Assessment of digestible lysine requirements in lipopolysaccharide-challenged pigs

Abstract To evaluate the effect of an E. coli lipopolysaccharide (LPS) challenge on the digestible lysine (Lys) requirement for growing pigs, a nitrogen (N) balance assay was performed. Seventy-two castrated male pigs [19 ± 1.49 kg body weight (BW)] were allocated in a 2 x 6 factorial design composed of two immune activation states (control and LPS-challenged) and 6 dietary treatments with N levels of 0.94, 1.69, 2.09, 3.04, 3.23 and 3.97% N, as fed, where Lys was limiting, with six replicates and one pig per unit. The challenge consisted of an initial LPS dose of 30 μg/kg BW via intramuscular (IM) injection and a subsequent dose of 33.6 μg/kg BW after 48 h. The experimental period lasted 11 days and was composed of a 7-day adaptation and a subsequent 4-day sampling period in which N intake (NI), N excretion (NEX) and N deposition (ND) were evaluated. Inflammatory mediators and rectal temperature were assessed during the 4-day collection period. A 3-way interaction (N levels × LPS challenge × time, P < 0.05) for IgG was observed. Additionally, 2-way interactions (challenge × time, P < 0.05) were verified for IgA, ceruloplasmin, transferrin, haptoglobin, α-1-acid glycoprotein, total protein, and rectal temperature; and (N levels × time, P < 0.05) for transferrin, albumin, haptoglobin, total protein and rectal temperature. LPS-challenged pigs showed lower (P < 0.05) feed intake. A 2-way interaction (N levels × LPS challenge, P < 0.05) was observed for NI, NEX and ND, with a clear dose-response (P < 0.05). LPS-challenged pigs showed lower NI and ND at 2.09% N and 1.69 to 3.97% N (P < 0.05), respectively, and higher NEX at 3.23% N (P < 0.05). The parameters obtained by a nonlinear model (N maintenance requirement, NMR and theoretical maximum N deposition, NDmaxT) were 152.9 and 197.1 mg/BWkg 0.75/d for NMR, and 3,524.7 and 2,077.8 mg/BWkg 0.75/d for NDmaxT, for control and LPS-challenged pigs, respectively. The estimated digestible Lys requirements were 1,994.83 and 949.16 mg/BWkg 0.75/d for control and LPS-challenged pigs, respectively. The daily digestible Lys intakes required to achieve 0.68 and 0.54 times the NRmaxT value were 18.12 and 8.62 g/d, respectively, and the optimal dietary digestible Lys concentration may change depending on the feed intake levels. Based on the derived model parameters obtained in the N balance trial with lower cost and time, it was possible to differentiate the digestible Lys requirement for swine under challenging conditions.

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Effects of chromium supplementation on physiology, feed intake, and insulin related metabolism in growing pigs subjected to heat stress

Translational Animal Science ◽

10.2527/tas2017.0014 ◽

2017 ◽

Vol 1 (1) ◽

pp. 116-125 ◽

Cited By ~ 4

Author(s):

F. Liu ◽

J. J. Cottrell ◽

U. Wijesiriwardana ◽

F. W. Kelly ◽

S. S. Chauhan ◽

...

Keyword(s):

