Differences in splanchnic metabolism between late gestation and early lactation dairy cows.

In the transition from the pre- to postcalving state, the demands on the cow increase from support of gestation to high rates of milk production. This extra demand is met partly by increased intake but may also involve altered metabolism of major nutrients. Six multiparous Holstein cows were used to monitor changes in net fluxes of nutrients across the portal-drained viscera and liver (splanchnic tissues) between late gestation and early lactation. Blood samples were obtained simultaneously from the portal, hepatic, and subcutaneous abdominal veins and the caudal aorta 18 d before expected calving and 21 or 42 d after calving. On the day of blood sampling and the 3 d preceding sampling, cows were fed every 2 h. The precalving (1.63 Mcal of net energy for lactation/kg and 1,326 g of metabolizable protein/d) and postcalving (1.72 Mcal of net energy for lactation/kg and 2,136 g of metabolizable protein/d) diets were based on corn silage, alfalfa hay, and corn grain. Dry matter intake increased postcalving. Net splanchnic release of glucose increased postpartum because of tendencies for both increased portal absorption and net liver release. Increased removal of lactate, rather than AA, contributed to the additional hepatic gluconeogenesis. Although portal absorption of AA increased with intake at the onset of lactation, hepatic removal of total AA-N tended to decline. This clearly indicates that liver removal of AA is not linked to portal absorption. Furthermore, net liver removal relative to total liver inflow even decreased for Gly, His, Met, Phe, and Tyr. Together, these data indicate that in early lactation, metabolic priority is given to direct AA toward milk protein production rather than gluconeogenesis, in cows fed a corn-based ration.

Effects of reduced dietary calcium and phytase supplementation on calcium and phosphorus utilisation in broilers with modified mineral status.

1. The impact of modified mineral status and dietary Ca:P ratio on Ca and P utilisation was measured in chicks with or without phytase supplementation. 2. In a preliminary study, 4 diets were given to chicks from 3 to 15 d of age: D1 (6.5 g P/kg and Ca:P = 1.5) and D2, D3 and D4 (6.0, 5.4 and 5.0 g P/kg, respectively, and Ca:P = 1.2). Growth performance was similar across diets. Tibia ash was similar in chicks given D1 and D2, but was gradually depressed from D2 to D4 (-22%). 3. In the depletion period, two groups of chicks, with similar performance, but with different mineral status were achieved by feeding them, from 5 to 15 d of age, diets with a similar Ca:P ratio of 1.2, but containing 6.3 or 5.2 g P/kg. 4. During the subsequent 11 d of the repletion period, chicks from each of the two previous groups were given one of the 4 diets containing 5.7 g P/kg, but differing in their Ca (8.3 and 5.3 g Ca/kg) and microbial phytase (0 or 1000 FTU, Natuphos levels in a 2 x 2 x 2 factorial arrangement. 5. At the end of the repletion period, the initially depleted chicks could not be differentiated from the non-depleted chicks, indicating the capacity of chicks to compensate for their initial depleted mineral status. 6. Interaction between dietary Ca and phytase levels was not significant. Phytase improved growth performance and bone characteristics. Reduced dietary Ca enhanced feed intake and growth rate, but depressed bone dry matter and ash weight. 7. At the end, diets supplemented with phytase maximised bone ash weight when chicks were fed with a Ca:P ratio of 1.5 but elicited the highest growth rate when chicks were fed with a Ca:P ratio of 0.9.

Consequences of dietary calcium and phosphorus depletion and repletion feeding sequences on growth performance and body composition of growing pigs.

