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C D Knight

Publications and source records attributed to C D Knight.

At least 19 recordsLinked to original sources
PubMed2006

A multiple regression model approach to contrast the performance of 2-hydroxy-4-methylthio butanoic acid and DL-methionine supplementation tested in broiler experiments and reported in the literature.

The purpose of this paper was to compile all available literature comparing the relative performance of 2-hydroxy-4-methylthio butanoic acid (HMTBA) with DL-methionine (DLM) in broiler chickens and using multiple regression techniques, to estimate the predicted dose responses and relative performance of the 2 Met compounds for gain and feed conversion (FC). A database was developed that contained all available broiler studies in which HMTBA and DLM were both present in the same study; weight gain was recorded; Met addition, age of birds, and duration of study were defined; and an unsupplemented control treatment was present. Sixty-two references complied with these criteria and included 100 experiments with 427 observations for HMTBA and 411 for DLM. Multiple regression analysis of the database was used to identify the experimental and dietary conditions that contributed to the gain and FC responses of each source of Met activity. All identified variables contributed similarly to each Met source prediction model and both gain and FC models described a quadratic dose response. Under the average conditions of the database, the predicted responses for gain and FC models did not significantly differ between HMTBA and DLM. However, a trend was observed (P < or = 0.1) for the peak gain response for HMTBA to be numerically greater than DLM, suggesting benefits of HMTBA over DLM in the region of supplementation that is commercially relevant. The experimental and nutritional conditions that contribute to the response to HTMBA and DLM were identified and are discussed in the paper. This statistical approach provided a means to summarize the results obtained from a multitude of studies conducted over the last 5 decades and has provided a meaningful estimate of the relative performance of the 2 sources of Met activity. The lack of differences between the 2 predicted models under experimental and commercial conditions supports an overall conclusion of equal performance of DLM and HTMBA when compared on an equal molar basis.

Animal Nutritional Physiological Phenomena↗
PubMed2006

Evidence for 2-hydroxy-4(methylthio) butanoic acid and DL-methionine having different dose responses in growing broilers.

The objective of this study was to compare the gain-response curve to dietary levels of 2-hydroxy-4(methylthio) butanoic acid (HMTBA) and DL-Met (DLM) across 4 floor pen trials in which different diets were used. Six replicates of 38 or 41 birds per pen (trials 1 to 2 and 3 to 4, respectively) were used in a 2 x 3 factorial arrangement. A control with 12 replicates was also included. The 2 Met sources were fed at 3 equimolar levels equally spaced, with the highest level added at requirements from 1 to 48, 49, 43, or 49 d for trials 1, 2, 3, and 4, respectively. Commercial-type TSAA-deficient control diets contained sorghum, wheat, corn, or corn plus meat and bone meal for trials 1, 2, 3, and 4, respectively. Performance improved at all times for most parameters after supplementing with HMTBA or DLM (P < 0.05). No differences were found in the birds fed HMTBA or DLM at any age and trial (P > 0.05), except for trial 1, in which 17-d-old birds performed better when fed HMTBA than DLM (P < 0.05). In each trial, linear, quadratic, and exponential regressions were conducted upon the gain response of birds fed HMTBA and DLM separately. Equations with better goodness of fit were used to compare the estimated gain responses to feeding HMTBA vs. DLM. In 3 trials, the shape of the gain-response curve differed when feeding HMTBA vs. DLM. In trials 3 and 4, feeding HMTBA at commercial levels resulted in greater gain responses than DLM (P < 0.05), whereas, in trials 2 and 4, at very deficient levels, DLM-fed birds outperformed those fed HMTBA (P < 0.05). When the 4 trials were combined, the dose-response curve with the best goodness of fit was linear for HMTBA and quadratic for DLM. It can be concluded that the 2 Met sources have a different dose-response form, HMTBA could outperform DLM at commercial levels, and DLM could outperform HMTBA at deficient levels.

Animal Nutritional Physiological Phenomena↗
PubMed2006

Estimation of the true ileal digestible lysine and sulfur amino acid requirement and comparison of the bioefficacy of 2-hydroxy-4-(methylthio)butanoic acid and DL-methionine in eleven- to twenty-six-kilogram nursery pigs.

