Effects of increasing dietary arginine supply during the three first weeks after weaning on pig growth performance, plasma amino acid concentrations, and health status.

A total of 425 weaned pigs (Exp. 1: 225 pigs [5.8 ± 0.

Dental Correction Does Not Alter Postprandial Nutrient Concentrations in Healthy Mares.

Irregular wear patterns are theorized to cause poor feed digestion and weight loss in the horse. The objective of this study was to test the hypothesis that dental correction would increase postprandial nutrient concentrations and reduce fecal particle size (FPS) in clinically healthy mares. The study was conducted in 16 mares of mature age (4-17) who had not received dental care in the previous year.

Impact of ergot alkaloid and steroidal implant on whole-body protein turnover and expression of mTOR pathway proteins in muscle of cattle.

Introduction: Holstein steers ( = 32) were used to determine if the ergot analog, bromocriptine decreases muscle protein synthesis through inhibitory action on the mTOR pathway a direct effect on signal proteins, and if these negative effects can be alleviated with anabolic agents.

Methods: Steers were treated with intramuscular administration of bromocriptine (vehicle or 0.1 mg/kg BW) and a subdermal commercial steroidal implant containing trenbolone acetate (TBA) and estradiol 17β (with or without), in a 2×2 factorial design.

Differential effect of two dietary protein sources on time course response of muscle anabolic signaling pathways in normal and insulin dysregulated horses.

The objective of the study was to characterize the temporal changes of phosphorylation patterns of mTOR signaling proteins in response to two dietary protein sources in insulin dysregulated (ID, = 8) and non-ID ( = 8) horses. Horses were individually housed and fed timothy grass hay and 2 daily concentrate meals so that protein was the first limiting nutrient and the total diet provided 120% of daily DE requirements for maintenance. On sample days, horses randomly received 0.

Effects of Bromocriptine on Glucose and Insulin Dynamics in Normal and Insulin Dysregulated Horses.

The objectives of the study were to study the effects of the synthetic ergot alkaloid (EA), bromocriptine, on glucose and lipid metabolism in insulin dysregulated (ID, = 7) and non-ID ( = 8) mares. Horses were individually housed and fed timothy grass hay and two daily concentrate meals so that the total diet provided 120% of daily DE requirements for maintenance. All horses were given intramuscular bromocriptine injections (0.

Development and Evaluation of a Muscle Atrophy Scoring System (MASS) for Horses.

Loss of skeletal muscle mass likely compromises performance and welfare in horses and thus routine monitoring would be valuable. Currently available methods to assess muscle mass require expert knowledge and are often expensive. To provide a simple method, a muscle atrophy scoring system (MASS) was created and tested by three evaluators (raters) in 38 horses of varying age, breed, and health status.

Nutritional Influences on Skeletal Muscle and Muscular Disease.

Skeletal muscle comprises 40% to 55% of mature body weight in horses, and its mass is determined largely by rates of muscle protein synthesis. In order to support exercise, appropriate energy sources are essential: glucose can support both anaerobic and aerobic exercise, whereas fat can only be metabolized aerobically. Following exercise, ingestion of nonfiber carbohydrates and protein can aid muscle growth and recovery.

Pathways regulating equine skeletal muscle protein synthesis respond in a dose-dependent manner to graded levels of protein intake.

Activation of the mechanistic target of rapamycin (mTOR)-controlled anabolic signaling pathways in skeletal muscle of rodents and humans is responsive to the level of dietary protein supply, with maximal activation and rates of protein synthesis achieved with 0.2 to 0.4 g protein/kg body weight (BW).

Amino acid requirements in horses.

Evaluating amino acid requirements, specifically threonine requirements, in horses will enable better feed formulation and result in economic production, improved animal health, and reduced environmental pollution. However, the current knowledge of protein and amino acid requirements in horses is still limited. Because horses have a unique digestive system and consume a variety of feed ingredients, their protein digestibility may be affected than other species by different feed composition, and thus amino acid requirements are susceptible to vary between situations.