Heat Stress ◽

Insulin Sensitivity ◽

Respiration Rate ◽

Rectal Temperature ◽

Feed Intake ◽

Insulin Response ◽

Thermal Exposure ◽

Growing Pigs ◽

Model Assessment ◽

Intravenous Glucose

Abstract Improving insulin sensitivity may reduce impacts of heat stress (HS) in pigs by facilitating heat dissipation. Chromium (Cr) has been reported to improve insulin sensitivity in pigs. Therefore, the aim of this experiment was to investigate whether Cr supplementation can mitigate HS in growing pigs. Thirty-six gilts were randomly assigned to 2 diets containing 0 (control) or 400 ppb Cr. After 14 d the supplemented pigs were allocated to either 8 d thermoneutral (20°C constant; TN) or cyclic HS (35°C, 0900 h to 1700 h) conditions and continued their respective diet (n = 9 per group). Growth performance was recorded during the 14-d supplementation period. The physiological responses to HS were monitored by measuring respiration rate, rectal temperature, blood gas chemistry, and feed intake during thermal exposure. Kinetics of plasma glucose, insulin and NEFA were studied by intravenous glucose tolerance test (IVGTT) on d 8 of thermal treatment. Results showed Cr alleviated the HS-increased rectal temperature (P < 0.05) and respiration rate (P < 0.01) at 1300 h and 1600 h during thermal exposure. However, Cr did not mitigate the reduction in average daily feed intake which was reduced by 35% during HS or the HS-induced respiratory alkalosis. Chromium tended to increase average daily gain (0.86 vs. 0.95 kg, P = 0.070) during the 14-d supplementation under TN conditions before thermal exposure, which might be associated with the potential of Cr in improving overall insulin sensitivity, as evidenced by a reduced insulin resistance index calculated by Homeostatic Model Assessment (HOMA-IR; 0.65 vs. 0.51, P = 0.013) and a tendency of reduced fasting plasma insulin concentration (1.97 vs. 1.67 μU/mL, P = 0.094). Heat stress decreased the acute insulin releasing rate (P = 0.012) and consequently slowed glucose clearance rate (P = 0.035) during IVGTT. Besides, HS enlarged the values of area under the curve of NEFA during IVGTT (P < 0.01), indicating a reduced lipid mobilization. In conclusion, HS reduced insulin response to IVGTT. Chromium supplementation exhibited a potential in improving insulin sensitivity and mitigating HS symptoms in growing pigs.

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Adaptation of growing pigs to changes in environmental temperature

Animal Science ◽

10.1017/s0003356100029421 ◽

1971 ◽

Vol 13 (1) ◽

pp. 51-57 ◽

Cited By ~ 27

Author(s):

S. R. Morrison ◽

L. E. Mount

Keyword(s):

Growth Rate ◽

Body Weight ◽

Respiratory Rate ◽

Temperature Change ◽

Water Intake ◽

Rectal Temperature ◽

Feed Intake ◽

Environmental Temperature ◽

Growing Pigs ◽

Ad Libitum

SUMMARYPigs fed ad libitum were exposed to changes from 22 to 33°C and from 33 to 20°C. Responses were investigated in two groups of animals kept for three successive periods of four weeks at 22°, 33° and finally 20°C.Twenty-four hr after the first change, from 22 to 33°C, there was a decline in body weight; after the second change, from 33 to 20°C, there was a large increase. After the change to 33°C, feed intake by the second day and growth rate for the first week were about the same as at the end of the four weeks, but about 12 days were required for water intake, rectal temperature and respiratory rate to reach steady values.After the change from 33 to 20°C, steady values for respiratory rate and rectal temperature were reached in one and 12 days respectively. The rate of gain in weight increased to reach a peak nine days following the temperature change and then declined.

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236 Effects of mitoquinol during acute heat stress exposure in growing pigs

Journal of Animal Science ◽

10.1093/jas/skaa054.202 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 118-118

Author(s):

Edith J Mayorga ◽

Erin A Horst ◽

Brady M Goetz ◽

Sonia Rodríguez-Jiménez ◽

Megan A Abeyta ◽

...

Keyword(s):

Heat Stress ◽

Fatty Acid ◽

Skin Temperature ◽

Blood Urea Nitrogen ◽

Rectal Temperature ◽

Feed Intake ◽

Growing Pigs ◽

Stress Exposure ◽

Acute Heat Stress ◽

Ad Libitum

Abstract Objectives were to determine the effects of mitoquinol (MitoQ) on performance, metabolism, and inflammation during acute heat stress (HS) in growing pigs. Crossbred barrows (n=32; 59±1 kg BW) where blocked by BW and randomly assigned to 1 of 4 therapeutic-environmental treatments: 1) thermoneutral (TN) control (n=8; TNCtl), 2) TN and MitoQ (n=8; TNMitoQ), 3) HS control (n=8; HSCtl), or 4) HS and MitoQ (n=8; HSMitoQ). The trial consisted of two experimental periods (P). During P1 (2d), pigs were fed ad libitum and housed in TN conditions (20.6±0.1°C). During P2 (24h), HSCtl and HSMitoQ pigs were exposed to continuous HS (35.2±0.03°C); while TNCtl and TNMitoQ remained in TN conditions. Mitoquinol was orally administered twice daily (0700 and 1800 h; 40 mg/d) during P1 and P2. Pigs exposed to HS had increased rectal temperature, skin temperature, and respiration rate (1.46°C, 6.79°C, and 101 bpm, respectively; P< 0.01) compared to their TN counterparts. Acute HS markedly decreased feed intake (67%; P< 0.01). Additionally, HS pigs lost BW compared to their TN counterparts (-4.7 vs. +1.6 kg, respectively; P< 0.01); however, the reduction in BW was less severe in HSMitoQ compared to HSCtl pigs (-3.85 vs. -5.50 kg, respectively; P< 0.01). Circulating glucose increased in HSMitoQ relative to HSCtl pigs (15%; P=0.04). Non-esterified fatty acid (NEFA) concentrations were increased in HS compared to TN pigs (P< 0.01), although this difference was influenced by increased NEFA in HSCtl relative to HSMitoQ pigs (251 vs. 142 μEq/L; P< 0.01). Insulin:feed intake tended to increase in HS relative to TN pigs (P=0.09). Overall, no differences in blood urea nitrogen or cell blood counts were observed across treatments (P >0.10). In conclusion, acute HS exposure negatively altered animal performance and metabolism; however, administering MitoQ appeared to ameliorate the HS response.

