Characterization of a line of pigs previously selected for increased litter size for RBP4 and follistatin.

The objective of this study was to determine if selection response for increased litter size in pigs could be partially attributed to three type 1 marker loci coding for genes known to affect litter size: oestrogen receptor (ESR), retinol-binding protein 4 (RBP4) and follistatin (FS). In the high litter size line (LS), pigs from the largest litters, based on number of pigs born alive (NBA), were retained to parent the next generation. A randomly selected control line (LC) was maintained. Gilts were reared in litters of 10 pigs or less to minimize maternal effects. Pigs were measured at generations 10-12. Additional traits scored were number of fully formed pigs (NFF) and number of mummified fetuses (MUM). Breeding values for NFF and NBA were greater (p < 0.05) in LS than LC in generations 11 and 12, but no significant line differences were found for MUM. The A allele of the ESR locus was fixed in both lines. After adjustment for effects of genetic drift, frequency of the two alleles segregating for the FS and RBP4 loci did not differ significantly between lines. No significant additive or dominance effects of the FS markers were detected for NFF, NBA and MUM in either LS or LC. Response to selection for increased litter size could not be attributed to effects at the ESR, RBP4 or FS loci.

Conjugated linoleic acid evokes de-lipidation through the regulation of genes controlling lipid metabolism in adipose and liver tissue.

Conjugated linoleic acid (CLA) is a unique lipid that elicits dramatic reductions in adiposity in several animal models when included at < or = 1% of the diet. Despite a flurry of investigations, the precise mechanisms by which conjugated linoleic acid elicits its dramatic effects in adipose tissue and liver are still largely unknown. In vivo and in vitro analyses of physiological modifications imparted by conjugated linoleic acid on protein and gene expression suggest that conjugated linoleic acid exerts its de-lipidating effects by modulating energy expenditure, apoptosis, fatty acid oxidation, lipolysis, stromal vascular cell differentiation and lipogenesis. The purpose of this review shall be to examine the recent advances and insights into conjugated linoleic acid's effects on obesity and lipid metabolism, specifically focused on changes in gene expression and physiology of liver and adipose tissue.

The effect of dietary phosphorus on heat shock protein mRNAs during acute heat stress in male broiler chickens (Gallus gallus).

A 2 x 2 factorially arranged completely randomized experimental design was used to study the relationship between inorganic phosphorus (Pi) and heat shock protein (HSP) mRNA expression in different organs of commercial broiler cockerels during acute heat stress (HS). Brain, heart, liver and spleen were assayed for hsp70, hsp90alpha and hsp90beta mRNA. At 1 day of age, chickens were assigned randomly to two dietary Pi treatment groups (Pi-: 0.16%; Pi+: 0.5%). At 3 weeks of age, half of the chickens in each Pi group were subjected to HS (Ta=41 degrees C, 60 min) while the other half was maintained in a thermoneutral environment (CN, Ta=25 degrees C). The results showed inter-organ variation in the expression of HSP mRNAs. Brain expressed the most HSP mRNAs while spleen expressed the least. When broilers were subjected to HS, the expression of HSP mRNAs was influenced positively by the consumption of the Pi+ diet. However, analysis of variance revealed that Ta influenced HSP transcription more than phosphorus availability. Thermal stress caused induction of hsp90alpha and hsp90beta in heart, liver and spleen, but hsp90alpha and hsp9beta mRNA levels were stable in brain. Transcription of hsp70 increased (P< or =0.05) in all organs from chickens in HS groups when compared to chickens in CN groups. Although Pi+ did not show any significant increases in the expression of hsp mRNAs, there were consistently larger HSP mRNA values in liver and spleen tissues. The high expression of hsp90alpha and hsp90beta in brain of chicks in both CN and HS conditions could be due to the involvement of hsp90 in steroid hormone receptors or the high metabolic activity of neurons in the central nervous system.

Ascorbic acid decreases heat shock protein 70 and plasma corticosterone response in broilers (Gallus gallus domesticus) subjected to cyclic heat stress.