Effects of dietary amino acid supplementation on measures of whole-body and muscle protein metabolism in aged horses.

The objective of this study was to examine markers of whole-body and muscle protein metabolism in aged horses fed a diet typical for North American aged horses, supplemented with amino acids. In a replicated Latin square design, six aged horses (20 ± 1.1 years) were studied while receiving each of three isocaloric, isonitrogenous diets, a control treatment concentrate (CON; 100 mg/kg BW day lysine, 84 mg kg  day threonine, 51 mg kg  day methionine), LYS/THR (134 mg kg BW day lysine, 110 mg kg BW day threonine, 52 mg kg BW day methionine) and LYS/THR/MET (132 mg kg BW day lysine, 112 mg kg BW day threonine, 62 mg kg BW day methionine).

Using the indicator amino acid oxidation technique to study threonine requirements in horses receiving a predominantly forage diet.

Threonine has been reported to be the second limiting amino acid in typical equine diets, but its actual requirement has not been determined in horses. To evaluate amino acid metabolism and requirements, the indicator amino acid oxidation (IAAO) method has been successfully used in other species. The objective of this research was to estimate threonine requirements in mature horses fed timothy hay and concentrate in 4:1 ratio using the IAAO method.

Effects of a docosahexaenoic acid-rich microalgae nutritional product on insulin sensitivity after prolonged dexamethasone treatment in healthy mature horses.

Objective: To determine effects of a microalgae nutritional product on insulin sensitivity in horses.

Animals: 8 healthy mature horses. PROCEDURES :Horses (n = 4/group) received a basal diet without (control diet) or with docosahexaenoic acid-rich microalgae meal (150 g/d) for 49 days (day 0 = first day of diet).

Whole-body phenylalanine kinetics and skeletal muscle protein signaling in horses with pituitary pars intermedia dysfunction.

Objective: To compare whole-body phenylalanine kinetics and the abundance of factors in signaling pathways associated with skeletal muscle protein synthesis and protein breakdown between horses with pituitary pars intermedia dysfunction (PPID) and age-matched control horses without PPID.

Animals: 12 aged horses (6 horses with PPID and 6 control horses; mean age, 25.0 and 25.

Effects of advanced age on whole-body protein synthesis and skeletal muscle mechanistic target of rapamycin signaling in horses.

Objective: To determine the effects of advanced age on whole-body protein synthesis and activation of the mechanistic target of rapamycin (mTOR) signaling pathway in skeletal muscle of horses.

Animals: Six 22- to 26-year-old (aged) and six 7- to 14-year-old (mature) horses.

Procedures: Whole-body protein synthesis was measured with a 2-hour primed constant infusion of (13)C sodium bicarbonate, followed by a 4-hour primed constant infusion of 1-(13)C phenylalanine.

Effect of gluteus medius muscle sample collection depth on postprandial mammalian target of rapamycin signaling in mature Thoroughbred mares.

Objective: To determine the effect of biopsy collection depth on the postprandial activation of mammalian target of rapamycin (mTOR) signaling factors, particularly protein kinase B, ribosomal protein S6 kinase, ribosomal protein S6, and eukaryotic initiation factor 4E binding protein 1 in middle-aged horses.

Animals: 6 healthy Thoroughbred mares (mean ± SD age, 13.4 ± 3.

Developmental regulation of the activation of translation initiation factors of skeletal muscle in response to feeding in horses.

Objective: To determine whether feeding-induced activation of translation initiation factors, specifically protein kinase B, ribosomal protein S6 kinase (S6K1), ribosomal protein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1, in horses is affected by age.

Animals: 6 yearlings, six 2-year-old horses, and 6 mature horses.

Procedures: After an 18-hour period of feed withholding, horses consumed a high-protein meal (2 g/kg) at time 0 and 30 minutes (postprandial state) or continued to have feed withheld (postabsorptive state).

Amino acid supplementation does not alter whole-body phenylalanine kinetics in Arabian geldings.

