Percent Protein Diet Research Articles

Reproductive Performance of Osteochillus vittatus Outside of the Natural Environment

Osteochilus vittatus is a species of bonylip barb in the Cyprinidae family of freshwater fish. Reproductive performance of O. vittatus outside of the natural environment is one of the important aspects to be observed. This study’s goal was to assess O. vittatus’s reproductive activity outside of its natural habitat. The research was carried out at the Research Institute for Fish Breeding, Subang, West Java from August to December 2021. Fifty females and thirty males were kept in concrete ponds. The fish were fed a 38 percent protein diet, and their gonad development was monitored monthly. Fish that had matured gonads were spawned and their reproductive performance was observed. The sperm motility and velocity of O. vittatus males were analyzed using a sperm analyzer (CASA). The ovi somatic index was 29.671±98.14 percent, total fecundity was 167,167±7371,11 eggs/100 g female, fertilization rate was 43.97±31.70 percent and hatching rate was 57.50±38.62 percent. The sperm volume was 12.42±4.19 mL, with percent motility and velocity of 93.50±4.36 and 84.00±3.83 respectively. The percentages of static, non-progressive motile, and progressive motile of fish sperm were 4.075±3.88, 103.28±19.02, and 29.85±16.32 percent respectively. Based on the study, we can conclude that O. vittatus has the ability to reproduce outside of its natural habitat.

Weight gain during the menopause transition: Evidence for a mechanism dependent on protein leverage.

Weight gain during the menopause transition: Evidence for a mechanism dependent on protein leverage.

The contribution of nutrition and quality of sleep and happiness in under-five-year-old children.

This study aimed to evaluate the relation between happiness perception of children and quality of sleep, appetite, dietary intake and nutritional status. A cross-sectional study evaluating happiness, quality of sleep, appetite, dietary intake and nutritional status in 296 Indonesian children less than five-years of age. There was no significant difference on perceived happiness between urban and rural areas (P = 0.087). The proportion of children that are perceived as happy by mothers (55.1%) is significantly higher (p < 0.001) as perceived as happy by fathers (50.7%). A significant lower dietary energy intake with a higher percentage of dietary protein to total energy intake was observed among those children that are perceived as happy. However, after adjusted to body weight, there was no significant difference in the amount of protein intake between those perceived as happy and unhappy. Amongst the nutritional status indicators, this study found a significantly higher Height-for-Age Z score among the children that perceived as happy. Height-for-age Z score and dietary protein intake in children aged 2-5 years are associated with quality of sleep and appetite, and may therefore affect children's happiness. Not only parental care but also appropriate nutrient intakes influence the child's happiness.

Impact of Carbohydrate on Glucose Variability in Patients with Type 1 Diabetes Assessed Through Professional Continuous Glucose Monitoring: A Retrospective Study

IntroductionThe aim of this study was to objectively analyze the correlation between dietary components and blood glucose variation by means of continuous glucose monitoring (CGM).MethodsPatients with type 1 diabetes mellitus (T1DM) who received CGM to manage their blood glucose levels were enrolled into the study, and the components of their total caloric intake were analyzed. Glycemic variation parameters were calculated, and dietary components, including percentages of carbohydrate, protein and fat in the total dietary intake, were analyzed by a dietitian. The interaction between parameters of glycemic variability and dietary components was analyzed.ResultsSixty-one patients with T1DM (33 females, 28 males) were enrolled. The mean age of the participants was 34.7 years, and the average duration of diabetes was 14 years. Glycated hemoglobin before CGM was 8.54%. Participants with a carbohydrate intake that accounted for < 50% of their total caloric intake had a longer DM duration and a higher protein and fat intake than did those with a carbohydrate intake that accounted for ≥ 50% of total caloric intake, but there was no between-group difference in total caloric intake per day. The group with a carbohydrate intake that accounted for < 50% of their total caloric intake also had lower nocturnal continuous overlapping net glycemic action (CONGA) 1, − 2 and − 4 values. The percentage of protein intake had a slightly negative correlation with mean amplitude of glycemic excursions (MAGE) (r = − 0.286, p < 0.05) and a moderately negative correlation with coefficient of variation (CV) (r = 0.289, p < 0.05). One additional percentage of protein calories of total calories per day decreased the MAGE to 4.25 mg/dL and CV to 0.012 (p < 0.05). The optimal dietary protein percentage for MAGE < 140 mg/dL was 15.13%. The performance of predictive models revealed the beneficial effect of adequate carbohydrate intake on glucose variation when combined with protein consumption.ConclusionsAdequate carbohydrate consumption—but not more than half the daily total calories—combined with protein calories that amount to approximately 15% of the daily caloric intake is important for glucose stability and beneficial for patients with T1DM.Electronic supplementary materialThe online version of this article (10.1007/s13300-019-00707-x) contains supplementary material, which is available to authorized users.

