Biomedical subjects

F R Dunshea

Publications and source records attributed to F R Dunshea.

At least 19 recordsLinked to original sources

PubMed2002

Short-term infusion of LongR(3) insulin-like growth factor (IGF)-I decreases hepatic IGF-I mRNA but not IGF binding protein-3 mRNA expression in pigs.

Infusion of pigs with an insulin-like growth factor-I (IGF-I) analogue (LongR(3)IGF-I) that does not bind to IGF-binding proteins decreases growth rate and the plasma concentration of growth hormone (GH), IGF-I, IGFBP-3, and insulin. This study was designed to determine whether the decrease is due to changes in IGF-I and IGFBP-3 gene expression. IGF-I or LongR(3)IGF-I (180 microg/kg/day) was infused into 55-kg finisher pigs for 4 days using Travenol infuser pumps. Plasma IGF-I concentration was measured by radioimmunoassay and plasma IGFBP-3 and IGFBP-2 were estimated by Western ligand blotting. Steady-state levels of IGF-I and IGFBP-3 mRNA were measured by RNase protection assay. Neither IGF-I nor LongR(3)IGF-I had a significant effect on hepatic IGF-I class 1 mRNA expression, whereas hepatic IGF-I class 2 mRNA expression was significantly reduced by both peptides. Plasma IGFBP-3 levels were unaffected by IGF-I treatment but were reduced by LongR(3)IGF-I treatment. The decrease in IGFBP-3 was not due to decreased gene expression in porcine liver or kidney, since neither IGF-I nor LongR(3)IGF-I treatment altered IGFBP-3 mRNA. This study infers a direct effect of the IGF analogue LongR(3)IGF-I on GH through its inhibition of plasma IGF-I concentration and class 2 IGF-I mRNA. The decrease in plasma IGFBP-3 was not accompanied by a decrease in hepatic or renal IGFBP-3 mRNA, suggesting that in this case, plasma IGFBP-3 protein levels are posttranslationally regulated or are derived from tissues other than liver or kidney.

Animals↗

PubMed2002

Effects of dietary fat and conjugated linoleic acid on plasma metabolite concentrations and metabolic responses to homeostatic signals in pigs.

Sixteen female cross-bred (Large White x Landrace) pigs (initial weight 65 kg) with venous catheters were randomly allocated to four treatment groups in a factorial design. The respective factors were dietary fat (25 or 100 g/kg) and dietary conjugated linoleic acid (CLA; 0 or 10 g CLA-55/kg). Pigs were fed every 3 h (close to ad libitum digestible energy intake) for 8 d and were bled frequently. Plasma glucose and non-esterified fatty acid (NEFA) responses to insulin and adrenaline challenges were determined on day 8. Plasma concentrations of NEFA were significantly increased (10.5 and 5.4 % for low- and high-fat diets respectively, P=0.015) throughout the experiment, suggesting that there was a possible increase in fat mobilisation. The increase in lipolysis, an indicator of ss-adrenergic stimulated lipolysis, was also evident in the NEFA response to adrenaline. However, the increase in plasma triacylglycerol (11.0 and 7.1 % for low- and high-fat diets respectively, P=0.008) indicated that CLA could have reduced fat accretion via decreased adipose tissue triacylglycerol synthesis from preformed fatty acids, possibly through reduced lipoprotein lipase activity. Plasma glucose, the primary substrate for de novo lipid synthesis, and plasma insulin levels were unaffected by dietary CLA suggesting that de novo lipid synthesis was largely unaffected (P=0.24 and P=0.30 respectively). In addition, the dietary CLA had no effect upon the ability of insulin to stimulate glucose removal.

Analysis of Variance↗

PubMed2001

Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight.

