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Biomedical subjects

D C Mahan

Publications and source records attributed to D C Mahan.

At least 91 records · Page 5Linked to original sources
PubMed1986

Dietary calcium and phosphorus for lactating swine at high and average production levels.

An experiment utilizing 198 first-and 77 second-litter sows evaluated the effects of five dietary Ca:P levels at two litter sizes (six to seven or 11 to 12 pigs/litter) over a 21-d lactation period for two parities. Lactation dietary P levels ranged from .50 to .90% in .10% increments with Ca concurrently increased in a 1.3:1 ratio using dicalcium phosphate and limestone as the inorganic mineral sources. A 14% protein, corn-soybean meal diet was formulated with .80% Ca and .60% P for gestation while lactation diets varied in their Ca and P contents. Randomly selected sows from each treatment group and parity were slaughtered with various bones collected for analyses. A counterpart set of nongravid gilts remained on trial and were slaughtered at the end of the two-parity period with bones collected. Sow dietary mineral level did not affect sow or pig performance, nor was there an interaction between dietary mineral level, parity or litter size nursed. Serum and milk Ca, P or Mg were unaffected by dietary Ca:P at 7 or 21 d of lactation, but milk Ca and P increased from parity I to II. Percent rib and vertebra bone ash decreased from parity I to II for sows nursing the larger litters; other bones were unresponsive to dietary mineral level. Femur thickness decreased from parity I to II but was not influenced by dietary Ca:P level. Bone-bending moment of the ribs, metacarpals and metatarsals were not influenced by diet, but a lower metacarpal bending moment was observed for sows nursing larger litters. All bones from nongravid females had higher percentage of bone ash, bending moment and shaft thickness when compared with reproducing sows. These results suggest that reproductive state (i.e., reproducing vs non-reproducing), litter size and parity affected sow Ca:P mineral skeletal reserves more than dietary Ca:P levels.

Animals↗
PubMed1985

Effect of dietary gestation and lactation protein levels on reproductive performance and body composition of first-litter female swine.

A 2 X 3 factorial split-plot experiment was conducted to determine the effect of dietary protein on the performance and calculated body compositions of 45 first-litter sows using the D2O dilution technique at various reproductive stages. Animals were initially fed 1.82 kg daily of a 14% protein diet to 14 d post-coitum. Subsequently, two gestation protein levels (5 or 14%) were daily fed at 1.82 kg from 15 d postcoitum to parturition with three dietary lactation protein levels (5, 14 or 23%) fed from parturition to 28 d postpartum. Maternal body compositions were determined at 17, 35, 70, 85 and 105 d postcoitum and 7, 14 and 28 d postpartum using prediction equations reported previously. Gravid sows demonstrated higher maternal tissue accretion of all body chemical components from 14 to 70 d than from 70 to 105 d postcoitum. Sows fed the 5% protein gestation diet had more maternal fat but less protein accretion than those fed the 14% protein at each measurement interval. During the last trimester, those sows fed the 5% protein diet catabolized body protein reserves. Gravid sows fed the 14% protein gestation diet catabolized more maternal protein and water between 105 d postcoitum and 7 d postpartum than those fed the 5% protein diet. Litter and pig birth weights were lower and postpartum mortality higher for sows fed the 5% rather than the 14% protein gestation diet. Sows fed the 5% protein lactation diet mobilized more maternal tissue, particularly fat, between 7 and 28 d postpartum than those fed 14 or 23% protein lactation diets. These results suggest that labile maternal body protein reserves are used by gravid and nursing dams to fulfill reproductive needs and that dietary protein sequence affects the dam's performance and body composition.

Animals↗
PubMed1985

Effect of swine weaning age on body fat and lipogenic activity in liver and adipose tissue.

