M. D. Lindemann

Effect of dietary ractopamine on tenderness and postmortem protein degradation of pork muscle

Twenty-four finishing pigs with a mean starting weight of 82kg were assigned to two dietary regimens: (1) a corn-soybean meal basal diet (control; n=12), and (2) the basal diet supplemented with 20ppm ractopamine HCl (RAC; n=12). After 28-30 days on the feeding trial, pigs were slaughtered, and the growth and carcass characteristics were measured. Furthermore, the 3rd-13th rib section of longissimus muscle was excised at 48h postmortem, sliced into 19-mm thick chops, vacuum packaged, stored at 2°C, and subjected to Warner-Bratzler shear force (WBSF) and electrophoretic tests after 2, 4, 7, 10, 14, and 21 days (postmortem). RAC feeding increased (P<0.01) pig carcass weight and percent lean, but it also increased the day-2 muscle WBSF by 20% (P<0.01). The shear force difference between control and RAC pig muscles gradually decreased and vanished by day 10 (P>0.05) when both muscle groups became more tender. The muscle from RAC-fed pigs exhibited a slower protein degradation rate than muscle from the control animals, notably for proteins in the 15-45kDa range. The results suggested that the tenderness difference between ractopamine-treated and control pig muscles was related to the proteolysis rate, and could be diminished with adequate postmortem ageing.

Effects of organic acids with and without a microbial culture on performance and gastrointestinal tract measurements of weanling pigs

In Study 1, 25-day-old crossbred weanling pigs (n = 144) were fed a 20% crude protein maize-soyabean meal basal diet. Supplementation with 1.5% citric acid tended to improve gain and the efficiency of feed utilization (F:G) during the first 4 weeks with no effect during week 5; 1.5% fumaric acid caused smaller and non-significant improvements in gain and F:G. Feed intake was unaffected by organic acids. The pH, chloride ion and volatile fatty acid concentration of intestinal contents from the stomach, jejunum, cecum and lower colon of 27 pigs killed at the end of Study 1 were not significantly affected by dietary organic acids. With the exception of fumarate, the concentration of non-volatile acids was not affected by diet. The stomach and jejunum of pigs given fumaric acid had a greater concentration (P < 0.05) of fumarate than those of pigs given the control and citric acid diets. In Study 2 (n = 192), no interactive effect of dietary fumaric or citric acid with a live microbial culture (Lactobacillus acidophilus) was observed. Fumaric acid supplementation increased (P < 0.03) gain and the microbial culture improved gain (P < 0.08) and F:G (P < 0.02) during the 5 week test; 1.5% citric acid had no effect. In conclusion, the addition of citric or fumaric acid and/or a microbial culture produced inconsistent improvements in gain and F:G, with little effect on intestinal digesta measurements.

Effect of chromium source on tissue concentration of chromium in pigs

The concentration of Cr in several tissues in response to high-level, short-term supplementation was used to determine the relative bioavailability among 4 organic Cr sources and to assess the relative safety of high levels of supplementation. Crossbred pigs (n = 40; mean BW = 48.1 +/- 0.9 kg) were allotted to 5 diets: a control diet with no added Cr, or 5,000 microg/kg of Cr from Cr tripicolinate (CrTP), Cr propionate (CrPrp), Cr methionine (CrMet), or Cr yeast (CrY). Twenty gilts were housed individually and barrows were housed in pairs. Average duration of feeding before slaughter was 75 d. For the total experiment, pigs fed the unsupplemented diet had less ADG than pigs fed CrY (P < 0.05). Serum clinical chemistry values, obtained during the final week of the experiment, demonstrated few effects with no responses that would raise concern about metabolic changes in response to the Cr sources. The effects of the forms of Cr fed on carcass measurements and meat quality were also minimal. All Cr sources reduced cooler shrink (P < 0.05) and most resulted in some meat color change on d 1 postslaughter. For tissue Cr content, 4 of 5 tissues (bone, kidney, liver, and ovary) were increased (P < 0.05) in Cr content by supplementation with CrTP and CrMet, whereas only 2 tissues (bone and kidney) were increased (P < 0.05) by CrY, and none were increased by CrPrp. In all tissues of response, CrTP exceeded CrMet and CrMet exceeded CrY. Comparing the relative increase in tissue Cr for all responsive tissues (bone, kidney, liver, and ovary) gave a range of responses, for which the mean bioavailability relative to CrTP across tissues was 13.1% for CrPrp (0.2 to 19.0%), 50.5% for CrMet (36.2 to 79.1%), and 22.8% for CrY (2.5 to 47.9%). In summation, these results show very clear Cr effects on multiple tissues, which is conclusive evidence of absorption and deposition. The lack of a negative response in growth performance, carcass measures, and clinical chemistry at the increased quantities used herein provides assurance that normal quantities of addition are extremely safe.

