Reduction In Nitrogen Excretion Research Articles

Genetic analysis of protein efficiency and its association with performance and meat quality traits under a protein-restricted diet

BackgroundAn essential component in the development of sustainable pig production is the reduction of nitrogen excretion in fattening pigs. Pig feeds typically contain high levels of dietary crude protein, and due to incomplete conversion to muscle tissue, excess nitrogen is excreted, resulting in environmental problems such as nitrate pollution and greenhouse gas emissions. Therefore, improving protein efficiency (PE), i.e., the proportion of dietary protein that remains in the carcass, is desirable. The aim of this study was to estimate the heritability (h2) of PE and its genetic correlations with phosphorus efficiency, three performance, seven meat quality and two carcass quality traits when pigs were fed a 20% protein-restricted diet, using 1071 Swiss Large White pigs. To determine PE, the intake of feed with known nutrient content was accurately recorded for each pig and the nitrogen and phosphorus content of the carcass was determined using dual-energy X-ray absorptiometry.ResultsWe found an average PE of 0.39 ± 0.04 and a heritability of 0.54 ± 0.10. PE showed a high genetic correlation with phosphorus efficiency (0.61 ± 0.16), moderate genetic correlations with feed conversion ratio (− 0.55 ± 0.14) and average daily feed intake (− 0.53 ± 0.14), and a low genetic correlation with average daily gain (− 0.19 ± 0.19). While PE has favourable genetic correlations with the performance traits and some meat quality traits, there is a potentially unfavourable correlation of PE with meat colour (redness [rg = − 0.27 ± 0.17]; yellowness [rg = − 0.31 ± 0.18]) and intra-muscular fat (IMF; rg = − 0.39 ± 0.15). Feed conversion ratio (FCR) also showed unfavourable genetic correlations with meat lightness, redness yellowness, IMF and cooking loss.ConclusionsPE is a heritable trait that can be considered in breeding programs to reduce the environmental impact of pig production. We found no strong negative correlation of PE with meat quality traits, and that there is potential to indirectly select for improved phosphorus efficiency. Selecting nutrient efficiencies might be a more suitable strategy to reduce nitrogen pollution from manure than focusing on FCR because the latter also shows genetic antagonism with some meat quality traits in our population.

Amino Acid Supplementation to Reduce Environmental Impacts of Broiler and Pig Production: A Review.

Poultry and swine farming are large contributors to environmental impacts, such as climate change, eutrophication, acidification, and air and water pollution. Feed production and manure management are identified as the main sources of these impacts. Reducing dietary crude protein levels is a nutritional strategy recognized to both decrease the use of high-impact feed ingredients and alter manure composition, reducing emissions of harmful components. For a successful implementation of this technique, feed-grade amino acid supplementation is crucial to maintaining animal performance. Reducing crude protein lowers nitrogen excretion, especially excess nitrogen excreted in urea or uric acid form, improving nitrogen efficiency. At the feed-gate, low–crude protein diets can reduce the carbon footprint of feed production through changes in raw material inclusion. The magnitude of this reduction mainly depends on the climate change impact of soybean meal and its land-use change on the feed-grade amino acids used. Reducing dietary crude protein also lowers the environmental impact of manure management in housing, storage, and at spreading: nitrogen emissions from manure (ammonia, nitrates, nitrous oxide) are reduced through reduction of nitrogen excretion. Moreover, synergetic effects exist with nitrogen form, water excretion, and manure pH, further reducing emissions. Volatilization of nitrogen is more reduced in poultry than in pigs, but emissions are more studied and better understood for pig slurry than poultry litter. Ammonia emissions are also more documented than other N-compounds. Low–crude protein diets supplemented with amino acids is a strategy reducing environmental impact at different stages of animal production, making life cycle assessment the best-suited tool to quantify reduction of environmental impacts. Recent studies report an efficient reduction of environmental impacts with low–crude protein diets. However, more standardization of limits and methods used is necessary to compare results. This review summarizes the current knowledge on mitigation of environmental impacts with low–crude protein diets supplemented with amino acids in poultry and swine, its quantification, and the biological mechanisms involved. A comparison between pigs and poultry is also included. It provides concrete information based on quantified research for decision making for the livestock industry and policy makers.