Dietary amino acid requirements of pebbly fish, Alestes baremoze (Joannis, 1835) based on whole body amino acid composition

Alestes baremoze is a valuable food fish with a wide geographical distribution in East, North and West Africa. Currently, the nutritional requirements of A. baremoze have not yet been determined, which hinders attempts towards developing appropriate feed formulations for its culture. This study was thus conducted to estimate essential amino acid (EAA) requirements of A. baremoze using the A/E ratio method, as a guide in formulating its diet. Fish samples used in the study were categorised into four classes according to their fork lengths (1–12 cm; 13–24 cm; 25–36 cm and 37–48 cm), with each class consisting of 10 fish. Results from the amino acid composition analysis revealed significant difference (P < 0.05) in the concentration of tryptophan, lysine, methionine, threonine, phenylalanine, isoleucine and valine amongst the different class sizes of A. baremoze. The A/E ratios of A. baremoze muscle tissue were in the same range with those obtained from other fish species, except for tryptophan. When expressed as a percentage of dietary protein, the EAA requirements of A. baremoze, were however not significantly different (P > 0.05) within the four classes. The EAA requirement profiles for A. baremoze were found to be similar to those observed in other omnivorous fish species. Considering the importance of A. baremoze as a potential species for freshwater aquaculture, the present data provides guidance to the development of test diets with appropriate amino acid inclusions until dose response treatments are carried out.

Reduced fishmeal allowance with constant protein input for juvenile channel catfish Ictalurus punctatus

In this study, we evaluated different dietary fishmeal and protein levels on growth performance, intestinal structure and intestinal microbial community of juvenile channel catfish, Ictalurus punctatus. A total of 1800 fish distributed into 36 tanks were fed with nine different diets containing three protein levels (300, 330 and 360 g/kg) with three fishmeal (FM) levels (0, 30 and 60 g/kg) for 90 days. The results showed that significant interactions between the protein level and FM level were observed in final weight (FW), weight gain (WG), Na⁺, K⁺‐ATPase and alkaline phosphatase (AKP) activities. The significant lowest FW, WG, Na⁺, K⁺‐ATPase and AKP activities were observed in fish fed with no fishmeal and 300 g/kg protein dietary while the highest were shown in 60 g/kg fishmeal and 330 g/kg protein treatment. Additionally, the microvillar length of the mid‐intestine in catfish was significantly affected by the interaction between dietary protein level and fishmeal level. The intestinal samples were dominated by three major phyla, Firmicutes, Proteobacteria and Fusobacteria. Genera Romboutsia and Turicibacter accounted for probably 800 g/kg of the phylum Firmicutes; meanwhile, genus Cetobacterium represented more than 900 g/kg of the phylum Fusobacteria. In conclusion, this study indicated that channel catfish juveniles can be fed with a practical diet without fishmeal as long as the protein level increased to 360 g/kg; however, if the percentage of dietary protein was 300 g/kg, it seemed that fishmeal need to be supplied as a protein source.

Dietary protein influences the life-history characteristics across generations in the African striped mouse Rhabdomys.

