Digestible Protein Intake Research Articles

Development of dynamic growth and body composition models for Nile Tilapia (Oreochromis niloticus): An exploratory approach to protein and energy metabolism

The aquaculture sector has been steadily growing and thus there is an increasing need to develop mathematical models that allow the estimation of production-related parameters. Prediction of fish growth, feed requirements and waste outputs, are essential in order to ensure the profitability and sustainability of the production activities. Bioenergetic models have been widely used to estimate growth based on energy budgets, but they have some limitations by not explicitly considering the mass-balance of the main macronutrients (e.g., protein). In turn, nutrient-based models are more explanatory, as they consider both energy and nutrient inputs, and estimate fish growth by simulating nutrient accumulation in the fish body. Although some bioenergetic and nutrient-base models for predicting Nile tilapia growth exist in the literature, their suitability is not entirely clear, since their development is often based on uncertain or suboptimal criteria (e.g., relying solely on calibration goodness-of-fit measures).In this work, Nile tilapia growth datasets covering a wide range of rearing conditions and feed compositions were collected from the scientific literature. An exploratory analysis of the collected data was performed to clarify the relationships between energy/protein intake and gain. In this analysis, a direct relationship was observed between digestible energy intake and energy gain, as well as between digestible protein intake and protein gain. Protein gain showed better efficiency than energy gain, even at higher intake levels and without clear evidence of a saturation effect. While digestible energy intake negatively affects energy retention efficiency, digestible protein intake does not significantly impact protein retention efficiency. Furthermore, while energy retention efficiency varies with fish body weight, the same effect was not observed for protein retention efficiency. Finally, though DP/DE ratio has no apparent effect on energy retention efficiency, it seems to negatively affect protein retention efficiency. Considering these observations, plausible growth models with different levels of complexity were developed and calibrated under a diverse set of assumptions. Additionally, two growth models already published for Nile tilapia were calibrated using the same datasets, and their performance was compared with the models developed in the present study. The exploratory analysis of the data suggests a direct relationship between digestible energy intake and energy gain, and between digestible protein intake and protein gain. Furthermore, fish body weight seems to affect the energy retention efficiency. The results of model evaluation showed that energy-protein flux models (EP models) have lower errors in predicting fish growth than pure bioenergetic models (MAPEbw ∼ 9% against ∼13%, respectively), showing the importance of considering protein intake when estimating Nile tilapia growth. Furthermore, assuming the fixed standard metabolic body weight exponents of 0.80 and 0.70 (for energy and protein, respectively), rather than estimating them from the data, seemingly improved the predictive ability of the models. This approach demonstrates the benefits of coupling bioenergetics with nutrient-based models to predict growth and body composition of Nile tilapia along time.

Interactive effects of protein and energy intake on nutrient partitioning and growth in Nile tilapia

Studies of fish growth response to changes in dietary protein and energy content are often conducted with fish fed to apparent satiation or at fixed percentages of their body mass. Such designs result in simultaneous changes in protein and non-protein energy intake, thereby failing to distinguish their separate effects on nutrient partitioning and growth. The present study was designed to address this limitation and test the existence of distinct protein- and non-protein energy-dependent growth phases in Nile tilapia (Oreochromis niloticus). All-male Nile tilapia (63 g, SD = 1.3) were subjected to an 8 × 2 factorial design consisting of eight levels of digestible protein (DP) intake (0.44–1.25 g/day) and two levels of non-protein digestible energy (NPDE) intake (16.0 and 22.4 kJ/day). Fish (n = 960) were housed in 60-litre tanks with two replicates per treatment and hand-fed twice a day for 42 days. Nutrient balances were calculated from changes in body mass, analysed body composition and digestible nutrient intake. Linear regression models were compared to linear-plateau regression models to determine whether protein gain followed distinct protein- and non-protein energy-dependent phases or not. Body mass gain increased linearly with increasing DP intake and was significantly higher (2.6 vs 2.3 g/d, P < 0.05) in fish receiving a high NPDE intake. This increase mainly reflected a higher mean fat gain (0.29 vs 0.20 g/d) rather than a higher protein gain (0.42 vs 0.39 g/d) in fish fed a high vs low level of NPDE intake. The comparison of linear and linear-plateau models did not give clear support for the presence of distinct protein and non-protein energy-dependent phases in protein gain. These results indicate that non-protein energy intake has a modest protein-sparing potential, and that protein gain is simultaneously limited by protein and energy intake in Nile tilapia.