Two experiments were conducted to evaluate the effects of weaning swine at 2 or 5 wk of age on postweaning performance and fat metabolism. In the first experiment, 52 pigs were weaned at 2 or 5 wk of age with body weights determined from birth to 8 wk. The early weaned group was fed a 20% protein corn-soybean meal-oat diet containing 25% dried whey from 2 to 5 wk while both groups were fed a 20% protein cereal grain-based diet from 5 to 8 wk of age. In a second experiment, a total of 90 pigs weaned at similar ages and fed the same diet sequences were killed at weekly intervals from 2 to 8 wk of age to evaluate body fat content and lipogenesis in liver and adipose tissue. Lipogenic capacity was measured by incorporation of acetate-1 14C into the total lipid fraction in liver slices and adipose tissue minces or by monitoring liver ATP citrate lyase activity. The results demonstrate that pigs weaned at 2 wk experience a slower postweaning growth rate with lower empty body weights than those either concurrently nursing the dam or weaned at 5 wk of age. Both groups had similar body weights from 6 to 8 wk of age. The body fat content of nursing pigs increased from 2 to 5 wk of age. Pigs weaned at 2 wk lost approximately 25% of their body fat the first week postweaning while later-weaned pigs did not lose body fat postweaning. Body fat composition of both groups was similar by 8 wk of age. Lipogenic activity was higher in liver than in adipose tissue from 2 to 5 wk of age and remained relatively constant throughout the trial. Adipose tissue lipogenic activity was lower in the nursing pig but increased dramatically at 5 wk in the early-weaned group and 7 wk of age in the late weaned group. These results suggest that weaning age can affect postweaning body fat composition and that adipose contributes a greater lipogenic capacity than liver tissue as the pig matures.

Adipose Tissue↗
PubMed1985

Effects of combining protein sources on lysine utilization by starter pigs.

The effect of combining protein sources on lysine utilization was evaluated using 450 crossbred starter pigs, average initial weight 6.8 kg and final weight 17.4 kg, in four replicates of 12 dietary treatments. Pigs were fed ad libitum a corn-soybean meal basal diet containing .65% total lysine, supplemented with one of four lysine sources: L-lysine X HCl, soybean meal, meat and bone meal and a combination of meat and bone meal and soybean meal with each providing equal lysine. The levels of supplemental lysine added to the basal diet by addition of the lysine sources were: 0, .15 and .30% L-lysine X HCl and .10, .20 and .30% for soybean meal, meat and bone meal and combination. All diets were calculated to meet or exceed the National Research Council recommendations for amino acids other than lysine. Gain and feed intake were measured over the treatment period. There was an effect (P less than .05) due to treatment on both average daily gain and gain/feed, but no effect calculated due to the independent variable of lysine intake for each of the lysine sources tested and the dependent variable of average daily gain or gain/feed. Response to the supplemental protein sources was linear. Gain and gain/feed were maximized when soybean meal fortified the basal diet. The data indicate that in weanling pigs to 17 kg body weight, lysine utilization from protein sources is not seriously affected by feeding the source in combination.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Biological characteristics for assessing low phosphorus intake in growing swine.

A total of 195 swine from 18 to 35 kg were used to evaluate various biological responses of growing swine fed low P diets at different Ca:P ratios. Three replicates of a randomized complete-block design in a 3 X 3 factorial arrangement of treatments were used. Total dietary P levels of .12, .31 and .50% were fed in 1:1, 1.5:1 or 3:1 Ca:P ratios. Diets were formulated using corn starch, dextrin and soy protein concentrate, with monosodium phosphate and limestone used to supply appropriate dietary treatment levels of Ca and P. Gain and feed performance were generally influenced by both Ca:P ratio and dietary P level. Serum inorganic P decreased linearly as Ca:P ratio widened and increased linearly as dietary P increased. Serum Ca concentrations responded inversely to serum inorganic P in response to both Ca:P ratio and dietary P level. Serum alkaline phosphatase was not affected by Ca:P ratio, but declined quadratically with increasing dietary P level. Bone bending moment was influenced by both dietary P level and Ca:P ratio. Bone component weights (ash, organic matrix), percentage bone ash and net accretion of bone ash and organic component weights were not influenced by Ca:P ratio but increased linearly as dietary P level increased. These results suggest that bone component weights, net ash accretion and percentage bone ash were more sensitive criteria than bone bending moment or serum alkaline phosphatase, which in turn were more sensitive than serum inorganic P, Ca, Mg and growth performance characteristics in response to dietary P level.