Leptin can act as a satiety factor and exert neuroendocrine effects, but most studies have been performed in fasted animals. We aimed to determine the effect of chronic under-nutrition on the response to a 3-day intracerebroventricular infusion of leptin with regard to food intake and the secretion of pituitary hormones. Ovariectomised ewes (n=6) had a mean (+/-s.e.m. ) bodyweight of 56+/-0.8 kg on a diet available ad libitum (ad lib) or 33.4+/-1 kg on a restricted diet. The differential bodyweight was achieved by dietary means over a period of 6 months prior to the commencement of the study. Leptin (4 microg/h) or vehicle (artificial cerebrospinal fluid (aCSF)) was infused into the third cerebral ventricle for 3 days. Blood samples were taken prior to commencement and on day 3 of infusion for the assay of plasma hormone levels. The experiment was repeated one week later in a cross-over design. Food intake and metabolic status were monitored daily. The luteinising hormone (LH) pulse amplitude was lower (P<0.05) but plasma growth hormone (GH) levels were higher (P<0.05) in the food-restricted animals. Plasma levels of glucose, lactate, insulin, urea and triglycerides were similar in the two groups but non-esterified fatty acid levels were higher (P<0.01) in the animals on an ad lib diet. Leptin reduced (P<0.05) food intake only in the animals fed an ad lib diet. Leptin increased (P<0.05) the secretion of LH in the food-restricted group only and increased (P<0.05) GH irrespective of bodyweight. In conclusion, leptin does not alter food intake in animals on a restricted diet but can increase the secretion of LH in the same animals. The treatment of leptin was not sufficient to reduce plasma GH levels in the food-restricted animals, suggesting that other factors or mechanisms must be involved in the regulation of this axis.

Analysis of Variance↗

PubMed2001

Vaccination of boars with a GnRH vaccine (Improvac) eliminates boar taint and increases growth performance.

Peri- and postpubertal boars accumulate substances (e.g., androstenone and skatole) in their fatty tissue that are responsible for boar taint in pork. The objective of this study was to assess the efficacy of a GnRH vaccine, Improvac, in eliminating boar taint. Three hundred male (200 intact boars, 100 barrows) crossbred (Large White x Landrace) pigs were used in a 2 x 3 factorially arranged experiment. The respective factors were sex group (barrows, boars treated with placebo, or boars treated with Improvac) and slaughter age (23 or 26 wk). Vaccines were administered 8 and 4 wk before slaughter. All Improvac-treated pigs exhibited anti-GnRH titers. Testes and bulbo-urethral gland weights in treated pigs were reduced by approximately 50% (P < 0.001) and serum testosterone levels were below 2 ng/mL in the majority of treated boars (94 and 92% across both age groups at 2 and 4 wk, respectively). Boar taint, as assessed by the concentration of androstenone and skatole in s.c. fat, was suppressed to low or undetectable levels in 100% of Improvac-treated boars. No Improvac-treated pigs had significant concentrations of either androstenone (> 1.0 microg/g) or skatole (> 0.20 microg/g). In contrast, 49.5% of placebo-treated controls had significant androstenone and 10.8% had significant skatole levels, resulting in 10% of the control boars with high concentrations of both compounds. The mean concentrations of taint compounds in the Improvac-treated pigs were not significantly different from those in barrows. Improvac-treated boars grew more rapidly (P = 0.051 and < 0.001 for pigs slaughtered at 23 and 26 wk of age, respectively) than control boars over the 4 wk after the secondary vaccination, possibly because of reduced sexual and aggressive activities. Compared with barrows, Improvac-treated boars were leaner and had superior feed conversion efficiency. The vaccine was well tolerated by the pigs, and no observable site reactions could be detected at the time of slaughter. Vaccination of boars with Improvac allows production of heavy boars with improved meat quality through prevention and control of boar taint.

Adipose Tissue↗

PubMed2000

Comparison of silver-ion high-performance liquid chromatographic quantification of free and methylated conjugated linoleic acids.

Silver-ion high-performance liquid chromatography was used to fractionate a mixture of conjugated linoleic acid (CLA) isomers (as the free fatty acids, CLAFFA) in commercial CLA mixtures and biological samples. Due to the unchanged retention mechanism, it was assumed that the elution order of the isomers remained the same as that of methyl esters separated on the same column. The most abundant isomers, cis/trans 10, 12-18:2 and cis/trans 9,11-18:2, were separated better as free acids on a single column than in the methyl ester form. Quantification of the CLA standard was used as the reference profile to evaluate different methylation methods commonly used to prepare CLA methyl esters for quantitation. Acid-and base-catalyzed derivatization methods resulted in CLA intraisomerization and losses in total conjugated dienes content. Acid (HCl and BF3) methylations significantly elevated the level of trans,trans isomers and significantly reduced the cis/trans isomers. Base methylation, tetramethylguanidine/methanol, resulted in loss of trans,trans isomers, and a substantial loss of total underivatized conjugated dienes. Other catalysts such as the trimethylsilyldiazomethane produced additional peaks of unidentified artifacts. The analysis of CLAFFA appears to provide more accurate quantification of CLA isomers in commercial and biological samples.