Animal‐defined resources reveal nutritional inadequacies for woodland caribou during summer–autumn

AbstractPopulations of woodland caribou (Rangifer tarandus caribou) are declining throughout their range and many are at risk of extirpation, yet the role of nutrition in these declines remains poorly understood, in part owing to a lack of information about available nutritional resources during summer. We quantified rates of intake of digestible protein and digestible energy by tame caribou foraging in temporary enclosures in the predominant plant communities of northeastern British Columbia, Canada, during summer–autumn and compared intake rates to daily requirements for protein and energy during lactation. We tested hypotheses related to the nutritional adequacy of the environment to support nutritional requirements during lactation (with and without replenishment of body reserves) and simulated scenarios of foraging by caribou in these plant communities to better understand how wild caribou could meet nutritional demands on these landscapes. Nutritional resources varied among plant communities across seasonal, ecological, and successional gradients; digestible energy intake per minute and per day were significantly greater in younger than older forests; dietary digestible energy and per‐minute and daily intake of digestible protein were greater, though not significantly so, in younger than older forests; and dietary digestible protein was greater in older than younger forests, though differences were not significant. Tame caribou were unable to satisfy protein and energy requirements during lactation, even without replenishment of body reserves, at most sites sampled. Further, foraging simulations suggested widespread nutritional inadequacies on ranges of wild caribou. Selection for habitats offering the best nutrition may mitigate some nutritional inadequacies, but given low availability of vegetation communities with high nutritional value, performance (e.g., calf production, growth, replenishment of body fat and protein) of caribou may be depressed at levels of nutrition documented herein. Our results, coupled with recent measurements of body fat of wild caribou in northeastern British Columbia, refute the hypothesis that the nutritional environment available to caribou during summer in northeastern British Columbia is adequate to fully support nutritional demands of lactating caribou, which has implications to productivity of caribou populations, recovery, and conservation.

The interaction of feeding regime and dietary specification on growth and nutrient utilisation in Yellowtail Kingfish Seriola lalandi

Feeding regimes on fish farms are often disrupted for logistical reasons or adverse environmental conditions. Issues such as these are commonplace with respect to the sea pen culture of Yellowtail Kingfish Seriola lalandi (YTK) in Australia. These disruptions represent periods of feed restriction which lead to reduced productivity. However, production losses may be ameliorated using different feeding strategies or the use of nutrient dense aquafeeds. To examine the potential of these options we conducted an eight-week experiment with sub-adult YTK (stocking weight ~ 0.80 kg) investigating three feeding regimes crossed with two dietary specifications. The feeding regimes were selected following industry consultation; feeding once daily 7 days per week (control), once daily Monday to Friday (economic) or once daily on randomly selected days of the week (random). Regardless of regime all feed was offered to apparent satiation. A standard specification (Std-Spec; 386 g DP kg−1, 15.1 MJ DE kg−1) and high specification diet (High-Spec; 460 g DP kg−1 and 19.2 MJ DE kg−1) were formulated using a similar suite of ingredients. Each of the 6 treatment combinations was fed to three replicate tanks of fish and results were examined using two-way ANOVA. There was a general absence of interaction between the main effects for most production indices. Specific growth rate (SGR) and relative feed intake (RFI) were significantly better in YTK fed 7 days per week than in YTK fed under more restricted regimes, but feeding regime did not affect FCR. The SGR, FCR and condition factor of YTK were significantly better when fed the High-Spec diet than in YTK fed the Std-Spec diet. The RFI of fish fed under restricted regimes was significantly lower than YTK fed 7 days per week, irrespective of diet specification, indicating YTK were not capable of hyperphagia. However, the RFI of YTK fed the Std-Spec diet was significantly higher than YTK fed the High-Spec diet, confirming nutrient or energy density was likely controlling feed intake. Examination of data on digestible protein, fat and energy intake indicated YTK were eating primarily to satisfy their protein requirement and sub-optimal energy intake was indirectly limiting growth. Our results demonstrate YTK have a limited capacity to increase their feed intake as a means of overcoming moderate feed restriction in order to meet nutrient and energy demands. We recommend feeding YTK of this size a high specification diet to apparent satiation once per day 7 days a week in order to maximize their growth, feed efficiency and physical condition.

