RESUMO.A degradação das pastagens tem sido um grande problema para a pecuária brasileira, em que o uso das mesmas na produção de ruminantes é a forma mais econômica de alimentação. Essas, quando bem manejadas e utilizadas respeitando-se suas características fisiológicas e exigências climáticas e de fertilidade do solo, mantêm-se produtivas por muito tempo. No entanto, estima-se que 80% dos 50 a 60 milhões de hectares de pastagens cultivadas no Brasil Central encontram-se em algum estado de degradação, ou seja, são incapazes de sustentar os níveis de produção e qualidade exigida pelos animais. Essa degradação é decorrente de vários fatores que atuam isoladamente ou em conjunto, desde a espécie forrageira, sua implantação e o manejo. Assim, faz-se necessário a utilização de técnicas para a recuperação de pastagens, de forma a otimizar o aproveitamento da área, recuperar as propriedades químicas, físicas e biológicas do solo e viabilizar a produção de proteína animal, devido ao aumento da capacidade de suporte da pastagem. A presente revisão tem como objetivo apresentar alguns aspectos ligados à degradação das pastagens e as principais técnicas utilizadas para a recuperação dessas Palavras chave: conservação do solo, produção animal, sistema silvopastoril Degraded pastures and recovery techniques: ReviewABSTRACT. The degradation of pastures has been a great problem for the Brazilian livestock, in which the use of them in the production of ruminants is the most economic form of feeding. These, when well managed and used respecting their physiologic al characteristics and climatic requirements and soil fertility, remain productive for a long time. However, it is estimated that 80% of the 50-60 million hectares of pasture grown in Central Brazil are degradated, which means that they are unable to sustain the production levels and quality required by the animals. This degradation is due to several factors acting in isolation or together, from the forage species, its implantation and the management. Thus, it is necessary to use techniques for the recovery of pastures, in order to optimize the utilization of the area to recover the chemical, physical and biological properties of the soil and to enable the production of animal protein, due to increased pasture support capacity. The present review aims to present some aspects related to the degradation of pastures and the main techniques used to recover these pastures.

RESUMO.O uso da silagem pré-secada do capim Tifton 85 (Cynodon spp.) pode ser uma alternativa de volumoso de qualidade para a alimentação animal. Objetivou-se avaliar o comportamento de bezerras da raça Holandesa alimentadas com silagem pré-secada do capim Tifton 85, em substituição à silagem de milho (0, 33, 66 e 100%). Dezesseis animais foram distribuídos em quatro tratamentos e permaneceram em sistema de confinamento durante 21 dias. As avaliações comportamentais foram realizadas nos quatro últimos dias do período experimental durante 24 horas, através da rota de coleta instantânea, com intervalo amostral de 10 minutos e rota de amostragem do tipo scan. As frequências de micção, defecação e ingestão de água também foram registradas. Foi utilizado um delineamento inteiramente casualizado com quatro tratamentos (0, 33, 66 e 100% de substituição da silagem de milho por silagem pré-secada do capim Tifton 85) e quatro repetições (número de animais por tratamento). O tempo de ruminação foi influenciado pelas dietas, sendo os maiores valores (39,76 %) observados para os animais alimentados exclusivamente com silagem de milho. O comportamento dormindo sofreu influência da alimentação variando de 5,81 a 9,28%, para os níveis de 0 e 66% de substituição da silagem de milho por silagem pré-secada do capim Tifton 85, respectivamente. A frequência que os animais beberam água, defecaram e urinaram não apresentou diferença entre os tratamentos. A substituição da silagem de milho pela silagem pré-secada do capim Tifton 85 não provocou alterações no comportamento dos animais no período estudado. Palavras chave: bovino, conservação de volumosos, forragem, ruminanteHolstein heifers' behavior fed with pre-dried silage from Tifton 85 grass (Cynodon spp.)ABSTRACT. The use of pre-dried silage from Tifton 85 grass can be a good option of quality forage for animal feeding. The main objective was to evaluate the behavior of the Holstein heifers fed with pre-dried silage, the grass Tifton 85, replacing the corn silage (0, 33, 66 and 100%). Sixteen animals were distributed in four treatments and remained in feedlot system for 21 days. Behavioral assessments were carried out in the last four days of the trial period during 24 hours, through the instant collection route, with sampling intervals of 10 minutes and type scan sampling route. The frequency of urination, defecation and water intake were also recorded. A completely randomized design with four treatments (0, 33, 66 e 100% of corn silage replacement for pre-dried grass silage of Tifton