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Postprandial insulin and nutrient concentrations in lipopolysaccharide-challenged growing pigs reared in thermoneutral and high ambient temperatures1

Journal of Animal Science ◽

10.1093/jas/skz204 ◽

2019 ◽

Vol 97 (8) ◽

pp. 3354-3368

Author(s):

Paulo Henrique Reis Furtado Campos ◽

Elodie Merlot ◽

David Renaudeau ◽

Jean Noblet ◽

Nathalie Le Floc’h

Keyword(s):

Ambient Temperature ◽

Amino Nitrogen ◽

Thermal Conditions ◽

Experimental Period ◽

Repeated Administration ◽

Growing Pigs ◽

Nutrient Concentrations ◽

Ambient Temperatures ◽

Lps Challenge ◽

Postprandial Insulin

Abstract The aim of this study was to evaluate the associated effects of ambient temperature and inflammation caused by repeated administration of Escherichia coli lipopolysaccharide (LPS) on insulin, energy, and AA metabolism. Twenty-eight pigs were assigned to one of the two thermal conditions: thermoneutral (24 °C) or high ambient temperature (30 °C). The experimental period lasted 17 d, which was divided into a 7-d period without LPS (days −7 to −1), and a subsequent 10-d LPS period (days 1 to 10) in which pigs were administered 5 repeated injections of LPS at 2-d intervals. Postprandial profiles of plasma insulin and nutrients were evaluated through serial blood samples taken on days −4 (P0), 4 (P1), and 8 (P2). Before the LPS-challenge (P0), postprandial concentrations of glucose, lactate, Gln, Ile, Leu, Phe, Tyr, and Val were greater in pigs kept at 24 °C than at 30 °C (P < 0.05). In contrast, Arg, Asp, Gly, His, and Met postprandial concentrations at P0 were lower at 24 °C than at 30 °C (P < 0.05). At both 24 and 30 °C conditions, pigs had greater postprandial concentrations of insulin (P < 0.01) and lower concentrations of NEFA (P < 0.01) and α-amino nitrogen (P < 0.05) at P1 and P2 than at P0. Compared with P0, postprandial concentrations of glucose were greater (P < 0.05) at P1 in pigs kept at 24 °C, and at P1 and P2 in pigs kept at 30 °C. At both ambient temperatures, pigs had lower (P < 0.05) postprandial concentrations of Ala, Gly, His, Ile, Leu, Pro, Ser, Thr, Trp, and Val at P1 and P2 than at P0. Arginine postprandial concentration at P1 was lower than at P0 in pigs kept at 24 °C (P < 0.05), whereas no difference was observed in pigs at 30 °C. Relative to P0, Gln and Tyr concentrations were lower at P1 and P2 in pigs kept at 24 °C (P < 0.01), whereas lower Gln concentration was observed only at P2 (P < 0.01) and lower Tyr only at P1 (P < 0.01) in pigs kept at 30 °C. Our study shows a hyperglycemic and hyperinsulinemic state in LPS-challenged pigs and a greater magnitude of this response in pigs kept at 30 °C. Furthermore, LPS caused important changes in BCAA, His, Thr, and Trp profiles, suggesting the role these AA in supporting the inflammatory response. Finally, our results suggest that LPS-induced effects on postprandial profiles of specific AA (Arg, Gln, Phe, and Tyr) may be modulated by ambient temperature.

