RESUMO -O objetivo deste experimento foi avaliar os efeitos dos níveis de concentrado das dietas sobre os consumos e as digestibilidades aparentes totais e parciais de matéria seca (MS), matéria orgânica (MO), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN) e carboidratos totais (CHO). O efeito das coletas realizadas durante o dia e a noite, para as digestibilidades aparentes totais e parciais da MS e MO, também foi avaliado. Quatro novilhos Nelore, não-castrados, fistulados no rúmen, abomaso e íleo, alimentados à vontade com rações que continham 25,0; 37,5; 50,0; 62,5 Intake and Total and Partial Apparent Digestibilities of Diets with Different Levels of Concentrate, in Nellore BullsABSTRACT -The objective of this experiment was to evaluate the effects of the concentrate level in the diets on the intakes and total and partial apparent digestibilities of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fiber (NDF) and total carbohydrates (CHO). The effect of collections carried out during the day and the night, for the DM and OM total and partial apparent digestibilities, was also evaluated. Four Nellore bulls, fistulated in the rumen, abomasum and ileum, fed diets ad libitum with 25.0; 37.5; 50.0; 62.5; and 75.0% of concentrate, were randomly allotted to a completely randomized block design. The chromium oxide was used as indicator, in the dose of 20 g/day. The intakes of DM, OM, total digestible nutrients (TDN) and EE increased and that of NDF decreased linearly with the increase of the concentrate in the diets. The minimum estimated total apparent digestibilities of 67.27% for DM and 68.31% for OM were with 36.71 and 41.5% of concentrate in the diets, respectively. The ruminal apparent digestibilities of DM and OM averaged 63.35 and 71.42%, respectively. The increase of concentrate in the diets reduced the ruminal digestion of NDF, but resulted in linear increase in TDN and total DM digestibility of the diets. There were no differences for the total and partial apparent digestibilities of DM and OM obtained in collections accomplished during the day or the night.Key Words: bulls, concentrate, digestibility, intake Rev. bras. zootec., v.28, n.2, p.395-403, 1999 1 Parte da Tese apresentada à UFV para obtenção do título "Magister Scientiae". Projeto financiado pelo FINEP/CNPq. 2 Aluno de Doutorado/Escola de Veterinária/UFMG. 3 Professor Titular da UFV. Bolsista do CNPq. 4 Professor Titular da UFV. 5 Bolsista PIBIC/CNPq. IntroduçãoO consumo é um dos pontos importantes que pode limitar o nível de produtividade em bovinos de corte, ou seja, maiores ganhos de peso em intervalo mais curto. O consumo é regulado por vários fatores: animal (peso vivo, nível de produção e estado fisioló-gico), alimento (fibra, densidade energética, volume, entre outros) e condições de alimentação (disponibilidade de alimento, freqüência de alimentação, dentre outros), como descrito por MERTENS (1992).Segundo THIAGO e GILL (1990), há dois fatores que limitam o con...
-The objective of this study was to evaluate animal performance and carcass characteristics of 64 Nellore young bulls at 22 months of age finished in a feedlot and slaughtered at five body weights (350; 455; 485; 555 and 580 kg) fed diets containing coated or uncoated urea. The experimental design adopted was completely randomized, set in a 4 × 2 factorial arrangement, and for the variables assessed in the control animals, it was 5 × 2. No effect of interaction between slaughter weights and diets were observed, so the variables were analyzed separately, compared by polynomial contrasts and by the F test, respectively. The time animals remained in the feedlot to reach slaughter weights was 66, 88, 145 and 194 days. Average daily gain (ADG) showed quadratic behavior, with a maximum of 1.44 kg/day with animals of 491.7 kg. Dry matter intake (DMI) (kg/day) was similar in all the treatments, but it decreased linearly as body weight increased. The bionutritional efficiency worsened linearly as body weight rose. The elevation in slaughter weight resulted in linear decrease in the percentage of beef round and increase in forequarter. Backfat thickness and rib eye area of the longissimus increased linearly and the percentages of muscle and protein in the carcass reduced and those of fat and ether extract increased linearly as body weight increased. Average daily gain, DMI, feed efficiency and carcass characteristics were not affected by diets containing coated or uncoated urea. However, animals fed coated urea presenter better crude fiber and neutral detergent fiber intake.