Adipose Tissue↗

PubMed2000

Long-term alterations in adiposity affect the expression of melanin-concentrating hormone and enkephalin but not proopiomelanocortin in the hypothalamus of ovariectomized ewes.

We have developed a ruminant model to study long-term alterations in adiposity on the expression of appetite-regulating peptides in the hypothalamus. In this model endocrine and metabolic status are fully defined as well as body composition. The current study sought to define the effects of altered adiposity on the expression of genes for neuropeptide Y (NPY), POMC, enkephalin (ENK), and melanin-concentrating hormone (MCH). Ovariectomized ewes with high (60 +/- 1 kg) (FAT) or low (37 +/- 3 kg) body weights (THIN) were blood sampled every 10 min for 8 h to determine metabolic and endocrine status. The animals were then killed and the brains perfused for in situ hybridization. Body composition analysis was performed on the carcass using dual energy x-ray absorptiometry; this indicated that the FAT animals were 36 +/- 1% fat, whereas the THIN animals were 15 +/- 2% fat. The LH interpulse interval was lower and mean GH concentrations were higher in the THIN animals; cortisol and TSH levels were not different between the two groups but free T4 and free T3 levels were lower; the FT3:FT4 ratio was higher in THIN ewes. Levels of insulin, lactate, and nonesterified fatty acids were lower in the THIN group, and plasma glucose and urea concentrations were similar in THIN and FAT animals. Levels of gene expression of NPY and MCH were higher in THIN ewes. POMC expression was similar in the two groups. In the THIN animals, ENK expression was lower in the paraventricular and ventromedial nuclei but higher in the periventricular region. In conclusion, we have shown that alterations in adiposity influence the expression of appetite-regulating peptides in the absence of ovarian steroids. The appetite stimulators, NPY and MCH, appear to be involved in the metabolic response to altered adiposity, whereas ENK in the periventricular region may be linked to the secretion of GH and possibly LH. Our results suggest that altered expression of appetite- regulating peptides can be linked with the endocrine and metabolic adaptations that occur with long-term changes in adiposity.

Adipose Tissue↗

PubMed2000

Interrelationships between dietary lysine, sex, and porcine somatotropin administration on growth performance and protein deposition in pigs between 80 and 120 kg live weight.

Sixty male and 60 female crossbred pigs were allocated to an experiment to investigate the effects of porcine somatotropin (pST) administration (0 or 6 mg/d) and dietary lysine content on growth performance, tissue deposition, and carcass characteristics over the live weight range of 80 to 120 kg. Pigs receiving pST were given diets containing 6.9, 7.8, 8.8, 9.7, 10.6, or 11.5 g lysine/kg, whereas control pigs received diets containing 4.8, 5.8, 6.9, 7.8, 8.8 or 9.7 g lysine/kg. These dietary levels ranged from 0.40 to 0.70 g available lysine/MJ of DE for pST-treated pigs and from 0.28 to 0.58 g available lysine/MJ of DE for control pigs. Pigs were individually housed in pens, and there were five replicates of each treatment. All diets contained 14.5 MJ of DE/kg and were offered for ad libitum consumption to pigs between 80 and 120 kg live weight. Growth rate increased exponentially and food conversion ratio (FCR) decreased exponentially with increasing levels of lysine. In addition, there was a significant sex x pST interaction such that pST reduced the sex difference in FCR. Growth rate was faster in boars than in gilts and was increased by pST at the higher levels of dietary lysine. Similarly, FCR was lower for boars than for gilts and was decreased by pST at the higher dietary lysine levels. The optimum growth rate and FCR were defined as the lysine level at which growth rate and FCR were 95% and 105%, respectively, of the lysine plateau. The optimum growth rate and FCR were achieved at similar dietary lysine contents and were approximately 0.35 and 0.52 g available lysine/MJ of DE for control and pST-treated pigs, respectively. Protein deposition in the carcass increased exponentially with increasing dietary lysine level, was higher in boars than in gilts, and was increased by pST at the higher dietary lysine contents. Sex had no effect on dietary lysine required to maximize protein deposition. The dietary lysine contents required to ensure 95% of plateau protein deposition of 104 and 153 g/d were 0.39 and 0.55 g available lysine/MJ of DE for control and pST-treated pigs, respectively. The increase in lysine requirement with pST seems to be commensurate with the increase in protein deposition.