Alkaline Phosphatase↗
PubMed1985

Effect of dietary calcium on selenium retention in postweaning swine.

Two experiments were conducted to evaluate the effect of dietary Se and Ca on Se utilization in postweaning swine. Two levels of dietary Se (.3 or 5.0 ppm) supplemented as sodium selenite and four levels of total dietary Ca (.50, .80, 1.10 or 1.40%) in a 20% protein, corn-soybean meal diet were evaluated. Inorganic Ca was supplied from dicalcium phosphate and limestone. In Exp. I, 135 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed a basal diet for 7 d and then their treatment diets for a 28-d period. Plasma and tissue were collected at the end of the trial for Se concentration and glutathione peroxidase (GSH-Px) activity. Dietary Ca had no effect on gain or feed measurements but 5.0 ppm Se depressed daily gain slightly. When 5.0 ppm dietary Se was fed, there resulted higher liver, kidney, heart and longissimus muscle Se concentrations than when .3 ppm was provided, but dietary Ca had no effect on tissue Se values within each dietary Se level. Plasma GSH-Px increased when higher dietary Se was provided, whereas neither heart nor liver GSH-Px activity was affected by dietary Se or Ca level. In Exp. II, a 5-d balance trial was conducted with 32 barrows after adjustment to their treatment diet for a 28-d period. Selenium retention increased quadratically as dietary Ca increased, whereas Ca retention was not affected by dietary Se. These results suggest that low dietary Ca levels may reduce total Se retention but not Se metabolism within body tissue.

Animals↗
PubMed1985

Effect of dietary phosphorus on selenium retention in postweaning swine.

Two experiments were conducted to evaluate the effect of dietary Se and P levels on Se retention in postweaning swine. A 20% protein corn-soybean meal diet at two dietary Se levels (.3 and 5.0 ppm) and four total P levels (.50, .70, .90, 1.10%) were fed. Supplemental Se was provided from sodium selenite with inorganic P from dicalcium phosphate. In Exp. I, 151 pigs weaned at 4 wk of age were allotted by sex, litter and weight and fed their treatment diets for 28 d after a 7-d adjustment to a basal diet. Dietary Se level had no effect on performance measurements. As dietary P level increased, there was an increase in daily gain, feed intake and a decrease in feed to gain ratio. Dietary P resulted in similar plasma, longissimus muscle and kidney tissue Se values within each dietary Se level, while liver Se declined as dietary P level increased. Dietary P level had no effect on plasma, heart or liver glutathione peroxidase (GSH-Px) activity. In Exp. II, 32 barrows, after being fed their diets for a 28-d period, were placed in individual metabolism crates where a balance trial was conducted. Dietary P level reduced absolute and percentage Se retention, particularly at dietary P levels of .90 and 1.10%. Phosphorus retention was not affected by dietary Se. Neither dietary P nor Se level had any effect on N retention. These results suggest an effect of dietary P level on Se retention and liver Se, particularly at dietary P levels above the pig's P requirement, while the effect is minimal at or below the pig's P requirement.

Animal Feed↗
PubMed1985

Effect of inorganic selenium supplementation on selenium retention in postweaning swine.

A total of 64 weanling pigs was used in a randomized complete-block experiment to evaluate the efficacy of various inorganic Se levels on weekly Se balance measurements over a 5-wk post-weaning period. Four-week-old weaned pigs were fed a 20% protein, corn-soybean meal diet supplemented with 0, .3, .5 or 1.0 ppm Se from sodium selenite. Eight pigs were allotted by weight, litter and sex to each metabolism crate. A 2-d preliminary period followed by a 5-d collection period was conducted for five weekly periods. Feed intake was provided ad libitum but was similar between dietary Se levels. Fecal Se excretion increased each week and with increasing dietary Se level. Apparent digestibility of Se was relatively constant for each period when inorganic Se was fed, averaging approximately 70%, whereas it ranged between 30 to 40% for pigs fed the basal diet during wk 2 through 5. Urinary Se decreased during the postweaning periods for pigs fed the basal diet, but increased linearly as dietary Se increased during the initial 2-wk postweaning period and then quadratically during wk 3 through 5. There was a net loss of Se from the body when the Se-unsupplemented basal diet was fed during the initial 2 wk postweaning, whereupon, it became positive. Selenium retention in pigs supplemented with inorganic Se increased each week of the trial. When Se retention was expressed in relation to Se intake, the resulting regression was linear (R2 = .99), suggesting that Se retention in the postweaning pig increased in direct proportion to the amount consumed when diets contained up to 1.0 ppm Se.