The level of dietary protein determines the onset of reproduction, affects offspring growth and maturation, and hence influences life-history traits and fitness. However, to date, the long-term life-history consequences of protein deficiency are not well understood. We studied the transgenerational effects of different levels of dietary protein on the life-history and level of maternal behavior of the striped mouse Rhabdomys dilectus chakae in captivity. Breeding pairs were assigned to three treatments based on the percentage of dietary protein: baseline (BP; 19%); high protein (HP; 24%); and low protein (LP; 10%). Reproductive output and offspring ontogeny was diminished in the LP treatment compared to the other treatments. Transgenerational effects were studied by breeding F2 females raised on the LP or HP diets on the same (HP-HP, LP-LP) or altered diets (HP-LP, LP-HP). The LP-LP treatment had no reproductive success, while reproductive capacity in the remaining treatments was determined mainly by the diet of mothers at breeding. Pups from protein-restricted females (LP, HP-LP) showed post-weaning compensatory growth. Timing of sexual maturity was age-dependent in female and mass-dependent in male offspring. Females fed low protein diets during breeding (LP, HP-LP) displayed lower levels of maternal behavior than females from the other treatments. This study demonstrates that the level of dietary protein influences the life-history of R. d. chakae in predictable ways. The taxon responds to changes in dietary protein at breeding, largely regardless of its nutrition during rearing. Such phenotypic flexibility in life-history parameters allows Rhabdomys to adaptively respond to unpredictable environmental changes.

Differential effects of dietary protein on early life-history and morphological traits in natterjack toad (Epidalea calamita) tadpoles reared in captivity

The production of high quality amphibian larvae through optimal diets is a critical component of amphibian conservation breeding programs. Larval period, survival, body weight and total length are frequently used as metrics of adequate nutrition. However, the effects of nutrition on tadpole and metamorph morphology are rarely tested in detail. In the present study, we analyzed the most common metrics and six other larval and post-metamorphic morphological traits in natterjack toads (Epidalea calamita) fed with three different commercial fish diets, varying in protein content (32.0%, 38.3%, and 46.2%). Our results suggest that early life-history (tadpole growth, development, and survival) and morphological traits of E. calamita tadpoles are differentially affected by the percentage of dietary protein. As protein content increased, tadpoles exhibited larger bodies along with shorter tail fins; however, with no significant differences in total length. Larval period was similar across treatments but mortality was lower in high-protein diet. At high-protein diets the metamorphs revealed significantly longer bodies, and wider heads and hind legs, but there was no significant difference in the average weight across all dietary treatments. Based on our results, feed containing 46.2% protein promotes growth, development and survival of E. calamita tadpoles better than either of the other two feeds tested. The use of other body measures beyond weight, tadpole total length, and snout-vent length in studies of amphibian nutrition in captivity may assist the selection of appropriate diets to optimize tadpole survival and metamorph fitness.

Investigating the appropriate mode of expressing lysine requirement of fish through non-linear mixed model analysis and multilevel analysis

Accurate estimates of lysine requirement are essential to fish feed formulation. However, controversy exists regarding the most appropriate mode to express lysine requirement. In the fish nutrition literature, essential amino acid (AA) requirement has been expressed as a percentage of diet, a percentage of dietary crude protein or a ratio to dietary digestible energy (DE). The controversy lies in the different assumptions regarding the effects of dietary protein and DE on lysine requirement. Non-linear mixed model analysis and multilevel analysis were carried out to investigate whether dietary protein or DE affected lysine requirement of fish. The non-linear mixed model analysis suggests that expressing lysine requirement as a percentage of dietary protein provides a better goodness of fit to the modelling dataset than expressing requirement as a fixed concentration of diet, which in turn is generally better than expressing requirement as a ratio to DE. Results from the multilevel analysis confirm that dietary protein content has a significant effect on lysine requirement, while DE does not. The findings of the present study could contribute to a better understanding of the underlying dietary factors that affect AA requirements of fish. The results of the present study could also be useful for developing nutritional guidelines and feed formulations for fish.

Dietary protein requirement of juvenile shi drum, Umbrina cirrosa (L.)

