Effects of porcine growth hormone on glucose metabolism of pigs: I. Acute and chronic effects on plasma glucose and insulin status

The acute and chronic effects of porcine growth hormone (pGH) administration on glucose homeostasis of pigs were investigated in the present study. Twelve Yorkshire barrows (average BW = 65 kg) fitted with femoral artery catheters were allotted to three groups. Pigs received acute, intra-arterial injections of either pituitary pGH, a recombinantly derived pGH analog (ppGH or rpGH, 100 micrograms/kg BW) or saline. Acute injection of pGH did not affect fasting plasma glucose or insulin status. Pigs then were treated daily by i.m. injection for 24 d with 70 micrograms ppGH/kg BW. Serum glucose and insulin concentrations during the fed and fasted states were higher in pGH-treated than in control pigs. On d 25, an acute intra-arterial injection of ppGH (100 micrograms/kg BW) elicited increases in plasma glucose and insulin in pigs chronically treated with pGH. The area circumscribed by the glucose and insulin response curves 5 min to 7 h postinjection was 40% (P less than .005) and 177% (P less than .001), respectively, higher in ppGH-treated than in control pigs. These data indicate that pGH does increase plasma glucose and insulin in the fed and fasted states; however, this response is only observed after chronic pGH administration. In addition, pGH is capable of increasing plasma glucose and insulin acutely in the pig. This effect, however, only is observed in pigs treated chronically with pGH. The mechanisms by which pGH elicit these effects on glucose homeostasis are not known.     

Effect of energy source fed to sows during late gestation on neonatal blood metabolite homeostasis, energy stores and composition

Four experiments utilizing 49 primiparous and 34 multiparous sows were conducted to evaluate the effect of feeding either starch, soybean oil or medium-chain triglyceride (MCT) during late gestation (d 100 to parturition) on neonatal fasting blood glucose homeostasis (Exp. 1 and 2), d-100 maternal circulating insulin, glucagon and glucose concentrations (Exp. 3 and 4), neonatal energy stores (Exp. 3 and 4) and colostrum composition (Exp. 1, 2, 3 and 4). In all cases, sows were fed 7.2 Mcal/d of a diet that supplied 279 g of protein daily. During fasting, pigs from MCT-fed dams had higher blood glucose concentrations (P less than .05) than pigs from starch-fed dams. No differences between treatments were observed for total carcass fat, liver glycogen or carcass glycogen of pigs killed prior to suckling. In general, colostrum fatty acid profiles were influenced by diet; however, the shifts in fatty acids differed for experiments. Starch-fed sows had higher blood insulin and lower blood glucagon (P less than .05) than lipid-supplemented sows; however, sow blood glucose remained constant across treatments. This study indicates that any positive effects of feeding soybean oil to sows during late gestation are most likely mediated by a change in fatty acid composition of colostrum; any beneficial properties of MCT feeding most likely are mediated through improved blood glucose maintenance of the neonate when it is subjected to fasting conditions.     

Effect of streptozotocin-induced diabetes in primiparous swine on subsequent reproductive performance

A follow-up study was conducted to determine the effects of streptozotocin-diabetes during the first parity on subsequent reproductive performance of sows. Only in the first parity, two doses of streptozotocin (50 and 100 mg/kg body weight) were administered to two groups of pregnant gilts at 80 d of gestation; a third group of gilts served as a control. Second-parity reproductive performance showed that gestation length, placental weight, mean birth weight of the litter, litter size and number of pigs born alive were not affected (P greater than .05) by maternal diabetes. Maternal serum glucose and fructose were greater (P less than .01) in high-dose sows than in the low-dose and the control dams. Serum free fatty acids (FFA) were higher (P less than .05) in high-dose dams than in control dams at d-1 and d 112 of gestation; no differences were observed between the high-dose and the low-dose during the same period. Liver and kidney weight, as well as DNA and RNA content, were greater (P less than .01) in pigs from high-dose dams than in those of the other treatments. Liver protein was elevated (P less than .01) in the progeny of high-dose dams. Dry matter and percent lipid were higher (P less than .05 and P less than .01, respectively), in pigs from high-dose sows than those from other treatment. Serum glucose, fructose and FFA of piglets were not affected by previous treatment of the dam.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of administration of growth hormone-releasing factor to sows during late gestation on growth hormone secretion, reproductive traits, and performance of progeny from birth to 100 kilograms live weight.