Evaluation of xylanase and a fermentable xylo-oligosaccharide on performance and ileal digestibility of broiler chickens fed energy and amino acid deficient diets.

The objective of this study was to evaluate the effect of a product consisting of a combination of xylanase and xylo-oligosaccharide (STBIO) on performance and ileal digestibility of broiler chickens fed energy and amino acid (AA) deficient diets. Day-old male Ross 308 broiler chicks were randomly allocated to 8 pens per treatment, with 25 chicks per pen. Treatments based on wheat-corn-soybean meal diets were arranged in a 3 × 2 factorial design: a positive control that met or exceeded nutrient recommendations (PC), a negative control diet with a 50 kcal/kg apparent metabolizable energy (AME) reduction (NC1) and NC1 with a 3% reduction in AA content (NC2), each with or without supplementation of 100 g/t of the STBIO. Body weight gain (BWG), feed intake, feed conversion ratio corrected for mortality (FCR) and the European production efficiency factor (EPEF) were recorded from 0 to 42 d. On d 42, ileal samples were collected to determine dry matter (DM), organic matter (OM), ash, protein and energy digestibility. A significant interaction was observed for BWG and feed intake (P < 0.001). The energy and AA reduction reduced (P < 0.05) BWG when compared to the PC. The effect of STBIO on BWG was greater in NC1 (+451 g/bird) than in NC2 (+314 g/bird) or PC (+176 g/bird) diets (P < 0.05), and that in NC2 with STBIO was equal to that in PC without STBIO, and that in NC1 with STBIO was equal to that in PC with STBIO. No interactions were observed on the EPEF or FCR; however, STBIO improved EPEF (P < 0.001) and FCR (P < 0.001) irrespective of the energy reduction or AA density. The intake of digestible DM, OM, ash and energy for the finisher period was increased with STBIO supplementation (P < 0.01). A significant interaction was observed for the intake of digestible protein. NC1 and NC2 reduced the intake of digestible protein; however, when STBIO was supplemented, it was improved in both diets to similar levels to the PC. The stimbiotic supplementation improved performance of broiler chickens fed all diets, particularly those deficient in AME and AA.

Effect of Dietary Protein Level during Estrus Cycle: Nutrient Digestibility, Quality of Embryo and Pregnancy Rate by Embryo Transfer in Thai Crossbred Goats during Hot Season

Tis study aimed to evaluate the embryo quality and embryo transfer rate of Thai crossbred goats fed different levels of protein in total mixed rations (TMR) during the hot season. Twenty-four non- pregnant Thai crossbred goats with an average body weight of 26±5.9 kg were assigned with a random complete block design (RCBD). Dietary treatments contained 8, 13, and 18 % crude protein (CP) in TMR. The feeding trial lasted for 42 days. Does (female goat) were scheduled to determine embryo quality by surgical laparotomy and flushing. At the end of the feeding trial, the digestion trial was conducted by the total collection method for a 5-day period. The results showed that the average total feed intake and feed conversion ratio did not differ among all treatments (p ˃ 0.05), however, digestible protein intake had increased from 70.39, 79.77 to 89.11 g/d in 8, 13, and 18 % CP group, respectively. Increasing CP levels in TMR resulted in linearly increased goat final body weight (30.25, 28.75, and 32.00 kg), weight gain (3.00, 4.00, and 4.25 kg), and average daily gain (ADG) (87.84, 114.87 and 121.63 g/d). Embryo quality (1, 1, and 3.5 morular follicle state) and pregnancy of embryo transfer rate (25, 25, and 50 %) of the animal received CP level at 8 and 13 % less than that 18 %. These results indicated that dietary protein level during program superovulation regimen affected the good quality of an embryo and the pregnancy rate in an embryo transfer in Thai crossbred goats.

Protein and Energy Requirements for Maintenance and Growth in Juvenile Meagre Argyrosomus regius (Asso, 1801) (Sciaenidae).