The effects of dietary chromium (III) picolinate on growth performance, blood measurements, and respiratory rate in pigs kept in high and low ambient temperature.

Three experiments were conducted to investigate the effects of thermal stress and dietary Cr on growth performance and physiological variables in weanling pigs. In Exp. 1, a total of 54 pigs (BW of 5.95 +/- 0.84 kg) were allotted to a 2 x 3 factorial arrangement using 2 ambient temperatures (23.7 or 40.5 degrees C during d 14 to 28 postweaning) and 3 dietary concentrations of Cr (0, 1,000, or 2,000 microg/kg) as Cr(III) picolinate. In Exp. 2, a total of 54 pigs (BW of 5.94 +/- 1.29 kg) were allotted in the same treatment arrangement but with different ambient temperatures (26.5 or 16.0 degrees C during d 14 to 26 postweaning). In Exp. 3, a total of 36 pigs (BW of 6.40 +/- 0.72 kg) were allotted in the same treatment arrangement with ambient temperatures of 25.9 or 13.8 degrees C during d 14 to 28 postweaning. During d 0 to 14 of all experiments, a neutral ambient temperature (NT) was maintained. In Exp. 1, pigs in high ambient temperature (HT) gained less BW (575 vs. 663 g/d; P < 0.001) and consumed less feed (926 vs. 1,074 g/d; P = 0.001) than pigs in NT during d 14 to 28. However, G:F was not affected by ambient temperature (0.623 vs. 0.618 g/g; P = 0.702). Dietary Cr had no effect on growth performance. Pigs in HT had less plasma cortisol (42.0 vs. 53.7 ng/mL; P = 0.012) and glucose (6.68 vs. 6.96 ng/mL; P = 0.018). Respiratory rate of pigs in HT was greater compared with the pigs in NT (114.6 vs. 65.0 breaths/min; P < 0.001) on d 27. In Exp. 2 and 3 (pooled), pigs in low ambient temperature (LT) had decreased G:F (0.636 vs. 0.663 g/g; P < 0.01) associated with a tendency toward a greater ADFI (1,026 vs. 942 g; P = 0.079) during d 14 to 26 (28). Ambient temperature or dietary Cr supplementation had no effect on blood measurements. In Exp. 3, the respiratory rate measured on d 22 and 27 was less (43.2 vs. 54.2 breaths/min and 42.2 vs. 57.0 breaths/min, respectively; P < 0.001) in the pigs in LT than the pigs in NT with no effects of dietary Cr supplementation. These results indicate that growth performance is affected by thermal stress and plasma cortisol is decreased by heat stress, but these effects are not moderated by dietary Cr.

Relative bioavailability of phosphorus in inorganic phosphorus sources fed to growing pigs

The relative bioavailability of P in 5 sources of inorganic P was determined using growing pigs. The 5 sources of inorganic P were dicalcium phosphate (DCP), monocalcium phosphate (MCP) containing 50% MCP (MCP50), MCP containing 70% MCP (MCP70), MCP containing 100% MCP (MCP100), and monosodium phosphate (MSP). A total of 11 diets were formulated. The basal diet was formulated to contain 0.10% P, and 10 additional diets were formulated by adding 0.07 or 0.14% P from each of the 5 P sources to the basal diet. Growing pigs (n = 44; initial BW: 16.8 ± 4.3 kg) were individually housed and randomly allotted to the 11 experimental diets. Feed was provided on an ad libitum basis throughout the 28-d experimental period. At the conclusion of the experiment, all pigs were killed, and 4 bones (i.e., the third and fourth metacarpals on both front feet) were harvested. Bone-breaking strength, bone ash, and Ca and P concentrations were determined. The concentration of bone ash increased (P < 0.05) as MCP50, MCP70, MCP100, or MSP were added to the basal diet, and the concentration of bone P also increased (P < 0.05) as MCP70, MCP100, or MSP were added to the basal diet. The relative bioavailability of P in each of the feed phosphates was determined using slope ratio methodologies based on breaking strength, and expressed relative to MSP. The slope of the regression line for diets containing MSP or MCP100 was steeper (P < 0.05) than the slope for pigs fed the diet containing DCP, but not different (P > 0.05) from that of pigs fed diets supplemented with MCP50 or MCP70. In conclusion, P in MSP and MCP100 is more bioavailable than P in DCP, but there were no differences within MCP sources.

Effects of corn distillers dried grains with solubles on quality traits of pork.

