Utilization Of Dietary Protein Research Articles

Biochemical and physiological bases for utilization of dietary amino acids by young Pigs

Protein is quantitatively the most expensive nutrient in swine diets. Hence it is imperative to understand the physiological roles played by amino acids in growth, development, lactation, reproduction, and health of pigs to improve their protein nutrition and reduce the costs of pork production. Due to incomplete knowledge of amino acid biochemistry and nutrition, it was traditionally assumed that neonatal, post-weaning, growing-finishing, and gestating pigs could synthesize sufficient amounts of all "nutritionally nonessential amino acids" (NEAA) to support maximum production performance. Therefore, over the past 50 years, much emphasis has been placed on dietary requirements of nutritionally essential amino acids as building blocks for tissue proteins. However, a large body of literature shows that NEAA, particularly glutamine, glutamate, arginine and proline regulate physiological functions via cell signaling pathways, such as mammalian target of rapamycin, AMP-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and NEAA-derived gaseous molecules (e.g., nitric oxide, carbon monoxide, and hydrogen sulfide). Available evidence shows that under current feeding programs, only 70% and 55% of dietary amino acids are deposited as tissue proteins in 14-day-old sow-reared piglets and in 30-day-old pigs weaned at 21 days of age, respectively. Therefore, there is an urgent need to understand the roles and dietary requirements of NEAA in swine nutrition. This review highlights the basic biochemistry and physiology of absorption and utilization of amino acids in young pigs to enhance the efficacy of utilization of dietary protein and to minimize excretion of nitrogenous wastes from the body.

Partitioning of heat production in growing pigs as a tool to improve the determination of efficiency of energy utilization.

In growing pigs, the feed cost accounts for more than 60% of total production costs. The determination of efficiency of energy utilization through calorimetry measurements is of importance to sustain suitable feeding practice. The objective of this paper is to describe a methodology to correct daily heat production (HP) obtained from measurements in respiration chamber for the difference in energy expenditure related to physical activity between animals. The calculation is based on a preliminary published approach for partitioning HP between HP due to physical activity (AHP), thermic effect of feeding (TEF) and basal metabolic rate (fasting HP; FHP). Measurements with male growing pigs [mean body weight (BW): 115 kg] which were surgically castrated (SC), castrated through immunization against GnRH (IC), or kept as entire male (EM) were used as an example. Animals were fed the same diet ad-libitum and were housed individually in two 12-m3 open-circuit respiration chambers during 6 days when fed ad-libitum and one supplementary day when fasted. Physical activity was recorded through interruption of an infrared beam to detect standing and lying positions and with force transducers that recorded the mechanical force the animal exerted on the floor of the cage. Corrected AHP (AHPc), TEF (TEFc), and HP (HPc) were calculated to standardize the level of AHP between animals, assuming that the ratio between AHPc and ME intake should be constant. Inefficiency of energy utilization (sum of AHPc and TEFc) was lower than the inefficiency estimated from the slope of the classical relationship between HPc and ME intake but was associated with higher requirements for maintenance. Results indicate that EM pigs had higher FHP but lower TEFc than IC and SC pigs. These results agree with the higher contents in viscera of EM pigs that stimulate their basal metabolic rate and with the reduced utilization of dietary protein to provide energy for maintenance energy requirements and fat deposition (FD).

Long chain omega-3 fatty acids: Micronutrients in disguise

Considerable information has accumulated to show that DHA and EPA have unique roles that differ from other n-3 fatty acids and the n-6 fatty acids, with increasing understanding of the mechanisms through which these fatty acids reduce risk of disease. DHA and EPA regulate hepatic lipid and glucose metabolism, but are present in foods of animal origin, which are generally high in protein with variable triglycerides and low carbohydrate. Biological activity at intakes too low to provide significant amounts of energy is consistent with the definition of a vitamin for which needs are modified by life-stage, diet and genetic variables, and disease. Recent studies reveal that DHA may play a central role in co-coordinating complex networks that integrate hepatic glucose, fatty acid and amino acid metabolism for the purpose of efficient utilization of dietary protein, particularly during early development when the milk diet provides large amounts of energy from fat.