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19 Assessment of Nitrogen Intake, Excretion and Deposition in lipopolysaccharide-Challenged Pigs

Journal of Animal Science ◽

10.1093/jas/skaa054.067 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 37-38

Author(s):

Joyce Barcellos ◽

Warley J Alves ◽

Carolaine R Ferreira ◽

Filipe Monteiro ◽

Gabriel Viana ◽

...

Keyword(s):

Dry Matter ◽

Nitrogen Retention ◽

N Deposition ◽

Growing Pigs ◽

Nitrogen Excretion ◽

Control Group ◽

E Coli ◽

Nitrogen Levels ◽

Lps Challenge ◽

Nitrogen Intake

Abstract This study was conducted to assess the effect of E. Coli lipopolyssacharide challenge (IC) on Nitrogen Balance (NB) in growing pigs (19 kg). Three NB trials were performed in a complete RBD, with six nitrogen levels (NL), two sanitary status (control and IC) and two individual replicates per treatment (6 x 2 x 6). Pigs were intramuscular injected with 30 and 34 μg LPS/kg for two consecutive days. Dietary NL ranged from 1.06 to 4.48 % (dry matter), with lysine being limiting in all diets. NB trials lasted 11 days in which feces and urine were collected at the last four days to determine N intake (NI), N excretion (NEX) and N deposition (ND). Data were analyzed as two-way ANOVA and polynomial contrasts were used. Body weight were unaffected by the factors under study (P >0,05). LPS-challenged pigs had a lower (P< 0,05) feed intake compared with control group (372,98 vs. 417,82). Interaction between NL and IC were observed (P< 0,05) for NI, NEX and ND. NL linearly increased NI, NEX and ND, with different equations for both groups (P< 0,05): ND = 127,86 + 246,95 NL in control group whereas ND = 150,66 + 155,4 in LPS group. LPS-challenged pigs fed the three highest NL exhibited a decrease in NI compared with control group (P< 0,05). From NL2 to NL6, ND was also impaired in LPS-challenged pigs compared with control. Nitrogen excretion was higher in LPS-challenged pigs fed the two highest NL compared with pigs from control group (P< 0,05). In conclusion, LPS challenge impairs nitrogen retention in growing pigs by 37%. These outcomes can be used further for modelling procedures to estimate lysine requirements of pigs in different sanitary status.

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The relationship between mineral and nitrogen balances in growing pigs fed diets supplemented with zinc oxide

Canadian Journal of Animal Science ◽

10.4141/cjas96-059 ◽

1996 ◽

Vol 76 (3) ◽

pp. 409-415 ◽

Cited By ~ 2

Author(s):

Torben Larsen ◽

Hanne Damgaard Poulsen

Keyword(s):

Zinc Oxide ◽

Trace Elements ◽

Trace Element ◽

Feed Intake ◽

Zinc Supplementation ◽

Calcium Absorption ◽

Nitrogen Retention ◽

Experimental Period ◽

Growing Pigs ◽

Zinc Absorption

The present study was conducted to determine if there were effects of increasing levels of dietary zinc supplementation on the turnover of zinc and other minerals and trace elements in growing pigs. Thirty crossbred female pigs, with an initial body weight of approximately 25 kg, were randomly assigned to five diets with increasing levels of supplemented zinc (as zinc oxide); i.e. from the intrinsic level of 42 mg kg−1 diet to 72, 105, 170, and 255 mg kg−1, respectively. The animals were subjected to two 7-d balances in metabolic cages, separated by 15 d in pens. Balances consisted of controlled feed intake, i.e. approximately 10% below the expected ad libitum intake, and quantitative collection of feces and urine. Zinc supplementation did not affect nitrogen absorption, excretion, or retention (P > 0.05). The inclusion of zinc oxide did not affect (P > 0.05) weight gain of the animals throughout the 34 d experiment. Neither mineral nor trace element balances, except for zinc, were affected (P > 0.05) by zinc supplementation. Urinary excretion of zinc was not affected (P > 0.05), but zinc absorption and retention calculated in absolute amounts or in proportion to nitrogen retention (i.e. lean body accretion) increased several-fold when diets were supplemented with zinc oxide. Mineral and trace element absorption in proportion to nitrogen retention appeared remarkably constant throughout the experimental period, although feed intake and body size increased with time. Only calcium absorption and retention, determined in proportion to nitrogen retention and as fractions of ingested calcium increased (P < 0.001), 14 and 9%, respectively, with time. In general, mineral and trace element absorption and retention, expressed in proportion to nitrogen retention, appear to be a useful expression for comparisons between observations across time intervals. Key words: Zinc, absorption, retention, interaction, minerals, trace elements