The effect of a calcium (Ca) and phosphorus (P) depletion and repletion strategy was studied in four consecutive feeding phases of 28 days each. In all, 60 castrated male pigs (14±1.6 kg initial BW) received 60% (low (L) diet; depletion) or 100% (control (C) diet; repletion) of their Ca and digestible P requirements according to six feeding sequences (CCCC, CCCL, CLCC, CCLC, LCLC and LLLL; subsequent letters indicate the diet received in phases 1, 2, 3 and 4, respectively). Pigs bone mineral content in whole-body (BMCb) and lumbar vertebrae L2 to L4 (BMCv) was measured in every feeding phase by dual-energy X-ray absorptiometry. Growth performance was slightly (<10%) affected by depletion, however, dietary treatments did not affect overall growth. Compared with control pigs, depletion reduced BMCb (34%, 38%, 33% and 22%) and BMCv (46%, 54%, 38% and 26%) in phases 1 to 4, respectively. Depletion increased however digestible P retention efficiency from the second to the fourth phases allowing LLLL pigs to present no differences in BMCb and BMCv gain compared with CCCC pigs in phase 4. Growth performance in repleted compared with control pigs was lower in phase 2, was no different in phase 3 and was lower in CLCC pigs in phase 4. Repletion increased body P and Ca retention efficiency when compared with control pigs (respectively, 8% and 10% for LC v. CC, P<0.01; 8% and 10% for CLC v. CCC, P<0.10; 18% and 25% for CLCC, CCLC, LCLC v. CCCC, P<0.001). Moreover, BMCv gain was higher in CLC pigs (P<0.001) and gains of body P, Ca, BMCb and BMCv in phase 4 were also higher in repleted than in CCCC pigs (respectively, 14%, 20%, 20% and 52%; P⩽0.02). Repletion reduced body P, Ca, BMCb and BMCv masses in phase 2 but no differences were found in phase 4 compared with control pigs. Lumbar vertebrae L2 to L4 bone mineral content was more sensitive to depletion and repletion sequences than BMCb especially in the first phase probably due to a higher proportion of metabolically active trabecular bone in vertebrae than in the whole skeleton. Dietary Ca was, however, oversupply in L compared with C diets (3.1 v. 2.5 Ca:digestible P ratio, respectively) suggesting that P has probably driven the regulations. Phosphorus and Ca depletion and repletion increases dietary P utilization efficiency and can help to reduce dietary P supply, but the underlying mechanisms need elucidation before its practical application.

Effect of glutamine supplementation on splanchnic metabolism in lactating dairy cows.

The suggestion that glutamine (Gln) might become conditionally essential postpartum in dairy cows has been examined through increased postruminal supply of Gln. Net nutrient flux through the splanchnic tissues and mammary gland was measured in 7 multiparous Holstein cows receiving abomasal infusions of water or 300 g/d of Gln for 21 d in a crossover design. Milk yield increased significantly (by 3%) in response to Gln supplementation, but the 2.4% increase in milk protein yield was not statistically significant. Glutamine treatment had no effect on portal or hepatic venous blood flows. Net portal appearance of Gln and Glu was increased by Gln supplementation, accounting for 83% of the infused dose with, therefore, only limited amounts available to provide additional energy to fuel metabolism of the portal-drained viscera. The extra net portal appearance of Gln was offset, however, by a corresponding increase in hepatic removal such that net Gln splanchnic release was not different between treatments. Nonetheless, the Gln treatment resulted in a 43% increase in plasma Gln concentration. Infusions of Gln did not affect splanchnic flux of other nonessential amino acids or of essential amino acids. Glutamine supplementation increased plasma urea-N concentration and tended to increase net hepatic urea flux, with a numerical increase in liver hepatic O2 consumption. There were no effects on glucose in terms of plasma concentration, net portal appearance, net liver release, or postliver supply, suggesting that Gln supplementation had no sparing effect on glucose metabolism. Furthermore, mammary uptake of glucose and amino acids, including Gln, was not affected by Gln supplementation. In conclusion, this study did not support the hypothesis that supplemental Gln would reduce glucose utilization across the gut or increase liver gluconeogenesis or mammary glutamine uptake to increase milk protein synthesis.

Effect of postruminal glutamine supplementation on immune response and milk production in dairy cows.