Three experiments were conducted to determine the true ileal digestible (TID) Lys and sulfur AA (SAA) requirement and to compare the bioefficacy of 2-hydroxy-4-(methylthio)butanoic acid (HMTBA) and dl-MET as Met sources in nursery pigs. Experiment 1 included 2 studies: 1 was 662 nursery pigs (Triumph 4 x PIC C22; initial BW 12.2 +/- 0.18 kg) allotted to 1 of 5 dietary treatments with TID Lys concentrations ranging from 1.10 to 1.50%; and the second study was 665 nursery pigs (Triumph 4 x PIC C22; initial BW 12.3 +/- 0.18 kg) allotted to 1 of 5 dietary treatments with TID SAA concentration ranging from 0.63 to 0.90%. In Exp. 2, 638 nursery pigs (Triumph 4 x PIC C22; initial BW 13.0 +/- 0.16 kg) were allotted to the same 5 SAA dietary treatments as in Exp. 1. In Exp. 3, 1,232 pigs (Triumph 4 x PIC C22; initial BW 11.0 +/- 0.30 kg) were allotted to 1 of 7 dietary treatments. The basal diet (diet 1) was supplemented with high concentrations of synthetic AA but no Met; this resulted in a dietary concentration of TID Lys of 1.30% and TID SAA of 0.50%. Diets 2 to 7 were the basal diet supplemented with 3 equimolar levels of HMTBA or dl-MET to provide TID SAA concentrations of 0.56, 0.62, and 0.68%, respectively. In Exp. 1, increasing TID Lys from 1.10 to 1.50% increased ADG (quadratic; P < 0.05) and improved G:F (linear; P < 0.002). The pooled data of Exp. 1 (SAA study) and Exp. 2 indicated that increasing TID SAA from 0.63 to 0.90% increased ADG (quadratic; P < 0.01) and improved G:F (quadratic; P < 0.01). Various methods of analyzing the growth response surface indicated that the optimal TID Lys concentration ranged from 1.28 to 1.32% for ADG (Exp. 1), and the optimal TID SAA concentration ranged from 0.73 to 0.77% for ADG and 0.80 to 0.83% for G:F (pooled Exp. 1 and 2), respectively. In Exp. 3, increasing TID SAA concentrations from 0.50 to 0.68% resulted in a linear improvement of ADG (P < 0.001), ADFI (P < 0.05), and G:F (P < 0.001). The best fit comparison of HMTBA and dl-MET was determined by the Schwartz Bayesian Information Criteria index, which indicated the average relative efficacy of HMTBA vs. dl-MET was 111%, with 95% confidence interval of 83 to 138%, within the range of TID SAA tested. Thus, the TID Lys and SAA requirements of modern lean-genotype pigs from 11- to 26-kg were greater than the 1998 NRC recommendations, and both HMTBA and dl-MET as Met sources can supply equimolar amounts of Met activity.

Amino Acids, Sulfur↗
PubMed2005

Impact of glutamine and Oasis hatchling supplement on growth performance, small intestinal morphology, and immune response of broilers vaccinated and challenged with Eimeria maxima.

Seven hundred and twenty hatchling broilers were allotted to 12 treatment groups. Groups 1 and 2 were fasted for 48 h posthatch; groups 3 and 4 were fasted for 48 h followed by ad libitum access to a 1% glutamine (Gln) diet; groups 5 and 6 had ad libitum access to a common diet; groups 7 and 8 had access to a 1% Gln diet posthatch; groups 9 and 10 were fed regular Oasis hatchling supplement; and groups 11 and 12 were fed Oasis sprayed with 1% Gln for the first 48 h posthatch. The birds in treatment groups 2, 4, 6, 8, 10, 11, and 12 were vaccinated with Eimeria maxima posthatch, and all birds were orally challenged with high dose E. maxima on d 22. During the first 2 wk, birds in group 7 had the highest gain and feed efficiency among treatments (P < 0.01). Compared with birds in the nonGln groups, birds in the Gln group had higher gain, feed efficiency, and livability (P < 0.05). Among the Fast (groups 1 to 4), Feed (groups 5 to 8), and Oasis (groups 9 to 12) groups, birds in the Feed groups had the highest gain during d 0 to 21 (P < 0.01). During d 22 to 28, birds in the Fast groups had the lowest BW and livability (P < 0.01), and the nonvaccinated birds had lower gain and feed efficiency relative to vaccinated birds (P < 0.01). Birds in the Feed and Oasis groups had higher villus height (VH) of mid small intestine than Fast groups at d 2 and 7 (P < 0.05), and nonvaccinated birds had higher VH than vaccinated birds (P < 0.01) at d 7 after hatch. On d 14, there were differences in serum interferon-gamma (P < 0.05) levels among treatments. During d 22 to 28, vaccinated birds had lower lesion scores in the mid small intestine than nonvaccinated birds (P < 0.01), and birds in the Feed or Oasis groups had lower lesion scores compared with the Fast groups (P < 0.02). These results indicated the importance of immediate access to feed posthatch, the beneficial effects of feeding Oasis hatching supplement and Gln after hatch, as well as the necessity of the vaccination program against coccidiosis challenge.