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PENGARUH PENGGUNAAN VIRGIN COCONUT OIL (VCO) DALAM RANSUM TERHADAP PERFORMANS TERNAK BABI FASE STARTER

ZOOTEC ◽

10.35792/zot.36.1.2016.9986 ◽

2015 ◽

Vol 35 (2) ◽

pp. 86

Author(s):

Alfred Tamawiwy ◽

M. Najoan ◽

J S Mandey ◽

F. N Sompie

Keyword(s):

Water Consumption ◽

Feed Intake ◽

Control Diet ◽

Coconut Oil ◽

Growing Pigs ◽

Virgin Coconut Oil ◽

Daily Water ◽

Pig Performance ◽

Daily Gain ◽

Daily Water Consumption

ABSTRACT EFFECT OF UTILIZATION OF VIRGIN COCONUT OIL (VCO) IN THE DIET ON PIG PERFORMANCE. Utilization of fats and oils in pig diets is of great importance due to their high energy value. VCO is obtained by cold press processing of the kernel from the coconut fruit. Utilization of virgin coconut oil (VCO) in the diets on pig performance. The present study was designed to elaborate the effect of utilization of VCO in the diets on energy and protein digestibility of growing pigs. The experiment was conducted using 20 castrated male pigs aged 1.5 - 2.0 months weighing 12,0±2,0 kg. The data were analyzed according to the linear model procedure for ANOVA appropriate for Randomized Block Design with 5 treatments and 4 replications. Treatments were formulated as follow: R0 = 100% control diet + 0% VCO; R1 = 99.5% control diet + 1.0% VCO; R2 = 98.0% control diet + 2.0% VCO; R3 = 97.0% control diet + 3.0% VCO; and R4 = 96.0% control diet + 4.0% VCO. Parameters measured were: daily feed intake, daily gain, daily water consumption. The results showed that the utilization of VCO up to 4% in the diets had no significant effect (P > 0.05) on daily feed intake, daily gain, daily water consumption of pigs. It can be concluded that the addition of VCO up to 4.0% in the diets has no significant meaning on pig performance. Key words: Virgin coconut oil (VCO), Performance, Growing pigs

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Identification of blood immune and metabolic indicators explaining the variability of growth of pigs under contrasted sanitary conditions

BMC Veterinary Research ◽

10.1186/s12917-021-02872-3 ◽

2021 ◽

Vol 17 (1) ◽

Author(s):

N. Le Floc’h ◽

F. Gondret ◽

R. Resmond

Keyword(s):

Body Weight ◽

Feed Intake ◽

Goodness Of Fit ◽

Growing Pigs ◽

Metabolic Changes ◽

Housing Conditions ◽

Blood Profile ◽

Blood Concentrations ◽

Antioxidant Power ◽

Sanitary Conditions

Abstract Background Health and growth of pigs are affected by the hygiene of housing. Lower growth performance observed in poor hygiene of housing conditions is explained by reduced feed intake and metabolic changes caused by the activation of body defences. In a previous experiment, we reported contrasted average values of body weight gain, concentrations of circulating metabolites, redox and immune indicators in blood of pigs housed in good or poor hygiene conditions during the growing period. This study addressed inter-individual variability in these responses to determine whether a particular blood profile explains average daily gain (ADG) of the pig. Results The data originated from 160 growing pigs, half of which subjected to a hygiene challenge for 6 weeks (W0 to W6) and the others housed in good hygiene conditions. Pigs originated from two lines divergently selected for residual feed intake (RFI). Individual body weights were recorded during this period, and relative ADG (rADGW0-W6) was calculated as the ADG corrected by the initial body weight measured at W0. Blood samples were taken before (W0) and 3 weeks (W3) after the beginning of the challenge. The analysed dataset consisted of 51 metabolites and indicators of immune and inflammatory responses measured on 136 pigs having no missing value for any variables, when calculated as the differences W3 minus W0 in circulating concentrations. An algorithm tested all possible linear regression models and then selected the best ones to explain rADGW0-W6. Six variables were identified across the best models and correlated with rADGW0-W6 with a goodness of fit (adjusted R2) of about 67%. They were changes in haptoglobin, global antioxidant capacity of plasma (Biological Antioxidant Power or BAP), free fatty acids, and 3 amino acids: leucine, tryptophan, and 1-methylhistidine. The effects of housing conditions and RFI lines were comprised in the variables of the selected models and none of these conditions improved accuracy of the predictive models, leading to genericity of the pinpointed metabolic changes in relation to variability of ADG. Conclusions This approach allows us to identify blood variables, whose changes in blood concentrations correlated to ADG under contrasted sanitary conditions.