It is known that ascorbic acid (AA) supplementation can ameliorate the chicken's responses to heat stress. The influence of AA on heart heat shock protein 70 (hsp70) and plasma corticosterone (CS) was evaluated in young male broiler chickens fed either no AA (N-AA) or 500 mg AA /kg (AA) and exposed to cyclic high temperatures (21 to 30 to 21 degrees C) over a 3.5 h period on three consecutive days. Dietary AA supplementation elevated plasma AA and maintained it at high levels after heating, but in N-AA birds, only heat elevated plasma AA. In N-AA fed chickens, plasma CS was elevated and was further increased by heat stress as compared with AA-fed birds. Heart hsp70 expression was greater in N-AA-fed chickens compared to AA-fed chickens, and heat stress further elevated hsp70 in both N-AA- and AA-fed birds. The hsp70 increase after heat was two-fold greater in N-AA- vs. AA-fed birds. Plasma CS and heart hsp70 were positively correlated, plasma AA and heart hsp70 were negatively correlated, and plasma CS and AA were negatively correlated. It was concluded that chickens experience a less severe stress response after exposure to high temperatures when they are provided dietary AA.

Ionophores have limited effects on jejunal glucose absorption and energy metabolism in mice.

Two experiments, Trial 1 (in vitro) and Trial 2 (in vivo), were conducted to examine the effects of ionophores, monensin, laidlomycin, and laidlomycin propionate on whole-animal O2 consumption, organ weights, jejunal glucose absorption, and O2 utilization, as well as growth, feed and water consumption, and feed efficiency. In Trial 1, 30 male Swiss-Webster mice, 8 wk old, were used to measure the in vitro effects of each of the ionophores at concentrations of 1.62 or 16.2 mM. Six combinations of three ionophores at two concentrations resulted in a total of eight treatments. All eight treatments were exposed to jejunal rings from a single mouse for a total of 30 observations per treatment. Jejunal rings were exposed to each ionophore treatment for 15 min. Laidlomycin propionate (16.2 mM) decreased (P < 0.02) glucose absorption, as estimated by H3-3-O-methyl glucose uptake compared with all other treatments, whereas laidlomycin propionate (1.62 mM) increased (P = 0.032) jejunal DM content compared with 16.2 mM laidlomycin propionate. In Trial 2, 40 5-wk-old mice were allotted into four treatments--control and 16.2 mM each of monensin, laidlomycin, and laidlomycin propionate--for a total of 10 observations per treatment. Ionophores were administered via the drinking water for 14 d. No ionophore treatment had any effect on whole-mouse O2 consumption. Monensin increased (P = 0.004) stomach size and decreased (P = 0.049) the efficiency of BW gain compared with controls. Laidlomycin propionate decreased (P = 0.032) the percentage of whole jejunum oxygen consumption due to oubain-sensitive respiration compared with control. The efficiency of intestinal glucose absorption was not changed due to treatment in either trial. Under the conditions of these studies, monensin, laidlomycin, and laidlomycin propionate had minimal and inconsistent effects on jejunal function and energy utilization in mice. This investigation suggests that changes in the energetic requirements of animals treated with ionophores are not an issue in animal production.

Effect of ascorbic acid and acute heat exposure on heat shock protein 70 expression by young white Leghorn chickens.

Dietary ascorbic acid (AA) and heat stress (HS) affect heat shock protein 70 (hsp70) and body temperature (BT) of strain cross white Leghorn chickens. At five weeks of age, chicks fed either no supplemental AA (N-AA) or 200 mg/kg AA (AA) were subjected to either HS (42 degrees C) or maintained in control (CN, 23 degrees C) ambient temperature (T(a)) for 1 h. Body temperature (BT) was recorded for each bird before collection of heart and liver for hsp70 assay. In the CN AA-fed groups, neither the lower constitutive hsc70 nor the decreased hsp70 response to HS in the heart and liver were sex-dependent. The BT was increased by HS, but neither AA nor sex of the bird affected BT response. A diet X T(a) interaction revealed that BT of CN AA-fed chickens was lower than in N-AA-fed chickens, but BT of HS AA-fed chicks was greater than BT in HS N-AA-fed chickens. The BT and hsp70 responses were positively correlated. A lower expression of hsp70 indicated less of a stress response in the AA-fed chickens.