Animal Feed↗
PubMed2005

Estimation of the ideal ratio of true ileal digestible sulfur amino acids:lysine in 8- to 26-kg nursery pigs.

Four experiments were conducted to determine the ideal ratio of true ileal digestible (TID) sulfur AA to Lys (SAA:LYS) in nursery pigs at two different BW ranges using both DL-Met and 2-hydroxy-4-(methylthio)-butanoic acid (HMTBA) as Met sources. In Exp. 1, 1,549 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 8.3 +/- 0.08 kg) were allotted to one of nine dietary treatments. The basal diet (Diet 1) was a semicomplex corn-soybean meal-based diet (1.32% TID Lys) with no supplemental HMTBA or DL-Met (47.7% TID SAA:LYS). Diets 2 to 9 consisted of the basal diet supplemented with four equimolar levels of DL-Met or HMTBA (52.7, 57.7, 62.7, and 67.7% TID SAA:LYS). In Exp. 2, 330 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 11.4 +/- 0.10 kg) were allotted to one of nine dietary treatments. The basal diet (Diet 1) was a corn-soybean meal-based diet (1.15% TID Lys) with no supplemental HMTBA or DL-Met (49% TID SAA:LYS). Diets 2 to 9 consisted of the basal diet supplemented with four equimolar levels of DL-Met or HMTBA (54, 59, 64, and 69% TID SAA:LYS). In Exp. 3, 1,544 nursery pigs (Triumph 4 x PIC Camborough 22; initial BW 12.4 +/- 0.13 kg) were allotted to one of nine dietary treatments as in Exp. 2. In Exp. 4, 343 nursery pigs (Genetiporc; initial BW 12.8 +/- 0.56 kg) were allotted to one of six dietary treatments. The basal diet (Diet 1) was a corn-soybean meal-based diet (1.05% TID Lys) with no supplemental DL-Met (49% TID SAA:LYS). Diets 2 to 5 consisted of the basal diet supplemented with four levels of DL-Met (54, 59, 64, and 69% TID SAA:LYS), and Diet 6 was the basal diet supplemented with one equimolar level of HMTBA to satisfy 59% TID SAA:LYS ratio. In all experiments, increasing the TID SAA:LYS ratio resulted in quadratic improvements in ADG (P < or = 0.09) and G:F (P < or = 0.05). Three different methods were used to estimate the optimal TID SAA:LYS ratio for each experiment. The two-slope broken-line regression model, x-intercept value of the broken-line and quadratic curve, and 95% of upper asymptote across the four experiments indicated that the average optimal TID SAA:LYS ratios were 59.3, 60.1, and 57.7% for ADG and 60.6, 61.7, and 60.1% for G:F, respectively. Thus, the optimal TID SAA:LYS ratio for 8- to 26-kg pigs based on the average value of these three estimates was 59.0% for ADG and 60.8% for G:F.

Amino Acids, Sulfur↗
PubMed2002

Rumen degradation and availability of various amounts of liquid methionine hydroxy analog in lactating dairy cows.

