Desempenho e qualidade de carne em novilhas de corte alimentados com dois níveis de concentrado e proteína não degradável no rúmen e influência da maturidade fisiológica sobre parâmetros qualitativos da carcaça e da carne bovina

• Autor(a) principal: Duarte, Marcio de Souza
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5659
• topic: Confinamento; Insulina; PDR; PNDR; Confinement; Insulin; PDR; RUP; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::NUTRICAO E ALIMENTACAO ANIMAL

The present work was developed based on two experiments. The first experiment was conducted aiming to evaluate the effects of ruminal energy-protein synchronization on feed intake, nutrients digestibility, feed conversion, animal performance, carcass yields and composition, composition of the carcass gain, percentage of commercial cuts and meat quality of feedlot heifers. In this trial, twenty crossbreed heifers (240+6kg) were used, all of them coming from the same contemporary group. At the beginning, four animals were slaughtered as reference group and the sixteen animals remaining were assigned to a completely randomized design in 2x2 factorial schemes, two levels of concentrate (40 and 80%, based on dry matter) and two levels of ruminally undegradable protein (RUP). These animals were individually fed during 112 days and slaughtered at the end of the trial. There was no interaction (P>0.05) between the level of concentrate and RUP. The dry matter intake (DMI), feed intake and nutrients digestibility were not affected (P>0.05) by RUP level. However, the animals fed higher level of RUP diets had higher (P<0.05) average daily gain (ADG) compared with the animals fed lower level of RUP diets. The level of concentrate did not affect (P>0.05) the DMI, feed conversion and ADG, but the intakes of TDN, NDFcp and EE, were superior (P<0.05) in the animals fed higher concentrate diets. The digestibilities of all nutrients, except the NDFcp, were greater (P<0.05) for the 80% concentrate diets. There was no affect (P>0.05) of RUP level on carcass yields. Similarly, the percentage of commercial cuts, the composition of the carcass and the composition of the carcass gain were not affected (P>0.05) by the level of RUP and concentrate. However, the animals fed 80% concentrate diets had a larger (P<0.05) rib eye area (REA) compared with the animals fed 40% concentrate diets. No differences (P>0.05) in Warner-Bratzler shear force, myofibrillar fragmentation index, percentage of total cooking loss, and chemical composition of the Longissimus dorsi, were found among the levels of concentrate and RUP. It can be concluded that the level of RUP did not affect the feed intake and nutrients digestibilities, but improved the feed conversion and increased the ADG. Neither level of RUP nor level of concentrate affected the carcass composition, composition of carcass gain, percentage of commercial cuts and the meat quality of the feedlot heifers. The second experiment was conducted to evaluate the beef carcass traits and meat quality of cattle differing in numbers of permanent incisors. Sixty-three Nellore bulls, non-castrated, all from the same farm and grown on pasture, were used. The animals were selected at a large commercial beef plant. Immediately after the slaughter, the numbers of incisors were recorded after a visual examination by looking directly at the teeth and the carcasses were grouped in four categories according to teeth maturity (two, four, six or eight). After 24-h chill, data of carcass weight, pH, rib eye area (REA) and 12th rib fat thickness were collected. After carcass data collection, a boneless Longissimus section between the 9th and 11th rib was removed, vacuum packaged, frozen and held at -200C. The REA and the 12th rib fat thickness increased (P<0.05) as the number of permanent incisors increased. However, no differences (P>0.05) in carcass ultimate pH were found among the four dental classes. There was no effect (P>0.05) of dental maturity on percentage of evaporative and total cooking losses, but differences in percentage of thawing and drip losses were found (P<0.05) among the four dental classes. The Longissimus intramuscular fat and water content were affected (P<0.05) by the dental maturity. However, there was no difference (P>0.05) in percentage of protein and ashes among the dental classes. With the exception of b* values, the dental maturity did not affect (P>0.05) the instrumental color of the Longissimus. The Warner-Bratzler shear force (WBSF), the myofibrillar fragmentation index (MFI) and collagen solubility were affected (P<0.05) by dental maturity, whereas the WBSF has increased while the MFI and collagen solubility decreased as the number of permanent incisors increased. An increase of WBSF was associated (P<0.01) with decreased MFI (r = -0,36) and collagen solubility (r = - 0,14). It can be concluded that the physiological maturity, based on dental classification, affects the carcass traits and meat quality of Nellore cattle. It can also be concluded that meat from non-castrated Zebu cattle up to four permanent incisors has a desirable tenderness.