This study was undertaken to determine the dietary protein requirement of shi drum (Umbrina cirrosa L.) with an initial weight of 86.3±0.4 g. The fish were fed five isoenergetic diets containing dietary protein levels ranging from 35% to 59% by 6% increments [the estimated digestible protein (DP) levels ranged between 29.6% and 52.8%], and the growth response over a 10-week period was monitored. Each experimental diet was given to triplicate groups of fish. The final weight, weight gain and daily growth coefficient increased with the dietary protein level, reaching a plateau at the dietary level of 47% protein. The feed conversion ratio improved with increasing dietary protein level. The daily feed intake was significantly lower in fish fed 53% and 59% protein diets compared with those fed 35% protein diet. However, protein intake showed an increasing trend with increasing dietary protein and became significantly different between the 59% and the 35% protein diets. The protein efficiency ratio, protein retention and condition factor were not affected significantly by the dietary treatments. The final body composition was not influenced by the treatments. The recommended dietary protein percentage and DP/digestible energy (DE) ratio for juvenile shi drum diets are 51.4% (45.6% DP) and 28.5 g DP MJ DE−1 respectively.

Egg and whole-body amino acid profile of African bonytongue (Heterotis niloticus) with an estimation of their dietary indispensable amino acids requirements

African bonytongue, Heterotis niloticus, is a river fish from the Central and West Africa basin. The species presents a great potential for fish farming and has been increasingly raised in Central and South Cameroon. The total amino acid and proximate composition of the whole body of egg, larva, juvenile, immature, and adult Heterotis were determined. Ash, moisture, whole-body protein, and lipid contents were significantly affected by size (P < 0.05). On the other hand, the amino acid composition of the whole-body tissue, when expressed as a percentage of dietary protein, was not significantly different among ontogenetic stages (ranging from 0.2 to 400 g mean body mass). The amino acid composition of the eggs was quite different to the one of whole-body tissue with lower levels of methionine, proline, and glycine, and higher levels of arginine, histidine, isoleucine, leucine, threonine, valine, serine, and alanine. The A/E ratios of adult Heterotis muscle tissue are similar to those obtained for other fish species, except for histidine and tryptophan. Based on whole-body or muscle tissue indispensable amino acids (IAA) to A/E ratios, the IAA requirement profiles for Heterotis (from larva to adult) were estimated and are similar to those of other omnivorous fish species, except for tryptophan and histidine.

Nutritive value of partially dehulled and extruded sunflower meal for post-smolt Atlantic salmon (Salmo salar L.) in sea water

This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high-temperature extruded (≤149°C) partially dehulled SFM (SFMEX) for post-smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (‘Guelph system’) for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ∼116 g) in 4000-L outdoor fibreglass tanks supplied with 25–40 L min−1, filtered, oxygenated (dissolved oxygen, 7.0–8.5 mg L−1), 11–12°C sea water (salinity, 29–31 g L−1), were fed twice daily to satiation one of five steam-pelleted dry diets that contained 422 g of digestible protein (DP) kg−1 and ∼16.4 MJ of digestible energy (DE) kg−1 on a dry weight basis for 84 days. Low-temperature-dried anchovy meal (LT-AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFMEX progressively replaced up to 33.0% of the DP provided by LT-AM in the basal diet (SFMEX≤271 g kg−1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39–1.45% day−1), feed efficiency (1.19–1.26), percentage of dietary protein retained (45.8–47.5), gross energy utilization (46.5–49.4%), per cent survival (96.0–99.3) or terminal whole body and muscle proximate compositions. We conclude that SFMEX can comprise ≥271 g kg−1 of the dry diet or ≥22.7% of the digestible dietary protein of post-smolt Atlantic salmon in seawater without any adverse effects on their performance.