Ruminal escape of various amounts of methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid (HMB)] was measured in an experiment designed as a 4 x 4 Latin square using four lactating dairy cows with cannula in the rumen and duodenum. The cows were fed a diet composed of corn silage, alfalfa haylage, rolled barley grain, canola meal, and blood meal, three times per day. The cows were fed the liquid analog each day for 1 wk before the experiment was started. On the day of the experiment, each cow received an intraruminal bolus dose of 0, 25, or 50 g of the liquid analog (Alimet feed supplement, 88% HMB) or 51.2 g of a dry calcium salt of the analog (86% HMB; MHA) mixed with 0.5 kg of ground barley grain. A liquid phase marker (Co-EDTA) was administered as a bolus dose into the rumen at the time of administration of the methionine hydroxy analogs. Rumen and duodenal contents, and blood serum were collected at 0, 1, 3, 6, 9, 12, and 24 h relative to the time of dosing. Rumen and duodenal samples were analyzed for Co and HMB, and serum was analyzed for free methionine. Fractional rate constants for the passage of the liquid marker (k(p)) and the decline of HMB concentration in the rumen (k(rHMB)) were determined by nonlinear regression. Liquid passage from the rumen was similar among the four analog treatments (0.136 +/- 0.012/h; mean +/- SEM). Ruminal escape of HMB as a percentage of the dose (100% x k(p)/k(rHMB)) did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (42.5, 41.0, and 34.9 +/- 9.0%, respectively) and averaged 39.5%. Duodenal appearance of HMB as a percentage also did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (16.2, 26.8, and 22.7%, respectively) and averaged 22%. Omasal absorption of HMB was variable ranging from 12.3 to 26.3% and averaged 17.6%. Serum methionine concentration peaked at 3 and 6 h after dosing and increased in proportion to the amount of the analog administered. It was concluded that 39.5% of the methionine hydroxy analog escaped rumen degradation, the percentage of the dose that escaped the rumen was not affected by the amount or form of the methionine analog fed, and the analog that escaped ruminal degradation was likely absorbed and metabolized to methionine.

Animal Feed↗
PubMed1999

Ruminal escape, gastrointestinal absorption, and response of serum methionine to supplementation of liquid methionine hydroxy analog in dairy cows.

Availability of liquid methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid] was evaluated in two experiments using four cannulated lactating dairy cows. The first experiment was designed as a 4 x 4 Latin square. Each cow received a pulse dose of 0, 30, 60, or 90 g of the methionine analog in the rumen each day for 10 d. Duodenal samples were collected at 16, 20, and 24 h after dosing for the last 5 d and pooled. The methionine analog was not detected in duodenal contents because it passed rapidly from the rumen relative to the sampling protocol. In the second experiment, cows were offered 90 g of the methionine analog and 600 ml of Cr-EDTA (3.5 g of Cr) mixed with ground corn for a period of 20 min after which any remains of the treatment were placed in the rumen. The concentration of the analog peaked in ruminal and duodenal fluid at 1 and 3 h, respectively. Based on the fractional rate constants for ruminal and duodenal disappearance of the methionine analog and passage of the liquid, it was determined that 50.0 +/- 2.8% of the methionine analog escaped ruminal degradation and became available for intestinal absorption (44.6 +/- 5.7%) or was absorbed from the omasum (5.4 +/- 3.3%). Serum methionine concentration peaked 6 h after analog dosing at a level that was three times the predose level, indicating that the methionine analog that escaped ruminal degradation was absorbed and metabolized to methionine.

Animals↗
PubMed1998

The relative effectiveness of 2-hydroxy-4-(methylthio) butanoic acid and DL-methionine in young swine.

We compared the effectiveness of 2-hydroxy-4-(methylthio) butanoic acid (HMB) and DL-methionine (DLM) as sources of L-methionine activity in methionine-deficient primary cultures of pig liver cells and methionine-deficient early-weaned pigs. Viable hepatocytes were obtained from minced pig liver and maintained in a high density, differentiated, nonproliferation cell culture system. Culture medium was supplemented with HMB, DLM, or L-methionine, and cells were pulse-dosed with L-[14C(U)]leucine for 24 h to determine the level of protein synthesis. Leucine incorporation per milligram of protein indicated a six-to eightfold increase in protein synthesis (P < .01) with methionine levels between 5 and 10 microM, regardless of source of methionine activity. Two 24-pen replicate methionine dose titrations were conducted with 95 early-weaned commercial crossbred pigs. The pelleted corn, dried whey, and porcine plasma basal diet contained 1.5% lysine, .23% methionine, and .48% cystine and was supplemented with 0, .05, or .10% methionine activity as DLM or HMB for 21 d. There was a 134, 104, and 61% increase (P < .01) in cumulative ADG for each successive week on study with a 30 and 19% improvement in feed/gain (P < .01) after 7 and 14 d. Performance responses due to source of methionine activity did not differ and slope ratio potency determinations (gain vs intake of methionine source) of HMB vs DLM indicated a 119, 111, and 95% relative activity for cumulative weekly performance. These results support the hypothesis that HMB and DLM provide equimolar levels of methionine activity in swine.