Seventeen multiparous Holstein cows were used to examine the effect of an increased duodenal supply of Gln on immune function and production. Cows received continuous abomasal infusions of water (control: n = 8) or 300 g/d of Gln (n = 9) for 21 d starting within 48 h of calving. There were nonsignificant increases in milk and milk protein yields in response to Gln supplementation. Glutamine treatment had no effect on plasma glucose, nonesterified fatty acids (NEFA), or beta-hydroxybutyrate (BHBA) concentrations but did tend to increase plasma urea N concentration. The Gln treatment resulted in an increase of 108 microM in the plasma Gln concentration. Total essential AA concentrations decreased with the Gln treatment, whereas total nonessential AA concentrations were unaffected. T Lymphocyte proliferation did not differ between the control and Gln-treated cows. Treatment had no effect on the relative abundance of CD8 T cells but did increase the abundance of CD4 T cells. Cytokine production, as measured by IFN-gamma concentration determined in vitro in concanavalin-A-stimulated peripheral blood mononuclear cells, was similar between the treatments. Over the first 3 wk following calving, Gln supplementation had limited effects on milk production, metabolic parameters, and immune function.

Effect of a lysine depletion-repletion protocol on the compensatory growth of growing-finishing pigs.

The effect of Lys restriction followed by a repletion period on the performance of growing pigs was studied during 3 feeding phases, each lasting 28 d. A total of 47 castrated male pigs (G Performer 8.0 × Fertilis 25 pigs; Genetiporc Inc., Saint-Bernard, QC, Canada; initial BW of 26.7 ± 2.7 kg) were given each d 70% or 100% of their Lys requirements according to 1 of the following 5 sequences: 70-70-70, 70-70-100, 70-100-70, 70-100-100, or 100-100-100 (for each sequence, numbers indicate the Lys supply percentage in phase 1, 2, and 3, respectively). Individual Lys requirements were estimated daily on the basis of each pig's actual BW and feed intake and BW gain patterns obtained by regression using each pig's historical data. At the end of phase 1, the pigs given 100% of their Lys requirements had higher ADFI ( = 0.01), ADG ( < 0.01), and average daily protein deposition ( < 0.01) than did the pigs given 70% of their requirements. Similar results were observed during phases 2 and 3. At the end of phase 2, the pigs in the 70-100 sequence did not display any compensatory response, given that their ADFI, ADG, and average daily protein deposition did not differ from those of the pigs in the 100-100 sequence. Similar results were observed during phase 3. Although no compensatory growth was observed during the growing phases, the fact that the pigs in the 70-100-100 treatment were able to catch up in terms of BW and body protein mass to the pigs in the 100-100-100 sequence could indicate that a small degree of compensation did occur; these research results cannot ascertain that any compensatory growth occurred.

Evaluation of a method estimating real-time individual lysine requirements in two lines of growing-finishing pigs.

The implementation of precision feeding in growing-finishing facilities requires accurate estimates of the animals' nutrient requirements. The objectives of the current study was to validate a method for estimating the real-time individual standardized ileal digestible (SID) lysine (Lys) requirements of growing-finishing pigs and the ability of this method to estimate the Lys requirements of pigs with different feed intake and growth patterns. Seventy-five pigs from a terminal cross and 72 pigs from a maternal cross were used in two 28-day experimental phases beginning at 25.8 (±2.5) and 73.3 (±5.2) kg BW, respectively. Treatments were randomly assigned to pigs within each experimental phase according to a 2×4 factorial design in which the two genetic lines and four dietary SID Lys levels (70%, 85%, 100% and 115% of the requirements estimated by the factorial method developed for precision feeding) were the main factors. Individual pigs' Lys requirements were estimated daily using a factorial approach based on their feed intake, BW and weight gain patterns. From 25 to 50 kg BW, this method slightly underestimated the pigs' SID Lys requirements, given that maximum protein deposition and weight gain were achieved at 115% of SID Lys requirements. However, the best gain-to-feed ratio (G : F) was obtained at a level of 85% or more of the estimated Lys requirement. From 70 to 100 kg, the method adequately estimated the pigs' individual requirements, given that maximum performance was achieved at 100% of Lys requirements. Terminal line pigs ate more (P=0.04) during the first experimental phase and tended to eat more (P=0.10) during the second phase than the maternal line pigs but both genetic lines had similar ADG and protein deposition rates during the two phases. The factorial method used in this study to estimate individual daily SID Lys requirements was able to accommodate the small genetic differences in feed intake, and it was concluded that this method can be used in precision feeding systems without adjustments. However, the method's ability to accommodate large genetic differences in feed intake and protein deposition patterns needs to be studied further.

The effect of intake level on whole body kinetics and hepatic removal of somatotropin in growing beef steers.