Pleiotropy of quantitative trait loci for organ weights and limb bone lengths in mice.

We investigated the genetic basis of several limb bone lengths and weights of organs in mice produced from a cross of the F1 between CAST/Ei (wild strain) and M16i (selected for rapid growth rate) back to M16i. From previous correlation studies, we hypothesized that quantitative trait loci (QTLs) would exhibit greater pleiotropy within than between the limb length and organ weight character sets. Using interval mapping procedures and significance testing at the chromosome-wise level, we discovered 14 putative QTLs affecting weight of the liver, spleen, heart, and/or kidney, 9 of which affected more than one organ; and 12 QTLs for limb lengths, all of which affected the length of two or more of the limb bones in these mice. As was hypothesized, most QTLs affected either organ weights or limb lengths independently of each other, although five QTLs were found that affected both sets of characters. The direction of the effect of these QTLs was almost always consistent within and between characters, with little evidence for antagonistic pleiotropy.

Inbred lines of mice derived from long-term growth selected lines: unique resources for mapping growth genes.

Lines of mice selected for many generations for high or low growth in several laboratories around the world have been collected, and from these, inbred lines are being developed by recurrent full-sib mating in Edinburgh. There are seven high selected lines and four low lines (each low line is from the same base population as one of the high lines), and the histories of each are summarized. Mean body weight of males at 70 days of age in the Edinburgh laboratory in the heaviest inbred line (77 g) is 4.8-fold higher than in the lightest line (16 g), and 1.9-fold higher than in the least extreme high line (41 g). Litter size, food intake, and fat content also differ substantially. These inbred extreme selected lines are a uniquely valuable resource for QTL or gene mapping, candidate gene identification, and elucidation of epistatic effects.

Segregation ratios and growth rate in inactive ovine metallothionein 1a-ovine growth hormone transgenic mice.

Objectives were to determine whether the oMt1a-oGH transgene shows normal Mendelian segregation and whether oMt1a-oGH mice exhibit normal growth without the zinc supplementation required to increase plasma oGH levels and stimulate growth. Transgenic mice were reciprocally backcrossed for four generations to high growth and control lines to form lines GM and GR, respectively. In the fifth generation, hemizygous transgenic mice (T/-) were crossed within each line. Pooled across backcross generations, there was a deficit (P < 0.001) of T/- progeny in lines GM (31.6%) and GR (22.2%) compared with expected (50%). In the T/- x T/- cross, the combined percentage of homozygous (T/T) and hemizygous transgenic mice was less (P < 0.001) than expected (75%) in both GM (44.2%) and GR (38.5%). Backcross T/- mice had lower (P < 0.05) 3-wk BW and lower (P < 0.001) 6-wk BW and 3- to 6-wk postweaning gains than nontransgenic mice. Similar genotypic differences were found in the T/- x T/- cross. No significant growth differences were found between T/T and T/- progeny. Using segregation ratios from the T/- x T/- mating, the relative fitness estimates of T/T, T/-, and -/- (nontransgenic) mice were 0.345, 0.223, and 1.0, respectively, in line GM and 0.218, 0.205, and 1.0 in line GR. Fitness estimates in the back-cross for T/- and -/- were 0.463 and 1.0 in line GM and 0.285 and 1.0 in line GR. Abnormal segregation ratios may be due to germline mosaicism or reduced fitness due to differential embryo survival. Reduced growth of oMt1a-oGH transgenic mice when the transgene is switched off suggests a subtle developmental abnormality, which may contribute to a reduction in fitness.

Quantitative trait loci for directional but not fluctuating asymmetry of mandible characters in mice.

Non-directional variation in right minus left differences in bilateral characters, referred to as fluctuating asymmetry (FA), often has been assumed to be largely or entirely environmental in origin. FA increasingly has been used as a measure of developmental stability, and its presumed environmental origin has facilitated the comparisons of populations believed to differ in their levels of stability. Directional asymmetry (DA), in which one side is consistently larger than the other, has been assumed to be at least partially heritable. Both these assumptions were tested with interval mapping techniques designed to detect any quantitative trait loci (QTLs) affecting FA or DA in 15 bilateral mandible characters in house mice resulting from a cross of the F1 between CAST/Ei (wild strain) and M16i (selected for rapid growth rate) back to M16i. For purposes of the analysis, all mandibles were triply measured and 92 microsatellite markers were scored in a total of 350 mice. No significant QTLs were found for FA, but three QTLs significantly affected DA in several characters, confirming both assumptions. The QTLs for DA were similar in location to those affecting the size of several of the mandible characters, although they accounted for an average of only 1% of the total phenotypic variation in DA.

