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52a Reunião Anual da Sociedade Brasileira de
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Derivados de purina e síntese de proteína microbiana em ovinos castrados e não castrados submetidos à
diferentes níveis quantitativos de restrição alimentar 1
José Nery Rocha Junior2, Elzania Sales Pereira3, Andrea Pereira Pinto3, Ana Claúdia Nacimento Campos3, Carla
Renata Figueiredo Gadelha3, Monalisa Eva Evangelista dos Santos 2, Karoliny Farias Castelo Branco2
1
Parte de dissertação de mestrado do primeiro autor, financiada pelo CNPq
Mestrando do Programa de Pós-Graduação em Zootecnia da Universidade Federal do Ceará, Ceará, Brasil. E-mail:[email protected]
3
Docente doDepartamento de Zootecnia, CCA/UFC, Fortaleza-CE, Brasil.
2
Resumo: Objetivou-se avaliar a produção e a síntese de proteína microbiana (Pmic) através dos derivados de purina
(DP) na urina de ovinos Santa Inês castrados e não castrados, submetidos a diferentes níveis de restrição alimentar.
Trinta ovinos machos da raça Santa Inês, com aproximadamente 60 dias de idade foram utilizados. Quinze animais
foram aleatoriamente selecionados e castrados. Posteriormente, distribuídos em baias individuais em delineamento
inteiramente casualizado em esquema fatorial 3x2, com 3 níveis de restrição alimentar (0; 30 e 60%) e 2 classes
sexuais (castrados e não castrados). A relação volumoso:concentrado foi de 60:40. Quinzenalmente foram coletadas
amostras de urina spot para obtenção de creatinina e estimativa do volume urinário (VU). As variáveis de
creatinina, VU, DP, purinas totais e purinas absorvidas, foram responsivas aos níveis de restrição alimentar. Não
foram encontradas diferenças (P>0,05) para ácido úrico, expresso em (mg/kg0,75.dia-1) e (mmol/kg0,75.dia-1). A
Produção de Pmic foi reduzida (P<0,05) com a elevação dos níveis de restrição. Não foi observada diferença
(P>0,05) entre os níveis de restrição de 30 e 60% para eficiência de síntese de Pmic. Concluí-se que, a restrição
alimentar altera o metabolismo proteico de ovinos.
Palavras–chave: jejum, nutrição, ruminantes
Purine derivatives and microbial protein synthesis in castrated and no castrated sheep submitted to
different levels of quantitative food restriction
Abstract: This study aimed to evaluate the production and synthesis of microbial protein (MICP) through the
purine derivatives (PD) in the urine of castrated and non-castrated Santa Ines sheep under different levels of food
restriction. Thirty males of Santa Inês sheep, with approximately 60 days of age were used. Fifteen animals were
randomly selected and castrated. Subsequently divided into individual pens in a completely randomized design in a
3x2 factorial arrangement, with 3 food restriction levels (0, 30 and 60%) and two genders (castrated and
uncastrated). The roughage: concentrate of 60:40. Fortnightly spot urine samples were collected to obtain creatinine
and estimated urinary volume (UV). Creatinine variables, UV, PD, total purine and absorbed purines, were
responsive to dietary restriction levels. There were no differences (P>0.05) for uric acid, expressed as
(mg/kg0,75.dia-1) and (mmol/kg0,75.dia-1). The MICP production was reduced (P<0.05) with increasing levels of
restriction. There was no difference (P>0.05) between the restriction levels 30 and 60% for MICP synthesis
efficiency. It is concluded that dietary restriction affects the protein metabolism of sheep.
Keywords: fasting, nutrition, ruminant
Introduction
The excretion of urine PDs has been considered effective technique to measure microbial nitrogen flow to
the intestine. According to Stangassinger et al. (1995) purine are readily absorbed as nucleosides and free bases in
the lumen of the small intestine and are subject to extensive degradation by specific enzymes in its passage through
the intestinal mucosa. Since it is scientifically known that sheep and cattle differ between endogenous
concentrations of purine derivatives and of the efficiency of use of exogenous purines. Thus, this study aimed to
evaluate the excretions of creatinine to estimate urinary volume and subsequently measurement of purine
derivatives to estimate microbial protein synthesis in castrated and uncastrated Santa Ines sheep subjected to
different levels of restriction food.
