An experiment was conducted to evaluate the effects of chromium picolinate (CrP) on growth performance, carcass composition, and tissue accretion rates in pigs from 27 to 109 kg BW. Seven littermate sets of Yorkshire-Hampshire barrows, individually penned, were fed a fortified, corn-soybean meal basal diet (.95% lysine from 27 to 55 kg; .80% lysine from 55 to 109 kg) supplemented with 0 or 200 micrograms/kg of Cr from CrP. Addition of CrP increased (P < .09) ADG but did not affect ADFI or feed:gain ratio. Average and 10th rib backfat and longissimus muscle area were not affected by Cr supplementation. The right side of the carcass was physically dissected into muscle, fat, bone, and skin. Additionally, five pigs were killed for determination of initial body composition. Dietary CrP addition increased (P < .02) the percentage of muscle and decreased (P < .06) the percentage of fat. Total gain of dissected bone and skin were not different between treatments, but CrP increased (P < .06) the total gain of dissected muscle and decreased (P < .02) the total gain of dissected fat. Also, CrP increased the daily accretion rates of muscle (P < .05) and bone (P < .03) and decreased the daily accretion rate of fat (P < .05). The left side of the carcass was ground for determination of water, protein, lipid, and ash. The addition of CrP to the diet increased the percentage (P < .09) and accretion rate (P < .09) of water and increased the percentage (P < .004), total gain (P < .02), and accretion rate (P < .02) of protein while decreasing (P < .04) the percentage of lipid. Pigs fed CrP also had a decreased (P < .004) percentage of lipid in the dissected carcass muscle. Water, protein, and ash from the dissected muscle were not different between treatments. These results suggest that CrP supplementation throughout the entire growing-finishing phase increases the total gain and accretion rate of muscle while decreasing the total gain and accretion rate of fat. This results in carcasses with an increased percentage of muscle and decreased percentage of fat.
We conducted two experiments to determine whether the efficacy of chromium picolinate (CrP) on growth performance, carcass composition, and tissue accretion rates is dependent on the lean gain potential of the pigs. In Exp. 1, 40 barrows (20 from each of two genetic backgrounds; two pigs per pen, five pens per treatment) were fed a fortified, corn-soybean meal basal diet (.95% lysine from 19 to 55 kg BW; .80% lysine from 55 to 109 kg BW) without or with 200 microg/kg of Cr from CrP. The addition of Cr had no effect on performance, carcass measurements, or accretion rates of carcass protein or lipid, regardless of the lean gain potential of the pigs. In Exp. 2, 60 group-penned pigs (three pigs per pen; five pens per treatment) were fed a fortified, corn-soybean meal basal diet without or with 200 microg/kg of Cr from CrP from 21 to 104 kg BW. Within the dietary Cr treatments, half of the pigs received daily injections of 3 mg of porcine somatotropin (pST) from 54 to 104 kg BW. The pST administration resulted in faster growth rates (P < .007), improved feed efficiency (P < .001), increased longissimus area (P < .001), and decreased 10th-rib backfat (P < .001). Administration of pST also increased the percentage and accretion rate of carcass protein (P < .001) and decreased the percentage and accretion rate of carcass lipid (P < .001). The addition of CrP to the diet had no effect on any variable measured in either the untreated or pST-treated pigs. In these studies, Cr was ineffective at altering the composition of the carcass and its effects were not dependent on the pig's potential for lean gain.
Two experiments were conducted to assess the bioavailability of P in five sources of defluorinated phosphate (DFP) that differed in P solubility in neutral ammonium citrate (NAC). In Exp. 1, 384 2-d-old male chicks were fed a corn-cornstarch-dextrose-soybean meal basal diet (1.22% lysine, 1.00% Ca, .45% P) or the basal with .05 or .10% P from monosodium phosphate (MSP), or .10% P from DFP with 60, 70, 75, 82, or 91% NAC soluble P. Each diet was fed to six pen replicates of eight chicks per pen for 14 d (58 to 402 g). Growth rate, feed/gain, and tibia breaking strength and ash concentration were improved (P < .001) by P supplementation, regardless of P source. Tibia strength and ash were regressed on P intake, and slope-ratios were calculated to assess the relative bioavailability of P in the DFP sources. The bioavailabilities of P in the 60, 70, 75, 82, and 91% NAC soluble DFP sources, relative to MSP (given a value of 100), were 81, 75, 84, 84, and 91%, respectively (linear, P < .08). In Exp. 2, 35 individually penned pigs were fed a corn-soybean meal basal diet (.95% lysine, .75% Ca, .33% P) or the basal with .15% P from MSP or from the five DFP sources. Each diet was fed to five pigs for 33 d (15.0 to 35.9 kg). Growth rate, feed/gain, and breaking strength of the metacarpals, metatarsals, and femurs were improved (P < .001) by MSP and DFP.(ABSTRACT TRUNCATED AT 250 WORDS)
Background-The myogenic response is a phenomenon in which blood vessels respond to increases and decreases in transmural pressure with constriction and dilation, respectively. Despite intense investigation into the signaling mechanisms underlying this response, the precise mechanisms remain unclear. It has been suggested that the myogenic response occurs when pressure or stretch evokes increases in vessel wall tension that results in vessel smooth muscle cell depolarization. This causes Ca 2ϩ entry through voltage-gated Ca 2ϩ channels. Of note, in vitro studies demonstrate that the magnitude of the myogenic response is dependent on the extracellular Ca 2ϩ . We tested the hypothesis that in conscious humans, physiological changes in extracellular Ca 2ϩ concentrations would be an important determinant of the myogenic response. Methods and Results-Venous blood ionized calcium was used as an index of interstitial calcium and was measured 5, 15, and then every 15 seconds for 75 seconds, then every 30 seconds for 90 seconds, then finally at the 300-second mark. Forearm blood pressure and flow velocity were determined after 10 minutes of forearm ischemia. We found that the rate of change in serum calcium levels varied as a function of transmural pressure (rϭ0.96). Moreover, the calcium concentration was inversely proportional to forearm blood velocity (rϭ0.99). Conclusions-We
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