Nutritional requirements of energy, protein and macrominerals for maintenance and weight gain of young crossbred Nellore × Holstein bulls on pasture

Abstract

-The objective of this study was to estimate requirements of energy, protein and macrominerals of young Nellore/Holstein crossbreds bulls supplemented on pastures of Brachiaria decumbens Stapf. Thirty-five young bulls, at 8.53±0.18 months of age and with initial body weight of 230.6±6.1 kg were used. Ten animals were slaughtered as reference, in different weight range, and the other animals were slaughtered at the end of the experimental period. For estimate of net energy requirements for weight, a regression equation between log of retained energy (RE) and log of empty body weight gain (EBWG) was constructed. Net requirements of Ca, P, Mg, Na and K were determined by the equation Y' = a.b.X b-1 , in which a and b represent the intercept and the coefficient of equation of prediction of macrominerals in body content, respectively.Requirements of metabolizable energy for maintenance (MEm) were obtained from retained energy in function of metabolizable energy intake (MEI). The requirements of MEm of Nellore/Holstein crossbreds young bulls on pasture was 125 kcal/EBW 0.75 /day. The efficiency of ME utilization for maintenance (k m ) of grazing Nellore/Holstein crossbred young bulls was 0.58 and 0.24 for gain. The total metabolizable protein requirements for an animal with 400 kg and with average daily gain of 1.0 kg, were 638.36 g/day. The dietetic requirements of Ca and P for an animal with 400 kg BW were 0.49 and 0.21% of DM, respectively. Daily metabolizable energy requirement for maintenance of grazing Nellore/Holstein crossbred young bulls was 11.6% greater than the values found for cattle in feedlot in Brazil (112 kcal/kg EBW 0.75 ).

Energy and protein requirements of crossbred cattle in feedlot

“…This value is less than the that estimated by Ferrell and Jenkins (1998) for purebred sires and their crossbred offspring (65 to 69%); by Valadares Filho et al (2006) for Zebu bulls (66%); by Prados (2012) and Rotta et al (2013) for Holstein x Zebu crossbreds in confinement (76.41% and 68.91%, respectively) and by Costa e Silva et al (2012) and Marcondes et al (2011a) for confined Nellore purebreds and crossbred Nellore x Angus and Nellore x Simmental bulls, respectively (67%). However, the value found in the present study is higher than the one estimated by Porto et al (2012), which was 58% for pasture-raised Nellore x Holstein crossbreds. These differences are related to the higher energy concentration in the feeds given to confined animals compared with pasture-raised cattle that were not given any supplements.…”

“…In other words, under the present study conditions, the net requirements for daily gain of 1 kg of BW were equivalent to the requirements for daily gain of 0.95 kg of EBW. The factor of 0.95 is close to the one recommended by NRC (2000) for cattle in general and by Backes et al (2005) for crossbred Holstein x Zebu cattle (factor of 0.96) as well as the factor found by Silva et al (2002) and Prados (2012) Porto et al (2012), which was 71.9 kcal EBW -0.75 day -1 for pastureraised Nelore x Holstein crossbreds, and by Prados (2012) and Rotta et al (2013), which were 68.9 and 78.7 kcal EBW -0.75 day -1 , respectively, for Holstein x Zebu crossbreds in confinement.…”

“…The participation of RDP in the total CP requirements increased as the BW increased, which thus reduced the need for dietary RUP to meet the total CP requirements. This pattern was found in various other studies (ALMEIDA et al, 2009;PORTO et al, 2012;SILVA et al 2002;SOUZA et al, 2012b) and means that during the finishing stage, the amount of dietary non-protein nitrogen may increase as the animal weight increases (SILVA et al, 2002).…”

“…Porto et al (2012), who assessed pasture-raised Nellore x Holstein crossbreds, and Prados (2012), who assessed ¾ Zebu and ¼ Holstein crossbreds in confinement, found a lower efficiency in use of ME for gain (24% and 21%, respectively). However, higher values were obtained by Costa e Silva et al (2012) The energy requirements are described in Table 4.…”

<b>Requirement of energy and protein of beef cattle on tropical pasture</b> - doi: 10.4025/actascianimsci.v35i4.21143

“…However, recent researches have been performed in grazing conditions (PORTO et al, 2012), although, due to the complexity and numerous factors related to animal response and due to the lack of assays on some phases of productive cycle, further investigation must be performed to improve information for such conditions. Current assay estimates protein and energy requirement of 4-18-month-old beef cattle on tropical pastures.…”