<b>Performance of Japanese quails fed diets with low-protein and isoleucine

Aiming to assess isoleucine levels in low protein diets for laying Japanese quails, 648 quails of 182 days of age were distributed in experimental block design with six treatments and six replicates of 18 birds each. Treatments consisted of a basal level corresponding to 0.672% isoleucine and supplemented with isoleucine to the levels of 0.816, 0.960; 1.104; 1.248%. The experimental diets were compared to a control diet containing 20% CP. The parameters studied were: performance, egg quality, total solids and nitrogen in the excreta. There was a linear increase only for isoleucine intake with increasing levels of isoleucine in the diets. The comparison of mean values of each combination of isoleucine levels for diets with 16% CP with the control with 20% CP showed that the intake of CP and isoleucine, egg weight, nitrogen excretion and yolk color were significantly affected. For Japanese quail fed diets with 16% CP, with isoleucine level at 0.672%, meets the requirements for obtaining satisfactory performance and egg quality and promoted a reduction in nitrogen excretion.

Reduction of nitrogen excretion and emission in poultry: A review for organic poultry

ABSTRACTOrganic poultry is an alternative to conventional poultry which is rapidly developing as a response to customers' demand for better food and a cleaner environment. Although organic poultry manure can partially be utilized by organic horticultural producers, litter accumulation as well as excessive nitrogen still remains a challenge to maintain environment pureness, animal, and human health. Compared to conventional poultry, diet formulation without nitrogen overloading in organic poultry is even more complicated due to specific standards and regulations which limit the application of some supplements and imposes specific criteria to the ingredients in use. This is especially valid for methionine provision which supplementation as a crystalline form is only temporarily allowed. This review is focused on the utilization of various protein sources in the preparation of a diet composed of 100% organic ingredients which meet the avian physiology need for methionine, while avoiding protein overload. The potential to use unconventional protein sources such as invertebrates and microbial proteins to achieve optimal amino acid provision is also discussed.

Aspectos sobre a utilização de aminoácidos totais e digestíveis nas rações para poedeiras

The modernization of poultry laying hens resulted in birds more productive with lower body weight, lower feed intake and higher production efficiency. This modernization resulted in the need for feeding programs increasingly modern and efficient metabolically, especially for amino acids, meeting the demand biological maintenance, gain and production of the birds. In this context, knowledge of the forms of amino acids supplementation in the diet, on the basis total or digestible, is fundamental because of its participation in the formation of pullet and in the production and quality of eggs of hens and reduction in production costs. Diets based on digestible amino acids can provide productive and economic maximization and reduction in nitrogen excretion by birds. Methods for determining the digestibility of amino acids in foods can be: in vitro, indirect and direct, the latter being the most widely used scientifically.

Evaluation of the environmental implications of the incorporation of feed-use amino acids in pig production using Life Cycle Assessment