The effect of level of intake of a high concentrate diet (0.6, 1.0 and 1.6 x maintenance requirements, M) on whole body somatotropin (St) kinetics was evaluated in six growing, multicatheterized beef steers (398+/-27 kg), using a double 3x3 Latin Square design with 21 d-periods. Simultaneously to St kinetics, net hepatic removal of St was measured in 4 of the 6 steers. On the last day of each period, concentrations and net fluxes of St were determined, first in basal conditions for 5 hr, and then, during a primed (0.5 mg of St) infusion of bovine St (1.5 mg/hr) administered for 3 hr. The following results are LSM +/- SEM for 0.6, 1.0, and 1.6 x M, respectively. Increasing feed intake linearly decreased (P<0.01) basal St concentrations (5.6, 4.6, 3.1+/-0.62 ng/ml), mainly through a linear increment (P<0.01) in the metabolic clearance rate (32.7, 37.1, 43.4+/-2.60 l/hr), although secretion rate also tended to decrease (P = 0.09; 189, 185, 135+/-27.2 microg/hr). During the infusion period, net liver removal of immunoreactive ST averaged 60% of the total inflow of St. This confirms the liver is capable of removing large amounts of St, suggesting it has an important role in metabolic clearance of the hormone. Net liver removal of St, however, was not affected by intake. There was a strong correlation between the metabolic clearance rate of St with either whole body protein synthesis (r = 0.75, P<0.01) or protein retention (r = 0.68, P<0.01). Together these results indicate the importance of postsecretory metabolism of St in determining both arterial plasma concentrations of St and whole body protein anabolism.

Effect of a major gene for growth on protein synthesis in mice.

Rates of protein synthesis of mice with a major gene (hg) for rapid postweaning gain (line Ch) and their normal counterparts (line CH) were determined at 21, 31 and 42 d of age with an intraperitoneal injection of a flooding dose of 14C-leucine. A preliminary experiment demonstrated that the relationship between the specific activities of leucine in acid-soluble supernatants and carcass protein corresponded to the theoretical precursor-product relationship, indicating that the method is valid for estimating protein synthesis rates. Using this method at 21, 31 and 42 d of age, whole-body protein fractional synthesis rates (FSR) were 43.7, 32.7 and 29.1%/d and 41.9, 32.6 and 33.1%/d for lines CH and Ch, respectively. Although differences between lines were not significant, FSR decreased with age. Absolute synthesis rate (ASR), where ASR = (FSR) X (whole body protein), was greater (P less than .001) at 21, 31 and 42 d of age in line Ch as compared with CH, and increased (P less than .001) with age. The relative contributions of liver, gastrointestinal tract, heart-kidney-lung and remaining carcass to whole body protein ASR were not affected by line, but did change (P less than .05) with age. Whole body protein fractional breakdown rate (FBR), calculated as FSR minus whole body protein fractional growth, indicates that differences between lines CH and Ch whole-body FSR and(or) FBR exist only between 24 and 33 d of age, and that the maximum value of this difference probably does not exceed 10%.

A dynamic model of protein digestion in the small intestine of pigs.

A dynamic mathematical model of the digestion of proteins in the small intestine of pigs was developed. The model integrates current knowledge on the transit of digesta along the small intestine, endogenous secretions, digestion of proteins, and absorption of amino acids into a mechanistic representation of digestion. The main characteristics of the model are the following: the small intestine is divided into several segments of variable length but with equal digesta retention time; the rate of transfer of digesta between segments is based on the progression of myoelectric migration complexes; pancreatic and biliary secretions are poured into the first segment, whereas intestinal secretions enter all intestinal segments; protein hydrolysis is described by first-order equations; and an intestinal absorption capacity is used to estimate absorption of hydrolyzed protein. Simulation results are consistent with observed data, although more information is needed to represent reality more closely. The sensitivity analysis shows that parameters for protein hydrolysis largely determine protein digestibility. The absorption capacity of the small intestine limits the absorption of amino acids at the beginning of a meal and modulates the appearance of amino nitrogen in the portal vein. It also shows that amino acid absorption can be limiting to protein digestibility when large amounts of protein are eaten in a single daily meal. The model is useful in evaluating the dynamics of protein digestion and absorption of feedstuffs. The model can be used in evaluating protein digestion of different feedstuffs and feeding strategies.