Animals↗
PubMed1984

Effect of inorganic selenium supplementation on selenosis in postweaning swine.

A total of 72 pigs weaned at 4 wk of age were allotted by litter and weight to nine treatment groups and fed 20% protein cornsoybean meal diets supplemented with various levels of inorganic Se during a 37-d postweaning period. Eight groups were fed diets with 0, 2.5, 5.0, 7.5, 10, 15, 20 or 40 ppm Se provided as sodium selenite, while a ninth was offered the 0- and 40-ppm Se diets in separate feeders. Gains and feed intakes were similar during the trial for the 0- and 2.5-ppm Se diets. Both gain and feed intake declined as dietary Se levels above 5.0 ppm increased. At a dietary Se concentration of 40 ppm, feed consumption ceased within a few days of feeding and subsequent gains were negative. Pigs offered both the 0- and 40-ppm Se diets preferentially selected the basal as compared with the 40-ppm Se diet. When the feeders were switched at 28 d they refused the 40-ppm Se diet within a few hours. After a 17-d period, pigs fed the 20- or 40-ppm Se diet were not able to coordinate their walk, with many exhibiting an inability to stand. Alopecia was demonstrated in pigs fed 15 ppm Se or higher at 17 d, but was evident in the 5.0-ppm group at 37 d. At the termination of the trial, abnormal hoof formation at the coronary band was evident in pigs fed diets containing Se greater than or equal to 5 ppm.(ABSTRACT TRUNCATED AT 250 WORDS)

Alopecia↗
PubMed1984

In vivo body composition estimation in nongravid and reproducing first-litter sows with deuterium oxide.

An experiment was conducted with 64 first-litter sows to evaluate the efficacy of a D2O dilution procedure for measuring in vivo body composition during the reproduction cycle. Eight gilts were each infused at breeding, 57 and 105 d postcoitum and at 5 and 25 d postpartum, with equivalent numbers of nongravid controls infused at corresponding periods except at 5 d postpartum. Results from D2O dilution were compared with body water estimates obtained from chemical analysis. An early-equilibrating D2O pool (before 15 min) was similar quantitatively to empty body (ingesta free) water in nongravid and lactating animals, but not in pregnant sows. Because of inconsistent D2O equilibration patterns in gravid sows, the early pool was considered to have equilibrated with part but not all of the water in the conceptus products. Total body D2O space measurement obtained from data following equilibration of D2O in the entire body (1 to 2 h) overestimated total body water (including gastrointestinal water) by approximately 19%. Coefficients of determination for equations relating total body D2O space to empty body and maternal body water were .96 and .88, respectively, in gestating sows and .67 and .74, respectively, for lactating sows, while coefficients of variation were below 6% in all cases. Prediction equations were developed to estimate empty and maternal body components (protein, fat and ash) from body weight and D2O space. Accuracy of protein and ash weight prediction is lowest with this procedure because it involves the composite error of estimation of the other body components.

Adipose Tissue↗
PubMed1984

An evaluation of various biological characteristics in assessing low phosphorus intake in weanling swine.