Feed-use (FU) amino acids, at constant performance, make it possible to reduce the protein content of pig feeds and nitrogen excretion by the animals. The aim of this study was to assess the environmental impact of pig production in a conventional farm by Life Cycle Assessment (LCA) according to several scenarios of FU amino acid incorporation. Two modalities of waste management (slurry or solid manure), two hypotheses of protein sources (soybean meal only, or soybean meal, rapeseed meal and pea) and two soybean origins (Centre-West Brazil vs. average Brazilian soybean) were considered. In each scenario investigated, gestating, lactating, pre-starter and starter feeds were formulated. Fattening pigs were fed either with only one feed (1P), or with two feeds (2P) or according to multiphase feeding (MP). In three scenarios, feeds were least-cost formulated: without incorporation of FU amino acids (NoAA), with FU amino acid incorporation and reduced protein content (LowCP), and FU amino acid incorporation with free protein content (Min€). In the fourth scenario (MinCP), feeds were formulated to minimize protein content. The average protein content of pig feeds decreased, from 190g/kg in 1P-NoAA down to 123g/kg in MP-MinCP while FU amino acid incorporation increased. At the same time, the incorporation of soybean meal into feeds decreased from 197kg/t down to 70kg/t in MP-MinCP. This reduction of soybean meal incorporation was concomitant with a decrease in feed cost. The incorporation of FU amino acids in low protein diets clearly reduced the impacts of pig production on Climate Change (CC), Acidification (AC) and Eutrophication (EU). The lowest CC, AC and EU potential impacts were reached with the Min€ or MinCP scenarios, for which tryptophan and valine were incorporated in pig feeds. The impacts on terrestrial ecotoxicity, cumulative energy demand and land occupation were less sensitive to the studied scenarios. The combination of FU amino acid incorporation and multiphase feeding of growing-finishing pigs produced the largest reduction of CC, AC and EU impacts. The underlying mechanisms include the substitution of soybean meal and extruded soybean by cereals and FU amino acids and the reduction of nitrogen excretion which further reduces nitrous oxide and ammonia emissions. This study suggests that environmental impacts of pig production in France can be further reduced through feeding practices, especially for acidification, eutrophication and climate change.

Effects of acute changes in salinity and temperature on routine metabolism and nitrogen excretion in gambusia ( Gambusia affinis) and zebrafish ( Danio rerio)

Acute stress may affect metabolism and nitrogen excretion as part of the adaptive response that allows animals to face adverse environmental changes. In the present paper the acute effects of different salinities and temperatures on routine metabolism, spontaneous activity and excretion of ammonia and urea were studied in two freshwater fish: gambusia, Gambusia affinis and zebrafish, Danio rerio, acclimated to 27 °C. The effects on gill morphology were also evaluated. Five salinities (0‰, 10‰, 20‰, 30‰ and 35‰) were tested in gambusia, while four salinities were used in zebrafish (0‰, 10‰, 20‰ and 25‰). Each salinity acute stress was tested alone or in combination with an acute temperature reduction to 20 °C. In gambusia, both salinity and temperature acute stress strongly stimulated urea excretion. Routine oxygen consumption was barely affected by acute salinity or temperature stress, and was reduced by the combined effects of temperature and high salinity. Gills maintained their structural integrity in all stressing conditions; hyperplasia and hypertrophy of mitochondria-rich cells were observed. In zebrafish, temperature and salinity acute changes, both alone and in combination, scarcely affected any parameter tested. The major effect observed was a reduction of nitrogen excretion at 20 °C–25‰; under these extreme conditions a significant structural disruption of gills was observed. These results confirm the high tolerance to acute salinity and temperature stress in gambusia, and demonstrate the involvement of urea excretion modulation in the stress response in this species.

OPTIMISATION OF NUTRIENT USE TO MAXIMISE PROFITABILITY AND MINIMISE NITROGEN EXCRETION IN PIG MEAT PRODUCTION SYSTEMS

Reduction of environmental mineral pollution, while maintaining profitability, is one of the major challenges faced by the pig industry today. This paper describes a computer-based growth simulation study undertaken to demonstrate how economic profitability can be maintained whilst the environmental effects associated with nitrogen wastes are minimised. For this purpose, a computer program linking a linear program, a stochastic pig growth model and a genetic algorithm (GA) was developed. The objective function to be maximised by the GA is the weighted difference of gross margin and nitrogen excretion cost. Simulations were conducted to investigate how different pig genotypes (fat, normal, lean) and different relative economic weighting of gross margin (1) and nitrogen excretion (0, 1, 5, 10, 20, 40, 80 or 120) affect the nitrogen excretion and profitability under practical or GA optimised feeding strategies in Switzerland. In all the cases investigated, nitrogen excretion is reduced and profitability increased when the pigs are from a leaner genotype. Across all genotypes a 45% reduction in nitrogen excretion can be achieved with only a 3.5% drop in profitability when diets designed to maximize profitability and minimize nitrogen excretion are fed. The maximal nitrogen retentions observed were 44.9%, 52.6% and 57% for the fat, normal and lean genotypes respectively. It is concluded that a more sustainable pork meat production system can be achieved by using better genotypes and optimizing the diet composition.