The effects of growth hormone-releasing factor (GHRF) injections to sows during late gestation were investigated in two experiments. In the first one, four treatments were applied to eight catheterized sows according to two 4 x 4 Latin squares: oral administration of 2 mg of pyridostigmine, a cholinesterase inhibitor, per kilogram of BW (PYR group); i.m. injection of 50 micrograms of GHRF/kg BW (GHRF group); a combination of the pyridostigmine and GHRF treatments (PYR+GHRF); or i.m. injection of glucose (control). Pyridostigmine slightly increased the plasma concentration of growth hormone (GH). Growth hormone responses to GHRF and PYR+GHRF treatments were similar, with significantly elevated GH concentrations from 5 to 240 min after GHRF injection. In the second experiment, 36 sows were allocated to two treatments at 102 d of gestation. Until farrowing, they were injected twice daily with 50 micrograms of GHRF/kg BW (GHRF group) or isotonic glucose (control). The DM, N, fat, and energy content of 24 pigs per group was determined at weaning at 22 d. Six pigs per litter had ad libitum access to feed until slaughter at 100 kg BW and their carcasses were evaluated. Treatment with GHRF increased pregnancy duration (114.8 vs 113.6 d, P less than .05), weight of pigs at 13 d (3.69 vs 3.54 kg, P less than .05) and at weaning (5.74 vs 5.48 kg, P less than .05), and improved pig survival (86 vs 71%, P less than .05). Lipid (on a DM basis) and energy contents of the pigs slaughtered at weaning were significantly higher in the GHRF group than in the control group (14.4 vs 12.5% and 2,178 vs 2,029 kcal/kg, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of fructose consumption during lactation on sow and litter performance and sow plasma constituents

The effects of dietary consumption of high-fructose corn syrup (HFCS) and dextrose during a 28-d lactation on sow and litter performance and sow plasma constituents were examined in 45 multiparous and 36 primiparous crossbred sows. Isocaloric and isonitrogenous corn-soybean meal diets were formulated to contain either 20% fructose or 20% glucose. Diets were fed on a metabolic BW basis from d 0 to d 28 of lactation. Litter and pig weights on d 28 were not affected (P greater than .05) by treatment. Litter size was greater (P less than .10) at weaning for primiparous sows fed HFCS, but multiparous sows weaned heavier (P less than .05) pigs. Sow weight change during lactation was not influenced by diet, but primiparous sows lost more (P less than .05) weight during lactation and had longer intervals to estrus than multiparous sows did. Milk yields on d 17 and 21 of lactation were not different (P greater than .05) for sows fed HFCS vs dextrose, but sows fed HFCS tended to have greater (P = .05) percentage of milk fat. Preprandial concentrations of fructose in plasma were low in sows fed HFCS and nondetectable in those fed dextrose but were elevated (P less than .05) after consumption of HFCS. Conversely, similar (P greater than .05) concentrations of glucose in plasma preprandially were followed by greater (P less than .05) postprandial glucose concentrations in sows fed dextrose. Although postprandial concentrations of insulin were not affected (P greater than .05) by diet, sows fed dextrose had greater (P less than .05) preprandial insulin concentrations in plasma. Concentrations of nonesterified fatty acids and growth hormone in plasma and response to a glucose challenge were not affected (P greater than .05) by feeding HFCS. However, concentrations of insulin in plasma following glucose infusion were less (P less than .05) during the glucose challenge period on d 25 than on d 13 of lactation.     