The meagre is a carnivorous species and might be a suitable candidate species for the diversification of aquaculture in the Mediterranean region. This is based on its high growth and flesh quality. Nevertheless, there is little information available about its growth rates and nutrient requirements. The objective of this study was to determine the protein and energy requirements of juvenile meagre (Argyrosomus regius). Two trials for different weights of 53 and 188 g were conducted with rations from starvation to apparent satiation with the scope of studying its nutritional needs. In the first trial, the initial mean body weight of the fish was 53 g, and they were fed at feeding rates, measured as a percentage of the body weight, of 0, 0.75, 1.5, 2.5, 3.5, and 4.5%, with two replicates per treatment. In a second trial, another group with approximately 188 g of initial body weight was fed at feeding rates of 0, 0.5, 1.5, and 2.5%, with two replicates per treatment. The optimum thermal growth coefficient was obtained with a feed intake of 2.2% day-1 in trial A and 1.73% day-1 in trial B. The digestible protein (DP) intake for maintenance was determined as 0.57 g kg-0.7 day-1, the DP intake for maximum growth was 6.0 g kg-0.7 day-1, and the point for maximum efficiency in protein retention was 1.8 g kg-0.7 day-1. The requirement for digestible energy (DE) intake for maintenance was recorded at 25.4 kJ kg-0.82 day-1, the DE intake to maximize growth was 365 kJ kg-0.82 day-1, and the point for maximum efficiency in energy retention occurs with a digestible energy intake of 93 kJ kg-0.82 day-1. The requirements and retention efficiency of protein and energy in Argyrosomus regius tend to be within the range other fish species. The maintenance needs are in agreement with species with low voluntary activity and growth requirements in agreement with fast-growth species.

Differences in energy utilization efficiency of digested protein, fat and carbohydrates in snakehead (Channa striata)

This study aimed to assess if the relationship between digestible energy (DE) intake and energy retention (RE) is dependent on dietary macronutrient composition; and to quantify the energy utilization efficiency of digested protein (dCP), fat (dFat) and carbohydrates (dCarb) for growth in snakehead (Channa striata). This was achieved by conducting a 42-day feeding trial on snakehead (29.1 g) with a 4 × 2 factorial design. Nutrient digestibility, nitrogen and energy balances were measured. Four diets were formulated, which had contrasting levels of protein, fat and carbohydrates. Each diet was tested at 2 feeding levels, in order to estimate within each feeding level the relationship between DE and RE. Snakehead (a carnivore) is well able to digest starch. Starch digestibility ranged from 93% to 99.5%. The linear relationship between RE and DE intake was affected by diet. Diets with a high Carb content had a lower slope (0.45 versus 0.53 to 0.56), which indicates that DE is less efficiently used for RE. Multiple regression of RE as a function of dCP, dFat and dCarb (in g.kg-0.8.d−1) intake was also applied to estimate the energy utilization efficiency of each digestible macronutrient. A linear relationship was found between RE and dCP, dFat and dCarb. Snakehead are a lean fish, which we observed prioritise digestible protein intake for protein gain. The estimated energy efficiencies of dCP, dFat and dCarb (respectively, kNE;dCP, kNE;dFat, and kNE;dCarb) for energy retention were 53, 79 and 5%, respectively. Snakehead can digest starch at the high level but cannot metabolise digested starch for growth efficiently.

Growth performance and gonad yield of sea urchin Paracentrotus lividus (Lamarck, 1816) fed with diets of increasing protein: energy ratios

The establishment of a commercially sustainable aquaculture production of Paracentrotus lividus depends on the development of diets able to fulfil the species nutritional requirement and the production of market valuable roe. As dietary protein level and protein: energy ratio (P:E) are major limiting factors for sea urchin growth and gonad development, six isolipidic (≈ 7%) practical diets of increasing protein content (20, 25, 30, 35, 40 and 46 % dry matter, DM) and protein: energy ratios (P:E) (15, 18, 21, 24, 27 and 28 mg P/kJ) were fed to triplicate groups of adult sea urchins for 107 days to identify the dietary protein level and P:E able to promote the highest nutrient utilisation, best growth and gonad enhancement. The trial results showed that protein apparent digestibility coefficients ranged between 69 and 86 %, without significant differences among groups. Digestible energy intake and feed conversion ratio (FCR) decreased with increasing dietary protein levels and protein: energy ratios, whilst digestible protein intake remained similar in all groups. The retention and gain of protein and energy remained unaffected by dietary treatments, resulting in a specific growth rate of 0.3 % per day across treatments, and in a final body weight between 22 and 24 g. All diets significantly increased the gonadosomatic index (GSI) attaining 7.4–8.5%. Both GSI and gonad protein gain picked with a dietary P:E of 21 mg P/kJ (diet P30), whereas gonad protein content picked when P:E was 24 mg P/kJ (diet P35). These results, in association with the decreasing FCR with increasing dietary protein levels, suggest that diets with 30 % DM of protein and a P:E of 21 mg P/kJ are the most appropriate to promote both high somatic growth and high gonad yield in adult P. lividus.