The high cost of feed grains has led swine producers to seek alternative feedstuffs, such as distillers dried grains with solubles (DDGS). However, little is known about the effects of high levels of DDGS in swine diets on pork quality. The objective of this study was to evaluate belly processing and bacon, sausage, and loin quality of pigs fed high levels of DDGS. Sixty pigs averaging 34 kg BW were fed fortifi ed corn-soybean meal diets containing 0%, 15%, 30%, or 45% DDGS. At 120 kg BW, the pigs were humanely harvested and bellies, loins, and shoulders were removed from the left side of each carcass. Flex tests of bellies indicated that they became softer (linear, P < 0.03) as DDGS levels increased. The PUFA in backfat and belly fat increased linearly (P < 0.005), as did iodine values with increasing 0DDGS in the diet. Bellies were pumped to target 12% brine retention, cooked, and sliced at a commercial facility. Slicing yield was not affected by DDGS level fed. Fresh bacon slices were scored 1 to 6 with 1 representing no visible cracks in the fat and 6 representing a spider weblike shattering of the fat. Shatter scores decreased (linear, P < 0.001) with increasing dietary DDGS. Bratwurststyle sausage was produced by combining ground Boston butts and picnics to target 30% fat, blended with commercial seasonings, and stuffed into natural casings. Loose sausage was placed on trays, overwrapped with polyvinyl chloride wrap, and stored under constant, cool white fl orescent lighting (1,300 lx) at 4°C. Objective color values (L*, a*, and b*) were taken on loosepackaged sausage mix at 6 locations at the same time daily for 7 d. Sausage was also sampled for thiobarbituric acid reactive substances (TBARS) at the same time daily on d 0, 3, 5, and 7. Color scores of sausage were not consistently affected by DDGS level in the diet and the changes were slight. The TBARS in sausage from pigs fed the 30% and 45% DDGS diets increased to a greater extent from d 0 to 7 than in those fed the control or 15% DDGS diets. An 8-member, trained panel evaluated the sensory attributes of bacon slices, sausage, and loin chops. The DDGS resulted in a softer texture (P < 0.004) and increased juiciness (P < 0.04) in sausages, but no differences in sensory scores were found in bacon slices or loin chops. The results indicate that the softer bellies, greater concentrations of PUFA in carcass fat, and greater iodine values associated with feeding increased DDGS did not negatively affect slicing yield of cured bellies, quality of fresh bacon slices, or eating quality of bacon, sausage, or loin chops.

Stimulus-secretion coupling in porcine adrenal chromaffin cells: Effect of dexamethasone

Recent studies from this laboratory established that dexamethasone (DEX) potentiates Ca2+ current via voltage‐gated Ca2+ channels (VGCC), and as a consequence potentiates agonist‐induced cytosolic Ca2+ transients in rat adrenal chromaffin cells. The present study examined whether DEX can also modulate VGCC activity and agonist‐induced cytosolic Ca2+ transients in porcine adrenal medullary chromaffin (PAMC) cells, and if so whether this results in alterations in catecholamine secretion. Forty‐eight‐hr exposure to 1 μM DEX significantly increased peak Ca2+ current (Δ + 138%; n = 6; P < 0.05) in PAMC cells. DEX treatment also significantly potentiated the increase in cytosolic Ca2+ in response to membrane depolarization with KCl (Δ + 20%; n = 29; P < 0.05), but did not affect the amplitude of Ca2+ transients elicited by nicotine or acetylcholine. Despite the potentiation of intracellular Ca2+, DEX treatment had no effect on KCl‐induced secretion of either norepinephrine or epinephrine. These data demonstrate that as in the rat chromaffin cell, DEX can also increase VGCC activity in PAMC cells. However, the subsequent potentiation of selected agonist‐induced increases in intracellular Ca2+ does not appear to be sufficient to alter catecholamine secretion. J. Neurosci. Res. 49:416–424, 1997.