Compensatory growth after various levels of dietary protein restriction in rainbow trout, Oncorhynchus mykiss

This study was conducted to determine the effects of various levels of dietary protein restriction for 3weeks (phase 1) on compensatory growth, nutrient utilization, body compositions and organ indices of rainbow trout (Oncorhynchus mykiss) during a nine-week realimentation phase (phase 2). Five experimental treatments consisted of four protein restricted diets including 15, 22.5, 30 and 37.5% protein (RP15, RP22.5, RP30 and RP37.5 respectively) and the control diet 45% (C45). All diets were prepared to be isoenergetic at levels of 22.5MJkg−1 gross or 16.3MJkg−1 digestible energy. Each of five treatment groups was tried in triplicate groups of 75 fish with an average initial weight of 62.06±0.38g. Protein restriction in phase 1 linearly decreased specific growth rates of weight and length (SGRW and SGRL), body weight and length as well as feed utilization. The restriction induced a linearly increasing trend in protein retention efficiency, feed intake, organ indices such as viscera, pyloric caecum and hepato-somatic, whole body lipid and lipid/lean body mass whereas it induced a decrease in whole body moisture and protein at the end of phase 1. Protein restriction, except RP37, caused a significant increase in SGRW during phase 2 compared with C45, being most pronounced in the first 3weeks. Repeated measures ANOVA revealed a convergence in trajectories of ln body weight and length at the end of the experiment, suggesting that a complete catch up occurred in body mass and structure. There was also replenishment in distorted organ indices and body compositions, except protein which was still less in R15 than C45. More efficient utilization of feed and dietary protein by previously protein restricted fish during phase 2 appears to be the reason of the compensatory growth. At the end of the experiment, protein restriction was found to be effective in reduction of N loss.

Scientific Opinion on Dietary Reference Values for protein

This opinion of the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) deals with the setting of Dietary Reference Values (DRVs) for protein. The Panel concludes that a Population Reference Intake (PRI) can be derived from nitrogen balance studies. Several health outcomes possibly associated with protein intake were also considered but data were found to be insufficient to establish DRVs. For healthy adults of both sexes, the average requirement (AR) is 0.66 g protein/kg body weight per day based on nitrogen balance data. Considering the 97.5th percentile of the distribution of the requirement and assuming an efficiency of utilisation of dietary protein for maintenance of 47 %, the PRI for adults of all ages was estimated to be 0.83 g protein/kg body weight per day and is applicable both to high quality protein and to protein in mixed diets. For children from six months onwards, age-dependent requirements for growth estimated from average daily rates of protein deposition and adjusted by a protein efficiency for growth of 58 % were added to the requirement for maintenance of 0.66 g/kg body weight per day. The PRI was estimated based on the average requirement plus 1.96 SD using a combined SD for growth and maintenance. For pregnancy, an intake of 1, 9 and 28 g/d in the first, second and third trimesters, respectively, is proposed in addition to the PRI for non-pregnant women. For lactation, a protein intake of 19 g/d during the first six months, and of 13 g/d after six months, is proposed in addition to the PRI for non-lactating women. Data are insufficient to establish a Tolerable Upper Intake Level (UL) for protein. Intakes up to twice the PRI are regularly consumed from mixed diets by some physically active and healthy adults in Europe and are considered safe.

Metabolism and chemical composition of phyllosoma larvae, with special reference to the tropical rock lobster Panulirus ornatus (Decapoda; Palinuridae)