Níveis de proteína bruta e de aminoácidos sulfurados totais sobre o desempenho, a qualidade dos ovos e a excreção de nitrogênio de poedeiras de ovos marrons

O experimento foi conduzido com o objetivo de maximizar a produção e a qualidade dos ovos e minimizar a excreção de nitrogênio nas excretas de poedeiras no final do primeiro ciclo de produção, por meio do fornecimento de aporte adequado de proteína bruta (PB) e aminoácidos sulfurados totais (AAST) na dieta. Foram utilizadas 432 poedeiras Isa Brown, com 52 semanas de idade, distribuídas em delineamento inteiramente casualizado, em esquema fatorial 3 x 3 (PB e AAST) e nove tratamentos (14 e 0,57; 14 e 0,64; 14 e 0,71; 15,5 e 0,57; 15,5 e 0,64; 15,5 e 0,71; 17 e 0,57; 17 e 0,64; 17 e 0,71 % de PB e AAST, respectivamente), com seis repetições de oito aves cada. A duração do experimento foi de 140 dias. Foram avaliadas as características de desempenho, qualidade dos ovos e excreção de nitrogênio nas excretas. A única característica de desempenho influenciada pelos tratamentos foi o peso dos ovos, que apresentou os maiores valores para as combinações de 15,5 e 0,71; 17 e 0,71; 15,5 e 0,64; 14 e 0,71 e 17 e 0,64% de PB e AAST, respectivamente. Não foram observadas diferenças significativas para consumo de ração, porcentagem de postura e de ovos quebrados, massa de ovos, conversão alimentar por dúzia e por massa de ovos e mortalidade. Para os parâmetros de qualidade dos ovos, foram observadas diferenças significativas apenas para as porcentagens de gema e de albúmem. A excreção de nitrogênio foi maior nas aves alimentadas com as rações contendo 17% de PB. Pode-se sugerir que a ração contendo 14% de PB e 0,57% de AAST pode ser utilizada, sem prejuízos no desempenho e na qualidade dos ovos, e ainda contribui para a redução da excreção de nitrogênio no ambiente e do custo da ração.

Effects of dietary lipid and phosphorus levels on nitrogen and phosphorus excretion in young yellowtail Seriola quinqueradiata: A preliminary observation

ABSTRACT: A feeding trial was conducted to investigate the effect of dietary lipid and phosphorus levels on nitrogen and phosphorus excretion of young yellowtail under on-site conditions for 4 months. Three levels of dietary lipid (200, 250 and 300 g/kg) and four levels of supplemental phosphorus (0, 2, 4 and 7 g/kg) were tested in a complete randomized design with a 3 × 4 factorial arrangement. Each net cage of 170 yellowtail were fed the experimental diets for 4 months and the fish grew from approximately 346–912 g, at water temperatures between 18 and 23°C. Dietary phosphorus levels did not cause any difference in weight gain, specific growth rate, feed conversion ratio and nitrogen retention. However, its increasing supplemental levels reduced phosphorus retention, consequently increasing its excretion, whereas nitrogen excretion remained uninfluenced. In contrast, increasing the dietary lipid level resulted in its greater deposition in the whole body of young fish leading to a reduction in nitrogen excretion. This study has shown that phosphorus levels need not necessarily be high in the diets of young yellowtail. In addition, dietary lipid can be manipulated favorably to produce environmentally suitable diets.