Animal Feed↗

PubMed1999

Moderate doses of porcine somatotropin do not increase plasma insulin-like growth factor-I (IGF-I) or IGF binding protein-3.

The growth rate of the young pig is generally much less than its potential and may be constrained by endocrine status as well as by nutrient intake. The aim of this study was to determine whether porcine somatotropin (pST) could increase growth in the nursing pig. Fourteen sows nursing litters of 6 (n = 7) or 12 (n = 7) piglets were utilized to establish a high and low plane of nutrition for sucking pigs. On Day 4 of lactation, the median two male pigs from each litter were randomly allocated to one of two doses of pST (0 or 60 micrograms/kg/d) until weaning on Day 31. Pigs were bled on Days 4, 13, 22, and 31 of lactation and the plasma was analyzed for insulin-like growth factor (IGF)-I, IGF-II, and IGF binding protein-3 (IGFBP-3). Pigs were weaned into conventional accommodation and further weighed on Days 63, 91, and 119. Pigs from litters of 6 grew more quickly and weighed 2.2 kg (P = 0.01) and 3.5 kg (P = 0.04) more than pigs from litters of 12 at 31 and 63 d of age, respectively. There was no effect of pST on preweaning growth of sucking pigs (261 vs. 258 g/d, P = 0.68), although growth rate increased in the final 3 d before weaning at 31 d (241 vs. 294 g/d, P = 0.01). IGFBP-3 was greater (1.09 vs. 0.78 micrograms/ml, P < 0.001), whereas IGF-I tended to be greater (206 vs. 176 ng/ml, P = 0.14), in pigs from the small litters. There was no effect of pST on plasma IGF-I (182 vs. 195 ng/ml, P = 0.454) or IGFBP-3 (0.93 vs. 0.94 microgram/ml, P = 0.85) concentrations. Plasma IGF-I and IGFBP-3 were highly correlated with the growth rate of nursing pigs (R = 0.638 and 0.756, respectively). There were no effects of pST (340 vs. 328 ng/ml, P = 0.48) or litter size (336 vs. 333 ng/ml, P = 0.88) on IGF-II. In conclusion, pST had no little or no effect on growth performance or plasma IGF-I, IGF-II, or IGFBP-3 in sucking pigs on either a high or low plane of nutrition.

Animals↗

PubMed1999

Dietary conjugated linoleic acids increase lean tissue and decrease fat deposition in growing pigs.

Conjugated linoleic acids (CLA) decrease the body fat content of rodents; the aim of this study was to determine whether dietary CLA altered carcass composition of pigs. Female Large White x Landrace pigs (n = 66) were used in this study. To obtain initial body composition, six pigs were slaughtered at 57 kg live weight, whereas the remaining pigs were allocated to one of six dietary treatments (0, 1.25, 2.5, 5.0, 7.5 and 10.0 g/kg CLA, containing 55% of CLA isomers). The diets, containing 14.3 MJ digestible energy (DE) and 9. 3 g available lysine per kg, were fed ad libitum for 8 wk. Dietary CLA had no significant effect on average daily gain (861 vs. 911 g/d for pigs fed diets with and without CLA, P = 0.15) or feed intake (2. 83 vs. 2.80 kg/d, P = 0.74). The gain to feed ratio was increased by dietary CLA by 6.3% (0.328 vs. 0.348, P = 0.009). Fat deposition decreased linearly (-8.2 +/- 2.09 g/d for each gram per kilogram increase in CLA concentration; P < 0.001) with increasing inclusion of CLA. At the highest level of CLA inclusion, fat deposition was decreased by 88 g/d (-31%). Similarly, the ratio of fat to lean tissue deposition decreased linearly (-0.093 +/- 0.0216 for each gram per kilogram increase in CLA concentration; P < 0.001) with increasing dietary CLA. The carcass lean tissue deposition response to dietary CLA was quadratic in nature and was maximized (+25%) at 5. 0 g/kg dietary CLA. Overall, dietary CLA increased the gain to feed ratio and lean tissue deposition and decreased fat deposition in finisher pigs.

Adipose Tissue↗

PubMed1999

Wheat bran affects the site of fermentation of resistant starch and luminal indexes related to colon cancer risk: a study in pigs.