Rates of oxygen consumption and ammonia excretion and chemical composition (water, ash and CN composition) were determined throughout larval development, from Stages I–IX, of Panulirus ornatus phyllosoma larvae raised in the laboratory. Dry mass (DM) specific oxygen consumption rates varied from 1.4 to 3.3 μl O 2 (DM) −1 h −1, showing a pattern of developmental decline. In contrast, specific ammonia excretion rates fluctuated irregularly from 0.02 to 0.067 μg NH 4–N (DM) −1 h −1, yielding oxygen consumption to ammonia excretion ratios (O:N atomic ratio) as wide as 51–180. With progressive development, ash decreased from 34% to 17% of DM while C composition increased from 33% to 41% of DM. No consistent changing pattern with development was seen for water contents (74–83% of WM), N composition (6.9–9.5% of DM) and C:N ratios (4.0–5.1). Supplemental data of both specific oxygen consumption and ammonia excretion rates of laboratory-raised Stage III P. homarus and wild Parribacus antarcticus phyllosoma (stage unknown) of this study and literature data on phyllosomas of other lobster species by previous workers were shown to be comparable to those of P. ornatus phyllosomas when the differences in DM and temperature were taken into account. No appreciable differences due to the origin of the specimens, whether wild or laboratory-raised, were evident. Comparison of the present results with those of stomatopod larvae and holoplanktonic crustaceans in the same tropical marine habitats revealed that phyllosoma larvae are characterized by somewhat lower DM specific oxygen consumption rates and N composition. The study revealed markedly reduced ammonia excretion rates in phyllosomas, suggesting reduced swimming activity and preferential utilization of dietary protein to somatic growth rather than metabolism.

Protein Distribution Needs for Optimal Meal Response

The adequacy of the RDA for protein (0.8 g/kg/d) continues to generate much scientific discussion. In particular, recent research suggests that adults require approximately 30 g of protein per meal to maximally stimulate muscle protein synthesis. The objective of this study was to assess the effect of daily protein distribution on muscle protein anabolism. Adult men and women participated in a randomized crossover 24 h study evaluating two diets each containing 90 g total protein/day. Diet 1 provided an even protein distribution: 30 g (breakfast), 30 g (lunch) and 30 g (dinner). Diet 2 provided a skewed protein distribution: 10 g (breakfast), 15 g (lunch) and 65 g (dinner). Stable isotope methodology with muscle biopsies and blood sampling was used to assess muscle protein synthesis in response to the breakfast meal (10 vs. 30 g protein) and the 24 h response. Visual analog questionnaires measured satiety. Preliminary results suggest muscle protein synthesis following the breakfast meal and after 24 h was approximately 25% greater in the evenly distributed protein group compared to the skewed diet. Indices of satiety were also improved following consumption of the evenly distributed protein diet. In conclusion, evenly distributing protein over the course of the day may promote increased utilization of dietary protein and greater satiety in adults.

Effects of increasing dietary protein levels on growth, feed utilization and body composition of Heterobranchus longifilis (Valenciennes, 1840) fingerlings

The effect of different dietary protein levels on growth performance and on feed utilization of catfish ( Heterobranchus longifilis ) fingerlings was carried out in aquaria. Five dietary protein levels 25, 30, 35, 40 and 45% were tried in triplicates. The result shows that 25% protein is too limited to ensure good growth and also the growth rate, weight gain and nitrogen metabolism increased progressively with dietary protein level to a maximum at 40%. However, there was no significant difference in feed conversion ratio (FCR), protein efficiency ratio (PER), specific growth rate (SGR), daily weight gain (DGW) and the daily feed intake between fish fed with 30% protein and those fed with 35% protein. There was no significant difference in PER and nitrogen loss (NL) between fish fed with 25 to 40% protein. Above 40% protein, nitrogen metabolism and PER decreased, showing the low utilization of dietary protein. The moisture, ash and gross energy content did not vary between dietary treatments. However, lipid and protein body content varied between treatments. Key words : Dietary protein, growth, nutrient utilization, body composition, Heterobranchus longifilis , fingerlings.