This study evaluated the nutritional interrelationship between the growing and finishing phases of crossbred cattle in determining their performance. One hundred and eight animals were used (8 months old, body weight [BW] 211 ± 20 kg). During the dry season, the animals received one of the following supplements: a mineral plus urea supplement (ad libitum, MSD), a protein supplement (1 g/kg BW per day, PR1), or a protein-energy supplement (5 g/kg BW per day, PE). During the rainy season, the animals received one of the following supplements: a mineral without urea supplement (ad libitum, MSR), a protein supplement (1 g/kg BW per day, PR2), or PE (5 g/kg BW per day). The experimental design was completely randomized using a 3 × 3 factorial scheme (for the rainy season) and a 3 × 3 × 2 factorial scheme (for the finishing phase). The supplementation and finishing systems were considered to be the treatments, and the animals were considered to be the experimental units. Dry season supplementation did not affect the average daily gain (ADG) during the rainy season (P = 0.12) or the finishing phase (P = 0.73). An increase in the level of rainy season supplementation reduced ADG by 12% during the finishing phase (P < 0.06). Providing PE during the dry and rainy seasons led to the animals being slaughtered 17 (P = 0.06) and 30 (P < 0.01) days earlier, respectively. Our results indicate that supplementation during the dry season (under poor-quality pasture conditions) does not affect the performance during the rainy season or the finishing phase. Furthermore, while providing PE during the rainy season can reduce ADG during finishing, the higher BW at the beginning of the finishing phase is sufficient to reduce the time of the finishing period.
RESUMO -Foram avaliados os efeitos dos níveis de concentrado nas rações sobre a eficiência de síntese microbiana, o balanço de compostos nitrogenados, a concentração de amônia e o pH do fluido ruminal, a taxa de passagem da digesta ruminal e as perdas endógenas de compostos nitrogenados (N). Foram utilizados cinco novilhos F 1 Simental x Nelore, não-castrados, fistulados no rúmen, abomaso e íleo, alimentados à vontade com dietas que continham 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado e distribuídos em delineamento quadrado latino 5x5. As concentrações de amônia e o pH ruminal foram determinados em amostras de fluido ruminal coletadas imediatamente antes do fornecimento das rações e 2; 4; 6; e 8 horas após. A taxa de passagem foi determinada pelo modelo unicompartimental, utilizando-se o óxido crômico como indicador. A eficiência de síntese microbiana, expressa em relação à matéria orgânica degradada no rúmen (MODR), aos carboidratos totais degradados no rúmen (CHODR) e ao NDT, foi influenciada quadraticamente pelos níveis de concentrado na dieta, estimando-se valores máximos de 41,22 gNmic/kg MODR, 39,89 gNmic/kg CHODR e 17,33g PBmic/100 g NDT, estimados para 52,16; 60,44; e 56,63% de concentrado na dieta, respectivamente. Quando expressa em MSmic/kg CHODR, a eficiência aumentou linearmente com o nível de concentrado. Foram estimados valores de 5,15 g N/kg MS ingerida para o nitrogênio metabólico fecal e 422 mg N/kg 0,75 para as perdas endógenas totais. As concentrações máximas de amônia para todos os tratamentos ocorreram a 3,6 horas após o fornecimento da ração. As taxas de passagem de 0,052; 0,052; 0,055; 0,055; e 0,042.h -1 foram verificadas para os tratamentos com 25,0; 37,5; 50,0; 62,5; e 75,0% de concentrado, respectivamente. A máxima eficiência microbiana foi obtida entre 52 e 60% de concentrado.Palavras-chave: amônia ruminal, concentrado, eficiência microbiana, pH ruminal, taxa de passagem Concentrate Levels in the Crossbred F1 Simental x Nellore Bulls Diets. Nitrogenous Balance, Microbial Efficiency and Ruminal ParametersABSTRACT -The effects of dietary concentrate levels were evaluated on the microbial synthesis efficiency, the nitrogenous compounds balance, the ammonia concentrations and the ruminal fluid pH, the ruminal digesta passage rate and the endogenous losses of nitrogen compounds (N). Five F 1 Simental x Nellore bulls fistulated in the rumen, abomasum and ileum, full fed diets with 25.0; 37.5; 50.0; 62.5; and 75.0% of concentrate and allotted to 5x5 Latin square, were used. The ammonia concentrations and the ruminal pH were determined in ruminal fluid samples immediately collected before and 2; 4; 6; and 8 hours after feeding. The unicompartimental model, using chromic oxide as indicator, determined the passage rate. The microbial synthesis efficiency, express in relation to the organic matter degraded in the rumen (OMDR), to the total carbohydrates degraded in the rumen (CHODR) and to TDN, was influenced in quadratic way by the concentrate levels in the diet, estimating maximum values ...
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