Cafeteria food waste (36 samples) fed in the growing and finishing experiment averaged 22.4% DM, 21.4% CP, 14.1% ADF, 27.2% ether extract, and 3.2% ash. The first experiment used 50 crossbred pigs randomly assigned to four diets. During the growing phase, pigs fed a CSM diet gained faster (P < .05) than pigs fed FW or FW plus energy supplements. However, the two groups fed FW plus energy supplements (at 25 or 50% of the intake of the CSM diet) gained faster (P < .05) than pigs fed FW alone (.61 and .65 kg/d, respectively, vs .46 kg/d). In the finishing phase, FW plus an energy supplement fed at 50% of the level of CSM intake resulted in gains that did not differ from those of pigs fed the CSM diet (.90 vs .99 kg/d; P > .05). A nutrient digestibility and nitrogen balance trial using eight growing barrows compared FW with the same CSM growing diet fed earlier. Dry matter digestibility was similar for the two diets (P > .05). However, CP digestibility was higher (P < .05) in the FW diet than in the CSM diet (88.2 vs 84.3%). Although the percentage of nitrogen retained was not different between FW and CSM diets (56.0 vs 55.2%; P > .05), the amount of nitrogen retained was greater for pigs fed the CSM diet (29.3 vs. 24.5 g/d; P < .05) because DMI was greater (1.7 vs 1.4 kg/d) for pigs fed CSM compared with FW. At the completion of the finishing experiment, six pigs were selected from both the CSM and FW diets and fed to finishing weight. The pigs were slaughtered, and the pork loins were removed for flavor and texture analysis. A consumer panel rated the meat quality from FW pigs as acceptable and overall flavor comparable to CSM pigs (P > .05). These results indicate that food waste has nutritive value and may be useful in swine diets.

Our objective was to determine whether neonates adapt to protein malnutrition by preserving the relative growth and metabolism of gastrointestinal tissue at the expense of skeletal muscle. We measured gastrointestinal, liver, and carcass tissue masses and blood flow, oxygen consumption, and net glucose and amino acid fluxes in vivo of the portal-drained visceral tissues (PDV) in neonatal pigs fed isocaloric diets containing either 30% protein [control (C)] or 15% [low protein (LP)] for 14 days. Relative protein mass and fasting blood flow and oxygen consumption of PDV tissue in either group were not different. Relative protein mass of liver and carcass was lower in LP pigs. Net essential amino acid absorption and insulin concentration after feeding were lower in LP pigs. Results demonstrate that protein malnutrition in neonatal pigs differentially altered rates of tissue growth, such that the proportion of body protein partitioned into gastrointestinal tissue was preserved, while that of skeletal muscle was reduced. Chronic reduction in amino acid absorption in protein-malnourished pigs resulted in a reduced insulin response to feeding, which presumably limited substrate availability and the anabolic stimulus for skeletal muscle protein accretion.