Desempenho e exigências nutricionais de bovinos alimentados com dietas contendo diferentes níveis de cálcio e fósforo

• Autor(a) principal: Prados, Laura Franco
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5751
• topic: Exigências nutricionais; Bovinos; Minerais; Nutritional requirements; Cattle; Minerals; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

This study was conducted to evaluate intake, digestibility and performance of crossbred cattle (¾ Zebu × ¼ Holstein) fed three levels of calcium and phosphorus diets; to determine energy and protein requirements of crossbred cattle (¾ Zebu × ¼ Holstein), uncastrated, and evaluate equations to predict carcass, non-carcass components and empty body chemical composition, obtained by Hankins & Howe (1946) and the BR-CORTE (2006 and 2010), using the section between the 9-11th rib. The first chapter aimed to evaluate the dry matter intake (DMI) and nutrients, average daily gain, digestibility, carcass dressing and loin eye area of crossbred cattle (¾ Zebu × ¼ Holstein), fed three levels calcium and phosphorus. We used 40 crossbred cattle (¾ Zebu × ¼ Holstein), with an initial weight of 214 ± 4 kg and a mean age of 11 ± 0.2 months. Four animals were slaughter to make up the reference group and 36 animals fed ad libitum were distributed in a completely randomized design, 3 × 3 factorial arrangement, three levels of calcium and phosphorus (low, medium and normal) and three feedlot time (56, 112 or 168 days) with four replications. Diets were isonitrogenous (126.1 g/kg) and consisting of corn silage and concentrate, the ratio of 60:40 on dry matter basis. To evaluate the total digestibilities were used stool samples obtained during three consecutive days, at the end of each feedlot time. There wasn t significant interaction between calcium and phosphorus levels and periods of confinement for any variable. The dry matter intake (DMI), crude protein (CP), ether extract (EE), organic matter (OM), non-fiber carbohydrates (NFC), calcium (Ca) and phosphorus (P), expressed in kg/day or g/day, were higher (P<0.05) for animals which remained more days at feedlot, when the DMI was represented as a function of body weight (BW) decreased (P<0.05) in this animals. The calcium intake was influenced by its level in the diet (P<0.05), being higher in animals fed normal levels of this mineral in the diet. The digestibility of nutrients were not affected (P>0.05) by any of factors studied. The average daily weight gain (ADG) of animals was not affected (P>0.05) by any of factors studied. The carcass dressing were lower (P<0.05) for animals which spent less time confined. It is conclude that dietary levels of calcium and phosphorus recommended by the BR-CORTE (2010) for feedlot crossbred cattle ( ¾ Zebu × ¼ Holstein) can be reduced, respectively, by 50 and 20%. The second chapter aimed to determine the energy and protein requirements for maintenance and weight gain of crossbred cattle (¾ Zebu × ¼ Holstein) and their efficiency. We used 50 crossbred cattle, uncastrated with an initial weight of 214 ± 4 kg and a mean age of 11 ± 0.2 months. Four animals belonged to reference groug, ten to maintenance group and 36 animals were distributed in a completely randomized design, 3 × 3 factorial arrangement, with three feedlot time (56, 112 or 168 days) and three calcium and phosphorus levels (low, medium and normal) diet. Four animals of maintenance group were sent to the laboratory of metabolism and calorimetry in UFMG to measure heat production through respirometry. Diets were composed of corn silage and concentrate (60:40) and isonitrogenous (126.1 g/kg). After slaughtering, two composite samples were obtained for each animal, called carcass and non-carcass. The net (NEm) and metabolizable (MEm) energy requirement for maintenance were obtained relating heat production (HP) and metabolize energy intake (MEI), while the net energy requirements for gain (NEg) and net protein requirements for gain (PNg) were obtained as a function of empty body weight (EBW) and the gain of empty body weight (EBG). The requirements NEm and MEm were respectively 68.9 and 90.1 kcal/EBW0,75/day. The km was 76%. The NEm requirement obtained in respirometric chamber was 85.5 kcal/BW0,75. The equations to NEg and NPg were NEg (Mcal/day) = 0.0505 ± 0.000986 × EBW 0.75 × EBG 1.095 and NPg (g/day) = 162.79± 18.2546 × EBG - 1,30 ± 5.3010 × NEg. The efficiencies for deposition of protein and fat were 70% and 15%. It is conclude that the NEm and MEm requirements crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated are, respectively: 68.9 and 90.1 kcal/EBW0,75/day, and the NEg and NPg requirements can be obtained by the respective equations: NEg (Mcal/day) = 0.0505 ± 0.000986 × EBW 0.75 × EBG 1.095 and NPg (g/day) = 162.79± 18.2546 × EBG - 1,30 ± 5.3010 × NEg. The third chapter aimed to test the equations for predicting chemical body composition proposed by Hankins & Howe (1946) and BR-CORTE (2006 and 2010) using the section between the 9-11th rib for crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated. We used 46 crossbred cattle (¾ Zebu × ¼ Holstein) uncastrated with an initial weight of 214 ± 4 kg and a mean age of 11 ± 0.2 months. Diets were composed of corn silage and concentrate (60:40), and isonitrogenous (126.1 g/kg). After slaughtering, the section was removed between the 9-11th rib of the right carcass, and it was complete dissected. Similarly, the right carcass of animal was complete dissected. We also evaluated the empty body weight, carcass dressing, percent of visceral fat, percent of organs and viscera and the carcass, not carcass and empty body weight chemical composition. The prediction efficiency between models were made by estimating the mean square error of prediction and its components, concordance correlation coefficient (CCC) and distribution of the prediction errors. The equations proposed by BR-CORTE (2006) estimated adequately crude protein and water of carcass and ether extract and water of empty body. The equations proposed by BR-CORTE (2010) estimated adequately crude protein and ether extract of carcass and crude protein of empty body. The equations proposed by Hankins & Howe (1946) estimated accurately only crude protein of carcass. New equations were generated to predict the chemical composition of non-carcass components. It is conclude that the equations proposed by BR-CORTE (2010) estimated correctly the crude protein and ether extract of carcass and crude protein of empty body for crossbred cattle, and that the equations proposed by BR-CORTE (2006) estimate properly the crude protein and water of carcass, and ether extract and water of empty body. The proposed equations to estimate the chemical composition of non carcass for crossbred cattle (¾ Zebu × ¼ Holstein) were CPNC = 15.55 + 0.11 × CPsec + 0.004 × EBW; EENC = 8.47 + 0.11 × EEsec + 2.99 × VF - 0.74 × OV and WNC = 60.31 + 0.25 × Wsec - 1.97 × VF.