Efficiency of growth in mice with a major gene for rapid postweaning gain.

Previous research in this laboratory demonstrated the existence of a major gene (hg), inherited as a homozygous recessive, which increases postweaning growth by 40 to 50% in C57Bl/6 mice (Ch) compared to the same genetic stock without the major gene (CH). Although its effect has not been previously evaluated, this single recessive allele is also in a line of mice selected for rapid postweaning gain for over 70 generations. Gh represents that line of mice with the major gene for growth (hg) in the growth-selected background and GH the growth-selected background without the major gene. Total body weight, daily weight gain, feed consumption and gain/feed, measured daily from 21 to 42 d of age, were all significantly greater (p less than .01) in the two lines with the hg/hg genotype (Ch and Gh) compared with their respective control lines (CH and GH). Differences in body composition at 42 d of age between CH compared with Ch and GH compared with Gh were accounted for by difference in body weight. Gross and net energetic efficiency, calculated assuming a similar maintenance energy requirement, were improved (P less than .01) in Ch and Gh compared to CH and GH, respectively. The results demonstrated that hg influences growth in growth-neutral and growth-selected backgrounds. The gene also alters energy metabolism by increasing energetic efficiency of growth and(or) decreasing maintenance energy requirement.

The effect of feed intake level on splanchnic metabolism in growing beef steers.

The effect of feed intake level (.6, 1.0, and 1.6 x maintenance energy and protein requirements, M) on splanchnic (portal-drained viscera [PDV] plus liver) metabolism was evaluated in six multicatheterized beef steers (398 +/- 27 kg), using a double 3 x 3 Latin square design. On the last day of each 21-d experimental period, six hourly blood samples were collected from arterial, portal, and hepatic vessels. Due to catheter patency, PDV fluxes were measured on five steers, and liver and splanchnic fluxes on four steers. Increasing intake elevated (P < .01) splanchnic release of total (T) amino acids (AA), through increases (P < .01) in PDV release of both essential (E) and nonessential (NE) AA, in spite of a tendency (P < .20) for increased liver removal of NEAA. The PDV release of AA N represented 27 and 51% of digested N for 1.0 and 1.6 x M, respectively. At 1.0 and 1.6 x M, the liver removed 34% of total AA released by the PDV. For individual AA, portal flux of most EAA increased (P < .05) with feed intake, and the increase (P < .10) in splanchnic flux was accompanied by increased arterial concentration for all EAA except histidine, lysine, and methionine. This suggests that these might be limiting AA for this diet. On a net basis, most individual NEAA were released by the PDV except glutamate and glutamine, which were removed by the digestive tract. There was a net removal of NEAA by the liver, except for aspartate and especially glutamate, which were released. Ammonia release by the PDV tended (P < .20) to increase with intake and represented 69, 53, and 45% of digested N at .6, 1.0, and 1.6 x M, respectively. Urea removed by the PDV, unaffected by intake, represented 32, 33, and 21% of the digested N. Arterial glucose concentration increased linearly (P < .01) with greater intake, whereas net liver and splanchnic glucose release increased in a quadratic (P < .05) manner. Net PDV glucose release represented 26% of net glucose hepatic release at 1.6 x M. Intake elevated (P < .10) both insulin and glucagon arterial concentrations, resulting from a larger increment of portal release (P < .01) than hepatic removal (P < .05). Intake-based variations in IGF-I and NEFA arterial concentrations (P < .05) were not related to changes in splanchnic metabolism. These results clearly show the crucial role of the splanchnic tissues in regulating the profile and quantity of AA and concentrations of glucose and pancreatic hormones reaching peripheral tissues.

