Scielo RSS <![CDATA[Revista Brasileira de Zootecnia]]> vol. 43 num. 11 lang. en <![CDATA[SciELO Logo]]> <![CDATA[Seed longevity of Eragrostis plana Nees buried in natural grassland soil]]> The objective of this research was to evaluate the seed longevity of Eragrostis plana Nees buried at different soil depths, in a natural-grassland area in the Pampa biome (46 m altitude, 30º05´S and 51º40´W) of Rio Grande do Sul State, Brazil. The experimental design was a split-plot type in complete blocks with two factors: seeds buried at five different depth levels (soil surface and 2.5, 5, 10 and 20 cm) and seven exhumation dates. The blocks were allocated in natural grassland grazed by cattle, allocated in a 12-m-long transection. Fifty-four permeable nylon bags filled with 100 seeds in each division, with five vertical divisions, were buried in each row. Seven exhumation dates were used: the first on October 14, 2003 and the last on January 14, 2006. The percentage of viable seeds of E. plana, collected at seven exhumation times and set at different depths in the soil horizon, were described by simple negative exponential equations. Based on the model, the percentage of viable seeds collected at the five depths, (soil surface and 2.5, 5, 10, and 20 cm), after 2.5 years of burial, were 0.1, 0.5, 1.0, 7.4 and 22.1%, respectively. Increase in depth is directly associated with physical and physiological seed integrity of E. plana. Negative simple exponential equations can be used to predict seed longevity of E. plana buried in nylon bags. This invader species accumulates soil seed-bank of high longevity. <![CDATA[Effect of follicular wave synchronization on superovulatory response of Girolando embryo donors]]> The objective of this study was to evaluate the effect of the follicular wave synchronization method on the superovulatory response of Girolando embryo donors. Seven cows and five heifers were divided into three treatments according to the method of the follicular wave synchronization prior to superovulation. The donors were superovulated with eight FSH decreasing doses, adding 133 mg per animal. The superovulatory response was evaluated using an ultrasound device to quantify the number of corpora lutea. The number and quality of recovered structures were also evaluated. Animal category (cow or heifer) and genetic group influenced the superovulatory response, in which heifers showed a greater response (100% in all treatments) compared with cows, which showed 85.7%, 57.1% and 57.1% superovulatory response for standing estrus, GnRH and P4 + BE groups, respectively. The genetic group also showed influence on superovulatory response, in which the 3/8 animals had an average of 10.3 corpora lutea per donor compared with the 3/4 animals, which showed 4.9. The follicular wave synchronization treatments did not show differences in superovulatory response, recovered structures and viable structures. The treatment of follicular wave synchronization with GnRH or with P4 + BE can be used in Girolando donors with the same efficiency as the standing estrus group, and 3/8 Girolando heifers respond better to the superovulatory treatment. <![CDATA[Ability of non-linear mixed models to predict growth in laying hens]]> In this study, the Von Bertalanffy, Richards, Gompertz, Brody, and Logistics non-linear mixed regression models were compared for their ability to estimate the growth curve in commercial laying hens. Data were obtained from 100 Lohmann LSL layers. The animals were identified and then weighed weekly from day 20 after hatch until they were 553 days of age. All the nonlinear models used were transformed into mixed models by the inclusion of random parameters. Accuracy of the models was determined by the Akaike and Bayesian information criteria (AIC and BIC, respectively), and the correlation values. According to AIC, BIC, and correlation values, the best fit for modeling the growth curve of the birds was obtained with Gompertz, followed by Richards, and then by Von Bertalanffy models. The Brody and Logistic models did not fit the data. The Gompertz nonlinear mixed model showed the best goodness of fit for the data set, and is considered the model of choice to describe and predict the growth curve of Lohmann LSL commercial layers at the production system of University of Antioquia. <![CDATA[Digestible lysine levels obtained by two methods of formulation of diets for 22-to-42-day-old broilers]]> The objective of this study was to evaluate the effect of digestible lysine levels in diets with or without supplementation of industrial amino acids on performance, carcass characteristics and nitrogen excretion in broilers of 22 to 42 days of age. Birds were distributed in a completely randomized experimental design in a 4 × 2 factorial arrangement, with four digestible lysine levels (9.0, 10.0, 11.0 and 12.0 g/kg) and two methods to obtain the lysine levels (variation in the proportion of corn and soybean meal, without supplementation; or supplementation of industrial amino acids), eight replicates and 20 birds per replicate. There was an interaction effect on the performance characteristics and on the weights and yields of prime cuts. In both diets, feed conversion improved linearly as the lysine levels were increased. Feed intake; weight gain; carcass, thigh and drumstick weights; and boneless breast yield increased and abdominal fat reduced linearly as the lysine levels were increased in the unsupplemented diet. The lysine levels of the supplemented diets linearly reduced the yield of drumstick and quadratically reduced the yields of bone-in and boneless breast up to the estimated levels of 10.4 and 10.7 g/kg, respectively. Diets without supplementation increased the excretion and retention of nitrogen. The levels of 9.0 and 12.0 g/kg digestible lysine obtained with supplementation of industrial amino acids and without it, respectively, provide the best performance and yield of prime cuts in the birds. Diets in which the digestible lysine levels are obtained without supplementation provide better performance responses and carcass characteristics compared with supplemented diets. <![CDATA[Effects of supplementation frequency on the ruminal fermentation and enteric methane production of beef