BACKGROUND: Recent studies suggest that resistant starch (effective in producing butyrate and lowering possibly toxic ammonia) is rapidly fermented in the proximal colon; the distal colon especially would, however, benefit from these properties of resistant starch. AIMS: To determine whether wheat bran (a rich source of insoluble non-starch polysaccharides), known to hasten gastrointestinal transit, could carry resistant starch through to the distal colon and thus shift its site of fermentation. METHODS: Twenty four pigs were fed four human type diets: a control diet, or control diet supplemented with resistant starch, wheat bran, or both. Intestinal contents and faeces were collected after two weeks. RESULTS: Without wheat bran, resistant starch was rapidly fermented in the caecum and proximal colon. Supplementation with wheat bran inhibited the caecal fermentation of resistant starch, resulting in an almost twofold increase (from 12.9 (2.5) to 20.5 (2.1) g/day, p<0.05) in resistant starch being fermented between the proximal colon and faeces. This resulted in higher butyrate (133%, p<0.05) and lower ammonia (81%, p<0.05) concentrations in the distal colonic regions. CONCLUSIONS: Wheat bran can shift the fermentation of resistant starch further distally, thereby improving the luminal conditions in the distal colonic regions where tumours most commonly occur. Therefore, the combined consumption of resistant starch and insoluble non-starch polysaccharides may contribute to the dietary modulation of colon cancer risk.

Ammonia↗

PubMed1999

Effect of growth hormone administration on IGF binding protein-3 mRNA levels in porcine tissues.

The effect of short-term GH treatment on steady-state insulin-like growth factor binding protein-3 (IGFBP-3) mRNA levels in liver, kidney, longissimus dorsi muscle, stomach and jejunum was examined in pigs. Ten female crossbred pigs were allocated to either saline or GH (70 microg/kg/day) treatment by subcutaneous injection for 4 days. They were allowed to feed ad libitum, and were weighed daily. At the end of the treatment period, the pigs were slaughtered and samples of liver, kidney, skeletal muscle, stomach and jejunum were collected and total RNA was extracted. Steady-state levels of IGFBP-3 mRNA were quantified by RNase protection assay and were compared with the level of IGF-I class 1 and class 2 transcripts. IGFBP-3 mRNA increased in response to GH in both liver and kidney, but not in the other tissues sampled. Hepatic IGF-I mRNA responded to short-term GH treatment with a fourfold increase in IGF-I class 1 mRNA and an eightfold increase in IGF-I class 2 mRNA, which was liver specific. IGF-I class 1 mRNA was not responsive to GH treatment in other tissues. The short-term nature of this treatment suggests that the increase in hepatic IGFBP-3 and IGF-I transcripts is a relatively early response to treatment with GH, and that the increase in plasma concentrations of IGFBP-3 in response to GH are derived from the liver, the kidney, or both.

Animals↗

PubMed1998

The effects of post-weaning progestagen treatment (Regumate) of early-weaned primiparous sows on subsequent reproductive performance.

This study investigated the effects of feeding the orally active progestagen, altrenogest (Regumate) post-weaning on the subsequent reproductive performance of early weaned sows. Ninety (90) Large White/Landrace first parity sows were randomly assigned to three treatments. Treatment 1 (EW) and treatment 3 (CW) sows were weaned on day 12 and day 24 post-partum, respectively while treatment 2 sows (EW-R) were weaned on day 12 post-partum and received an individual daily dose of 20 mg of Regumate on days 13 to 24 post-partum inclusive. Each sow was mated naturally at least twice at the first post-weaning or post-treatment oestrus and slaughtered on days 25-28 of pregnancy to determine the number of corpora lutea and embryos. Regumate-to-oestrus and weaning-to-oestrus intervals were similar for EW-R and CW sows (6.2 vs. 5.6 days). However, both intervals were significantly shorter (P < 0.01) than the weaning-to-oestrus interval of EW sows (7.3 days). An excellent synchronization of oestrus was achieved with Regumate treatment with 97% of treated sows in oestrus within 7 days of Regumate withdrawal compared with 64% for EW sows (P < 0.01) and 87% for CW sows (P > 0.05). Treatment with Regumate resulted in a significant increase in ovulation rate (16.9 vs. 15.4 and 14.9 for treatments EW-R, EW and CW, respectively; P < 0.05) and a non-significant increase in early embryonic survival (77% vs. 68% vs. 68% for treatments EW-R, EW and CW, respectively; P > 0.05). These results indicate that Regumate feeding is a potential management tool to alleviate the diminished reproductive performance associated with early weaning regimes since it leads to successful control of oestrus, higher ovulation and embryo survival rates and thus a greater potential litter size.