Nutrient metabolism and ingestive behavior of goats fed diets containing palm tree fruit

This study aimed to evaluate the nutrient metabolism and ingestive behavior of goats fed diets containing palm tree fruits. Twenty-one female goats fed three diets, one control and two with carnauba or tucum fruits, were assigned to a completely randomized design. There was a decrease in dry matter intake (DMI) from 0.183 and 0.223 kg/day for diets containing tucum and carnauba fruits, respectively, with higher intake of neutral detergent fiber (NDF) (0.41 kg/day) for diet containing carnauba fruit. The intake of digestible protein (78.04 gDP/day) and metabolizable energy (2.51 McalME/day) from the diet with tucum fruit met the nutritional requirements of the animals. The inclusion of tucum fruits resulted in lower intake, absorption and retention of nitrogen (19.20; 14.67 and 11.55 gN/day, respectively), with N balance (%Ningested) above 60%, in addition to the increase of 0.57 Mcal/kgDM of the digestible energy of the diets. As for the ingestive behavior, the diets containing fruits of carnauba demanded more time for rumination (453.65 min/day). The inclusion of tucum fruits in diets composed of corn, soybean and Tifton 85 hay meets the requirements of growing goats as regards to digestible protein and metabolizable energy. Diets containing carnauba fruit reduce the digestibility of dry matter due to the increase in the proportion of fiber and its low quality, which, together with the low feed efficiency, suggests the inclusion of carnauba fruit in a smaller proportion for growing animals or only in maintenance diets .

Predicting nutrient digestibility and energy value for broilers.

Digestibility coefficients of nutrients, metabolizable energy (ME), net energy (NE) and the ratio of NE to ME (NE/ME) of 20 diets were measured in broiler chickens (1 to 21 d). Dietary nutrients were formulated to keep similar ME/nutrient ratios, except for dietary protein, fat, and fiber using corn, soybean meal, animal protein blend, barley, poultry oil and an enzyme mixture of xylanase, glucanase, and phytase. Digestibility coefficients of nutrients and ME were measured in battery cages under free-access of feed, while NE was measured in floor pens feeding 75% of recommended ME intake each day. NE for maintenance was calculated on basis of mean metabolic weight using a coefficient from a previous study and NE for gain was calculated by body protein and fat gains using dual-energy x-ray absorptiometry. Digestibility coefficients of protein and neutral detergent fiber (NDF) were curvilinearly related to dietary protein and NDF, respectively, while digestibility coefficients of fat and starch were linearly correlated to dietary fat and starch, respectively. The inclusion of enzymes increased the digestion coefficient of NDF to predict the digestibility of protein, NDF, fat, and starch. MEn/gross energy ratio averaged 72.5% and was correlated to protein, fat, NDF, and starch. ME values were accurately predicted from chemical characteristics, where best equations were obtained from digestible nutrients. Energetic efficiencies of ME were 72% (NE/MEn) and 68% (NE/ME) and varied by about 20 and 18%, respectively. Ratios of energetic efficiency were 68% for digestible carbohydrates; 86% for digestible fat; and 76% (NE/MEn) and 59% (NE/ME) for digestible protein. According to the lowest residual standard deviation the best nutrient components to predict energy were digestible nutrients for predicting ME values (41kcal/kg); digestible protein intake, fecal organic matter, and body fat and protein for predicting heat increment values (111kcal/kg); and combination of ME and crude nutrient for predicting NE values (140kcal/kg).