cattle grazing in tropical pastures]]> The objective of this study was to evaluate the characteristics of ruminal fermentation and enteric methane production in beef cattle subjected to different supplementation frequencies while grazing on Brachiaria brizantha cv. Marandu pastures. Nine cattle (325±65.7 kg BW) fitted with ruminal and duodenal cannulas were used in the ruminal fermentation study, and 12 cattle (399±32.6 kg BW) were used in the enteric methane production study. The treatments included supplementation once daily, supplementation once daily except Saturdays and Sundays, or supplementation on alternate days. The supplementation was equivalent to 10 g kg−1 BW day−1 for all treatments. The design employed was completely randomized with three treatments and three replications. When all supplements were provided (day 1), no effects of supplementation frequency were observed on ruminal pH; concentration of NH3-N; concentration of acetic, propionic, or butyric acids; or total volatile fatty acids (VFA), but there were month effects. During the day on which only daily supplements were provided (day 2), significant differences were observed only on the molar concentration of acetic acid and total VFA; and month effects were noted on all variables. No significant differences were observed in ruminal fluid volume, dilution rate, N intake, bacterial N synthesis and enteric methane production among the studied supplementation frequencies. Differences were observed in the enteric methane production in the different months, with 85 g kg−1 of gross energy intake observed in September and 123 g kg−1 of gross energy intake observed in November. Lower supplementation frequency is a good option to lower labor costs with little or no consequences on ruminal fermentation characteristics and enteric methane production. <![CDATA[Evaluation of cation-anion diets in calcium metabolism in ruminants]]> The objective of this study was to evaluate the use of the dietary cation-anion balance (DCAB) on the calcium metabolism in male Nellore steers with a mean age of 10 months. Three experimental diets were tested: a cationic diet, a diet consisting of Tifton hay only, and an anionic diet with +15.2, +23.9 and −10.0 mEq/100 g DM of DCAB values in the diet. The anionic diet was calculated as the addition of salts of ammonium chloride and magnesium sulfate. Based on the isotope dilution technique, the negative DCAB value used in this study (−10.0 mEq/100 g DM) does not affect calcium metabolism, especially endogenous losses and true absorption. <![CDATA[Babassu mesocarp bran levels associated with whole or ground corn grains in the finishing of young bulls: carcass and meat characteristics]]> The objective of this study was to evaluate the effect of grinding corn and inclusion of babassu mesocarp bran (BMB) in the diet of crossbred dairy young bulls finished in feedlot on their carcass and meat characteristics. Twenty-four young bulls were fed four experimental diets containing two BMB inclusion levels (0 and 41.24%) and corn in two forms of processing (ground and whole grains) for 98 days, and then slaughtered in a commercial packing plant. Among the quantitative carcass characteristics, there was interaction only in fat trimmings/whole hot carcass weight and cold carcass yield. The whole hot carcass and hot carcass weights showed reduced means with the use of whole corn. The other quantitative variables were not separately affected by BMB inclusion levels or by the form corn was processed. There was interaction between the factors for pistol cut weight, edible portion and weight of the cuts of the pistol cut, in which the use of whole corn and BMB promoted reduction in the mean values. The use of the whole corn grain reduced the participation of flank cut and elevated the participation of the bone fraction in the carcass. Inclusion of 41.24% of BMB did not change the qualitative meat characteristics, but the use of corn grain resulted in darker meat. The use of whole corn resulted in alteration in the weight of cuts like eye of rump and striploin, which have a high commercial value. There was interaction between factors for the percentages of moisture and minerals of the meat, whereas the crude protein content was affected by the two factors. The use of diets with whole corn or with babassu mesocarp bran may modify the carcass and meat characteristics of finishing crossbred young bulls. <![CDATA[Elephant grass ensiled with wheat bran compared with corn silage in diets for lactating goats]]> The objective of this study was to evaluate the use of wheat bran as an additive in elephant-grass silage on intake and digestibility of the nutrients, ingestive behavior, and yield and chemical composition of milk. Eight goats with 45 days of lactation were distributed in a (4 × 4) Latin square design.The treatments consisted of corn silage (CS), elephant-grass silage without wheat bran (EGS), elephant-grass silage with 10% wheat bran (EGS+10%WB), and elephant-grass silage with 20% wheat bran (EGS+20% WB). There was no difference in dry matter (DM) intake between diets EGS and CS in g d−1. However, the animals fed EGS+10%WB had lower DM and organic matter (OM) intakes than the animals fed CS in g kg−1 d−1 of body weight. There were lower non-fiber carbohydrate and metabolize energy intakes by animals fed diets based on elephant-grass silages than those fed CS. The EGS+20%WB diet provided lower digestibility coefficients of DM, OM, crude protein, ether extract, neutral detergent fiber (NDF) and digestible nutrients of the diet than the diet with CS. The NDF digestibility coefficient with diet EGS was greater than that obtained with diet CS. The diets with corn and elephant-grass silages provided similar milk yield levels. However, the animals fed diets based on EGS+20% WB produced less total-solids-corrected milk than the animals fed CS. No difference was found in the milk physicochemical properties and ingestive behavior of goats in this study. Corn silage can be replaced by elephant-grass silage harvested at 50 days of regrowth and elephant-grass silage with 10% wheat bran without influencing goat performance, behavioral variables, physiological variables, milk yield or the milk physicochemical properties.