-The objective of this study was to evaluate the performance of F1 (Holstein × Zebu) cows in lactation according to different levels of substitution of soybean meal for a protein equivalent non-protein nitrogen originated from slow-release urea (SRU). Eight F1 (Holstein × Zebu) cows in the first third of lactation, with an average milk yield of 12.7 kg (±3.1 kg)/day and a live weight of 552 kg (±30 kg), were used. The experimental design was composed of two simultaneous 4 × 4 Latin squares, with the following treatments: 100% soybean meal and 0% SRU; 66% soybean meal and 34% SRU; 34% soybean meal and 66% SRU; and 0% soybean meal and 100% SRU. Sorghum silage, used as roughage, was supplied together with the concentrate. Feed intake and digestibility as well as milk yield and milk composition were measured. The obtained data were subjected to analysis of variance, adopting a 5% probability level. No intake variable showed significant differences among the treatments, and the mean values for the intakes of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) were 18.35 2.62 and 5.85 kg/day, respectively. The results for apparent digestibility also did not show differences among treatments, with DM, CP and NDF averaging 58.16, 58.64 and 36.21%, respectively. Milk yield and composition were similar among the treatments. The average 4%-fat-corrected milk yield was 13.39 kg/animal.day. Intake, digestibility and milk yield and composition variables are not changed according to the substitution of the soy protein for slow-release urea. Thus, for average-milk-yield crossbred animals, this substitution depends on economic variables only.

-The objective of this study was to evaluate the effects of different lipid sources in diets for lactating cows on milk yield and composition, conjugated linoleic acid (CLA) content, and fatty acid profile in the milk fat. Five primiparous Holstein cows were distributed in a 5 × 5 Latin square design. Treatments were: control (no lipid addition) and four other diets containing different lipids sources -ground raw soybean, cottonseed, soybean oil, and calcium salts of soybean fatty acids (CSSFA). The greater milk yield (kg/day) and milk lactose (g/kg) and solids non-fat (g/kg) contents were obtained with the animals fed diets with CSSFA. Regarding the fatty acid profile in the milk fat, the diets with CSSFA and ground raw soybeans produced the greatest concentrations of polyunsaturated fatty acids and C 18:2 . Supplementation with CSSFA provided a greater production (g/day) of CLA, resulting in almost twice the values shown by the other treatments. The use of different lipid sources does not affect the milk total solids (protein, fat, and lactose) and CSSFA has a positive influence on the fatty acid profile of the milk fat and amount of CLA produced. Additionally, milk yield is not affected by this supplement.Key Words: biohydrogenation, dairy production, fatty acids, supplementation Revista Brasileira de Zootecnia

-The objective was to evaluate intake and digestibility of nutrients, as well as milk production and composition of the milk from F1 Holstein × Gyr cows kept on pasture, supplemented with sugarcane and concentrate (28% CP). Five cows with 150±14 lactation days and average milk production of 7.1±2.1 kg/day were distributed in a 5 × 5 Latin square design. The treatments were: soybean meal-based concentrate; soy bean-based concentrate; ground soybean-based concentrate; roasted soybean-based concentrate; and ground, roasted soybean-based concentrate. Dry matter (DM), organic matter, crude protein (CP), neutral detergent fiber (NDF), total carbohydrates and total digestible nutrients intakes were not affected by the diet, but ether extract intake was higher for the animals fed soy bean-based diets than those fed soybean meal. The digestibility of DM, NDF and CP did not differ. The corrected milk yield differed between treatments; animals on the treatment with soy bean-based concentrate had the lowest production in relation to the others, which did not differ from each other. There was no difference between treatments for milk composition. Thus, soybean meal can be replaced by ground soy beans or roasted soy beans (ground or whole) in diets for low-yield cows reared on Brachiaria decumbens pastures with no harm to milk production or composition. Therefore, the use of these alternative raw materials is recommended whenever their inclusion represents lower feeding costs.