A total of 204 weanling pigs were utilized in an experiment of 3 X 3 factorial design (in three replicates) to evaluate the effects of feeding low P diets for a 35 d period on various growth, serum and bone measurement characteristics. Total dietary P levels of .23, .35 and .55% were fed in a Ca:P ratio of 1:1, 1.5:1 or 3:1. The basal diet was formulated using cornstarch, dextrin and soy protein concentrate with monosodium phosphate and limestone used to supply appropriate dietary levels of Ca and P. Growth, serum minerals and serum alkaline phosphatase were evaluated at 21 and 35 d of the trial. At the end of the experiment six pigs/treatment group were killed and bones were collected for various measurement criteria. Daily gain, feed intake and feed conversion were not affected by Ca:P ratio, but there was an increased gain and feed intake response to dietary P level. Serum inorganic P decreased with increasing dietary Ca:P ratio and also increased linearly as dietary P level increased. Serum alkaline phosphatase activity was not influenced by dietary Ca:P ratio, but did decrease as dietary P level increased. Bone bending moment increased quadratically as Ca:P ratio increased, but also increased linearly with dietary P level. Percentage bone ash, bone ash and organic matrix weights and the accretion of both the mineral and matrix components were not affected by Ca:P ratio, but each was influenced as dietary P increased. These data suggest that percentage bone ash, bone component weights and accretion measurement characteristics were more sensitive indicators of dietary P levels than bone bending moment, serum alkaline phosphatase and serum P, which in turn were superior to serum Ca, Mg and growth performance.

Alkaline Phosphatase↗
PubMed1983

Dietary calcium and phosphorus levels for growing swine from 18 to 57 kilograms body weight.

A randomized complete block design experiment was conducted using 408 crossbred pigs to evaluate the effects of six dietary Ca/P levels for growing swine (18 to 57 kg). Total dietary P levels ranged from .40 to .90% in .1% intervals with Ca concurrently increased at a 1.3:1 ratio in a 16% protein corn-soybean meal diet. Dicalcium phosphate and limestone were the source of inorganic Ca and P. For the overall trial, daily gain and feed intake improved as dietary Ca/P increased to an approximate level of .65/.50%. An inverse relationship occurred between serum Ca and P, with serum Ca declining and P increasing at the lower mineral levels. Femur, humerus, rib, metatarsal and metacarpal ash content increased quadratically (P less than .01) as dietary Ca/P increased with suggested dietary breakpoint inflections of .90% Ca and .70% P at 40 kg, and at .72/.55% levels at 57 kg body weight. Percentage ash of the head portion of the bone was lower than the shaft section. Bone shaft thickness and bending moments for metatarsals and metacarpals increased as dietary Ca/P levels increased, with higher values and higher dietary inflection points at 57 than at 40 kg body weight. Bone length was not influenced by dietary Ca/P level, but fat-free dried bone weight was, resulting in higher total bone ash and organic weight as Ca/P level increased.

Animals↗
PubMed1983

Changes in swine body composition from birth to 145 kg.

An experiment using 81 crossbred swine was conducted to evaluate quantitative and percentage chemical compositional changes of swine from 1.5 kg (birth) to 145 kg body weight. Groups of eight pigs were sacrificed at 1.5, 6.4 and 18 kg, and then at 18 kg increments to 145 kg. Body composition was determined by grinding the entire body, minus digesta, partitioning the carcass from other body components and chemically analyzing each subsample. Results indicated that weight of the carcass increased linearly with live weight, while the total weight of the other body components increased quadratically. Percentage fat in the empty body (ingesta-free) increased rapidly from birth to weaning (6.4 kg), plateaued until 36 kg and then increased, while water percentage declined dramatically from 1.5 to 6.4 kg, but then declined more gradually to 145 kg. Percentage protein increased from birth to 18 kg, plateaued and declined after 54 kg. When expressed on a fat-free basis, the percentage water decreased in a curvilinear manner with increasing animal weight while protein increased curvilinearly inverse to the change in water. Constancy of composition ("chemical maturity") between protein and water in the fat-free body was not attained by 145 kg. When expressed on an absolute empty body basis, water, protein and fat weight increased curvilinearly with increasing empty body weight; the rate of fat deposition increased faster during the latter growth stages while water and protein had declining deposition rates. Logarithmic and quadratic equations relating body composition to animal weight had similar R2 and lower coefficients of variation than linear or semilog functions. Gilts contained more water and less fat than barrows at similar slaughter weights, but sex differences were not apparent when expressed on a fat-free basis. The growth and fattening process was reflected in several carcass measurements. Backfat thickness, longissimus muscle area and body length increased as pig weight increased.

Aging↗
PubMed1983

Efficacy of deuterium oxide to estimate body composition of growing swine.