Peptide YY administration decreases brain aluminum in the Ts65Dn Down syndrome mouse model.

We have previously reported the Ts65Dn (Ts) mouse has impaired intestinal absorptive function and amino acid metabolism. Peptide YY (PYY) has enhanced glucose absorption in mice and turkeys. Other studies have reported that persons with Down syndrome have increased intestinal absorption of aluminum. Alzheimer's-like lesions have been reported in Ts mice. Trial 1 of this study examined brain Al concentrations, plasma metabolites and intestinal metabolism of 40 control and 40 Ts mice administered 300microg PYY/kg body weight or 0.9% saline for 3d. Trial 2 examined nutrient digestibility of 12 C and 12 Ts given PYY or saline for 14d. In Trial 1, PYY lowered (p<0.05) the brain Al pool (mg/g FBW) in both C and Ts mice by 80% compared to saline. Ts mice had increased plasma NH3 (329 vs. 269 microM, p<0.05), decreased plasma glucose (7.4 vs. 8.4 mM, p<0.01), elevated apparent energetic efficiency of jejunal glucose uptake (p<0.01) and elevated brain Al pool (0.41 vs. 0.12 microg, p=0.06) compared to C mice. In Trial 2, PYY increased small intestinal density (mg/cm) 12% in both genotypes (p<0.05), but did not alter nutrient digestibility. Brain Al accretion and hyperammonemia are proposed risk factors for Alzheimer's disease (AD). Ts mice and PYY appear to be suitable models for the study of metabolic and neurological anomalies in Down syndrome and AD.

Correlated responses to selection for large body size in oMt1a-oGH transgenic mice: reproductive traits.

Correlated responses in female reproductive performance were evaluated following short-term selection within full-sib families for increased 8-week body weight in two replicates of four lines of mice: two ovine metallothionein-ovine growth hormone (oMt1a-oGH) transgene-carrier lines, one from a high-growth background (TM) and one from a control background (TC), and two non-transgenic lines, one from each of these genetic backgrounds (NM and NC, respectively). A fifth line (CC), not containing the transgene, served as a randomly selected control. The initial frequency of the oMt1a-oGH transgene construct in the TM and TC lines was 0.5. The frequency of transgenic females sampled at generations 7 and 8 of selection was 84.0% and 6.1% in the TC and TM lines, respectively. No significant female infertility differences were detected between transgene-carrier and non-transgenic lines or between transgenic and non-transgenic mice within carrier lines, whereas high-growth background lines had a higher infertility than control background lines (P < 0.05). Correlated responses in the TC transgene-carrier line were suggestive of reduced reproductive performance as indicated by increased post-implantation mortality (P < 0.05), number of dead fetuses plus implants (P < 0.05), and loss of fetuses from day 16 to parturition (P < 0.001). For the first two traits, the negative correlated responses were accounted for by the reduced performance of transgenic compared with non-transgenic females. Embryos carrying the transgene may also have a lower viability. In contrast, the NC non-transgenic line did not exhibit reduced reproductive performance for these traits. The low frequency of the transgene in the high-growth background TM line was associated with reduced fitness and a lower additive effect for 8-week body weight compared with the control background TC line.

Response to 13 generations of selection for increased 8-week body weight in lines of mice carrying a sheep growth hormone-based transgene.