Comparative effects of organic and inorganic selenium on selenium transfer from sows to nursing pigs

To investigate the effects of supplemental Se on the transfer of Se to nursing pigs when sows are fed diets containing a Se level above the NRC recommendation (0.15 ppm), sows were fed diets containing no supplemental Se or supplemental (0.3 ppm) Se from sodium selenite or Se yeast. A nonSe-fortified corn-soybean meal basal diet with a high endogenous Se content served as the negative control (0.20 to 0.23 ppm Se). Fifty-two sows were fed diets from 60 d prepartum until 14 d of lactation. Six sows per treatment were bled at 60 and 30 d prepartum, at farrowing, and at 14 d postpartum to measure serum Se concentrations. Colostrum was collected within 12 h postpartum, and milk was collected at 14 d of lactation. Blood was obtained from 3 pigs each from 12 litters per treatment at birth and at weaning (d 14), and pooled serum was analyzed for Se and immunoglobulin G concentrations and glutathione peroxidase activity. Regardless of treatment, serum Se in sows declined throughout gestation and gradually increased during lactation. Sows fed Se yeast tended (P < 0.06) to have greater serum Se at farrowing than sows fed unsupplemented diets. Colostrum and milk (d 14) Se concentrations increased (P < 0.01) when sows were fed Se from yeast but not from sodium selenite. At birth, serum Se was increased (P < 0.01) for pigs whose dams were fed Se yeast compared with pigs from sows fed the basal diet. At 14 d of age, there was no difference in serum Se concentration of pigs from dams fed any of the treatments. Pig serum immunoglobulin G concentrations and glutathione peroxidase-1 activity were unaffected by dietary Se source. Supplementation of gestating and lactating sow diets with Se (0.3 ppm) from an organic or inorganic source reduced the number of stillbirths per litter. However, only pigs born to sows fed organic Se (Se yeast) had greater serum Se at birth. Organic Se increased Se concentration of colostrum and 14-d milk to a greater degree than inorganic Se.     

Effect of dietary folic acid supplementation on sow performance through two parities

One hundred fifty-three gilts were maintained in three breeding groups and fed gestation-lactation diets supplemented with either 0 (control), 1.65 or 6.62 mg of supplemental folic acid/kg of diet for two consecutive parities. Serum folate concentrations of sows were linearly (P less than .05) increased by dietary additions of folic acid during both gestation and lactation, but serum glucose and urea concentrations were unaffected by treatment. Serum folate concentrations decreased from breeding to d 60 and 90 of gestation and then increased through lactation for all treatments. Number of pigs born and live pigs at birth, d 14 and d 21 were quadratically (P less than .05) increased by folic acid additions. Average pig weights were similar among treatments (P greater than .10) on both d 0 and 14 of lactation but were less (P less than .01) than the other treatment groups on d 21 for pigs from sows fed the 1.65 mg/kg treatment. Litter weights were quadratically (P less than .01) increased on d 0 and d 14 by folic acid supplementation. Sow weight gain and backfat thickness loss were unaffected by treatment during gestation (P greater than .06); sow weight loss and backfat thickness loss increased quadratically with increasing level of folic acid during lactation (P less than .06 and .05, respectively). More control sows exhibited estrus by d 7 postweaning than sows receiving folic acid supplementation in parity I (P less than .05); however, no differences (P greater than .10) were detected among treatments by d 14, nor were any differences observed by d 7 in parity II. Conception rate was unaffected by folic acid additions. Dietary folic acid supplementation improved sow reproductive performance by increasing the number of pigs born alive.     

The effects of postweaning stressors on pig weight change, blood, liver and digestive tract characteristics

Postweaning growth lag in baby pigs weaned at 28 d was studied by using three weaning stress treatments. Treatments consisted of a control in which pigs continued to nurse the dam, had access to a dry feed at 14 d of age and were not weaned until after the study. Pigs were adjusted to liquid and dry feeds at 14 d of age in Treatments 2 and 3, but sows were removed from the pens at 28 d of age in Treatment 2, whereas sows were removed and room temperature lowered to 13 degrees C in Treatment 3. In Treatment 4, sows were removed but pigs were fed the dry diet only from 28 d of age. Blood and tissue were collected and evaluated every 12 h for 48 h on slaughtered pigs and blood was sampled every 12 h for 132 h from pigs catheterized in the vena cava. Pigs weaned with a dry diet in Treatment 4 were the only pigs to lose weight (P less than .01) and have typical symptoms of postweaning growth lag. These pigs had the lowest (P less than .01) mean plasma glucose, highest (P less than .01) free fatty acids and the highest (P less than .05) cortisol concentrations. Their mean duodenal pH also was higher (P less than .01), whereas pigs given both milk and dry diets and stressed by weaning in a warm or cool room (Treatments 2 and 3) had lower (P less than .01) duodenal pH values than pigs continuing to nurse the sow. In this study, pigs having access to milk and dry diets prior to weaning had no adverse symptoms when the sow was removed regardless of whether or not they were exposed to cold after weaning. However, pigs that were abruptly weaned with a dry diet had slow growth, low plasma glucose, high free fatty acids and low liver glycogen.     