An experiment involving 73 pigs was conducted to evaluate the efficacy of the deuterium oxide (D2O) dilution procedure for in vivo estimation of body composition in swine. Pigs were infused with known quantities of D2O at 6.4 and 18 kg and then at approximately 18 kg increments to 145 kg body weight. Postinfusion blood D2O concentrations were partitioned into early- and total-equilibrating pools. Results from D2O analyses were compared with empty (ingesta-free) and total body water values obtained from chemical analysis of the ground animals. Both early- and total-equilibrating D2O pools seemed to be good estimators of empty body weight. Total body D2O space was similar to total body water at 6.4 kg, but consistently overestimated body water (averaged 20%) as the pigs attained heavier weights. Early- or total-body D2O pool measurements accurately predicted chemically determined components with residual coefficients of variation below 5% and R2 greater than or equal to .90. However, total body D2O space provided as accurate an estimate of empty body water as the early-pool technique and may be easier to use because catheterization of blood vessels is not required. The incorporation of live weight and sex in multiple regression equations did not improve the accuracy of empty body water prediction over that obtained from D2O measurements alone. A method to estimate total body composition (water, protein, fat, ash) from the total body D2O space measurements is presented.

Animals↗
PubMed1983

Effects of pregnancy and lactation on the body composition of first-litter female swine.

A total of 64 gilts initially weighing 120 kg were used to evaluate body composition occurring during pregnancy and lactation. All animals were fed a 14% protein corn-soybean meal diet. Eight gilts were slaughtered each at breeding, 57 and 105 d postcoitum and at 5 and 25 d postpartum, with a corresponding number of nongravid females killed at similar periods except at 5 d postpartum. Chemical composition of the empty body (ingesta-free) and maternal body (empty body minus reproductive products) was determined. Gravid gilts were heavier with larger quantities of water, protein and fat than nongravid gilts by the termination of pregnancy, but these differences were attributable to the products of conception. After the reproductive tissue components were subtracted, no indication of pregnancy anabolism was evident. Hydration in gravid swine was evident at 105 d postcoitum but was attributed to the higher water contribution from conceptus products, not maternal tissue. Maternal body fat appeared to fluctuate during gestation and lactation, whereas body protein and ash content were less affected. Both the empty body and maternal body contained approximately 83.5% protein and 16.5% ash when expressed on a fat-free dry basis, suggesting that compositional changes during reproduction largely reflect water and fat content changes in the dam's body. Carcass measurements generally reflected body compositional data.

Animals↗
PubMed1982

Dietary Calcium and phosphorus levels for reproducing sows.

Thirty-six gilts were used to evaluate three dietary Ca/P levels over a three parity period on reproductive performance. Diets formulated to contain 14% protein with total Ca/P levels of .65/.50, .80/.60 or .90/.70%, respectively, were provided during both gestation and lactation. In each group, 10 gilts were bred and two remained unbred with diets fed at 1.8 kg/d during gestation and ad libitum during lactation. Nongravid gilts were fed 1.8 kg daily during the trial. Blood samples were collected at 60 and 100 d postcoitum and both blood and milk samples at 14 and 28 d postpartum. From each lactation and each sow group, three pigs were killed at birth and six pigs at 14 and 28 d postpartum. The rib was collected for bone ash analyses with the rib, humerus and femur collected from the progeny and examined for histopathologic lesions during the second parity. After three reproductive cycles, four sows and two unbred females/group were sacrificed and bone ash determined on femur, humerus, rib and vertebrae. The results indicated no significant difference in any sow reproductive of litter performance measurement during gestation or lactation or in milk Ca and P concentration. No histopathologic bone lesions were presented in the progeny. Sow bone ash values at the end of three reproductive cycles suggested that bone demineralization from lactating animals occurred, but not uniformly for all bones. The rib, vertebrae and humerus demineralized at a greater rate than the femur. Bone ash values for reproducing sows fed the .90/.70% Ca/p treatment for three parities were similar to those of nongravid females, which were similar for all treatment groups. The results suggested an average daily intake of 50 to 55 g Ca and 40 g P to maintain bone homeostasis in lactating sows.

Animals↗