The purpose of this study was to evaluate selection in lines of transgenic mice. Two replicates of lines that either carried or did not carry the sheep metallothionein-1a sheep growth hormone transgene (oMt1a-oGH) were established. The host lines had been previously selected for rapid growth or selected randomly. Within-litter selection for increased 8-wk body weight was carried out for 13 generations. The frequency of oMt1a-oGH was monitored in all generations in the transgenic lines, but no genotypic information regarding the transgene was used as an aid to selection. The oMt1a-oGH was activated from weaning, at 3 wk, until 8 wk of age by adding ZnSO4 to the drinking water. Zinc stimulation of the transgene was not done during mating, gestation, or lactation. Data on body weights and weight gains were analyzed with a conventional mixed model and with an animal model. Genetic progress was achieved in all lines subjected to directional selection. In the control background, response to selection for 8-wk body weight was larger in the nontransgenic lines than in the transgenic lines, whereas no difference was found in the selected background. The frequency of the transgene was increased from the initial .5 to .62 in the randomly selected background but decreased to .04 in lines from a selected background. The REML estimates of variance components and genetic gain estimates varied greatly between the two methods. In general, there was better agreement between the realized heritability estimates and the heritability estimates obtained from the conventional mixed model analysis than between realized heritability estimates and results obtained using the animal model. Favorable correlated responses were obtained for 3- and 6-wk body weights and on 3- to 6- and 6- to 8-wk weight gains. Correlated responses to selection were larger in the selected than in the nonselected background but were not affected by the presence of the transgene. Results suggest that constructs similar to the oMt1a-oGH, which allow tight regulation, may be successfully incorporated into commercial livestock and should have larger effects in populations that have not been subject to selection.

Factors influencing maternal behavior in the hubb/hubb mutant mouse.

We examined the maternal behavior of hubb/hubb mutant mice and normal control (+/hubb) siblings. From previous observations we noted that mutants groom their pups less, suckle less than normal, and often cannibalize the young. To date, these observations had not been quantified. Although prolactin (PRL) is linked to maternal behavior, it was difficult to measure because of the hyperirratibility of the mutant mice. Consequently, dopamine (DA) and its metabolite, dihydroxyphenylacetic acid (DOPAC), were measured in the median eminence in brains of both normal and mutant mice. Tyrosine hydroxylase, the rate-determining step in dopamine synthesis, was localized in the brain by immunohistochemistry. Five mutant and nine normal dams were observed for pup retrieval and crouching. Mean time for pup retrieval was slower (p < 0.06) for mutants (28.09 s) than for normal dams (18.49 s). Crouching was the same for both strains. Mutant pups were cold to the touch, and not well groomed. Brains from both strains were examined at Day 11 and Day 18 of gestation and Day 2 and Day 11 of lactation. Qualitatively, tyrosine hydroxylase localization in the arcuate nucleus and median eminence was the same in both strains for the gestation samples. The decrease in staining observed from gestation to lactation in the normal mice was increased in the mutants. Dopamine was similar in both strains at all stages, but DOPAC was significantly higher at early lactation in the mutants. We do not assume an absolute inverse relationship between dopaminergic activities and prolactin, but it is likely that the increase in DOPAC in the mutant reflects a decrease in prolactin, which could contribute to the diminished maternal care in the mutants.

Differential effects of fat and sucrose on body composition in A/J and C57BL/6 mice.

The C57BL/6 (B6) mouse is more sensitive to the effects of a high-fat diet than the A/J strain. The B6 mouse develops severe obesity, hyperglycemia, and hyperinsulinemia when fed this dietary regimen. This study was conducted to determine the effects of dietary fat and sucrose concentrations on body composition and intestinal sucrase (EC 3.2.1.48) and maltase (EC 3.2.1.20) activity in these two mouse strains. High-fat diets, regardless of sucrose content, resulted in significant weight gain, higher body fat, and lower body protein and water content in both strains of mice. The shift toward higher body fat and lower protein and water content was far greater in the B6 strain. Low-fat, high-sucrose diets resulted in lower body weight in both strains, as well as significantly greater body protein content in B6 mice. Analysis of intestinal sucrase showed that the enzyme was less active in B6 mice when the diet was high in sucrose. Both sucrase and maltase had lower activity in the presence of high dietary fat in both mouse strains. The percent reduction of intestinal enzyme activity due to dietary fat was similar in both strains. The B6 mouse exhibits disproportionate weight gain and altered body composition on a high-fat diet. This coupled with the reduced body weight and increased body protein on a low-fat, high-sucrose diet suggests that factors-relative to fat metabolism rather than sucrose metabolism are responsible for obesity.