Stimulation of pig growth performance by porcine growth hormone and growth hormone-releasing factor

The current study was undertaken to determine the effects of human growth hormone-releasing factor [hpGRF-(1-44)-NH2] on growth performance in pigs and whether this response was comparable to exogenous porcine growth hormone (pGH) treatment. Preliminary studies were conducted to determine if GRF increased plasma GH concentration after iv and im injection and the nature of the dose response. Growth hormone-releasing factor stimulated the release of pGH in a dose-dependent fashion, although the individual responses varied widely among pigs. The results from the im study were used to determine the dose of GRF to use for a 30-d growth trial. Thirty-six Yorkshire-Duroc barrows (initial wt 50 kg) were randomly allotted to one of three experimental groups (C = control, GRF and pGH). Pigs were treated daily with 30 micrograms of GRF/kg body weight by im injection in the neck. Pigs treated with pGH were also given 30 micrograms/kg body weight by im injection. Growth rate was increased 10% by pGH vs C pigs (P less than .05). Growth rate was not affected by GRF; however, hot and chilled carcass weights were increased 5% vs C pigs (P less than .05). On an absolute basis, adipose tissue mass was unaffected by pGH or GRF. Carcass lipid (percent of soft-tissue mass) was decreased 13% by GRF (P less than .05) and 18% by pGH (P less than .05). Muscle mass was significantly increased by pGH but not by GRF. There was a trend for feed efficiency to be improved by GRF; however, this was not different from control pigs. In contrast, pGH increased feed efficiency 19% vs control pigs (P less than .05). Chronic administration of GRF increased anterior pituitary weight but did not affect pituitary GH content or concentration. When blood was taken 3 h post-injection, both GRF- and pGH-treated pigs had lower blood-urea nitrogen concentrations. Serum glucose was significantly elevated by both GRF and pGH treatment. This was associated with an elevation in serum insulin. These results indicate that increasing the GH concentration in blood by either exogenous GH or GRF enhances growth performance. The effects of pGH were more marked than for GRF. Further studies are needed to determine the optimal dose of GRF to administer in growth trials and the appropriate pattern of GRF administration in order to determine whether GRF will enhance pig growth performance to the extent that exogenous pGH does.     

Pig weaning weight and changes in hematology and blood chemistry of sows injected with recombinant porcine somatotropin during lactation

Weaning weight of pigs on d 18 to 21 of age was used to determine the effects of recombinant porcine somatotropin (rpST) on lactational performance of their dams. Crossbred Landrace x Yorkshire sows (n = 180, 202 to 270 kg BW) were assigned to receive daily i.m. injections of either 0, 8, or 16 mg of rpST on lactation d 7 to 20. Initially, injections of 16 mg of rpST/d caused 100% mortality (four sows); thus, a dose of 4 mg of rpST/d replaced 16 mg. Subsequently, 5 of 19 and 1 of 17 sows died in response to daily injections of 8 and 4 mg of rpST, respectively, resulting in termination of the experiment. Before termination, 48 sows (16 from each of the 0-, 4-, and 8-mg treatment groups) completed a lactation of 18 to 21 d in duration. Analysis of these data indicated that daily injection of lactating sows with rpST increased (P less than .05) weaning weight of pigs only if they were from litters that averaged greater than or equal to 2.6 kg/pig on lactation d 7. The BW of sows was decreased by rpST (P = .07). Subsequent experiments revealed 1) that rpST-induced death of lactating sows was caused from hemorrhaging of ulcers that developed at the pars esophagea, 2) that there was vacuolation of the liver and kidney of dead sows, and 3) that daily injection of 16 mg of rpST into nonlactating growing pigs (50 to 100 kg BW) for 28 d did not cause death or any observable illness in spite of 100% mortality of lactating sows after two to nine injections.     