Estimation of Canadian and European lean yields and composition of pig carcasses by dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DEXA) was used on 110 pig carcasses to estimate fat, lean, bone mineral content and total tissue masses of the major primal cuts and overall carcasses. The DEXA estimations were compared and used to predict the dissected lean, fat (including skin), bone and weight of primal cuts and carcasses, as well as to predict the Canadian and the European lean yields. The best relationships were obtained when predicting the weight of ham (R(2)=0.99), loin (R(2)=0.99), shoulder (R(2)=0.96), belly (R(2)=0.93), half carcass (R(2)=0.98), ham lean (R(2)=0.89), loin lean (R(2)=0.89), shoulder lean (R(2)=0.87), and the meat weight used in the estimation of the Canadian (R(2)=0.92) and the European lean yield (R(2)=0.82). While the weight of fat in the carcass and primal cuts was accurately estimated by DEXA (R(2)>0.72), DEXA carcass composition estimations were less accurate when predicting dissected bone weights (R(2)<0.54).

Dietary addition of cellular metabolic intermediates and carcass fat deposition in broilers.

Ninety-six 1-day-old male broilers were fed a diet containing 0, 2, 4, 6, 8, or 10% of a 1:1 mixture of pyruvic acid (PY) and dihydroxyacetone (DH) for ad libitum consumption for 42 days. Feed intake, body weight gain, and feed efficiency decreased linearly (P < .001) with increasing levels of PY and DH. There were no significant differences among treatments for abdominal fat percentage. Carcass chemical analysis revealed small but significant (P < .05) differences among dietary treatments for protein and fat percentages. In a second experiment, 192 1-day-old male broilers were fed diets containing 5% of PY, lactic acid (LA), citric acid (CI), DH, or glycerol (GY) or mixtures (1:1) of DH or GY in combination with each organic acid. Bird performance was impaired (P < .05) by PY or CI but not by DH or GY. Lactic acid reduced (P < .05) feed intake by 9% without affecting weight gain. Lactic acid plus DH, CI plus DH, and CI plus GY mixtures decreased (P < .05) bird performance but other combinations had no effect. Pyruvic acid or CI decreased abdominal fat and carcass lipid percentages. Dihydroxyacetone increased (P < .05) carcass lipid percentage and GY increased (P < .05) abdominal fat percentage. Lactic acid plus DH increased (P < .05) carcass lipid percentage. Only PY and CI decreased carcass fat deposition, but they also impaired broiler performance.

Modeling the fate of dietary phosphorus in the digestive tract of growing pigs.

Environmental effects of excess P from manure and the soaring price of phosphates are major issues in pig production. To optimize P utilization, it is crucial to improve our capacity to predict the amount of P absorbed, while taking into account the main factors of variation. Mathematical modeling can represent the complexity of the processes and interactions in determining the digestive utilization of P in growing pigs. This paper describes and evaluates a model developed to simulate the fate of the dietary forms of P in the digestive tract of growing pigs, with particular emphasis on the effect of dietary Ca and exogenous phytase on P digestive utilization. The model consists of 3 compartments associated with specific anatomical sections: stomach, proximal small intestine, and distal small intestine. The main metabolic processes occurring in these sections are, respectively, P solubilization/insolubilization and phytate P hydrolysis, and P absorption and P insolubilization. Model parameters governing these flows were derived from in vitro and in vivo literature data. The sensitivity analysis revealed that the model was stable within a large range of model parameter values (±1.5 SD). The model was able to predict the efficacy of Aspergillus niger microbial phytase in accordance with literature values, as well as the decreased efficacy of plant phytase compared with microbial phytase. The prediction capabilities of the model were assessed by comparing actual and simulated P and Ca apparent total-tract digestibility (ATTD) based on published pig data not used for model development. Prediction of P digestibility across 66 experiments and 281 observations was adequate [P ATTD observed = 0.24 (SE, 0.943) + 0.98 (SE, 0.0196) × P ATTD predicted; R(2), 0.90; disturbance error (ED), 96.5%], whereas prediction of Ca digestibility across 47 experiments and 193 observations was less accurate (Ca ATTD observed = 11.1 + 0.75 × Ca ATTD predicted; R(2), 0.78; ED, 20.4%). A lack of agreement between experimental and simulated Ca digestibility was found. This model is, therefore, useful in evaluating P digestibility for different feedstuffs and feeding strategies. It can also be used to provide insight for improving dietary P utilization, especially from plant sources, by quantifying the effect of the mean sources of variation affecting P utilization.