The responses of light- and heavy-for-age pigs at weaning to dietary spray-dried porcine plasma

Light-for-age pigs are generally regarded as the most disadvantaged group at weaning for subsequent post-weaning performance and survival. The main objective of this study was to demonstrate that weaner diets containing spray-dried porcine plasma (SDPP) could assist light-for-age pigs to perform better than their heavier counterparts after weaning. A total of 96 pigs weaned at 21 days (d) were used in a 2 × 2 factorially designed experiment with the respective factors being live weight (LW) (light- 4.9 ± 0.67 kg LW or heavy- 6.9 ± 0.73 kg LW for-age pigs) and SDPP supplementation (0 g/kg vs. 50 g/kg and 25 g/kg, for phase I and II respectively). The concentration of immunoglobulins (Ig) G, M and A in the SDPP included in the diets was 108, 33 and 7 g/kg, respectively. Each treatment had 8 replicates (pens) with 3 pigs per pen. Phase I diets were fed for the first week and phase II diets for the following 2 weeks until the experiment ceased at 21 d after weaning. One pig per pen, randomly selected, was bled on d 7 and 14 to measure circulating levels of Ig, routine haematology indices and plasma urea nitrogen (PUN). The inclusion of SDPP in the diet improved (P < 0.001) performance of both light- and heavy-for-age pigs in the first week after weaning. These effects disappeared (P > 0.05) in the following 2 weeks and over the 3-week study, pigs supplemented with SDPP gained 20 g more per day (P = 0.09) than the control pigs. Haematology indices as well as Ig levels in plasma were similar between treatments except for IgG, which was highest (P < 0.05) in the heavy pigs not fed SDPP on d 14 of the experiment. Pigs fed SDPP diets had lower (P < 0.05) PUN levels than the pigs not fed SDPP on both d 7 and 14, indicating an increased efficiency of dietary protein utilisation as a result of SDPP supplementation. These results confirm the inclusion of SDPP in weaner pig diets to improve post-weaning performance but under the conditions of the experiment, failed to improve the production of light-for-age pigs compared to heavy-for-age pigs.

EFFECT OF FAT INCLUSION IN DIETS FOR RABBITS ON THE EFFICIENCY OF DIGESTIBLE ENERGY AND PROTEIN UTILIZATION

Two hundred ten Californian x New Zealand White rabbits (117 males, 93 females) were usad to study the influence of diet, slaughter weight (2.0, 2.25, and 2.5 kg), and sex on the efflciency of dietary digestible energy (DE) and protein (DCP) utilization determined by using the comparativa slaughter technique. Seven diets were formulated to have the sama ADF level (24%), diet C had no added fat, diets T, O, and S contained 3% of added beef tallow, oleins, and soybean oil, respectively. Diets TWS, OWS, and SWS contained the same level and types of fat than diets T, O, and S but included also a 18% of toasted whole soybeans to increase dietary ether extract (EE) by 3%. Neither fat addition nor slaughter weight influenced DE efficiency, but when the dietary EE level and the weight at slaughter were increased, DCP efficiency increased (P<0.001) and decreased (P<0.05), respectively. Females had a greater DE and a lower DCP efficiencies (P<0.01) than mares. Diets containing soybean oil showed a higher DE efficiency than those containing oleins.

Skeletal muscle cellularity and expression of myogenic regulatory factors and myosin heavy chains in rainbow trout (Oncorhynchus mykiss): Effects of changes in dietary plant protein sources and amino acid profiles

The nutritional regulation of skeletal muscle growth is very little documented in fish. The aim of the study presented here was to determine how changes in dietary plant protein sources and amino acid profiles affect the muscle growth processes of fish. Juvenile rainbow trout (Oncorhynchys mykiss) were fed two diets containing fish meal and a mixture of plant protein sources either low (control diet) or rich in soybean meal (diet S). Both diets were supplemented with crystalline indispensable amino acids (IAA) to match the rainbow trout muscle IAA profile. Diet S was also supplemented with glutamic acid, an AA present in high quantities in trout muscle. Rainbow trout fed diets C and S were not significantly different in terms of overall somatic growth or daily nitrogen gain, although their parameters of dietary protein utilisation differed. Distribution of skeletal white muscle fibre diameter and expression of certain selected muscle genes were also affected by dietary changes. In the white muscle, diet S led to a significant decrease (×0.9) in the mean and median diameters of muscle fibres, to a significant decrease (×0.6) in the expression of MyoD and to a significant increase (×1.7) in the expression of fast-MHC, with no significant changes in myogenin expression. There was no change in the expression of the genes analysed in lateral red muscle (MyoD, MyoD2, myogenin and slow-MHC). These results demonstrated that changes occurred in skeletal white muscle cellularity and expression of MyoD and fast-MHC, although overall growth and protein accretion were not modified, when a diet rich in soybean meal and glutamic acid was ingested. Present findings also indicated that the white and red muscles of rainbow trout are differently affected by nutritional changes.