Material e Methods
The experiment was conducted at Animal Science Department of the Federal University of Ceará. Thirty
males of Santa Ines sheep, of average weight of 13.00 kg ± 1.49 kg, and about 60 days of age were used. Fifteen
males were randomly selected and castrated with the use of Burdizzo. Later, they were divided into individual pens
completely randomized in a factorial 3x2, with three levels of feed restriction (0, 30 and 60%) and two genders
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52a Reunião Anual da Sociedade Brasileira de
Zootecnia
Zootecnia: Otimizando Recursos e Potencialidades
Belo Horizonte – MG, 19 a 23 de Julho de 2015
(castrated and no castrated). The total ration was composed of Tifton 85 hay (Cynodon dactylon) as forage and
concentrate diet based on corn and soybean of forage: concentrate ratio of 60:40.
Biweekly were collected spot urine samples to obtain estimates of creatinine in urine volume. The excretion
of creatinine and uric acid measurements were measured using commercial kits (Labtest®) by the end-point
method, using uricase and hydrogen peroxide and the use of picrate and acid, respectively. Allantoin was quantified
by colorimetric and xanthine and hypoxanthine enzymatically methods. The following formula was used to obtain
the urine volume: [(CP x daily creatinine excretion (mg.L-1)) / creatinine concentration (mg.L-1) in the spot urine
sample)]. Since the total excretion was estimated by the DPs sum of the amounts of uric acid, allantoin,
hypoxanthine and xanthine excreted in urine, expressed in mmol / day. Using the equation proposed by Chen and
Gomes (1992) for sheep: Y = 0.84x + (0.150 PC 0,75e-0.25x), where Y is the purine derivatives excretion (mmol .day1
); and X is the absorbed microbial purine (mmol.day-1) was estimated amount of absorbed microbial purine (X,
mmol.day-1) from the excretion of purine derivatives (Y, mmol .day-1).
By the same method, was measured rumen synthesis of nitrogenous compounds (Y, C g.day-1) as a function
of absorbed purine (X, mmol.day-1) by the equation: Y = 70X / 0.83 x 0.116 x 1000 where 70 is the N content of
purines (mg N.mol-1), 0.116 the relationship between N purine and Total bacterial N and 0.83 digestibility of
microbial purines. The estimation of microbial crude protein was obtained by multiplying the synthesis of microbial
nitrogen for 6,25 and the efficiency of microbial synthesis was calculated according to the quantity of total
digestible nutrients - NDT (NRC, 1985), in relation to organic matter degraded in the rumen - OMDR (ARC, 1980)
and depending on the amount of carbohydrates degraded in the rumen - CHODR (Cornell system - CNCPS -.
Sniffen et al, 1992). The variables were evaluated by analysis of variance using PROC GLM of the SAS system
version 9.0, and subjected to the test Student-Newman-Keuls 5% probability to compare the means.
Results and Discussion
Creatinine variables, UV, PD, efficiency and synthesis of MICP were responsive to dietary restriction levels
(Table 1). Knowing that creatinine is a metabolite of creatine, a substance synthesized by the muscles, it is inferred
that the smaller muscle deposition, caused by food restriction, influenced (P <0.05) in response to the estimated
total creatinine excretion and hence urine volume.