Assessing the response of hen weight, body composition, feather score, egg quality, and level of excreta nitrogen content to digestible balanced protein intake of laying hens

Ideally balanced dietary protein is critical for laying hen egg production and feed efficiency, but also affects other important characteristics. This research was designed to study the nonegg production and feed intake response of Lohmann-LSL Lite hens to 550, 625, 700, 775, and 850 mg d−1 of amino acid balanced digestible lysine (Dlys) from 27 to 66 wk of age. Data collection included hen weight (HW), feather scoring, tissue weights, egg specific gravity, egg component weights, and excreta nitrogen (N) content. The experiment was a completely randomized design and level of significance was fixed at P ≤ 0.05. Hen weight (quadratic, Q), pectoralis muscle (absolute, % – Q), and abdominal fat (absolute – linear, L; % – Q) increased with increasing Dlys intake. Although gastrointestinal segment weights and lengths were affected by Dlys intake, interpretation of results was confounded by other aspects of diet composition. Hen feather score (L) and excreta N content (Q) increased, and egg shell quality (L) decreased with increasing Dlys intake. Absolute egg component weights increased with Dlys intake, but effects on proportional weights were Q and relatively minor. In conclusion, balanced Dlys intake affected a variety of practical nonproduction characteristics in laying hens.

Effect of constant digestible protein intake and varying digestible energy levels on energy and protein utilization in Nile tilapia

In literature, the variability in the estimated optimal digestible protein to digestible energy ratio (DP/DE) is high. The present study aimed to estimate the optimal DP/DE ratio in Nile tilapia (Oreochromis niloticus) using different criteria (performance, energy and nitrogen balances parameters). Duplicate aquaria were randomly assigned to one of 16 diets. These diets covered a wide range of dietary DP/DE ratio (from 16.7 to 27 g MJ−1). DP levels ranged between 36 and 50% and DE levels between 17.5 and 22 MJ kg−1. Fish were fed restrictively based on a similar digestible protein amount at all 16 diets. Initial fish weight was 6.7 g. Broken line analysis showed that no optimal DP/DE ratio was present for Nile tilapia within the DP/DE ratio range studied. Regression analysis showed that growth declined as DP/DE ratio increased and seemed to level off at high DP/DE ratio (25 g MJ−1). FCR ranged between 0.8 and 1.1 and increased linearly with increasing DP/DE ratio. Decreasing the DP/DE ratio resulted in a linear increase in protein efficiency to a highest value of 53%. However, protein efficiency did not show a plateau or a maximum value. Moreover, decreasing the DP/DE ratio resulted in a very high fat content of the fish (over 16%). In conclusion, an optimal DP/DE ratio in Nile tilapia being fed restrictively seems to be absent or to be below 16 g MJ−1. A maximum protein deposition level is not present in 5–40 g Nile tilapia.

Partial and total replacement of fishmeal by a blend of animal and plant proteins in diets forSeriola dumerili: Effects on performance and nutrient efficiency

A 154‐day trial was performed to assess the use of an alternative protein blend (corn gluten, krill and meat meal) as a substitute for fishmeal in diets for juvenile yellowtail, using four isolipidic (140 g/kg) and isoenergetic diets (24 MJ/kg) with the same digestible protein content (50%). The control diet was FM100, without replacement, and in FM66, FM33 and FM0, fishmeal was replaced at 33 g/kg, 66 g/kg and 100 g/kg, respectively. At the end of the experiment, no differences in growth parameters were observed. Fish fed the FM0 diet exhibited the lowest survival (23%). This high mortality may be due to different factors, such as a dietary amino acid imbalance or some antinutrient factors contained in the alternative ingredients. Feed intake, feed conversion ratio, digestible protein intake and protein efficiency ratio were similar in all diets. However, digestible energy intake and protein efficiency retention were lowest in fish fed the FM0 diet. Apparent digestibility coefficients for protein, energy and amino acids diminished as a substitution for fishmeal increased. Significant differences were observed in the diet whole‐fish body profile amino acid retention (AAR) ratio for the seven essential amino acids. In summary, total fishmeal replacement by the blend assayed was not feasible for yellowtail. The FM66 diet resulted in good growth, high survival and good nutrient efficiency.

Determinação da ingestão diária de proteí­­na digestí­­vel para tilápia-do-nilo em diferentes fases de crescimento