Effect of reduced dietary calcium concentration and phytase supplementation on calcium and phosphorus utilization in weanling pigs with modified mineral status.

The present study was conducted to assess the effect of 2 dietary Ca concentrations on P and Ca digestive and metabolic utilization in weanling pigs fed diets providing practical concentrations of P, with or without phytase. The responses of pigs fed diets adequate or moderately deficient in Ca and P postweaning were compared. A total of 60 pigs weaned at 28 d of age were used. Two groups of 30 pigs with differing mineral status resulted from a 10-d depletion period, during which the animals received depletion diets (DD) that consisted of corn-soybean meal with either 1.42% Ca and 0.80% P (DD+) or 0.67% Ca and 0.43% P (DD-), designed to achieve the same Ca:digestible P ratio. At the end of the depletion period, a plasma sample was taken from each pig and 12 pigs (6 from each group) were slaughtered for bone assessment to establish the baseline mineral status. The animals fed the DD- diet had signs of P deficiency with reduced plasma P (13%; P < 0.01) and femur ash concentration (8%; P < 0.05), and increased plasma Ca (9%; P < 0.05) and alkaline phosphatase activity (31%; P < 0.01). For the subsequent 25-d period, the remaining 24 pigs from each group were fed 1 of 4 repletion diets: 1) 0.56% P, 1.06% Ca; 2) 0.56% P, 0.67% Ca; 3) diet 1 + 1,000 phytase units (FTU) of Natuphos phytase/kg; and 4) diet 2 + 1,000 FTU of Natuphos phytase/kg. Total feces and urine were collected from d 5 to 11, and a blood sample was taken from each pig at d 11 and 25. The initial moderate P deficiency (DD-) stimulated Ca absorption (5%; P < 0.01), irrespective of the repletion diet, and stimulated P absorption (5%; DD x phytase, P < 0.05), only when the diets contained phytase. At the end of the repletion period, because of these compensatory phenomena, the depleted pigs achieved full recovery of femur DM and ash weight when they received phytase, whereas ash concentration tended to remain reduced by 3% (P = 0.08). Phosphorus digestibility was improved in the diets supplemented with phytase (73.0 vs. 56.0%; P < 0.001), whereas an increase in dietary Ca decreased P digestibility (65.6 vs. 63.4%; P < 0.05). Those 2 effects were independent, indicating that dietary Ca reduced equally P digestibility with and without phytase and did not influence the efficiency of phytase in releasing P in the digestive tract. In pigs fed diets with phytase, however, the reduction of Ca (Ca:P from 1.9 to 1.3) increased urinary P losses 5-fold. Those extra losses were due to a lack of Ca for skeleton ash deposition, resulting in a 4% reduction in femur ash concentration. In the end, reducing the dietary Ca:P from 1.9 to 1.3 in a practical diet containing 0.56% P did not improve the efficiency of phytase in releasing P. Moreover, the reduction in dietary Ca (Ca:P) caused an imbalance between Ca and P that impaired bone mineralization.

Meta-analysis of phosphorus utilisation by broilers receiving corn-soyabean meal diets: influence of dietary calcium and microbial phytase.

Pollution relative to phosphorus excretion in poultry manure as well as the soaring prices of phosphate, a non-renewable resource, remain of major importance. Thus, a good understanding of bird response regarding dietary phosphorus (P) is a prerequisite to optimise the utilisation of this essential element in broiler diets. A database built from 15 experiments with 203 treatments was used to predict the response of 21-day-old broilers to dietary non-phytate P (NPP), taking into account the main factors of variation, calcium (Ca) and microbial phytase derived from Aspergillus niger, in terms of average daily feed intake (ADFI), average daily gain (ADG), gain to feed (G:F) and tibia ash concentration. All criteria evolve linearly (P < 0.001) and quadratically (P < 0.001) with dietary NPP concentration. Dietary Ca affected the intercept and linear component for ADG (P < 0.01), G:F (P < 0.05) and tibia ash concentration (P < 0.001), whereas for ADFI, it affected only the intercept (P < 0.01). Microbial phytase addition impacted on the intercept, the linear and the quadratic coefficient for ADFI (P < 0.01), ADG (P < 0.001) and G:F (P < 0.05), and on the intercept and the linear component (P < 0.001) for tibia ash concentration. An evaluation of these models was then performed on a database built from 28 experiments and 255 treatments that were not used to perform the models. Results showed that ADFI, ADG and Tibia ash concentration were predicted fairly well (slope and intercept did not deviate from 0 to 1, respectively), whereas this was not the case for G:F. The increase in dietary Ca concentration aggravated P deficiency for all criteria while phytase addition had a positive effect. The more P deficiency was marked, the more the bird response to ADFI, ADG, G:F and tibia ash concentration was exacerbated. It must also be considered that even if the decrease in dietary Ca may improve P utilisation, it could in turn become limiting for bone mineralisation. In conclusion, this meta-analysis provides ways to reduce dietary P in broiler diets without impairing performance, taking into account dietary Ca and microbial phytase.