Animals↗

PubMed1998

Assessment of apparent ileal digestibility of amino acids and nitrogen in cottonseed and soyabean meals fed to pigs determined using ileal dissection under halothane anaesthesia or following carbon dioxide-stunning.

Two experiments were conducted to determine apparent ileal digestibility of amino acids (AIDAA) and nitrogen (AIDN) in cottonseed meal (CSM) and soyabean meal (SBM) fed to growing pigs. In the first experiment, twenty-four male pigs (37.3 (SE 2.7) kg) were individually penned and randomized to either CSM or SBM diets. The diets contained 40% of the protein meal (either CSM or SBM) in a wheat starch-sucrose (1:1, w/w) base containing vitamins and minerals, and Cr2O3 as an indigestible marker. Pigs were acclimated to the experimental diets over a 3 d period and on day 4 through to day 14 were offered 1800 g/d of the diet. Diets were offered in three meals/d from day 4 to day 11 and in eight meals/d from day 12 to day 13. After the eighth hourly-meal on day 14, twelve pigs were anaesthetized with halothane while the remaining twelve pigs were CO2-stunned and processed using commercial slaughter procedures. Ileal digesta were collected from a 1500 mm portion of the terminal ileum of each pig and subsequently analysed for amino acids, N, organic matter and Cr. Results indicated that AIDAA of CSM and SBM were lower when digesta were collected following CO2-stunning than when digesta were obtained under halothane anaesthesia. Consistently, AIDN in CSM (0.51 v. 0.56) and SBM (0.55 v. 0.71) were lower (P < 0.05) in CO2-stunned pigs than in halothane-anaesthetized pigs. Furthermore, when digesta collection was conducted under halothane anaesthesia, AIDN of CSM was lower (P < 0.001) than that of SBM. In the second experiment, six male pigs (45 (SE 2.6) kg) were fitted with T-piece cannulas implanted in the terminal ileum, housed individually in metabolism cages, and randomly allocated to either CSM or SBM diets in a single reversal arrangement. Ileal digesta were collected for AIDAA and AIDN determination. Although statistical comparisons could not be made between the two experiments, the AIDAA and AIDN data obtained via cannulated pigs were similar to those values obtained using the halothane-anaesthesia method. Overall, the CO2-stunning method is not recommended for studies of amino acid or nitrogen ileal digestibilities, but may be useful for the study of other dietary constituents.

Amino Acids↗

PubMed1998

The effect of dietary magnesium aspartate supplementation on pork quality.

Large White x Landrace boars (n = 48) were used to determine the effect of dietary magnesium aspartate supplementation (MgAsp) on subsequent stress and meat quality indicators. Dietary MgAsp supplementation increased plasma magnesium levels compared with pigs fed the control diet. Pigs fed the MgAsp-supplemented diet had lower norepinephrine concentrations at slaughter than pigs fed the control diet. Pigs fed the MgAsp-supplemented and the control diet had similar glycogen concentrations in the longissimus thoracis (LT) and biceps femoris (BF) muscle, whereas pigs fed the MgAsp-supplemented diet had lower lactic acid in the LT and BF muscle compared to pigs fed the control diet. Negative handling of pigs before slaughter reduced muscle glycogen in the LT and the BF muscle and increased the lactic acid levels in the LT and BF muscle compared to when pigs were minimally handled at the abattoir. Comparison of meat quality traits indicates that MgAsp supplementation to pigs raised the muscle pH in the LT muscle at 40 min and 24 h after slaughter. Pigs that were fed the MgAsp-supplemented diet had lower percentage of drip loss, lower surface lightness L, and had no PSE carcasses compared to pigs fed the control diet. Also, pigs that were fed the control diet and negatively handled at the abattoir before slaughter had the highest percentage of drip loss and incidence of PSE compared to other treatment groups. The results indicate that dietary MgAsp supplementation to pigs can significantly improve ultimate meat quality and reduce the incidence of PSE meat.

Abattoirs↗

PubMed1997

Paradoxical increases of circulating nonesterified fatty acids in somatotropin treated cattle undergoing mild disturbances.