Fecal NIRS prediction of dietary protein percentage and in vitro dry matter digestibility in diets ingested by goats in Mediterranean scrubland

A method to elucidate the nutritional value of goats’ diets in ligneous environments is needed. Near infrared spectroscopy (NIRS) can be applied to fecal material to establish statistical relationships between the reflectance of fecal samples in the near infrared region and the diets consumed. We tested fecal NIRS for the prediction of dietary crude protein content (CP) and in vitro dry matter digestibility (DMD) in Damascus goats browsing Mediterranean scrubland dominated by Pistacia lentiscus and Phyllirea latifolia. Two datasets consisting of pairs of feces and dietary data were used; for the first ( n = 151), goats were hand-fed different ratios of legume hay and concentrate ( n = 60), or combinations of three browse species and concentrate ( n = 91), while for the second ( n = 153), data were collected during 10 observation days with grazing goats. On these days, pairs of dietary information and feces were derived from one observed goat but feces were also sampled from 12 to 15 resident goats grazing in the same paddock. Each dataset served for the validation of NIRS equations established with the other. For CP, in dataset 1, the values of R 2 for calibration were 0.98 (all data) and 0.90 (only browse) and the standard error of cross validation (SECV, internal validation) was 0.50%. When samples from dataset 2 were used for external validation, R 2 varied between 0.55 (all goats) and 0.85 (observed goats) and the standard error of prediction (SEP, external validation) was 2.2 and 1.6% in the same order. Using dataset 1, we determined that the condition for 95% confidence that two goats ate the same diet was a Mahalanobis distance ( H) of less than 0.5 between their fecal spectra. Using dataset 2, the values of R 2 for calibration varied between 0.90 (all goats) and 0.92 (only observed goats and residents with H < 0.5 from their fecal spectra) and SECV was approximately 0.50%. When samples from dataset 1 were used for external validation, R 2 was 0.47 (calibrations with all goats) and 0.50 (only observed goats and resident goats with H < 0.5 from the observed goats), and SEP varied between 0.8 and 1.2% in the same order. Lower R 2 and accuracy were found for in vitro DMD than those for CP. A dataset containing feces and dietary information from observed goats seems to be accurate and cost-effective to implement fecal NIRS determination of dietary CP and DM digestibility in grazing goats.

Isoleucine, leucine, and valine requirement of juvenile Indian major carp, Cirrhinus cirrhosus (Bloch, 1795)

Background. Mrigal, Cirrhinus cirrhosus (Bloch, 1795) (junior synonym C. mrigala ), is one of the most widely cultured Indian major carps.The main aim of this study was to quantify the dietary isoleucine, leucine, and valine requirements of mrigal juveniles.Materials and methods. Growth studies were conducted with juvenile mrigal to determine the minimal requirements for the branched-chain amino acids: isoleucine, leucine, and valine.The experimental diets were formulated from purified ingredients to contain 40% crude protein. Casein and gelatin served as protein sources and were supplemented with crystalline L -amino acids to provide an amino acid pattern found in mrigal muscle protein. The amino acids for which the requirements were being determined was were supplemented at varying levels. Dietary inclusion levels for isoleucine ranged from 0.88 to 1.45%, for leucine from 1.36 to 2.05%, and for valine from 1.23 to 1.75%.Results. he optimum dietary requirements for isoleucine, leucine, and valine for mrigal, estimated using break point analysis were 1.25%, 1.73%, and 1.55% of dry diet, respectively. These values correspond to 3.12% isoleucine, 4.33% leucine, and 3.87% valine when expressed as a percentage of dietary protein. Food conversion rate, specific growth rate, and survival were better in treatments with diets containing 1.25%for isoleucine, 1.73%for leucine, and 1.55%for valine. Conclusion. Results of this study clearly demonstrated that Cirrhinus cirrhosus could utilize free amino acids for growth. Further, the findings would be useful in formulating isoleucine, leucine, and valine balanced diets in controlled production of mrigal.

Estimating nutritional status of German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae), in the field