Background Crude ash is categorized as an empirical method playing an important role in the nutritional interpretation of animal feeds, allowing indirect estimation of total organic matter. Objective Our objective was to evaluate variations in laboratory procedures for crude ash quantification regarding physical parameters (i.e., time, temperature) and ashing aids and their influences on crude ash, repeatability, and discrimination power among feeds. Method The “control” method was based on a simple ignition time of 3 h at 550 °C. The variations are briefly described: increasing ashing time to 6 h; increasing temperature to 600 °C; and using two 3-h ignition cycles at 550 °C with ashing aids inclusion between them: fresh air supply, fresh air supply plus distillate water, and fresh air supply plus hydrogen peroxide. A color evaluation was also performed using a colorimetric technique. Twenty four study materials from eight different feed types were evaluated. Results The crude ash results differed among the method variations, but a consistent decrease in the estimates was observed when liquid aids were applied, which also improved repeatability. Ash residues did not present a consistent color pattern among methods, but the residues were darker when the control method was applied. Conclusions The method of obtaining ash residues in animal feeds based on the binomial 550 °C × 3 h does not have enough robustness and may overestimate crude ash in some feeds. Adjustments in either ignition time or temperature might improve crude ash test results, but the best test results are obtained using liquid ashing aids between two ignition cycles. Highlights The recommended method is based on the use of 550 °C and two 3-h ignition cycles with water added to the ash residue between cycles.

Our objectives were to evaluate the variability among animals regarding to the degradation rate of the potentially degradable fraction of dry matter, crude protein, and neutral detergent fiber, as well as to establish the minimum number of animals and provide a standardized design of sampling times for in situ ruminal degradation assays of tropical feeds with cattle. Seven feeds were evaluated, four concentrates and three forages. The incubations were performed using five rumen-cannulated Nellore heifers (328 ± 9.8 kg of body weight). The complete sets of incubation sampling times encompassed 16 time points for forage samples (0–240 h) and 13 time points for concentrate samples (0–144 h). The profiles were adjusted using both fixed and mixed model approaches. When the variation among animals on the degradation rate was considered using the mixed model approach, the precision of the adjusted degradation profiles was increased. Moreover, the utilization of a low number of animals increases the probability to obtain biased estimates of degradation rate and increased random variances. A minimum of three animals is recommended for in situ trials with cattle. Minimum designs of sampling times regarding number and position of incubation times were proposed, discussed, and recommended to assess the dynamics of tropical feed degradation.

Holstein × Gyr and Holstein are the primary dairy breed used in tropical systems, but when rearing under pasture, feed intake, behavior, and performance might differ between them. This study aimed to evaluate the voluntary intake, nutrient digestibility, performance, and ingestive behavior of Holstein and Holstein × Gyr (½ Holstein × ½ Gyr) heifers managed in an intermittent grazing system of Guinea grass (Panicum maximum Jacq. cv. Mombaca). The experiment was conducted during the summer season throughout four periods of 21 d. Two 8-heifers (four Holstein and four Holstein × Gyr) groups, averaging 258.6 ± 24.8 kg and 157.1 ± 24.99 kg body weight, were used. Each group grazed a separate set of 16 paddocks, and all heifers received a concentrate supplement daily. Heifers were weighed at the beginning and end of the experiment. Fecal, forage and concentrate samples were evaluated for their dry matter (DM), crude protein (CP), crude fat, ash, neutral detergent fiber (NDF), and indigestible NDF. Feeding behavior was evaluated through 24 h of live observation for 48 h of each experimental period. Grazing, ruminating, resting, and intake of concentrate times were recorded, and rumination criteria, bout criteria, mealtime, meal frequency, and meal duration were estimated. There was no difference in dry matter intake (DMI). The Holstein × Gyr heifers had greater NDF intake and average daily gain (ADG), and feed efficiency tended to show greater CP and NDF digestibilities. The forage DMI of Holstein × Gyr was 11.70% greater than the Holstein heifers. Holstein grazed less than Holstein × Gyr heifers in the afternoon. Ruminating time was 18.43% lower for Holstein than Holstein × Gyr heifers, and rumination criteria were greater for Holstein heifers. Holstein heifers presented more prolonged rumination bouts and resting time than Holstein × Gyr heifers. Holstein × Gyr can ingest and ruminate greater amounts of fibrous material. Holstein heifers select lower fiber material, and they need to spend more time ruminating small portions of feed. Overall, we do not recommend using young Holstein heifers in tropical pasture conditions because their ADG is low because of its lower adaptability to fibrous feed and heat stress. However, this management condition is appropriate for Holstein × Gyr heifers and results in an adequate performance.