Objetivou-se estimar a eficiência de utilização e a ingestão ótima de proteí­­na digestí­­vel para maximizar o ganho de peso e a conversão alimentar de juvenis de tilápia-do-nilo em diferentes fases de crescimento. Cada um dos quatro ensaios durou 45 dias, utilizando-se juvenis revertidos sexualmente com peso médio inicial de 2,01g (fase A); 14,26 g (fase B); 59,96 g (fase C) e 149,11 g (fase D). O delineamento adotado foi o inteiramente ao acaso, com cinco tratamentos e quatro repetições. Os ní­­veis de proteí­­na digestí­­vel variaram de 175 a 425 g kg-1 (fase A), de 163 a 390 g kg-1 (fase B), de 150 a 360 g kg-1 (fase C) e de 138 a 330 g kg-1 (fase D). As máximas respostas para ganho de peso foram estimadas com ingestões de proteí­­na de 88, 328, 713 e 855 mg peixe-1 dia-1 nas fases A, B, C e D respectivamente. Para maximizar a conversão alimentar estimaram-se ingestões de proteí­­na de 78, 272, 697 e 793 mg peixe-1 dia-1 para as fases A, B, C e D respectivamente. As eficiências de utilização da proteí­­na encontradas para as fases A, B, C e D foram 52, 51, 51 e 50% respectivamente.

Can the amount of digestible undegraded protein offered to ewes during late pregnancy affect the performance and immune response of their offspring to gastrointestinal nematodes?

Maternal nutrition during pregnancy is a major environmental influence on foetal development with consequent effects on postnatal performance. We hypothesised that the level of intake of digestible undegraded protein (DUP) by the dam in late pregnancy would impact on the effectiveness of the immune response by offspring to gastrointestinal nematode infection. Eighty-five twin/triplet-bearing ewes, which were indoors from mid-pregnancy, were randomly assigned to 4 treatment groups for the final 6 weeks of pregnancy. Treatments were silage plus one of two iso-energetic and iso-nitrogenous concentrates (differing in DUP concentration; 29 and 94g/kg DM) offered at one of two feed levels (18/30 and 24/35kg in total for twin/triplet-bearing ewes, respectively). Ewes with triplets had one lamb removed at birth so that all ewes nursed 2 lambs when put to pasture as one flock in a 5-paddock rotational grazing system; all lambs were slaughtered after 29 weeks. Faecal egg count (FEC) and levels of serum IgA and IgE specific for Teladorsagia circumcincta were assessed for all lambs at various time points between 10 weeks of age and slaughter. Animal performance (live weight, live-weight gain, carcass weight) was recorded for all lambs. Worm burden at slaughter was determined for a sample of 12 lambs from each treatment. Nematodirus spp. FEC, ‘other strongyles’ FEC, and serum IgA and IgE specific for T. circumcincta were unaffected either by the concentration of DUP in the concentrate or by the level of concentrate offered to ewes in late pregnancy (P>0.1). Likewise, the dietary regime of the dams had no effect on lamb performance (P>0.1). It is concluded that increasing the DUP intake of ewes in late pregnancy had no effect on the immune response of their offspring to gastrointestinal nematode infection acquired through grazing naturally infected pasture.

Protein deposition and energy recovery in gilthead sea bream (Sparus aurata): Evaluation of nutritional requirements

The energy and protein requirements for gilthead sea bream were studied until commercial weight. Gilthead sea bream with different body weights (from 24 to 422g) were fed from starvation to apparent satiation, studying protein and energy in the interval of 21–25°C. Energy recovery (ER) was expressed in relation to the digestible energy intake (DEI), ER=173.1∗(1−e(−0.00407∗(DEI-59.84))), and protein deposition (PD) was expressed with regard to digestible protein intake (DPI), PD=2.97∗(1−e(−0.152∗(DPI-1.393))).Maintenance needs in summer conditions were found to be 1.393gkg−0.7day−1 of the digestible protein intake and 59.84kJkg−0.82day−1 of the digestible energy intake. The response curves to the graded levels of intake of energy and protein should allow the diet formulation under several growth conditions and all sizes until commercial weight. Statement of relevanceThe feed conversion rate in Sparus aurata is not yet optimized, showing high values in farms. The knowledge of the efficiencies at different feeding rate, for the whole range of commercial weights, until 450g, should help to improve the efficiency of feeding.