Prenatal stress effects on pig development and response to weaning

Exposing a pregnant sow to stress has been shown to affect the resulting offspring. Our objective was to determine if rough handling of pregnant sows altered the physiology of her offspring and if these alterations were different from an experimentally induced model of prenatal stress. Sow treatments consisted of i.v. injections of ACTH (1 IU/kg of BW), exposure to rough handling for 10 min (Rough), or no treatment (Control) once a week during d 42 to 77 of gestation. To determine the plasma cortisol response to treatments, blood (5 mL) was collected from 30 sows after treatment administration. To conduct the prenatal stress study, a separate group of 56 sows was used in 1 of 4 replicates. At birth, production data were collected for each litter, including birth weight, number born, anogenital distance, and pig viability. At weaning, pigs were blocked by BW and sex, and placed in a nursery pen of 6 pigs, with 2 pigs from each treatment group. To assess the effect of treatments on cortisol, corticosteroid-binding globulin (CBG), and hematological cell profiles, blood was collected every other day for 10 d after weaning. Application of treatments caused plasma cortisol concentrations to be greatest in ACTH sows compared with Control sows (P < 0.001), with Rough sows having intermediate values (P = 0.07). Treatments did not affect the number of pigs born, number of stillborn, or pig viability (P > 0.40). The ratio of cortisol to CBG did not differ between treatments (P = 0.09). Hematological variables did not differ between treatments (P > 0.19). Pigs born to ACTH sows had a smaller anogenital distance compared with controls (P < 0.03), with pigs from Rough sows being intermediate. Our data indicate that swine exposed to prenatal stress (ACTH injection) can have alterations in sexual morphology without effects on growth or the immune cell populations measured in this study.     

Effects of adding fat to the sow lactation diet on lactation and rebreeding performance

One-hundred-three multiparous sows were randomly assigned to one of two lactation diets containing either no supplemental animal fat (C) or 10% added fat (F) during two seasons, summer (S) and winter (W), in a 2 X 2 factorial arrangement of treatments. Sows were placed on their respective dietary treatments 1 wk prior to farrowing and were fed these diets ad libitum throughout the 28-d lactation period. Weekly feed intake and total feed intake were not affected by diet or season, while weekly metabolizable energy (ME) intake tended to be higher during week 1 and 3, and was higher (P less than .04) during wk 2 for sows fed diet F. Sow weight loss from farrowing to 21 d of lactation and to weaning (28 d) were unaffected by diet or season. Average pig birth weight was .15 kg higher (P less than .01) for pigs born during S compared with those born in W. Sows receiving diet F had heavier litters at 21 d (P less than .01) and heavier average pig 21-d weights (P less than .01). This was primarily due to the 13.1% increase (P less than .04) in estimated milk yield and the higher fat concentration (P less than .001) of milk consumed by the pigs nursing sows fed diet F. Interval between weaning and rebreeding was shortened by 5.9 d (P less than .01) for sows during W than during S, and tended to be lower for sows fed diet F (7.3 d) compared with that of sows fed diet C (9.7 d).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of prepartum administration of 1,3-butanediol to sows on growth and survival of neonatal pigs