Jejunal function and plasma amino acid concentrations in the segmental trisomic Ts65Dn mouse.

Mice trisomic for the distal portion of MMU 16 (Ts65Dn) were examined for differences in jejunal function and plasma amino acids as compared to diploid controls. Eighteen control and 19 Ts65Dn mice were compared for whole-body and intestinal O2 consumption, jejunal glucose uptake, and plasma amino acid concentrations. Ts65Dn mice consumed less (P < 0.02) O2 per gram of fasted body weight. No significant differences were found in either active or passive glucose uptake. Oxygen consumption by jejunal tissue was not different between Ts65Dn and control mice. The apparent energetic efficiency of jejunal active glucose uptake (eta mol ATP expended/eta mol glucose uptake) was significantly higher (115.6 vs. 80.8; P < 0.05) in Ts65Dn mice. Histomorphometric analysis of jejunal mucosa showed that Ts65Dn mice had shorter villus height (P < 0.04) and decreased planar villus circumference (P = 0.05). No differences were found in total jejunal protein (microgram/g) or DNA (mg/g) concentrations. Significantly higher concentrations of plasma tyrosine, phenylalanine, valine, leucine, isoleucine, and citrulline (P < 0.05) were found in Ts65Dn mice. Lower plasma concentrations of hydroxyproline were detected in Ts65Dn mice (P < 0.05). These data suggest that Ts65Dn mice have anomalies in digestive function and amino acid metabolism as compared to normal, diploid controls.

Effects of zinc ion concentration on growth, fat content and reproduction in oMT1a-oGH transgenic mice.

Attachment of the sheep metallothionein la promoter to the sheep growth hormone gene (oMT1a-oGH) has resulted in a closely regulated transgene in mice that can respond to elevated levels of zinc ions provided in the drinking water. The objective of this study was to explore the effects of zinc ion concentration on postweaning growth, fat content, organ size, and female reproduction. At weaning (3 weeks of age), hemizygous oMT1a-oGH mice were assigned randomly to receive 0, 12.5, 25, 37.5, or 50 mM ZnSO4 in distilled drinking water for 5 weeks. Males were killed at 8 weeks and selected organs and fat pads were weighed. Females received tap water from 8 to 10 weeks and then were mated to unrelated non-transgenic fertile males to obtain ovulation rate and embryo survival. Mortality rate was increased (P < 0.05) at 37.5 mM (15.2%) and 50 mM (33.3%) ZnSO4 compared with lower levels. Postweaning growth was highest at 12.5 mM ZnSO4 followed by 25 and 37.5 mM, respectively. At 50 mM ZnSO4, 8 week-old males were 20% smaller than males not receiving a supplement while females did not differ from females not receiving a supplement. Epididymal (EFP) and subcutaneous (SFP) fat pad weights of males decreased linearly (P < 0.01) with increased dosage of ZnSO4, while on a percentage of body weight basis, EFP and SFP decreased quadratically (P < 0.01). Males receiving 12.5 mM ZnSO4 had their EFP and SFP as a percentage of body weight reduced (P< 0.01) to 54.1% and 65.9% of controls (0 mM), respectively. As a percentage of body weight, liver spleen and kidney weights increased with doses of 12.5, 25 and 37.5 mM ZnSO4 compared with no supplemental zinc, while testis weight as a percentage of body weight was reduced (P < 0.05); percentage heart weight was only reduced at 12.5 mM (P < 0.05). No significant differences in female fertility were associated with ZnSO4 treatment. Females receiving ZnSO4 supplement had higher ovulation rates than those that received no supplement, but there were no differences (P > 0.05) in ovulation rates among the zinc levels. A decrease (P < 0.05) in pre- and post-implantation embryo survival was detected at 37.5 mM ZnSO4. These results indicate that zinc dosage affects phenotypic expression of the oMT1a-regulated oGH transgenic mice, and the dose responses are trait-dependent.

Jejunal glucose uptake and oxygen consumption in turkey poults selected for rapid growth.