Chromium and swine nutrition

Swine are used as a model for humans in many biomedical research projects. Interest in the use of chromium as chromium picolinate (CrPic) for swine increased once it was shown that the dietary supplementation of this biologically available form of Cr in humans resulted in the deposition of more muscle mass and improved glucose tolerance (since swine are produced as a protein source for humans). Cr is biologically active in pigs via vena cava infusion of a synthetic glucose tolerance factor-Cr. A variety of organic Cr sources exist, but the two that have seen the greatest amount of research are organic Cr from yeast and from CrPic. Although these two forms have demonstrated biological responses in various trials, the magnitude and statistical significance of the responses have varied. Since January 1996, when the U.S. Food and Drug Administration (USFDA) began to allow the marketing of CrPic as a source of Cr at a level of up to 200 ppb in the complete diet, the swine industry has been able to use an organic form of Cr for the first time. The situations in swine production that could potentially be most responsive to Cr supplementation are those associated with rapid growth, advancing age, reproduction, health-stressors (crowding, transport, disease challenge, etc.), and dietary inadequacies. Improvements in carcass composition (i.e., more lean, less fat) were the first reported effects of supplemental organic chromium. In some studies, feeding CrPic increased the rate and efficiency of growth, nitrogen absorption, nitrogen retention, and dry matter digestibility. Additionally, since pregnant swine vary considerably in their response to a glucose load and ability to control serum glucose levels, with consequent effects on reproduction, the potential of Cr supplementation to improve reproductive performance has been of interest. Positive effects have been observed in conception rate and litter size, with increases of up to 20% (or 2 pigs/litter) reported. Improved tissue sensitivity to insulin has been reported in both growing and reproducing pigs with several forms of organic chromium; alterations in other hormones in reproducing females also have been reported. The biological responses and potential economic impact observed thus far have been notable and assure that research with this mineral will continue. J. Trace Elem. Exp. Med. 12:149–161, 1999.

Use of chromium as an animal feed supplement

The supplementation of chromium in farm livestock is a relatively new phenomenon with actual supplementation of diets occurring only in the 1990s. Currently, there are only four forms of chromium; namely, chromium picolinate (CrPic), chromium propionate (CrProp), chromium methionine (CrMeth), and chromium yeast (CrYst).that are allowed to be fed to farm livestock in North America and each of those forms has certain restrictions. The allowance of supplementation and the particular restrictions are based upon materials submitted by companies to the appropriate review agency. Certain conditions compromise or diminish the Cr status of animals including low availability of Cr from normal feedstuffs and the effect of stress on Cr excretion. Supplementation of young pigs immediately after weaning does not have any uniform effect on either growth measures or on immunocompetence, whereas supplementation of the growing animal has provided some responses of improved feed efficiency and improved muscling. Chromium supplementation of cattle resulted in an increase in insulin on several occasions. Supplementation has not demonstrated improvements in growth measures unless growth is depressed for some reason. Beyond the effects on glucose and insulin, Cr supplementation has clearly affected serum cortisol levels in multiple species.

Effect of inorganic or organic selenium supplementation on reproductive performance and tissue trace mineral concentrations in gravid first-parity gilts, fetuses, and nursing piglets

The objective of this experiment was to evaluate 2 supplemental forms of Se on reproductive performance and tissue trace mineral concentration in fetus and first-parity gilts during pregnancy and their progeny. Crossbred gilts (n=100) were selected at 183±2.7 d and 137±10 kg BW and fed a common diet. After 1 mo, 8 gilts were sacrificed to establish baseline liver Se concentration and the remaining 92 gilts allotted to receive Se (0.3 mg/kg diet) as inorganic Se (Na2SeO3) or a Se supplement that contains organoselenium compounds (Sel-Plex; Alltech Inc., Nicholasville, KY). At 267±5.7 d (171±11 kg), gilts were estrus-synchronized and bred. Gilts were then slaughtered at defined time points throughout gestation (d 0, 43, 58, 73, 91, 101, or 108 of gestation; n=6 to 12 gilts/time point). A week before the expected farrowing day, 10 pregnant gilts (5 from each treatment) were moved to farrowing crates and monitored. Two pigs from each litter were randomly selected and euthanized at d 0 (within 2 h after birth; nursing deprived), 7, 14, and 21 from each litter. During the gestation phase, maternal liver, and fetal body and liver were collected for determination of trace mineral concentration by inductively coupled plasma mass spectrometry. Total number of fetus, crown-rump length, and corpora lutea of gilts were recorded as well. During the lactation phase, pigs (without liver and gastrointestinal tract) and associated liver were analyzed for Se concentration. The results demonstrated that the source of Se generally did not affect the maternal reproductive traits and fetal characteristics. Also, the source of Se supplemented to the maternal diet did not, in general, affect Cu, Fe, Mn, or Zn concentrations in the tissues evaluated other than the observation of a greater maternal liver Mn content (P<0.01) in gilts fed Sel-Plex and a greater amount of Fe accumulated in the entire litter (P<0.01) in gilts fed Sel-Plex. However, with regard to Se concentrations, Se in fetal body, fetal liver, and maternal liver were greater (P<0.01) when Sel-Plex was fed. Postnatal pigs from gilts fed Sel-Plex had greater (P<0.05) Se retention in body and liver with similar growth performance during the 21-d period. The results demonstrate Se form differences wherein Sel-Plex is associated with greater Se accumulation in both maternal and fetal tissues.