In six trials, 158 late-term gravid sows were fed isocaloric amounts (8,500 kcal metabolizable energy/d) of a corn-soybean meal-based diet in which 20% of their daily metabolizable energy (ME) intake was supplied by either cornstarch or 1,3-butanediol (butanediol) from about d 105 of gestation to parturition. After parturition, all sows were allowed to consume a standard, corn-soybean meal-based lactation diet, ad libitum, during a 28-d lactation. Prepartum administration of butanediol, a stable, nonvolatile liquid that possesses anesthetic, antimicrobial and ketogenic properties, did not alter the voluntary feed intake or body weight changes of sows pre- or post-partum. Number of pigs born per litter, average pig birth weight and incidence of stillbirths were not influenced by the prepartum diet of the sows. However, the addition of butanediol to the prepartum diet increased (P less than .10) the number of pigs weaned per litter at 28 d by .51 pigs (8.17 vs 7.66) and improved (P less than .10) the survival rate of pigs from birth to weaning by 5.7 percentage units (84.1 vs 78.4%) compared with those of sows fed isocaloric additions of starch. Average pig weights at 28 d of age were similar for the two treatment groups (6.18 vs 6.08 kg) even though greater numbers of pigs were nursing sows fed the butanediol diet prepartum. The rate and efficiency of gain and survivability of weanling pigs during a 28-d postweaning period were not influenced by the prepartum diet of their dam.     

Response of swine to periparturient vitamin C supplementation

Two experiments were conducted, involving 68 third-litter sows and 20 first-litter gilts in Exp. 1 and 82 first-litter gilts in Exp. 2. On d 108 of gestation, the dams were moved into individual crates, stratified by parity and breed, and randomly assigned within strata, to one of two treatments: (1) fed a basal 16% protein corn-soybean meal diet, 1.8 and 2.7 kg once daily before farrowing and for the first 7 d of lactation, respectively, and then ad libitum until pigs were weaned at 28 d of age, and (2) fed the basal diet plus 1 g of L-ascorbic acid (vitamin C)/dam daily from d 108 of gestation through d 7 of lactation and on the same feeding schedule as for treatment 1. In Exp. 1, no effect of vitamin C supplementation was observed in sows or gilts on total pigs born/litter, number of live pigs/litter or average live pig weight at birth, 7 or 28 d of age, or on plasma vitamin C concentration of dams at d 108 of gestation or d 7 of lactation or of pigs at birth, 7 or 28 d of age. However, there was a lower (P less than .01) plasma vitamin C concentration of the dams at d 7 of lactation than at d 108 of gestation. Plasma vitamin C concentration also declined (P less than .01) as pigs aged. In Exp. 2, with all gilts, vitamin C supplementation again showed no effect on any of the reproductive traits measured in Exp. 1. It is concluded that daily supplementation of 1 g of vitamin C to either sows or gilts from d 108 of gestation through d 7 of lactation has no beneficial effect on the reproductive or lactation performance of swine.     

Yield and composition of milk and weight gain of nursing pigs from sows fed diets containing fructose or dextrose

Yield and composition of milk and growth of nursing pigs in response to dietary treatment were estimated from 25 lactating sows during a 22-d period. Eight sows were fed 6 kg/d of a corn-soybean control diet (C sows). Nine were fed the control diet in which approximately 6.5 g X kg body weight (BW-1) X d-1 of carbohydrate was supplied by fructose corn syrup (F sows) and eight were fed the control diet containing equivalent carbohydrate supplied by powdered dextrose (D sows). Blood samples collected via jugular cannulae were analyzed for plasma concentrations of fructose, glucose and insulin. Concentrations of fructose and glucose from F sows were significantly higher throughout the study than that from D and C sows, while insulin concentration was approximately 2.5-fold lower. Milk yield from F sows on d 14 and 21 was significantly higher and pigs weaned on d 21 were heavier than those from D and C sows. Sows fed the diet containing fructose experienced significant BW loss during lactation. Coefficients of gross correlation across treatments showed milk yield and litter weight gain to be negatively associated with percentages of protein, lipids and total solids in milk, but positively associated with concentrations of lactose and gross energy. Nursing pig weight gain at weaning was more responsive to total yields of milk and milk nutrients than to composition. These data support the hypothesis that source of metabolizable energy (ME) affects milk yield, composition and efficiency at which the sow converts dietary nutrients into milk.     