Effect of Prophylactic Intracerebroventricular Injection of Methylprednisolone on Nitrogen and Catecholamine Excretion in the Urine after Laparotomy in Rats

Background. This study was carried out to determine whether the prophylactic injection of glucocorticoid into the intracerebroventricular (icv) space reduced TNF-α and IL-1β mRNA synthesis in the brain after laparotomy, resulting in a reduction of nitrogen excretion in the urine.Patients and methods. Male SD rats (body wt, 225–250 g, n = 114) were catheterized into the icv space on day 0. On day 4, the rats were assigned to four groups: (1) Control, (2) laparotomy (Trauma), (3) intraperitoneal (ip) injection of methylprednisolone (MP) plus laparotomy (IPMP), and (4) icv injection of MP plus laparotomy (ICVMP). Either 3 or 24 h after surgery, the animals were sacrificed. TNF-α and IL-1β mRNA levels in tissues, including the brain cortex and hypothalamus, were measured by RT–PCR. The amounts of nitrogen and catecholamine excretion in the 24-h urine were determined.Results. The ip injection of MP reduced TNF-α and IL-1β mRNA levels in all the tissues 3 h after laparotomy compared with those of the Trauma group. The icv injection of MP prevented elevation of the TNF-α and IL-1β mRNA levels in the brain (cortex, TNF-α, ICVMP 0.43 ± 0.06, P < 0.05, vs Trauma; cortex, IL-1β, ICVMP 0.25 ± 0.09, P < 0.05, vs Trauma; hypothalamus, TNF-α, ICVMP 0.31 ± 0.04, P < 0.05, vs Trauma; hypothalamus, IL-1β, ICVMP 0.25 ± 0.14, P < 0.05, vs Trauma), but did not inhibit an increase in TNF-α and IL-1β mRNA levels in the liver and skeletal muscle. Both nitrogen and catecholamine excretions in the urine were decreased by ip and by icv injection of MP compared to those of the Trauma group (nitrogen, ICVMP 559.3 ± 52.0 mg/day, P < 0.05, vs Trauma; catecholamine, ICVMP 13.8 ± 1.8 μg/day, P < 0.05, vs Trauma).Conclusion. A reduction in TNF-α and IL-1β mRNA synthesis in the brain due to prophylactic injection of MP into the icv space reduced the catabolic response after laparotomy.

Incidences phytotechniques et zootechniques d'une réduction ou d'une suppression de la fertilisation azotée sur des prairies pâturées par des vaches laitières

Phytotechnical and zootechnical effects of a nitrogen fertilizer reduction or suppression on pasture grazed by dairy cows. Three levels of intensification were compared for a permanent pasture grazed over 6 consecutive years in a rotational grazing system. The three levels of intensification were as follow: a high nitrogen fertilizer input system with 136 kg N.ha -1 and with 3.35 cows.ha -1 - H-N group -, a system with a moderate fertilizer input in which nitrogen fertiliza- tion was reduced by 33% but with the same stocking rate - M-N group - with 91 kg N.ha -1 along with 3.35 cows.ha -1 and a system with no fertilization associated with a reduced stocking rate - 0-N group - with 2.51 cows .ha -1 . There were no effects of the treatments on grass character- istics - e.g. post grazing height, percentage of refusals, total nitrogen content, fiber content. The absence of nitrogen fertilization reduced the pre-grazing height and DM yield of the pasture. The clover content was reduced in the first and sixth years in nitrogen fertilized groups. The individual milk yield was not affected by the treatments (15.4 kg .d -1 ) but the milk yield per hectare was largely affected by the stocking rate. The protein content and cell count were unaffected by the treatments but butter fat content was higher in the 0-N group than in the other two groups (4.10 vs. 3.90%; P < 0.05). The average daily liveweight gain was not affected by the treatments (0.23 kg .d -1 ). The plasma and milk urea contents were significantly higher in fertilized groups than in 0-N group (164 vs. 151 mg N.l -1 in plasma and 194 vs. 175 mg N.l -1 in milk respectively; P < 0.05). Daily nitrogen excretion per animal was similar for both treatments but when expressed per ha and year, the excretion was higher in the fertilized groups. Thus, it has appeared that a 33% reduction of nitrogen fertilization with a sim- ilar stocking rate allowed to maintain performances either on an individual animal or a per hectare basis. Grazing management with no nitrogen fertilization but with an adjusted stocking rate induced a reduction in performances expressed per hectare but maintained similar individual performances as with high input systems. Furthermore, there were both a higher nitrogen efficiency and a reduction in nitrogen excretion per hectare. dairy cows / nitrogen fertilization / grazing / milk yield / nitrogen balance

