The influence of the body weight and the characteristics of the carcass about the creatinine excretion and the use of spot sample of urine to estimate the excretion of purine derivatives and the nitrogenous compounds in nelore heifers / Influência do peso corporal e das características de carcaça sobre a excreção de creatinina e utilização de coleta spot de urina para estimar a excreção de derivados de purinas e de compostos nitrogenados em novilhas nelore

AUTOR(ES)

Verônica Schinaider do Amaral Pereira

DATA DE PUBLICAÇÃO

2009

RESUMO

This study aimed to evaluate the relation between body weight, the amount of muscle in the carcass, the rib eye area and subcutaneous fat thickness with the daily excretion of creatinine in Nelore heifers of different weights. We also assessed the total creatinine excretion at intervals of 4 and 24 hours and the relation of purine derivatives (PD), urea (U) and nitrogenous compounds (NC) to creatinine (C), obtained from spot samples of urine at intervals of 2 hours. Fifteen heifers were used, grouped according to body weight in three groups, one group with four heifers with the average weight 127 kg 24,2 (low), three of 221 kg 22,3 (medium) and eight of 434 kg 29,2 (high). The animals from the higher body weight group (high) were randomly distributed into two subgroups, each one with four animals, and one of them (restricted high) the diet was provided near to the maintenance level (1,3% of body weight) and to the other group (voluntary high) the diet was provided ad libitum. For the low and medium group, the same diet, composed of 60% of roughage (corn silage), 30% concentrate (a mixture based on soybean hulls, ground corn, soybean meal, urea/ammonium sulfate, chloride sodium and minerals) and 10% of cotton seed, was provided ad libitum. The experimental period lasted nine days, after 30 days of adaptation. The collections of urine were performed, using number 22 or 26 Folley catheters, depending on the weight of the heifer. Considering the period of collection of 24 hours, the daily creatinine excretion expressed in g, mg/kg BW, mg/kg of empty body weight (EBW) and mmol/kg BW0,75 was influenced by body weight and the amount of muscle (MUS) in the carcass (P<0.05), according to the following regression equations: C (g) = 0,397530 + 0,0441496 BW - 0,0596162 MUS; C (mg/kg BW) = 28,0059 + 0,041690 BW - 0,144537 MUS; C (mg/kg EBW) = 30,3663 + 0,0614500 BW - 0,205820 MUS and C (mmol/kg BW0,75) = 0,735514 + 0,00253957 BW - 0,00565242 MUS. To estimate the creatinine excretion, body weight was the main determinant, and the use of other variables, muscle, and rib eye area and subcutaneous fat thickness was not sufficient to improve the results. The average daily excretion U, CN and PD were just affected by body weight. None of the excretion was influenced by the rib eye area and subcutaneous fat thickness. The daily creatinine excretion found in this study was 26,35 mg/kg BW. or 0,95 mmol/kg BW0,75. When the collection was done at intervals of 4 hours, the average daily creatinine excretion found was 0,91 mmol/kg BW0,75. When expressed in g and mmol/kg BW0,75 there was a significant difference (P <0.05) among groups, by being higher the creatinine excretion for those animals of greater body weight, when expressed in mg/kg BW was not influenced by body weight (P>0.05). There was no effect (P>0.05) of the collection periods (00h00-04h00, 04h00-08h00, 08h00-12h00, 12h00-16h00, 16h00-20h00, 20h00-00h00 hours) in the creatinine excretion expressed in any unit. From the collection of spot urine at intervals of 2 hours was observed the relationship PD:C has not varied during the day (P>0.05), allowing the calculation of the excretion of PD (mmol/day) to be done with obtained sample at any time of the day. There was effect (P<0,05) of the periods of the urine spot sample over the relations U:C and NC:C, which were analyzed by Fourier serie, obtaining two points daily close to the average of 7,77 to the relation of U:C and 6,42 to the relation NC:C. The two points got very close to food time (08h00 and 16h00). To estimate the nitrogenous compounds excretions, recommends two spot collections, right after the food is given. It is concluded that the lack of time effect of collection over the relationship of PD:C indicates that one can use the sample spot obtained at any time to determine, the excretion of PD, there is no need in the total collection urine.

ASSUNTO(S)

urina ruminantes ruminants nutricao e alimentacao animal urine

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