Lysine requirement relative to total dietary protein for optimum performance and carcass protein deposition of Iberian piglets

This work aims at establishing dietary Lys requirements [g Lys/kg crude protein (CP, N×6.25)] of post-weaned Iberian piglets based on responses on growth performance, carcass nutrient deposition and plasma metabolites. Sixty piglets (10.7±0.1kg initial BW) were randomly assigned into six isoenergetic diets based on corn, barley and soybean meal. Diets contained increasing Lys concentrations at a constant dietary CP content (165±0.7g/kg DM). l-Lys HCl was added at the expense of corn starch providing Lys:CP ratios (g/kg) of 43, 47, 52, 57, 64 and 72g/kg. Other amino acids and nutrients remained constant. Six additional piglets were slaughtered at the start of the experiment to estimate initial carcass composition. Piglets were individually housed in 2m2 pens in an environmentally controlled room until slaughter (25.3±0.4kg BW) to analyze carcass composition. Average daily gain, G:F and Gain:ME intake (g/MJ) increased linearly (P<0.001) on increasing Lys concentration. Using average daily gain as a response, the linear broken-line regression and the first derivative of the quadratic function gave the same estimation for Lys requirement (71.0g Lys/kg dietary CP, respectively). Lysine content of dietary protein has no effect upon the apparent digestibility of DM, OM and nitrogen. Carcass protein deposition (PD) increased linearly (P<0.001) and quadratically (P<0.05) on increasing dietary Lys, reaching maximum values (39.3–40.2g protein/d) with diets providing 57, 64 and 72g Lys/kg CP. Carcass PD:CP intake, and carcass PD:digestible protein intake increased linearly (P<0.001) and quadratically (P<0.05) on increasing dietary Lys concentration. The linear broken-line regression using carcass PD (g/d) as response criterion estimated Lys requirement as 58.6g Lys/kg dietary CP with a plateau PD value of 39.9g/d. The first derivative of the quadratic function relating carcass PD and dietary Lys content gave a value of 63.7g Lys/kg CP. Plasma urea concentration tended to decrease on increasing Lys concentration (P=0.06 and P=0.10, for linear and quadratic effects). For plasmatic urea, both linear and quadratic approach gave a similar estimate for Lys requirements, 61.2g Lys/kg dietary CP. It is concluded that the preferred estimate based on carcass PD – the more reliable measure of metabolic Lys utilization – is 63.7g Lys/kg CP, somewhat below the established for conventional piglets.

The advantages of Ulva (Chlorophyta) as an additive in sea urchin formulated feeds: effects on palatability, consumption and digestibility

The present study was performed to determine whether the palatability, consumption and digestibility of an artificial sea urchin diet could be improved by the addition of a highly preferred seaweed. Four species of macroalgae (Ulva rigida, Ecklonia maxima, Porphyra capensis and Gigartina polycarpa) were assessed by pairwise preference tests. Each macroalgal species was consumed at least once by Tripneustes gratilla and significant preferences always involved Ulva as the most preferred species. Four protein-rich artificial diets supplemented with varying amounts of Ulva [0, 50, 150 and 200 g kg−1 designated 0, 5, 15 and 20U, respectively] were then developed and fed to urchins over a 20-day period. Inclusion of 200 g kg−1 dried Ulva significantly improved the palatability of the artificial diet and mean dry feed consumption rates were higher in urchins fed the 20U and 15U diets compared with urchins fed diets with a lower Ulva content. Daily digestible protein (DP) intake also differed significantly, with urchins fed the 20U diet having a significantly higher DP intake compared with the 15U, 5U and 0U treatments. These results indicate that inclusion of the palatable seaweed Ulva acted as a feeding stimulant, increasing the acceptability of the diets and boosting protein intake.

Influence of digestible protein levels on growth and feed utilization of juvenile meagreArgyrosomus regius

This study investigates the effect of digestible protein levels in experimental diets for meagre (Argyrosomus regius). A group of 253 fish, 52 g of mean weight, was distributed in 12 tanks, three replicates per treatment. Four isolipidic diets (170 g kg−1 crude lipid) with different digestible protein levels (350 g kg−1, 430 g kg−1, 490 g kg−1 and 530 g kg−1) were formulated using commercial ingredients. The trial lasted 62 days. Meagre fed diets 430, 490 and 530 g kg−1 obtained higher TGC (2.47, 2.57, 2.69 × 10−3, respectively) than fish fed diet 350 g kg−1 (2.14 × 10−3). Group of fish fed diet with 350 g kg−1 DP showed the lowest ammonia excretion level. According to the in vitro digestibility trial diets with 350 and 430 g kg−1 DP released less amino acids in comparison with diet with 49% DP, although in vivo digestibility test did not show significant differences among diets 430, 490 and 530 g kg−1 DP. Using the quadratic regression, optimal digestible protein intake according to the ECR for rearing juvenile meagre was recorded in 0.8 g DP/100 g fish and day.