Animal Feed↗
PubMed1996

The moss, Physcomitrella patens, transformed with apoaequorin cDNA responds to cold shock, mechanical perturbation and pH with transient increases in cytoplasmic calcium.

The gene for apoaequorin has been used previously to indicate cytosolic calcium changes in higher plants. Here we report the transformation of the moss Physcomitrella patens with the cDNA for apoaequorin. Stable transformants were obtained in the wild type which reconstitute the calcium-sensitive luminescent protein aequorin in vivo after incubation in coelenterazine, and continue to grow normally. The wild type responds to cold-shock (0-10 degrees C) with increases in cytosolic calcium. Mechanical perturbation, in the form of touch, also induces transient increases in cytosolic calcium. A smaller response to pH, distinct from the touch response and exhibiting different kinetics, can also be detected.

Aequorin↗
PubMed1996

Genetics of larval urea tolerance in Drosophila melanogaster.

The genetic control of larval tolerance to urea, a nitrogenous waste-product occurring naturally in crowded Drosophila cultures, was investigated in a set of five laboratory populations of D. melanogaster that had been successfully subjected to selection for increased larval urea tolerance. Larva to adult survivorship and development time at three different levels of urea were assayed on the five selected populations, their five matched controls and a set of 10 F1 hybrid populations derived from reciprocal crosses between pairs of selected and control populations. As expected from the results of previous studies, the selected populations exhibited greater larval tolerance to the toxic effects of urea, relative to their controls. Comparison of the hybrid and parental populations with respect to both survivorship and development time indicated that the genetic control of urea tolerance in the selected populations is largely dominant, and has a significant X-linked component. The data also suggested that females from the selected populations exercise a nongenetic maternal effect on the development time of their progeny, regardless of urea level.

Adaptation, Physiological↗
PubMed1996

The feeding value of soybeans fed to rats, chickens, catfish and dairy cattle is not altered by genetic incorporation of glyphosate tolerance.

Animal feeding studies were conducted with rats, broiler chickens, catfish and dairy cows as part of a safety assessment program for a soybean variety genetically modified to tolerate in-season application of glyphosate. These studies were designed to compare the feeding value (wholesomeness) of two lines of glyphosate-tolerant soybeans (GTS) to the feeding value of the parental cultivar from which they were derived. Processed GTS meal was incorporated into the diets at the same concentrations as used commercially; diary cows were fed 10 g/100 g cracked soybeans in the diet, a level that is on the high end of what is normally fed commercially. In a separate study, laboratory rats were fed 5 and 10 g unprocessed soybean meal 100 g diet. The study durations were 4 wk (rats and dairy cows), 6 wk (broilers) and 10 wk (catfish). Growth, feed conversion (rats, catfish, broilers), fillet composition (catfish), and breast muscle and fat pad weights (broilers) were compared for animals fed the parental and GTS lines. Milk production, milk composition, rumen fermentation and nitrogen digestibility were also compared for dairy cows. In all studies, measured variables were similar for animals fed both GTS lines and the parental line, indicating that the feeding value of the two GTS lines is comparable to that of the parental line. These studies support detailed compositional analysis of the GTS seeds, which showed no meaningful differences between the parental and GTS lines in the concentrations of important nutrients and antinutrients. They also confirmed the results of other studies that demonstrated the safety of the introduced protein, a bacterial 5-enolpyruvyl-shikimate-3-phosphate synthase from Agrobacterium sp. strain CP4.

Animal Feed↗
PubMed1996

Utilization of supplemental agency nurses in an Army medical center.

The purpose of this study was to describe the perceived impact of supplemental agency nurses upon the quality of patient care, unit cohesiveness, and morale of permanently assigned personnel at an Army medical center. The study population consisted of 28 agency nurses and 138 permanently assigned nursing staff. The study was descriptive and exploratory in nature, utilizing the method of content analysis. Major themes that emerged from data analysis included economic, professional nursing, and patient care issues. Perceptions were that agency nurses provided the institution with necessary labor, but that the agency nurses had greater flexibility of hours and control over their practice. Permanently assigned nursing staff reported that the use of agency services hindered continuity of patient care, at times reduced the quality of care, negatively affected morale among personnel, and impacted adversely upon the time available for mission-related training.