Reduction of Nitrogen Excretion from Broiler

Reduction of Nitrogen Excretion from Broiler

養豚経営における窒素排せつ量削減と飼料費低減のトレード・オフ分析

養豚経営では, ふん尿の環境に与える負荷を軽減することが重要な課題になっている。その対策の一つとして, 栄養管理によって排泄される窒素を削減する方法がある。しかしこの方法には, 窒素の削減量に応じて飼料費が増加するというトレード・オフの関係がある。したがって, この方法の環境負荷軽減に対する有効性を検討するためには, このトレード・オフに対する養豚経営者の評価が必要である。そこで養豚経営者に対してトレード・オフ分析を行った結果, 窒素排泄量の削減よりも飼料費の低減を重視していることが明らかになった。

Potassium bicarbonate reduces urinary nitrogen excretion in postmenopausal women.

Previously we demonstrated that low grade chronic metabolic acidosis exists normally in humans eating ordinary diets that yield normal net rates of endogenous acid production (EAP), and that the degree of acidosis increases with age. We hypothesize that such diet-dependent and age-amplifying low grade metabolic acidosis contributes to the decline in skeletal muscle mass that occurs normally with aging. This hypothesis is based on the reported finding that chronic metabolic acidosis induces muscle protein breakdown, and that correction of acidosis reverses the effect. Accordingly, in 14 healthy postmenopausal women residing in a General Clinical Research Center and eating a constant diet yielding a normal EAP rate, we tested whether correcting their "physiological" acidosis with orally administered potassium bicarbonate (KHCO3; 60-120 mmol/day for 18 days) reduces their urinary nitrogen loss. KHCO3 reduced EAP to nearly zero, significantly reduced the blood hydrogen ion concentration (P < 0.001), and increased the plasma bicarbonate concentration (P < 0.001), indicating that pre-KHCO3, diet-dependent EAP was significantly perturbing systemic acid-base equilibrium, causing a low grade metabolic acidosis. Urinary ammonia nitrogen, urea nitrogen, and total nitrogen levels significantly decreased. The cumulative reduction in nitrogen excretion was 14.1 +/- 12.3 g (P < 0.001). Renal creatinine clearance and urine volume remained unchanged. We conclude that in postmenopausal women, neutralization of diet-induced EAP with KHCO3 corrects their preexisting diet-dependent low grade metabolic acidosis and significantly reduces their urinary nitrogen wasting. The magnitude of the KHCO3-induced nitrogen-sparing effect is potentially sufficient to both prevent continuing age-related loss of muscle mass and restore previously accrued deficits.

Reduction of nitrogen excretion by pigs between 20 and 50 kg live weight given low protein diets

The potential reduction in nitrogenous excretion by growing pigs, through the reduction of protein levels in diets, has not been consistently achieved without compromising performance. This may have been due to inadequate formulation of the diets. Formulation on the basis of the total amino acid content of feed ingredients may limit the nitrogen retention, and hence the rate of protein accretion (Lee et al., 1993). Therefore, the objective of the experiment reported here was to evaluate the nitrogen balance of pigs fed diets at two levels of protein, formulated on the basis of true ileal digestibility of the essential amino acids (Rhône-Poulenc Animal Nutrition, 1993) and the net energy available from the raw materials (Noblet et al., 1994).