Nutritional status of German cockroaches from the field (HUD apartments) was estimated using uric acid content to measure amount of protein consumed, and respiratory quotient (RQ) to measure fat and carbohydrate metabolized. Initial trials demonstrated the stability of these two indicators as nymphal cockroaches grow and with timing of meals. Nutrient consumption (and presumed availability) was estimated by comparing uric acid content and RQ of nymphal cockroaches collected from kitchens of HUD apartments with those reared in the laboratory and provided a series of meridic diets. Uric acid content was linearly related to percentage of dietary protein ( y=6.2 x−32.07, r 2=0.96) and RQ was linearly related to log 10(% fat:% carbohydrate) ( y=−0.148Log( x)+0.790, r 2=0.68). Field-collected German cockroaches contained 10.9±7.7 to 22.9±5.1 μg/mg uric acid and RQ of 0.770±0.024 to 0.803±0.260. Comparatively, cockroaches provided rodent chow had greater uric acid content (125.1±9.6 μg/mg) and RQ (0.878±0.022). Employing linear calibration and these regressions, diet consumed by German cockroaches in the field was estimated at 7±3% to 9±3% protein and equivalent amounts of carbohydrates and fat as an energy source. German cockroaches in the field consume less protein and carbohydrates, and more fat compared to those provided a standard laboratory diet such as rodent chow. Diet available in the field is considered suboptimal, resulting in physiological stress; the biological implications of this stress are discussed.

Changes in Body/Tissue Composition of Rats in Relation to Dietary Protein Levels during Rehabilitation.

Effect of rehabilitation with marginally sub-optimal and adequate levels of dietary protein following a 50 per cent diet restriction for 10 days was studied in adult rats, The data revealed hyperphagia, supernormal weight gain and greater food efficiency in rehabilitated animals which progressively tapered off on days 9 and lO, irrespective of the dietary protein level. However, the values remained slightly higher than their respective controls. The food efficiency ratio and nitrogen balance which followed the above pattern, on the other hand, returned to control levels in the group that was refed 20 percent protein diet. The weights of liver and muscles of 20 per cent protein diet group were higher than those of 10 per cent protein diet group, while the fat pad weight showed a reverse trend. This was observed only in the case of control and rehabilitated animals. The liver lipid and protein concentrations were less in rehabilitated rats as compared to their ad libitum fed counterparts. The carcasses of control as well as rehabilitated animals on 10 per cent protein diet had less moisture and more fat content than those on 20 per cent protein diet. The carcass in 20 per cent protein diet group had a higher protein content. A linear correlation was observed between body weight and body fat, while a reciprocal relationship existed between the body fat and body water regardless of whether the rats were rehabilitated or restricted fed.

Effects of dietary protein level on growth and body composition in mice divergently selected for fat content

A study was conducted to examine the effects of dietary protein percentage and selection for divergence in fat content on growth and body composition in mice. The three lines used had been selected as follows: high epididymal fat pad weight as a percentage of body weight (HF), low epididymal fat pad weight as a percentage of body weight (LF) and a randomly selected control (RC). Mice from each line were allotted at weaning (3 wk of age) to one of four dietary protein percentages: 12, 16, 20, and 24%. Growth and efficiency of feed conversion were measured at 2-wk intervals and mice were killed and body composition was measured at 9-wk of age. Overall, HF mice grew faster were more efficient at converting feed to body weight gain, and had empty carcasses with a higher percentage of tat (P &lt; 0.05) and a lower percentage of protein than LF mice. However, fat-free empty-body protein and ash percentages, protein gain, protein gain:protein intake, and protein gain:energy intake ratios were not different among genotypes. As dietary protein percentage increased, gain:feed ratio increased quadratically (P &lt; 0.05) in all genotypes and was maximized m mice consuming 16% protein. Protein gain was maximized in mice consuming 16% protein. Feeding diets providing protein percentages above or below 16% depressed protein gain and protein gain:energy intake ratio. Genetic line-by-dietary-protein-level interactions were generally not significant for growth, feed efficiency and body composition traits. Key words: Mice, dietary protein, growth, body composition, fat deposition

Effects of dietary protein percentage and beta-agonist administered to prepubertal ewes on mammary gland growth and hormone secretions.