Adult↗
PubMed1995

Prevention of seromas in mastectomy wounds. The effect of shoulder immobilization.

OBJECTIVE: To determine if postoperative shoulder immobilization decreases the incidence of postmastectomy seromas. DESIGN AND SETTING: A prospective randomized trial of three surgeons' experiences at a community hospital. PATIENTS: Thirty-eight patients who underwent modified radical mastectomy from March 1991 through February 1993. MAIN OUTCOME MEASURES: Incidence of postmastectomy seromas and time required for patients to gain 110 degrees of shoulder abduction after surgery. RESULTS: Thirteen (72%) of 18 wounds in the maximum range of motion cohort developed seromas (72%) compared with one (6%) of 17 in the minimum range of motion cohort (P = .0005). The average time required for the patients with maximum range of motion to gain 110 degrees of shoulder abduction was 2.6 weeks, whereas the patients with minimum range of motion required an average of 5.0 weeks (P = .0127). CONCLUSION: Postmastectomy shoulder immobilization significantly decreases the incidence of wound seromas. Although this protocol resulted in a delay in return to normal shoulder mobility, no patients sustained long-term musculoskeletal dysfunction.

Aged↗
PubMed1994

Effect of intermittent periods of high environmental temperature on broiler performance responses to sources of methionine activity.

The objective of these experiments was to study the effect of intermittent high temperature (IHT) on performance of broilers fed different sources of methionine activity. Two 20-d experiments were conducted in which individually caged 28-d-old cockerels were exposed to a 5-d period of constant high temperature (HT, 30 to 32 C) followed by an equal period of thermoneutral (TN) temperatures (22 C) with the 10-d temperature cycle repeated twice. Birds held at 22 C were TN controls. Grower diets contained 3,275 kcal/kg ME and 20% CP and were supplemented with either 2-hydroxy-4-(methylthio)butanoic acid (HMB, Alimet Feed Supplement) or DL-Met up to a maximum of .88 to .90% total sulfur amino acids (TSAA). In Experiment 1, gain:feed but not average daily gain was greater (P < .05) for HMB than DL-Met birds subjected to IHT (.451 vs .413, respectively), but no treatment differences were observed for TN birds. Results of Experiment 2 demonstrated a linear response to HMB and DL-Met dose in TN (P < .01); however, only HMB-supplemented birds responded similarly in IHT (P < .01). These results are consistent with lower availability of DL-Met as a result of IHT. In vitro experiments indicated that capacity for uptake of DL-Met into intestinal epithelial cells was reduced in heat-stressed birds. Uptake of D-Met was more severely affected than was L-Met. Consequently, a third performance experiment compared the ability of D-Met and L-Met to support growth under conditions of HT. The results indicated that the effect of HT on broiler performance was mediated through reduced utilization of D-Met.

Animals↗
PubMed1993

Ovariectomy and inhibin immunoneutralization acutely increase follicle-stimulating hormone-beta messenger ribonucleic acid concentrations: evidence for a nontranscriptional mechanism.