Metabolism and elemental composition of the euphausiids Euphausia pacifica and Thysanoessa inspinata during the phytoplankton bloom season in the Oyashio region, western subarctic Pacific Ocean

Rates of oxygen consumption ( R: μl O 2 [individual] −1 h −1), and ammonia excretion ( E: μg NH 4-N [individual] −1 h −1), O:N ratios (by atoms) and body water contents (% of wet mass [ WM], as an index of lipid accumulation) of Euphausia pacifica and Thysanoessa inspinata were monitored during 9–14 March and 6–30 April 2007, including the onset of the spring phytoplankton bloom in the Oyashio region. Regression analyses revealed that variations in R and E were generally correlated with dry body mass ( DM) for both euphausiids. When R and E were standardized to a body size of 10 mg DM, R std , E std , O:N ratios and water contents fluctuated from 6.3 to 10.1, 0.07 to 0.34, 31 to 232 and 73.8 to 78.1, respectively, for E. pacifica, and from 8.7 to 11.3, 0.06 to 0.71, 24 to 295 and 75.1 to 82.2, respectively, for T. inspinata. None of these variables were significantly correlated with temporal variations in SST (1.7 to 5.7 °C) or chlorophyll a standing stock (29.4 to 252.6 mg m −2, 0–100 m) at the study site. However, April E and O:N ratio data pooled for both euphausiids were significantly less and greater, respectively, than the pooled values in March, suggesting preferential utilization of dietary protein for body growth or reproduction under conditions of abundant food supply as found in April. No substantial differences were observed in water content, ash, C, N or C:N ratios (by mass) of the two euphausiids collected in either March or April. Water content, C, N, C:N ratio and ash data averaged for E. pacifica and T. inspinata over the March and April cruises were similar: 76.3 and 78.1% of WM, 36.1 and 37.5% of DW, 9.4 and 10.1% of DW, 3.82 and 3.71 by mass, and 10.6 and 10.8% of DM, respectively. Combining the R-DM and E-DM relationships established with the population structure data of Kim et al. (2010), we estimate that daily ingestion and ammonia-N regeneration by the combined populations of the two euphausiids were 1.5–24.1% (integrated mean: 4.9%) and 0.18–1.32% (0.41%), respectively, of primary production and associated N demand during the bloom.

Exercise intensity matters for both young and old muscles

Exercise intensity matters for both young and old muscles

Ideal amino acid balance for sows during gestation and lactation1

Improving efficiency of protein utilization is important for pregnant sows under restricted feed allowance and for lactating sows with limited feed intake. Sows have limited ability to support the growth of fetuses and mammary glands during late gestation and to support mammary growth and milk production, especially during first lactation period. A series of studies was conducted to characterize requirements and ideal ratios of AA for 1) fetal growth, 2) mammary gland growth of gestating sows, 3) maternal tissue gain of gestating sows, 4) mammary gland growth of lactating sows, and 5) maternal tissue gain of lactating sows. A total of 97 pregnant sows and their fetuses and a total of 174 lactating sows and their nursing piglets were used for these studies to collect fetal tissues, mammary tissues, and maternal tissues for AA analysis. Requirements and ideal ratios of AA for sows changed dynamically depending on stages of pregnancy. Suggested daily requirements for true ileal digestible Lys were 5.57 and 8.78 g, and relative ideal ratios for Lys:Thr:Val:Leu (on basis of AA weight) were 100:79:65:88 and 100:71:66:95 for d 0 to 60 and d 60 to 114 of gestation, respectively. Requirements and ideal ratios of AA for lactating sows changed dynamically depending on potential amounts of protein mobilization from maternal tissues, which are related to voluntary feed intake and milk production. Suggested ideal ratios for Lys:Thr:Val:Leu were 100:59:77:115 and 100:69:78:123 if BW losses of sows during 21 d of lactation are 0 and 33 to 45 kg, respectively. To optimize efficiency of dietary protein utilization by sows, the dietary AA content and ratios can be adjusted by stages of pregnancy (i.e., phase feeding) and by expected feed intakes or parities of sows during lactation (i.e., parity-split feeding) considering the dynamic changes in the requirements and ideal ratios of AA.