Energetics of protein synthesis in mice with a major gene for growth.

The effect of the level of food intake on protein synthesis rate in carcass, liver, gastrointestinal tract (GIT) and heart, kidneys and lungs (HKL) was determined in male mice with a major gene for rapid postweaning gain (line Ch) and normal controls (line CH) at 31 d of age. In both lines of mice, food restriction lowered carcass, HKL and liver absolute protein synthesis rates (ASRs) while GIT protein ASR was not affected by food intake. As a result, whole-body protein ASR increased with increasing food intake. It was estimated that heat production from protein synthesis (HrpsE) was responsible for 8.3 and 10.8% of the maintenance energy requirement of CH and Ch mice, respectively. It was also calculated that HrpsE represents 19.4 and 18.3% of the heat increment of growth of CH and Ch mice, respectively. Energetic efficiencies of protein deposition in CH and Ch mice were 58.6 and 66.7%, respectively.

Dietary fibers and supplementary iron in a milk replacer for veal calves.

Thirty 1-wk-old male Holstein calves were allotted randomly to six groups into a 3 X 2 factorial design. The control diet was skim milk, whey, tallow, vitamins, and minerals. Either Alpha-Floc or pectin was added at 5% dry matter. Supplementary iron was added at 30 and 50 ppm (dry basis). The six diets were fed for 14 wk. Calves without supplementary iron were mildly anemic at 6 wk and severely at 14 wk (7 and 5 g/dl hemoglobin). At 14 wk, both fibers had decreased blood hemoglobin in calves given supplementary iron. Feed refusal began at 8 wk with the appearance of anemia for calves unsupplemented with iron, but both Alpha-Floc and pectin decreased feed refusal. Supplementary iron practically eliminated feed refusal. Supplementary iron improved average daily gain and feed conversion, but dietary fibers had no effect. Adding Alpha-Floc and pectin to the diets reduced frequency of diarrheic feces. Mean carcass weight of calves fed supplementary iron was 11.6% higher than that of unsupplemented calves. Supplementary iron decreased liver lipids and increased glutamic oxaloacetic transaminase activity in blood plasma.

Serial composition during growth in mice with a major gene for rapid postweaning growth.

The chemical composition of growth in mice having a major gene for rapid post-weaning growth (hg/hg) was compared to that of their normal counterparts (Hg/-) at repeated intervals from 21 to 57 days of age. Male mice of both genotypes were sacrificed at 3 day intervals from 21 to 42 days of age and at 5 day intervals thereafter to day 57 of age for determination of body composition. By day 57 the hg/hg mice weighed 44.2 g while the Hg/- mice weighed 31.9 g. Analysis of changes in body water, protein, fat and ash across ages demonstrated that the hg/hg mice had significantly greater percents of body water and fat while having less protein and ash as compared to the Hg/- mice. When the effect of body weight was removed by covariance analysis, the difference in body lipid between genotypes was no longer significant. The hg/hg mice continued to maintain a slightly but significantly greater amount of water in the body while protein and ash levels remained lower than in Hg/- mice. Age also significantly influenced the amount of water, protein and ash in both mouse genotypes. It was concluded that the very slight, but significant differences in amount of water, protein and ash in the hg/hg mice were the result of a slower rate of maturing. The gene (hg) seems to have a general influence on all chemical components of growth and apparently does not alter any specific chemical component of growth.