After ovariectomy (ovx), FSH beta mRNA levels and serum FSH increase 2- to 3-fold within 12 h, and this persists in the presence of a GnRH antagonist. As a fall in plasma estradiol and progesterone appears to regulate FSH beta via increased GnRH secretion, it is thought that the acute (by 2 h) changes in FSH beta mRNA after ovx reflect falling levels of plasma inhibin. The current study addressed the following questions. 1) Does a reduction of circulating inhibin (via passive immunoneutralization or gonadectomy) increase FSH beta mRNA levels? 2) If so, are the acute increases in FSH beta mRNA associated with changes in the transcription rate? Adult male and female rats received 0.5 ml antiinhibin antiserum, iv, and were killed 2 or 12 h later. A second group of rats was gonadectomized; some received a GnRH antagonist and were killed at various intervals between 2 h and 7 days later. In adult males, no change in gonadotropin mRNA levels was observed after either addition of inhibin antiserum or removal of the testes. In contrast, in adult female rats, both ovx and inhibin antiserum increased FSH beta mRNA levels (2-fold) within 2 h, and a similar increase occurred in the presence of a GnRH antagonist. To determine if the increase in FSH beta resulted from increased mRNA synthesis, adult female rats were ovx, and half received a GnRH antagonist. Animals were killed 2 or 12 h later, and transcription rates were measured by nuclear run-off assay in pituitaries pooled from three rats. The transcription rate of the alpha-subunit, although not altered by ovx, was decreased in animals receiving the GnRH antagonist. Transcription of the LH beta gene was increased within 2 h after ovx, a change that was abolished by the GnRH antagonist. mRNA concentrations of either alpha or LH beta do not increase acutely after ovx, suggesting that GnRH regulates alpha and LH beta gene transcription and 12 h or more of mRNA synthesis are required to increase cytoplasmic concentrations. The FSH beta gene transcription rate was unchanged in both ovx and GnRH antagonist-treated animals, but serum FSH increased at 12 h. These data indicate that the rapid GnRH-independent increase in FSH beta mRNA levels seen immediately after ovx is not associated with altered mRNA synthesis and suggest that inhibin may also regulate FSH beta gene expression through nontranscriptional mechanisms.

Animals↗
PubMed1993

Effects of a porcine somatotropin implant on tissue mineral status of finishing pigs exposed to a thermoneutral or cold environment.

An experiment was conducted with 24 crossbred (Landrace x Yorkshire x Duroc) finishing pigs (mean BW 85 kg) to study the effects of a single 100-mg recombinant porcine somatotropin (rpST) implant on the tissue mineral status of pigs exposed to either a thermoneutral (TN; 18 to 21 degrees C, 50 to 55% RH) or cold (C; 5 to 15 degrees C, 50 to 70% RH) environment until BW averaged 110 kg. The implants used in this study delivered an average 2.4 to 2.5 mg of rpST/d during the course of the study. Control pigs were implanted with a placebo. All diets were supplemented with minerals at levels that either met or exceeded the requirements of an 85-kg pig. At slaughter (mean BW 110 kg), tissues were collected and analyzed for selected macro- and microminerals. Pigs treated with rpST had higher (P < .05) Ca concentrations and total Ca in liver and kidney and higher (P < .05) Ca concentrations in muscle. Total P, Mg, Na, and K were all higher (P < .05) in the liver and kidneys of rpST-treated pigs. In general, rpST had little influence on Cu, Zn, and Fe in tissues. No consistent trend was evident in the response of tissue minerals to environmental temperature. Results indicated that pigs treated with rpST and supplemented with adequate minerals accumulated more minerals in certain tissues than did pigs not given rpST.

Animals↗
PubMed1993

Performance, carcass composition, and blood hormones and metabolites of finishing pigs treated with porcine somatotropin in hot and cold environments.

Two experiments were conducted to assess the ability for recombinant porcine somatotropin (rpST)-treated pigs to perform and cope with the demands of hot and cold environments. In the first experiment, finishing pigs were exposed to either a thermoneutral (TN; 18 to 21 degrees C) or a hot environment (H; 27 to 35 degrees C) for 35 d. In the second experiment, pigs were exposed to a TN or cold environment (C; 5 to 15 degrees C). The rpST delivered by a 6-wk prolonged-release system had no effect on ADG, whereas both H and C reduced ADG by 29.4 and 11.8%, respectively. In the first experiment, rpST-treated pigs consumed 17.6% less feed than control pigs, whereas rpST-treated pigs in H consumed 24.4% less feed than rpST-treated pigs in TN. Overall feed/gain ratios through the first 4 wk of both studies were improved by 21.8 and 14%, respectively, by rpST (P < .05) and were 24.3% poorer in C (P < .05) than in H. The changes in blood concentrations of pST, IGF-I, and IGF-II associated with rpST were not influenced by the different environments. Total body composition of rpST-treated pigs had increased amounts of protein (P < .05) and decreased amounts of fat (P < .05); H further reduced fat (P < .05). The C resulted in reduced protein content (P < .05). No evidence of thermal imbalance due to rpST was found as assessed by rectal temperature, respiration rate, and heat production estimated by indirect calorimetry and chemical analysis.

Adipose Tissue↗