ASAS Centennial Paper: Landmark discoveries in swine nutrition in the past century12

During this centennial year of the American Society of Animal Science (ASAS), it is of interest to look back over the history of our Society and, in particular, to the many contributions made by researchers in the area of swine nutrition. A great number of basic and applied research studies involving the nutrition of weanling, growing, and finishing pigs, and gestating and lactating sows have been conducted by swine nutritionists during the past 100 yr. Most of these studies were conducted at universities by animal scientists or by the graduate students under their leadership. Others were conducted by nutritionists in the feed and pharmaceutical industries and government scientists at ARS/USDA research centers. Contributions were also made by animal scientists beyond our borders. Much of the research was published in the Journal of Animal Science during its 66 yr of existence. Before the first issue of the journal was published in 1942, some of the earlier studies were reported in the Proceedings of the Annual Meeting of the Society of Animal Production, the forerunner of ASAS. These research studies have progressively led to a better understanding of the role and utilization of dietary energy, protein, AA, carbohydrates, fats, minerals, and vitamins by pigs and have helped to quantify the nutrient requirements of pigs for various stages of growth, for sows during gestation and lactation, and to a limited extent, for boars. Determining the nutritional value of a wide array of feedstuffs, evaluating feeding strategies, and assessing the value of growth-promoting and carcass-enhancing agents have been important research contributions as well. To identify the particular studies that were among the most instrumental in contributing to our present knowledge of swine nutrition is, to say the least, a daunting assignment. To aid in this task, a survey of swine nutritionists was conducted in which they were asked to identify and rank the 10 most significant findings in swine nutrition during the past 100 yr. The results of that survey are presented in this paper.

Efficiency of energy and protein deposition in swine measured by dual energy X-ray absorptiometry (DXA)

Abstract. A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study DXA was compared directly with slaughter analysis as a method for measuring energy deposition in pigs. During growth from 30 to 60 kg the mean value for carcass energy deposition measured by DXA was 251 MJ compared to 249 MJ by chemical analysis (R2=0.94). Subsequently it was shown that both compensatory growth and the addition of ractopamine to the diet resulted in an improvement in efficiency of protein deposition (PE), however, ractopamine also resulted in a reduction in the efficiency of energy deposition (kg). Another study was conducted to compare the efficiency of utilization of dietary energy and protein by control and IGF-I transgenic pigs in response to dietary conjugated linoleic acid (CLA). Addition of CLA to the diet resulted in a reduction in kg, though there was no difference in kg based on genotype or sex. The PE was higher (P&lt;0.05) in the IGF-I transgenic pigs. DXA was also used to assess energy deposition in pigs that were either homozygous stress non-sensitive (NN), heterozygous (Nn) or homozygous stress sensitive (nn). During growth from 30 to 60 kg or 60 to 90 kg there were no differences in the efficiency of either energy or protein deposition. In conclusion, DXA can be used to replace the comparative slaughter technique for measuring energy and protein deposition in pigs, thus this approach is useful for identifying differences in energy and protein deposition in pigs of different genotypes or when subjected to various dietary treatments.