Effects of porcine growth hormone on glucose metabolism of pigs: II. Glucose tolerance, peripheral tissue insulin sensitivity and glucose kinetics

This study was conducted to determine whether the increase in serum glucose observed in pigs treated chronically with pGH is due to an increase in hepatic glucose output or to an impairment in glucose clearance. Barrows (n = 4 per treatment) were treated with pituitary derived pGH (ppGH), recombinant pGH analog (rpGH) or vehicle. Pigs were treated for 28 d by daily i.m. injections. Insulin tolerance and glucose tolerance tests (GTT) were performed on d 19 and 21, respectively, following treatment with pGH. Glucose turnover was quantified on d 28 using [6-3H]glucose. Chronically treating pigs with pGH resulted in a significant decrease (26%; P less than .05) in glucose clearance, as determined by the GTT. Glucose clearance was affected similarly by ppGH and rpGH. Intra-arterial glucose infusion markedly increased plasma insulin concentration in pGH-treated pigs. Peak plasma insulin response was 87% and 58%, respectively, higher (P less than .05) in ppGH- and rpGH-treated than in control pigs. Insulin infusion elicited a marked hypoglycemia in pigs; however, the extent and duration of hypoglycemia were significantly less in pGH-treated pigs (ppGH or rpGH). Glucose production rates were 23% higher (P = .085) in ppGH-treated than in control pigs. These results establish that the hyperglycemia induced by pGH is the result of an increase in hepatic glucose output and a concurrent impairment in glucose clearance.     

Endocrine adaptations of periparturient swine to alteration of dietary energy source

Lipid compared with carbohydrate calories in the diet of peripartal sows was examined for specific metabolic effects. Blood samples from second-parity Yorkshire sows fed isocaloric-isonitrogenous diets that differed by either glucose or corn oil supplying 20% of the daily metabolizable energy intake were assayed for growth hormone (GH), insulin and prolactin (PRL) concentrations. On d 97 to 103 of gestation, serum GH levels were reduced following feed intake; the reduction was greater (P less than .05) in glucose-fed sows during the postprandial period. Insulin concentration was increased following consumption of either diet, but to a greater (P less than .05) extent in glucose-fed sows corresponding to the greater (P less than .05) blood glucose response. Basal, fasting concentrations of PRL were not affected by dietary energy source; however, thyrotropin-releasing hormone (TRH) infusion resulted in a greater (P less than .05) PRL response of fat-fed sows. Samples obtained on d 8 to 11 of lactation revealed that TRH stimulated (P less than .05) GH secretion and the response was greater (P less than .05) in fat-fed sows. Plasma insulin concentration was increased (P less than .05) following feeding, and the increase was greater (P less than .05) in glucose-fed sows. Similar to the response measured in gestating sows, TRH-induced increases in PRL was greater in fat-fed, lactating sows. Sham-nursing did not influence maternal PRL concentration compared with the immediate increase noted following natural nursing. No effect of dietary energy source on reproductive performance characteristics was noted. Results of this study have shown that dietary lipid, compared with carbohydrate, selectively increased the sensitivity of the pituitary gland to a GH and PRL secretagogue such as TRH. The beneficial effects of lipid in the diet of peripartal swine may be attributable, in part, to the effect of dietary lipid on maternal pituitary PRL synthesis and(or) release.     

Suppression of somatotroph function induced by growth hormone treatment in neonatal pigs

The effect of recombinant porcine growth hormone (pGH) treatment on pituitary function was evaluated in young pigs. Piglets received intraperitoneal recombinant pGH implants (0.5 mg/d sustained release) or vehicle implants beginning at 3 d of age. Ten piglets were sacrificed at 4 and 6 wk of age (five piglets/treatment group) for the collection of pituitary glands, blood, and liver tissue. Blood samples also were drawn at 3 and 12 d of age. Serum concentrations of GH, prolactin (PRL), thyroid-stimulating hormone (TSH), insulin-like growth factor-1 (IGF-1) and IGF-2 were evaluated. Levels of IGF-1 and IGF-2 mRNA were determined in liver samples. Treatment with GH increased circulating levels of GH and IGF-1 (P < 0.01), but not PRL, TSH, or IGF-2. Hepatic IGF-1, but not IGF-2, mRNA levels were increased by pGH (P < 0.001). Cultured pituitary cells from each animal were challenged with 0.1, 1, and 10 nM GH-releasing hormone (GHRH); 2 mM 8-Br-cAMP; or 100 nM phorbol myristate acetate. The release of GH from cultured pituitary cells was stimulated by all secretagogues (P < 0.001). The secretion of GH, but not PRL or TSH, in culture was inhibited by previous in vivo GH treatment (P < 0.001). Similarly, cellular GH, but not PRL or TSH, content was lower in the GH-implant group (P = 0.005). Cell cultures from 6-wk-old piglets secreted more GH, but not PRL or TSH, than cultures from 4-wk-old piglets (P < 0.05). Likewise, cellular GH, but not PRL or TSH, content was greatest in cultures from 6-wk-old animals (P = 0.002). Piglet growth was not affected by exogenous GH treatment (P = 0.67). These results demonstrate that exogenous pGH treatment selectively down-regulates somatotroph function in young pigs.     

