Balanço de compostos nitrogenados e estimativa das exigências de proteína de mantença de bovinos Nelore de três condições sexuais

Abstract

RESUMO -Objetivou-se com este estudo avaliar o efeito de níveis crescentes de PB sobre o balanço de N e as exigências de proteína metabolizável para mantença em bovinos Nelore. Foram utilizados 12 bovinos Nelore, fistulados no rúmen e no duodeno, de três condições sexuais (quatro fêmeas, quatro machos castrados e quatro machos não-castrados), com idade aproximada de 16 meses e peso corporal médio de 254,8; 285,1 e 265,6 kg, respectivamente. Utilizaram-se três quadrados latinos 4 × 4, compostos de quatro animais, quatro níveis de PB (7, 10, 13 e 15%) e quatro períodos. Effects of increasing dietary crude protein levels on nitrogen balance and metabolizable protein requirements for maintenance in Nellore cattleABSTRACT -The objective of this trial was to investigate the effects of increasing dietary crude protein levels on N balance and metabolizable protein requirements for maintenance in Nellore heifers, bulls and steers averaging 16 months of age and body weight of 254.8, 285.1, and 265.6 kg, respectively. Animals were blocked by sexual category (heifers, bulls and steers) and randomly assigned to treatments in three replicated 4 x 4 Latin squares. Diets contained the following CP levels: 7, 10, 13, and 15%. Estimation of fecal DM output and duodenal DM flow was done using the internal marker indigestible ADF. Total collection of urine was conducted from day 13 to day 14 on each period. Metabolic fecal nitrogen, urinary endogenous losses and total endogenous losses were all estimated using a regression approach. No significant effect of sexual category was observed for any of the studied variables, excepting for N intake that was greater on steers than heifers. N intake, urinary and fecal N excretions, and N balance increased linearly when the dietary CP level varied from 7 to 15%. Fecal metabolic N and urinary endogenous N averaged 6.69 gN/kg of DMI and 0.133 g N/kg 0.75 across diets, respectively. The net protein requirement was estimated as 0.431 gN/kg 0.75 or 2.69 g of protein/kg 0.75 . No effect of sexual category on metabolizable protein requirements for maintenance (approximately 4.0 g/kg 0.75 ) was observed in this trial.

Protein, calcium and phosphorus requirements in the maintenance of captive-bred capybaras

“…The daily digestible protein required for the maintenance of rabbits, for example, is 3.03 g/kg LW 0.75 (Lv et al, 2009). If on the one hand the daily requirement of Nelore cattle is 4.03 g/kg LW 0.75 (Véras et al, 2007), on the other hand, that of peccaries -a wild species with potential for domestication − is 5.1 g/kg LW 0.75 (Carl & Brown, 1985). In turn, the calcium and phosphorus requirements are lower than those for domestic species.…”

“…Besides acting in the building and repair of tissues, proteins are essential to promote proper biological functioning (Pond et al, 2004). The daily requirement for digestible protein (DP) of capybaras is relatively low: 2.5 g DP/kg LW 0.75 (González-Jiménez & Escobar, 1975), whereas Nellore cattle (Bos indicus) require 4.0 g DP/kg LW 0.75 (Véras et al, 2007).…”

Nutrient Requirements of Zebu and Crossbred Cattle - BR-CORTE

“…In the first edition of the BR-CORTE, in 2006, the value of 2.69 g/BW 0.75 , obtained by Véras et al (2007), was adopted as the net protein required for maintenance.…”

“…Nevertheless, Brazilian feedlot normally adopt CP levels ranging from 9.3 to 16.6%, with average values of 13.4% CP (Oliveira and Millen, 2014), because higher CP levels stimulate intake and are related to high weight gain (Véras et al, 2007). However, Menezes et al (2016) showed that dry matter intake is not affected by dietary protein levels and the reduction of CP contents during finishing phase contributes to reduction of feeding costs.…”

Nitrogen requirements of white‐lipped peccary (Mammalia, Tayassuidae)

“…The white‐lipped peccary's nitrogen daily requirement—minimum N intake of 336.5 mg N/kg 0.75 /day—was near to that of domestic ruminants (Nellore cattle: 431 mg N/kg 0.75 ) fed with forage and concentrate diets [Véras et al, ], but lower than that of red deer (680 mg N/kg 0.75 /day) and white‐tailed deer (710 mg N/kg 0.75 /day), receiving forage and concentrate diets [Robbins, ], and the blue duiker (643.3 mg N/kg 0.75 /day), receiving fruit, browsing, and eating a concentrate diet.…”