A formação dos chamados compostos de coordenação, conhecidos mais usualmente como complexos metálicos (apesar de alguns centros de coordenação não serem espécies metálicas) constitui um importante fator determinante da quantidade de sais minerais excretados nas fezes de diferentes espécies animais. Esse processo químico ocorre no trato gastrintestinal (TGI) de distintas espécies animais, abrangendo ruminantes e não ruminantes. Tal formação ocorre através de proteínas, poli peptídeos, oligo peptídeos, polissacarídeos, oligossacarídeos, além de vários outras biomoléculas que apresentam diversos sítios oxigenados e/ou nitrogenados e/ou com algum outro átomo que apresente pares de elétrons não ligantes, os quais podem, agindo como bases de Lewis, atacar cátions metálicos, os quais agiriam assim como ácidos de Lewis, formando ligações covalentes coordenadas, podendo, portanto, formar complexos metálicos típicos. Considerando que no TGI de diversas espécies o número de pequenas biomoléculas, macromoléculas, íons e moléculas oriundas da dieta, com grande presença de celulose e proteínas, tais macromoléculas apresentariam um papel decisivo na retenção de um grande número de cátions oriundos da dissociação dos sais minerais ingeridos pelo animal. Os ânions, originados pela dissociação salina, pela atração eletrostática tendem a seguir os cátions, o que afetaria a absorção de sais no TGI. Estratégias têm sido propostas visando aperfeiçoar a absorção de sais minerais, tais como a utilização de sais quelatados e alguns ajustes no manejo, sobretudo no que se refere às alimentações salinas e de fibras e proteínas por parte de algumas espécies. O presente artigo de revisão didaticamente apresenta e discute os mecanismos básicos da formação de complexos metálicos no TGI e suas inerentes implicações, uma vez que tal tópico é fundamental para a compreensão da nutrição mineral e dos mecanismos que podem acentuar a absorção salina, o qual constitui importante componente do custo alimentar associado a várias espécies relevantes zootecnicamente. Considerando a importância desse tema para a compreensão da nutrição mineral de vários animais, de interesse em produção animal ou não, assim como os poucos artigos de publicação nessa área, acreditamos que é necessária uma maior ênfase em pesquisas sobre esse tema, o que poderia fornecer importante contribuição para os estudos sobre nutrição animal e áreas correlatas. Palavras-chaves: complexos metálicos, trato gastrintestinal, nutrição mineral Metal complexes in the gastrointestinal tract as a relevant topic for understanding mineral nutrition: Review

<p>The purpose of this study was to evaluate the kinetics of ruminal passage rate of particles from the subsequent associations: corn and signal grass; corn, signal grass and Calopogônio; corn, signal grass and Macrotiloma; and corn, signal grass and Estilosantes. It was used four crossbred holstein-zebu cattle with the rumen tubed in order to determine the the kinetics of ruminal passage rate of particles. The feces were collected at the times zero (immediately after addition of fibers complexed with chromium), 1, 2, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 56 , 64, 72, 80, 88, 96, 120, 132, 144 and 192 hours. The profile parameters of passage rate estimative were adjusted according to robust regression procedures. The average time of particles retention in the raft (ATPR1); the average time in the rumen liquid phase (ATRLP2) and the average time of total ruminal retention (ATTRR) were adjusted for the passage kinetics and estimated with the NLIN procedure of SAS. From the observed results, may be suggested that the transference rate <italic>λ</italic> has an inverse behavior to the escape rate <italic>κ</italic>, the <italic>τ</italic> average values, the average retention time and average particles retention time in the rumen liquid phase (ATRLP2) were not statistically different. The feed characteristics after the raft escape and reach to ATRLP2, were very similar; (ATTRR), related to treatments, were not statistically different (P<0,05). There were observed small TMRR numerical differences in different foods. The corn and signal grass; corn, signal grass and calopogônio; corn, signal grass and macrotiloma, corn, signal grass and estilosantes silage fibers had similar rates of<italic>λ</italic>, k, ATPR1, ATRLP2 and ATTRR. Therefore, the the kinetics of ruminal passage rate of particles is similar. Thus, the choice of the system should be based on other factors, such as viability of the management ease and silage cost.</p>