Effects of dietary additions of 1,3-butanediol or lard for sows on survival of neonatal pigs

In nine trials, 278 late-term gravid sows were fed isocaloric amounts (8,500 kcal metabolizable energy (ME)/d) of a fortified, corn-soybean meal based diet in which 20% of their daily ME intake was supplied by corn starch, 1,3-butanediol or lard from about d 106 of gestation to parturition. After parturition, the sow's daily ME intake was increased to 18,000 kcal. Sows fed starch and lard remained on their respective diets for the duration of a 28-d lactation; whereas, those initially fed butanediol were switched to the starch diet after parturition. Number of pigs born per litter, average pig birth weight and incidence of stillbirths were not influenced (P greater than .30) by the prepartum diet of the sow. However, the inclusion of isocaloric levels of butanediol for starch in the preparatum diet and lard for starch in the pre- and postpartum diets increased the number of pigs weaned per litter by .45 (P less than .13) and .16 pigs (8.25, 7.96 vs 7.80) and improved the survival rate of pigs from birth to weaning by 4.3 (P less than .13) and 2.7 percentage units (84.5, 82.8 vs 80.1%), respectively. Average pig weights at 28 d of age for litters of sows fed butanediol prepartally were similar to those of sows fed starch, but were less (P less than .01) than those of sows fed lard throughout lactation.     

Effects of a novel carbohydrate and protein source on sow performance during lactation

Ninety-one primiparous and multiparous sows and their pigs were used to evaluate the effects of a novel carbohydrate- and protein-based feed ingredient (Nutri-Pal, NP) on sow and litter performance during lactation. Nutri-Pal is a feed supplement for sows that consists of a blend of milk chocolate, brewer's yeast, whey products, and glucooligosaccharides. The dietary treatments consisted of a corn-soybean meal control and a corn-soybean meal plus 5% NP fed from d 110 of gestation to weaning. The diets were formulated to be equal in total Lys and ME. Sows were allotted to treatment based on parity, body weight, and the date of d 110 of gestation. There were 46 and 45 sows per treatment over four farrowing groups. Litters were standardized to 10 pigs and weighed within 1 d of farrowing, and all sows weaned at least 8 pigs at an average age of 21 d. Sows were weighed on d 110 of gestation, d 1 postfarrowing, and at weaning. Sows were fed three times daily during lactation. Sows were checked twice daily after weaning for signs of estrus. The weaning weight of sows fed NP was increased (P < 0.10) compared with those fed the control diet. Sows fed the control diet tended (P = 0.11) to lose more weight per day from d 110 of gestation to weaning than the sows fed NP. Otherwise, sow response variables (sow weight on d 110 of gestation and d 1 postfarrowing, d 110 of gestation to d 1 postfarrowing and lactation weight change per day, d 110 of gestation to d 1 postfarrowing, lactation, and total feed intake, days to estrus, pigs born alive or dead, and litter and average pig birth weight) were not affected (P > 0.10) by diet. There were no effects (P > 0.10) of diet on litter performance response variables (pigs weaned, litter and average pig weaning weight and gain, and survival percent). The NP feed ingredient had minor effects on sow productivity, but it did not affect litter productivity indices.