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Using different levels of energy and protein and their effects on bodyweight and blood chemistry of ostriches

Veterinary Research Communications ◽

10.1007/s11259-021-09792-5 ◽

2021 ◽

Author(s):

Tahereh Nikravesh-Masouleh ◽

Alireza Seidavi ◽

Magdalena Solka ◽

Mohammad Dadashbeiki

Keyword(s):

Weight Gain ◽

Total Cholesterol ◽

Feed Intake ◽

Experimental Period ◽

Blood Chemistry ◽

Blood Parameters ◽

Bodyweight Gain ◽

Transferase Activity ◽

Dietary Energy ◽

Protein Levels

AbstractTo determine the effect of different dietary energy and protein levels on bodyweight and blood chemistry, 36 ostriches at 2 to 9 weeks of age for feeding conditions and 18 for blood chemistry parameters was used. The birds were divided into six treatment groups. Energy and protein levels of diet were 2400 and 2600 kcal/kg and 20%, 22%, and 24%, respectively. The feed intake and bodyweight gain were determined a weekly. Blood chemical parameters including glucose, HDL, LDL, total cholesterol, triglycerides, total protein, albumin, globulin, aspartate amino-transferase and alanine amino-transferase activity were determined. The highest weight gain during the whole experiment was observed in ostriches offered 2400 kcal · kg−1 dietary energy and 20% protein. The lowest level of total cholesterol and protein was observed in treatment V (2600 kcal · kg−1 dietary energy and 22% protein). The lowest level of glucose and triglycerides was noted after treatment I. The highest albumin and globulin concentrations were in treatment III (2400 kcal · kg−1 dietary energy and 24% protein) and treatment II (2400 kcal · kg−1 dietary energy and 22% protein), respectively. The energy level had no effect (P < 0.05) on feed intake and weight gain in all experimental period. The results of this study showed that with increasing energy and protein levels, most blood parameters increased in ostriches but total cholesterol did not.

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Quality of colostral passive immunity and pattern of serum protein fluctuation in newborn calves

Scientia Agricola ◽

10.1590/s0103-90162003000300006 ◽

2003 ◽

Vol 60 (3) ◽

pp. 453-456 ◽

Cited By ~ 6

Author(s):

Patricia Pauletti ◽

Raul Machado Neto ◽

Irineu Umberto Packer ◽

Raul Dantas D'Arce ◽

Rosana Bessi

Keyword(s):

Total Protein ◽

Statistical Design ◽

Extended Period ◽

Experimental Period ◽

Passive Immunity ◽

Serum Total Protein ◽

Non Linear ◽

Medium Level ◽

Group 2 ◽

High Level

Immunity acquired by newborn animals is known as passive immunity, and for ruminants, antibody acquisition depends on the ingestion and absorption of adequate amounts of immunoglobulins from colostrum. This study relates different initial levels of acquired passive protection and serum total protein (TP) and immunoglobulin G (IgG). Serum immunoglobulin concentration and total protein were evaluated for female Holstein calves in the first sixty days of life. Animals were separated into three groups according to their initial level of passive immunity: group 1- animals with a low level of passive immunity (below 20 mg mL-1); group 2- animals with a medium level (between 20 and 30 mg mL-1), and group 3- animals with a high level (above 30 mg mL-1). Serum total protein was determined through the biuret method and IgG was determined by radial immunodiffusion. Data were analyzed as a completely randomized, split-plot statistical design. Fluctuation of the variables along the experimental period was determined through non-linear regression by the DUD method (PROC NLIN - Non Linear SAS). Animals with low antibody acquisition started to produce antibodies earlier, reflecting a compensatory synthesis. On the other hand, animals having adequate levels exhibited an extended period of immunoglobulin catabolism and the beginning of the endogenous phase was delayed. Regardless initial levels, the fluctuations in IgG contents occurred around adequate physiological concentrations, ranging from 20 to 25 mg mL-1.

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