Reduction of nitrogen excretion by pigs between 20 and 50 kg live weight given low protein diets

The potential reduction in nitrogenous excretion by growing pigs, through the reduction of protein levels in diets, has not been consistently achieved without compromising performance. This may have been due to inadequate formulation of the diets. Formulation on the basis of the total amino acid content of feed ingredients may limit the nitrogen retention, and hence the rate of protein accretion (Lee et al., 1993). Therefore, the objective of the experiment reported here was to evaluate the nitrogen balance of pigs fed diets at two levels of protein, formulated on the basis of true ileal digestibility of the essential amino acids (Rhône-Poulenc Animal Nutrition, 1993) and the net energy available from the raw materials (Noblet et al., 1994).

"Wear and Tear" Protein-Reply

To the Editor:— Dr. Wishnofsky is correct in that wear-and-tear is not scientific terminology but rather a figure of speech, and the amount of protein does not refer to an irreducible minimum with a diet which contains any protein. Gamble showed in studies of a week's duration that the protein-sparing action of more than 100 gm. of carbohydrate was negligible. However, Kolff found that after 12 to 20 days on a Borst diet, patients did have a slow reduction in nitrogen excretion, indicating a diminution in protein breakdown and an increase in protein-sparing action (probably mostly by carbohydrate) beyond the amount found by Gamble in his short-term experiments. A proteinfree diet, as Doctor Wishnofsky points out, would be of value in cases ofacuterenal failure but not in chronic cases, except in brief acute exacerbations.

THE EFFECTS OF INSULIN AND SOMATOTROPHIN ON THE GROWTH OF HYPOPHYSECTOMIZED RATS

Growth induced by exogenous insulin in hypophysectomized rats on an unrestricted diet is similar to that stimulated by somatotrophin. Both hormones promote skeletal growth and produce an increase in weight that is due to an increase in total body protein, fat, and water. However, insulin-treated animals consume more food, produce more fat, retain less water, and exhibit less skeletal growth than comparable rats treated with somatotrophin. Insulin and somatotrophin promote the synthesis of similar amounts of protein under our experimental conditions. Insulin-induced growth is enhanced and the disproportionate increase in fat is prevented by the simultaneous administration of somatotrophin. Insulin cannot stimulate protein anabolism in hypophysectomized rats restricted to the amount of food consumed prior to treatment. When the insulin-treated animals are allowed to consume glucose in addition to their basal ration there is a marked increase in the amount of ingested nitrogen retained. A comparable reduction in nitrogen excretion cannot be achieved when the carbohydrate supplement is replaced by fat. The results also indicate that under the experimental conditions described, the protein sparing action of glucose is dependent upon an adequate supply of insulin.

THE EFFECTS OF INSULIN AND SOMATOTROPHIN ON THE GROWTH OF HYPOPHYSECTOMIZED RATS

Growth induced by exogenous insulin in hypophysectomized rats on an unrestricted diet is similar to that stimulated by somatotrophin. Both hormones promote skeletal growth and produce an increase in weight that is due to an increase in total body protein, fat, and water. However, insulin-treated animals consume more food, produce more fat, retain less water, and exhibit less skeletal growth than comparable rats treated with somatotrophin. Insulin and somatotrophin promote the synthesis of similar amounts of protein under our experimental conditions. Insulin-induced growth is enhanced and the disproportionate increase in fat is prevented by the simultaneous administration of somatotrophin. Insulin cannot stimulate protein anabolism in hypophysectomized rats restricted to the amount of food consumed prior to treatment. When the insulin-treated animals are allowed to consume glucose in addition to their basal ration there is a marked increase in the amount of ingested nitrogen retained. A comparable reduction in nitrogen excretion cannot be achieved when the carbohydrate supplement is replaced by fat. The results also indicate that under the experimental conditions described, the protein sparing action of glucose is dependent upon an adequate supply of insulin.