Effects of various doses of bovine somatotropin (bST) on plasma concentrations of nonesterified fatty acids (NEFA) were studied in a 14-d Latin square with six Holstein heifers. Animals were given daily injections of excipient or bST at 12:00 p.m. and fed twice daily at 7:00 a.m. and 7:00 p.m. On Day 14, plasma NEFA remained low through the day except around the 7:00 p.m. feeding when they were substantially elevated. The elevation was significantly greater in bST-treated animals and corresponded to the excitement of the animals in anticipation of the evening feeding. To further investigate this phenomenon, a second experiment was conducted in which nine growing Holstein steers were fed hourly and received either daily intramuscular (i.m.) injection of excipient or bST (120 mg/kg BW) for 15 d in a crossover design. Daily profiles of NEFA were obtained under undisturbed conditions or concurrently with intensive handling. Although no elevations could be detected in any case in control animals, bST caused a substantial rise in NEFA concentration only when animals were subjected to intensive handling. This suggested that NEFA peaks noted in bST-treated heifers in the first experiment resulted from increased ability of adipose tissue to respond to adrenergic stimulation associated with the anticipation of feeding. Consistent with this hypothesis, plasma NEFA concentrations in bST-treated steers were increased to a greater extent during a challenge involving i.v. injection of epinephrine. This amplification of adipose tissue response by bST must be considered when conducting intensive studies. Even the minimal excitement associated with blood sampling can confound the results regarding lipid mobilization, and this may have contributed to the notion that ST is a lipolytic hormone.

Adipose Tissue↗

PubMed1997

IGF-I variants which bind poorly to IGF-binding proteins show more potent and prolonged hypoglycaemic action than native IGF-I in pigs and marmoset monkeys.

The relative acute hypoglycaemic potencies of IGF-I and several variants of IGF-I which bind poorly to the IGF-I binding proteins (IGFBPs) have been examined in marmosets (Callithrix jacchus) and the pig. In the marmoset study, IGF-I and des(1-3)IGF-I were compared in anaesthetised and conscious animals in a range of bolus doses from 42 to 270 micrograms/kg body weight. In the pig study, IGF-I was compared with four variants, des(1-3)IGF-I long-IGF-I, R3IGF-I and long-R3IGF-I (LR3IGF-I), which show reduced affinity for the IGFBPs as well as with insulin. Doses in the pig were 20 and 50 micrograms/kg body weight for the IGFs and 3 micrograms/kg for insulin. In each study serial blood samples were taken from 30 min before to 4 h after the bolus injection. Plasma glucose levels were decreased in a dose-responsive manner with the pig more sensitive than either the conscious or anaesthetised marmoset (maximum lowering 4.8, 3.7 and 2.5 mmol/l respectively). The IGF variants were consistently 2- to 3-fold more potent than IGF-I in each animal for lowering of plasma glucose to the nadir, with the potency reflecting the relative affinities for binding to the IGFBPs and the IGF-I receptors. Thus, hypoglycaemic potency was in the order IGF-I < long-IGF-I < R3IGF-I approximately LR3IGF-I < des (1-3)IGF-I. Notably the variants suppressed plasma glucose levels over a much longer period than did IGF-I, the cumulative suppression over four hours showing an approximately 4- to 8-fold increase in the extent of hypoglycaemia. The prolonged suppression was not simply proportional to the hypoglycaemic nadir; at doses equipotent for glucose lowering, the cumulative hypoglycaemic effect for the variants in either species was about 2-fold that for IGF-I. The differential effect of the variants in the marmoset could not be accounted for by correlated changes in plasma insulin, IGF-I or IGFBP levels in plasma. Indirect effects via inhibition of glucagon, or direct effects via hepatic insulin receptors are postulated to account for the results. There was a dose-related reduction in plasma amino acids in the pig but, unlike the case for plasma glucose, only one analogue, LR3IGF-I was more potent than IGF-I. The response to LR3IGF-I was accentuated at the high dosage but on the basis of the other variants tested this effect could not be ascribed to either of the incorporated molecular variations. Despite their more rapid clearance from the circulation, variants of IGF-I which show lower affinity for binding to IGFBPs show proportionately superior potency for sustained hypoglycaemic action. Since our data were obtained in animal models of accepted relevance to humans these results point to the possible superior efficacy of the variants, especially des(1-3)IGF-I, over IGF-I for use as an adjunct to insulin treatment of hyperglycaemic conditions.

Amino Acids↗

PubMed1997

Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs.