Available Lysine in Foods: A Brief Historical Overview

A brief historical overview is presented on the development of the science addressing lysine bioavailability in foods. Early observations that dietary protein utilization did not always correlate with gross amino acid composition led to an understanding that the amino acid lysine, in particular, can be easily damaged during food processing. Conventional amino acid analysis, involving a strong acid hydrolysis step, can lead to a significant degree of overestimation of lysine in processed foods. More recently, it has been found that not only food lysine content values but also estimates of lysine digestibility and digestible lysine contents may be erroneous. Estimates of absorbed (true ileal digestible) reactive lysine are accurate measures of available lysine. Technically, bioassays such as the slope-ratio assay determine utilized rather than available lysine.

Fontes protéicas e energéticas com diferentes degradabilidades ruminais para novilhos de corte

The objective of this study was to determine the effect of synchronization of starch (finely ground or steam-flaked corn) and protein (soybean meal or urea) rumen degradation on dry matter intake, total tract digestibility and rumen parameters of finishing Nelore steers. Four Nelore steers (300 kg LW) were utilized in a 4 x 4 Latin Square design, 2 x 2 factorial arragment: two corn processing methods (fine grinding vs. steam flaking) and two protein sources (soybean meal vs. urea). The diets contained 13% grass hay and 87% concentrate. Steam flaking decreased (p < 0.01) starch concentration in duodenal digesta, which would explain lower ruminal pH (p < 0.15) and concentration of N-NH3 (p < 0.01), plasma urea-N concentration (p < 0.01); and the increased molar concentration of ruminal propionate (p < 0.01). As compared to fine grinding, steam-flaking corn increased (p < 0.01) total tract digestibility of starch (98.8 vs. 88.6%), but decreased (p < 0.01) NDF digestibility (41.9 vs. 12.1%). Protein sources had no effect on the evaluated variables. Increasing starch degradability through steam-flaking of corn improved dietary protein utilization by beef steers.

Dietary plant protein utilization in Atlantic cod, Gadus morhua L.

The present trials aimed to investigate the effects of replacing fish meal with plant proteins in diets for cod, using a regression design where fish meal constituted the control. The plant protein diets were formulated to meet the amino acid requirements according to NRC (1993) and contained corn gluten meal, soybean meal, a mixture of these, or a mixture of wheat gluten meal and soybean concentrate. The plant protein fraction constituted up to 440 g kg )1 of the extruded diet. Two feeding experiments were conducted, one at high (11 � C) and one at low (6.5 � C) temperature. High growth and feed utilization were obtained in all diet groups at both temperatures. However, only in Exp.1 (11 � C), growth and feed utilization were linearly reduced by increases in dietary soybean and corn gluten meal, while no such effect was detected in Exp.2 (6.5 � C). Reductions in protein retention were seen at both temperatures with use of all evaluated plant protein sources. Due to large amounts of plant protein ingredients in diet, differences in diet amino acid composition were seen. These were partly reflected in the muscle free amino acid pool. Dietary plant ingredients did not affect whole body, liver or muscle proximate compositions, or liver indices. In both experiments, blood parameters were within the range of earlier reported normal values and indicated, together with low mortality, good fish health status. The results show that there is high potential to use protein-rich plant ingredients in diets for Atlantic cod.

EFFECT OF MIXED PROTEIN SCHEDULES ON NILE TILAPIA {ORE0CHROMIS NILOTICUS) PERFORMANCE IN COMBINATION WITH SOME FEED ADDITIVES I-MIXED PROTEIN SCHEDULES AND SODIUM CHLORIDE

The experiment was designed in a (4x3) factorial arrangement of treatments to investigate the effect of four different mixed protein schedules and three dietary Na/K ratios on Nile tilapia performance. The four protein schedules were achieved by alternating the diet (A ; 31%CP)and diet (B;24°/oCP)as follows (6-days~AX(5days~A/lday-B), (4days-A /2days-B) and (3days-A /3days-B).Meanwhile, sodium chloride was added to study the effect of Na/K ratio of 0.5 ,1.5 and 2 on utilization of dietary protein, amylase and lipase activity and serum thyroid hormone level. Moreover, the interaction between mixed protein schedules and Na/K ratio has been investigated. The results are summarized as follows: - The optimal protein schedule for tilapia performance was either