The effects of dietary protein and beta-agonist, (L-644,969) on mammary growth from weaning to puberty, hormone secretions, and milk yield were studied. Twelve lambs were assigned to each treatment in a 2 x 2 factorial arrangement with dietary protein at 15 or 20% and beta-agonist at 0 or 1 ppm of concentrate. Lambs were fed pelleted concentrate to achieve a target weight gain of 260 g/d. The treatment period continued for 102 d, with protein starting on d 1 and beta-agonist on d 20. Five lambs in each group were slaughtered at the end of treatment to investigate mammary growth before puberty. The remainder were maintained, and, after lambing, daily milk yield was recorded for 7 wk and ewes were then slaughtered. In prepubertal lambs, compared with control, the 20% protein diet had no effect on any variable measured in the mammary glands, whereas beta-agonist increased (P < .05) RNA:DNA ratio. In lactating ewes, the 20% protein diet enhanced mammary gland weight, parenchyma, parenchymal dry fat-free tissue (P < .05), and parenchymal fat (P < .01). The beta-agonist reduced mammary gland weight (P < .01), parenchyma, parenchymal dry fat-free tissue (P < .05), and parenchymal fat (P < .01). There was a nonsignificant trend for increased milk yield for ewes fed the 20% protein diet and decreased milk yield for beta-agonist. The beta-agonist increased somatotropin concentration, but there was no evidence that increased somatotropin concentration induced mammogenesis in lambs. In conclusion, increased dietary protein may play a role in stimulating mammogenesis in rapidly growing lambs before puberty.

Use of a Quadratic Response Model to Estimate Optimum Combinations of Nutritional Variables

Abstract Quadratic response surface modeling was used to estimate the optimum combination of feeding rate and percentage of dietary protein for growth of 3–6-week-old blue tilapia Tilapia aurea. Sixteen treatments consisting of all combinations of four dietary protein levels and four feeding rates were replicated in a recirculating-water aquarium system at 23°C for 3 weeks. Quadratic response surfaces fitted to the data were similar for the two replicates and identified treatment combinations supporting maximum growth. Dietary protein, feeding rate, and their interaction significantly affected food conversion by blue tilapia. The quadratic response surface model yielded results that generally agreed with published values for juvenile tilapias. This approach offers a promising research pathway to project optimum culture conditions from short-term trials.

Comparison of satiate feeding and restricted feeding of channel catfish with various concentrations of dietary protein in production ponds

A 2 × 3 factorial experiment was conducted with channel catfish ( Ictalurus punctatus) using satiate or restricted feeding with 26, 32 or 38% dietary protein concentrations in practical catfish diets. The diets were similar to commercial catfish feeds, with major ingredients being soybean meal, ground corn, fish meal and wheat middlings, and small amounts of vitamin and mineral supplements. The protein concentration of the diets was increased by substituting a fixed ratio of soybean meal to fish meal (5 : 1) for corn. Essential amino acids in all diets were adequate. Energy concentration of the diets was not regulated. Fish were grown from 60 g to marketable size at a stocking density of 13 590 fish per ha in 400-m 2 earthen ponds. Fish in the satiation feeding group were fed as much as they would consume each day for the 125-day spring-summer experimental period. Fish in the restricted feeding group were not fed more than 60 kg/ha day −1; this rate was reached at approximately day 70 of the experiment. There was a significant interaction between feeding regime and dietary protein concentration on weight gain. Weight gain of fish fed to satiation decreased linearly as dietary protein content increased, while weight gain of fish under restricted feeding increased linearly with increasing dietary protein percentage. Weight gain of fish fed to satiation was positively correlated with feed consumption, which decreased linearly as dietary protein concentration increased. Dietary protein concentration had no influence on feed conversion under satiate feeding, but had a positive effect on feed conversion under restricted feeding. Feed conversion of fish fed to satiation was higher than that of fish under restricted feeding. Dietary protein had a quadratic effect on dressing percentage; it increased as dietary protein increased from 26 to 32% and decreased as dietary protein increased from 32 to 38% for both satiate and restricted feeding. Body fat content of fish in both feeding regimes was negatively correlated with the protein/digestible energy ratio of the diets. Body fat content of fish fed to satiation was higher than that of fish fed at the restricted rate. These results indicate that feeding rate significantly influences weight gain and body composition of channel catfish. In addition, channel catfish can obtain sufficient nutrients from a 26%-protein, amino-acid-balanced practical diet for maximum weight gain with satiate feeding, but when fed to less than satiation higher-protein diets are required.