Growth hormone (GH) improves growth performance in the pig. Analogues of insulin-like growth factor-I (IGF-I) that bind poorly to IGF binding proteins (IGFBP) stimulate growth in the rat but, in contrast, inhibit growth in the pig. This study was designed to determine the effect of IGF peptides alone or in combination with porcine GH (pGH) on growth characteristics and plasma hormone concentrations in finisher pigs. A four-day infusion of Long [R3] IGF-I (LR3IGF-I; 180 micrograms/kg/day) decreased the average daily gain, food intake, and plasma IGFBP-3, IGF-I and insulin concentrations. The mean plasma GH concentration was decreased by 23% and the area under the GH peaks was reduced by 60%. Co-administration of pGH (30 micrograms/kg/day) with LR3IGF-I had no interactive effect on growth performance, and plasma insulin, IGFBP-3 and IGF-I concentrations remained suppressed. The area under the GH peaks was not restored with this combination treatment although mean plasma GH concentrations were elevated in all animals receiving pGH. Infusion of IGF-I (180 micrograms/kg/day) decreased plasma insulin and mean GH concentrations but had no significant effect on IGFBP-3 concentrations. Average daily gain and feed intake were not changed by IGF-I treatment. A combination of IGF-I and pGH injection (30 micrograms/kg/day) increased plasma IGFBP-3 concentrations but plasma insulin levels remained suppressed. Plasma glucose levels were unaffected by any treatment. The study demonstrates that both IGF-I and LR3IGF-I suppress plasma GH concentrations in finisher pigs. This, in turn, may be responsible for the reduction in the plasma concentration of IGF-I, IGFBP-3 and insulin seen in LR3IGF-I-treated animals. The decrease in these parameters may contribute to the inhibitory effect of LR3IGF-I on growth performance in the pig.

Animals↗

PubMed1996

The testis is not the major source of circulating follistatin in the ram.

The aims of this study were to determine the plasma concentrations of follistatin in rams and to assess if the testis contributes to circulating follistatin and if there is uptake or production of follistatin by the head in rams. Catheters were inserted in the carotid artery, jugular vein and spermatic vein of intact rams during the non-breeding season (experiment 1; n = 5) and breeding season (experiment 2; n = 4). In experiment 1, blood samples were collected from 5 rams every 10 min for 4 h, commencing 20-60 min after surgery. After 2 h of sampling 1 microgram gonadotrophin-releasing hormone (GnRH) was injected intravenously. In experiment 2, blood samples were collected from 4 of the rams used in experiment 1 by venipuncture 30 and 15 min before surgery and every 15 min throughout surgery. Commencing 1 h after surgery, matched samples were taken from each of the vessels every 10 min for 4 h (1-4 h after surgery), then every hour for 20 h (4-24 h after surgery) and then every 10 min for 4 h (24-28 h after surgery). In both experiments, follistatin secretion was non-pulsatile and there were no significant differences between the concentrations of follistatin in any of the vessels. There was a significant (P < 0.05) increase in the concentrations of follistatin in each of the vessels throughout the 4 h of 10-min sampling in both experiments. In experiment 2 plasma concentrations of follistatin in the jugular vein were significantly (P < 0.05) lower before surgery than at other stages of the experiment. During the non-breeding season (experiment 1) the concentrations of follistatin in all vessels were about 2-fold higher (P < 0.001) than during the breeding season (experiment 2). Concentrations of follistatin were measured in the testicular tissue of the ram, bull, monkey and rat and were found to be 13.6, 2.1, 2.5, 0.8 ng/g testis respectively. In experiment 3, blood samples were collected every 15 min for 4 h from castrated rams (n = 6) in the absence of treatment with testosterone propionate (TP) and after 7 days of treatment with a physiological dose of TP during the breeding and non-breeding seasons. There was no effect of stage of breeding season or TP on the plasma concentrations of follistatin and these concentrations in the castrated rams were similar to the concentrations in the intact rams in experiment 2. In experiment 4, the function of Leydig cells was stimulated by administration of human chorionic gonadotrophin but this had no effect on plasma concentrations of follistatin. These experiments show that the concentrations of follistatin in the plasma of rams are measurable, that the testis is not the major contributor to circulating follistatin and that there is no significant uptake or production of follistatin by the head in rams. It appears that the contribution of the testis to circulating follistatin may vary with the stage of the breeding season, being greater during the non-breeding season than the breeding season. The gonadotrophins and testosterone do not appear to have a direct effect on the secretion of follistatin in rams. The increase in concentrations of circulating follistatin during surgery and more frequent blood sampling suggest a stress-related effect on the production of follistatin.

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