Stable isotope infusion methods have not been extensively used in horses to study protein metabolism. The objectives were to develop infusion and sampling methodologies for [1-(13)C] phenylalanine and apply these methods to determine whether the addition of supplemental amino acids to a control diet affected whole-body phenylalanine kinetics in mature horses. Arabian geldings were studied using a 6-h primed (9 μmol/kg), constant (6 μmol · kg(-1) · h(-1)) i.

Effect of feeding a high-protein diet following an 18-hour period of feed withholding on mammalian target of rapamycin-dependent signaling in skeletal muscle of mature horses.

Objective: To determine the effect of refeeding following an 18-hour period of feed withholding on the phosphorylation of translation initiation factors in the skeletal muscle of mature horses.

Animals: 8 adult horses.

Procedures: Following an 18-hour period of feed withholding, horses either continued to have feed withheld (postabsorptive state) or were fed 2 g/kg of a high-protein feed (33% crude protein) at time 0 and 30 minutes (postprandial state).

A multitracer stable isotope quantification of the effects of arginine intake on whole body arginine metabolism in neonatal piglets.

We have previously shown that deficient arginine intake increased the rate of endogenous arginine synthesis from proline. In this paper, we report in vivo quantification of the effects of arginine intake on total endogenous arginine synthesis, on the rates of conversion between arginine, citrulline, ornithine, and proline, and on nitric oxide synthesis. Male piglets, with gastric catheters for diet and isotope infusion and femoral vein catheters for blood sampling, received a complete diet for 2 days and then either a generous (+Arg; 1.

Nutritional consequences of interspecies differences in arginine and lysine metabolism.

Differences in lysine and arginine requirements among various species such as omnivores (humans, pigs, rats, dogs), carnivores (cats), herbivores (rabbits, horses), ruminants (cattle), poultry, and fish, are covered in detail in this article. Although lysine is classified as an indispensable amino acid across species, the classification of arginine as either an indispensable or dispensable amino acid is more ambiguous because of differences among species in rates of de novo arginine synthesis. Because lysine is most often the limiting amino acid in the diet, its requirement has been extensively studied.

Parenterally fed neonatal piglets have a low rate of endogenous arginine synthesis from circulating proline.

Parenterally fed neonatal piglets cannot synthesize sufficient arginine to maintain arginine status, presumably due to the intestinal atrophy that occurs with parenteral feeding. Parenteral feeding-induced atrophy can be reduced by the infusion of glucagon-like peptide 2 (GLP-2). GLP-2 infusion was hypothesized to increase the rate of endogenous arginine synthesis from proline, the major arginine precursor, in parenterally fed piglets receiving an arginine-deficient diet.

Coadministration of ornithine and alpha-ketoglutarate is no more effective than ornithine alone as an arginine precursor in piglets enterally fed an arginine-deficient diet.

Simultaneous administration of alpha-ketoglutarate and ornithine, in a 1:2 molar ratio, may improve the effectiveness of ornithine as an arginine precursor in neonatal piglets by shifting ornithine metabolism away from oxidation and toward the synthesis of arginine and other metabolically important compounds. To study this proposed mechanism, enterally fed piglets were allocated to receive 1 of 4 diets for 5 d: an arginine-deficient [1.2 mmol/(kg .

Citrulline is an effective arginine precursor in enterally fed neonatal piglets.

Although neonatal piglets can synthesize some arginine from proline, there is a limit to this synthesis, and piglets fed an arginine-deficient diet have diminished whole-body arginine status. To help elucidate where the limitation in arginine synthesis may occur, our objective was to determine the most effective arginine precursor in 1-wk-old enterally fed piglets. Piglets were administered either an arginine-deficient (basal) diet [1.

Arginine synthesis does not occur during first-pass hepatic metabolism in the neonatal piglet.

We have shown that first-pass intestinal metabolism is necessary for approximately 50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of either L-[guanido-14C]arginine or L-[4,5-3H]arginine were used to measure first-pass hepatic arginine synthesis in piglets enterally fed either deficient (0.