Exigências nutricionais e predição da composição corporal de bovinos Nelore puros e cruzados

• Ano de defesa: 2010
• Autor(a) principal: Marcondes, Marcos Inácio
• Orientador(a): Valadares Filho, Sebastião de Campos
• Banca de defesa: Detmann, Edenio , Paulino, Mário Fonseca , Valadares, Rilene Ferreira Diniz
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Creatinina; Bovinos; Exigências
• Palavras-chave em Inglês: Creatinine; Cattle; Requirements
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/1754

This work was conducted to evaluate intake, performance, feed efficiency, carcass characteristics of bovines from three genetic groups, fed high or low concentrate level; to determine energy and protein requirements of pure and crossbred Nellore cattle and to estimate its maturity; Validade Hankins and Howe equation to predict body composition and propose new equation to predict carcass and non-carcass composition of pure and crossbred Nellore cattle. The work was conducted in two phases. The first one was developed at Universidade Federal de Viçosa, where a trial was conducted using 69 animais (23 Nellore [NE], 23 Nelore- Angus [NA], and 23 Nellore-Simmental [NS], being 12 (4 for each genetic group) slaughtered before the beginning of the experiment as the baseline group, and nine were used to perform a digestibility trial. The remaining animals were divided into three dietary treatments (concentrate fed at 1 or 2% of body weight and at maintenance). At the conclusion of the experiment all these animals were slaughtered and body composition and empty body weight (EBW) were determined. The dry matter and nutrients intakes were higher in the high level of concentrate offer (LOC) both in kilograms and % of body weight, except neutral detergent fiber. Evaluating feed efficiency, the bionutritional index showed no differences in efficiency for LOC. Crossbreds appeared to be more efficient than NE. The net energy requirement for maintenance of Nellore, Nellore-Angus and Nellore-Simmental is 75.8 kcal/EBW0.75 and the metabolizable energy requirements for maintenance are 112.82 kcal/EBW0.75, and the energy retention efficiency as protein and fat are 26.71 and75.43%, respectively. There weren’t effects of genetic group in net protein requirements for gain and it’s suggested the model RP = EBW × (238.5 – 16.73 × (RE/EBG)) to estimate them. There weren’t found any genetic group effect on net and metabolizable protein requirement for maintenance, and its obtained values were 1.72 g/EBW0.75 and 3.09 g/BW0.75, respectively. Also, there weren’t genetic group effects on retained energy as protein, as well as in metabolizable protein efficiency for gain, being this efficiency of 37.5%. The overall equation to predict partial efficiency of metabolizable energy for gain (kg) was: 0.327±0.142/(0.539±0.317 + REP), where REP is retained energy as protein. Because our database consisted of Nellore and B. indicus and B. taurus crossbreds, it is necessary to further evaluate differences between Bos taurus and Bos indicus regarding (kg). The equation to predict partial efficiency of use of metabolizable energy for maintenance (km) was 0.513±0.024 + 0.173±0.061 × kg + a × EBG, where a = either 0.100(±0.021) or 0.073(±0.021) for Bos indicus or crossbreds, respectively. The exponential model suggest that Nellore cattle reach maturity with 445 kg and linear plateau suggest that maturity is reach with 428.5 kg, therefore a value of 437 kg was settle for maturity in Nellore cattle. A high relationship between soft tissue water (STW) and soft tissue ether extract (STEE) was observed (STEE = 0.920 – 1.147 × STW), however the soft tissue was not a good predictor of maturity, because it is too dependent on the diet. The bone chemical composition analysis showed that ether extract, water and ash becomes constant between 400 and 500 kg of EBW, and that CP in bones is constant (19.1%). These data also suggest that bone composition could be a good predictor of maturity. The body composition can be obtained by using data from 9-11th rib cut (Rib9-11) visceral fat, carcass dressing and empty body weight (EBW), and body compostion can be obtained by using Rib9-11, visceral fat, and percentage of organs plus viscera in EBW. The results of physical carcass composition indicated a breed effect on all components and a sex effect was observed for fat in the carcass. Visceral fat was the component with greatest influence on non-carcass components, affecting ether extract (EE), crude protein (CP), and water in head, EE and water in limbs and organs plus viscera (OV), and CP and water in hide and blood. Carcass dressing, carcass weight, hide percentage in EBW, OV percetange in EBW and EBW also affected non-carcass components. It is possible to conclude that animals consuming 2% of body weight in concentrate have higher intake and gain, but there are no differences in feed efficiency when compared with those consuming 1%. It also can be concluded that animals NS are more efficient than NA and CB are also more efficient than NE. The km can be predicted from kg and EBG and that breed can affect km. It also can be concluded that kg can be predicted from REP and neither sex nor breed affect kg. It can also be concluded that Nellore cattle reaches maturity with 437 kg of EBW and that CP in FFDM and CP, water and ash in bones are good predictor of maturity, however soft tissue composition cannot be used to predict maturity. Body and carcass composition of Nellore and crossbred cattle can be estimated by Rib9-11 plus easy to be measured variables in Nellore cattle, and estimation of head, limbs, hide and blood is possible and well recommended, once they almost don’t affect body composition. The use of OV equation is recommended only when their chemical analysis is not possible, once this component has a great variability and it is affected by the diet.