In Table 1, differences of the observed values of xanthine and hypoxanthine (mmol.day-1) and (mg.dia-1) at
levels of 30 and 60% compared to the level of 0% may be related to the metabolism of liver tissue, intestinal, lung
and kidney. Feed restriction physiologically promotes greater efficiency of nutrient use to meet the maintenance
requirements. So probably occurred greater use of ATPs for power generation in the restricted animals promoting
increased intracellular levels of hypoxanthine which can be justified to the largest concentration of xanthine and
hypoxanthine in mg/kg0,75.day-1 in level 60% restriction. This mechanism enables the conversion of xanthine
dehydrogenase to xanthine oxidase. According to Ørskov & Chen (2003), the activity of xanthine oxidase in the
tissue affects the excretion of endogenous purine derivatives, once that hypoxanthine can not be reused for the
synthesis of purine nucleotides when oxidized to xanthine by xanthine oxidase, for the production of uric acid.
Thus, no significant differences (P>0.05) in uric acid, expressed as (mg /kg0,75.day-1) and (mmol/ kg0,75.day-1) can be
attributed to higher values intracellular hypoxanthine in restricted animals.
It was observed that the amount of absorbed purine was also influenced (P <0.05) between power levels.
According to Chen and Ørskov (2003), prolonged fasting changes the metabolic activities of the animal and
therefore the rate of degradation of nucleic acids, a fact which implies directly in purine absorption and production
of microbial protein that showed a lower value with increasing levels constraint, probably due to quantitative
limitation of food in the rumen. Despite this, We noted that the nitrogen synthesis efficiency and MICP were not
different (P>0.05) in the levels of 30 and 60% which shows that animals tend to be more efficient in the use of
energy and protein available in rumen when in food restriction.
Table 1. Averages of creatinine variables, urinary volume, purine derivatives, and synthesis of micPB.
Variables
Total creatinine excretion
Allantoin
Uric acid
Xanthine+hypoxanthine
0%
582.10a
766.36a
217.49a
87.30a
Food restriction levels
30%
60%
(mg.day-1)
491.16b
378.81c
443.02b
258.26c
162.04b
136.29b
69.45b
67.67b
(L.day-1)
SEM
5.1707
5.4046
4.9504
1.4218
P-Value
<0.0001
<0.0001
<0.0001
<0.0001
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Urine volume
1.05a
Allantoin
Uric Acid
Xanthine+hypoxanthine
Total Purine
Absorbed Purines
5.76a
1.29a
0.52a
7.57a
7.32a
Allantoin
Uric Acid
Xanthine+hypoxanthine
TotalPurine
0.56a
0.13
0.05
0.76a
Production of Nmic
Production of Proteinmic
5.32a
33.27a
gN/kgNDT
gN/kgCHOT
gN/kgMO
11.93a
9.28a
7.80a
gPmic/kgNDT
gPmic/kgCHOT
gPmic/kgMO
74.56a
58.01a
48.74a
a-b
0.83b
0.81b
(mmol.day-1)
2.67b
1.68c
0.96b
0.81c
0.41b
0.40b
4.04b
2.89c
3.65b
2.39c
(mmol/kg0,75.day-1)
0.33b
0.24c
0.11
0.11
0.05
0.06
0.51b
0.41c
(g.day-1)
2.65b
1.74c
16.58b
10.87c
Nmic synthesis efficiency
7.00b
7.69b
6.20b
7.12b
5.36b
6.16b
Proteinmic synthesis efficiency
43.73b
48.04b
38.77b
44.52b
33.53b
38.51b
0.0172
<0.0001
0.0397
0.0295
0.0085
0.0667
0.0741
<0.0001
<0.0001
<0.0001
<0.0001
<0.0001
0.0056
0.0038
0.0012
0.0010
<0.0001
0.1045
0.0794
<0.0001
0.0541
0.3374
<0.0001
<0.0001
0.2673
0.2293
0.1963
<0.0001
<0.0001
0.0002
1.6708
1.4321
1.2265
<0.0001
<0.0001
0.0002
Means followed in line by different letters differ (P <0.05) by Student-Newman-Keuls test.
Conclusions
It is concluded that dietary restriction reduces the concentrations of purine derivatives and microbial protein
production, without however altering the microbial protein synthesis efficiency levels of 30 to 60%.
References
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