Two lines of turkey poults, one selected for rapid growth at 16 wk of age (F line) and the other a randombred control line (RBC2) were used to investigate the effect of selection for rapid growth on jejunal O2 consumption and glucose transport as well as whole-body O2 consumption. All trials used unsexed poults and were designed as a randomized complete block with day and line as independent variables. In Trial 1, 120 turkey poults, fed a standard starter ration (25.5% CP), were used to examine the effect of selection on feed intake, body weight gain, and efficiency from hatching (Day 0) to 13 d of age. At Day 14, 36 of 60 birds from each line were killed to measure intestinal length and weight and jejunal O2 consumption after 18 h of feed deprivation. Compared with the RBC2 line, the F line had relatively shorter but heavier small intestinal segments when adjusted by 18 h feed-deprived body weight (FBW; P < 0.001). The F line consumed more O2 over the entire jejunum adjusted to FBW than RBC2 line (43.8 vs 34.6 nmol O2/min.g FBW; P < 0.001). Jejunal ouabain- and cycloheximide-sensitive O2 consumption were greater (P < 0.05) in the F line. In Trial 2, 16 14-d-old poults from each line were used to measure in vitro jejunal glucose transport rate. There was no difference in glucose transport of the jejunum (nanomoles per minute per gram of FBW) between the lines. In Trial 3, 20 poults from each line were used to measure whole-body O2 consumption at 7 to 10 d of age. The F and RBC2 lines had similar whole-body O2 consumption rate per gram of FBW. These data suggest that selection of turkeys for rapid growth at 16 wk of age did not increase efficiency of jejunal glucose uptake in 14-d-old turkey poults.

Selection for growth does not affect apparent energetic efficiency of jejunal glucose uptake in mice.

Five-wk-old male mice from high growth (M16) and randomly bred control (ICR) lines, plus their reciprocal crosses, ICR x M16 and M16 x ICR, were used to investigate whether whole-body O2 consumption, jejunal respiration, jejunal glucose absorption and the apparent energetic efficiency of jejunal active glucose uptake in mice are altered by genetic selection for growth as well as by heterosis and maternal effects. Whole-body O2 consumption was measured in 12 mice from each line or cross. The mice were later killed for measurement of jejunal O2, using tissue respiration chambers and jejunal glucose transport determined by 3H-3-O-methylglucose accumulation. No heterosis or maternal effects were detected in jejunal glucose active transport and active glucose uptake. Selection for growth (M16 vs. ICR) increased daily gain (1.54 vs. 1.09 g, P < 0.001), small intestinal length and weight, but did not enhance jejunal glucose transport. The apparent energetic efficiency of jejunal active glucose uptake among lines was not different (54.0, 50.4, 51.6 and 47.1 nmol ATP expended/nmol glucose uptake for M16, ICR, M16 x ICR and ICR x M16, respectively, P > 0.63). Selection for growth in mice did not result in more energetically efficient jejunal glucose absorption.

Selection for body composition does not affect energetic efficiency of jejunal glucose uptake in mice.

Five-wk-old male mice from three lines were used to examine whether the apparent energetic efficiency of active jejunal glucose uptake in mouse jejunum is altered by genetic selection for different body composition. The mice lines were selected as follows: HE, high percentage of body fat with no change in body weight as a constraint; LF, low percentage of body fat; and RS, randomly bred control. Body weight was similar in all lines. Total jejunal O2 consumption and ouabain-sensitive O2 consumption were used to estimate the energy expenditure associated with glucose absorption and Na+/K(+)-ATPase activity. Tritiated 3-O-methyl-D-glucose was used to determine glucose uptake by mouse jejunum. Line LF, when compared with line HE, had lower body fat as indicated by epididymal fat pad weight (143 vs. 362 mg/mouse, P < 0.001). There were no significant differences in small intestinal weight, length and density (mg/cm) between LF and HE lines. Jejunal villus width was greater in line LF compared with line HE (115 vs. 92 microm, P < 0.002). Jejunal glucose transport and O2 consumption were not different between LF and HE lines. Ouabain-sensitive O2 consumption was not significantly different among the three lines. No differences were noted in the apparent energetic efficiency of active glucose uptake among lines.