Scielo RSS <![CDATA[Revista Brasileira de Zootecnia]]> vol. 43 num. 7 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Effect of salinity on performance and body composition of Pacific white shrimp juveniles reared in a super-intensive system]]> The objective of this study was to evaluate the effect of salinity on the culture water quality, performance and body composition of Litopenaeus vannamei juveniles (1.16±0.30 g) reared for 36 days in a super-intensive system without water exchange at salinities of 4, 16 and 32‰. Groups of 200 animals (140/m2) were stocked, with three replicates, in nine fiber-cement tanks (1.11 × 1.29 × 0.70 m) with a useful volume of 400 L. Physical and chemical parameters of water, such as temperature and dissolved oxygen before and after midday, pH, alkalinity, total suspended solids, total ammonium nitrogen, nitrite, nitrate, and phosphate, were monitored. Performance parameters like survival, weight gain, specific growth rate, feed conversion ratio and protein retention rate, were also evaluated. The proximate composition of the juveniles was analyzed through the moisture, protein, lipid and ash contents. The physical and chemical parameters of the water were influenced by the treatments. The increased salinity produced a significant increase in the alkalinity and the concentrations of total suspended solids, nitrite and phosphate. Of the parameters that were examined to evaluate the performance and proximate composition of the shrimp, only survival, protein retention rate and body lipid content were significantly influenced. The highest values were found at a salinity of 32‰. However, the analysis of the proximate composition of the bioflocs showed that the moisture, protein and lipid contents increased as the salinity decreased. Growth, use of feed and survival of L. vannamei juveniles reared in a super-intensive system without water exchange is positively influenced by an increase of salinity from 4 to 32‰. <![CDATA[Reaction norms models in the adjusted weight at 550 days of age for Polled Nellore cattle in Northeast Brazil]]> The objective of this study was to evaluate the genotype-environment interaction (GEI) in the body weight adjusted to 550 days of age (W550) of Polled Nellore cattle raised in Northeastern Brazil using reaction norms (RN) models. Hierarchical RN models included fixed effects for age of cow (linear and quadratic) and random effects for contemporary groups (CG) and additive genetic RN level and slope. Four RN hierarchical models (RNHM) were used. The RNHM2S uses the solutions of contemporary groups estimated by the standard animal model (AM) and considers them as environmental level for predicting the reaction norms and the RNHM1S, which jointly estimate these two sets of unknowns. Two versions were considered for both models, one with a homogeneous (Hm) and another with a heterogeneous (He) residual variance. The one-step homogeneous residual variance model (RNHM1SHm) offered better adjustment to the data when compared with other models. For the RNHM1SHm model, estimates of additive genetic variance and heritability increased with environment improvement (260.75±75.80 kg2 to 4298.39±356.56 kg2 and 0.22±0.05 to 0.82±0.01, for low- and high-performance environments, respectively). High correlation (0.97±0.01) between the intercept and the slope of RN shows that animals with higher genetic values respond better to environment improvement. In the evaluation of breeding sires with higher genetic values in the various environments using Spearman's correlation, values between 0 and 0.98 were observed, pointing to high reclassification, especially among genetic values obtained by the animal model in comparison with those obtained via RNHM1SHm. The existence of GEI is confirmed, and so is the need for specific evaluations for low, medium and high level production environments. <![CDATA[Pregnancy rate in lactating <strong>Bos indicus</strong> cows subjected to fixed-time artificial insemination and treated with different follicular growth inducers]]> The objective of this experiment was to evaluate the effects of replacing eCG with FSH or FSH/LH on the diameter of ovulatory follicles (DOF) and the pregnancy rates (PR) of lactating Bos indicus cows subjected to a synchronization of ovulation protocol and fixed-time artificial insemination (FTAI) based on progesterone, estradiol benzoate (EB), PGF2α, and estradiol cypionate (EC). On day 0, primiparous and multiparous Nellore cows (n = 329) at 68 days postpartum were body condition scored (BCS) and received a P4 implant (PRIMER 1.0 g P4) plus 2 mg EB intramuscularly (IM). At day 8, the implant was removed, and 250 μg cloprostenol were injected IM along with 0.5 mg EC. At the time of implant removal, the animals were divided into one of four treatments: cows received (G1) 1 mL of saline solution IM (Control; n = 80); (G2) 300 IU eCG IM (ECG300; n = 84); (G3) 15 mg FSH IM (Folltropin; n = 82); and (G4) 30 IU FSH/LH IM (Pluset; n = 83); all cows were subjected to FTAI 48-54 h after implant removal (day 10). Transrectal ultrasonography was performed to measure the DOF to FTAI and to estimate the pregnancy rate on day 35. A statistical analysis examined the effects of the treatment, technician, semen, BCS, calf age and parity on PR to FTAI. There was no significant difference in PR and DOF among the treatment groups (G1, 41.3%, 13.1 mm; G2, 46.4%, 14.5 mm; G3, 46.3%, 14.2 mm; and G4, 48.2%, 14.3 mm), but PR was higher in multiparous than in primiparous cows. Commercial FSH solutions (Pluset or Folltropin) do not promote increases in PR or DOF of lactating Nellore cows and are equal to eCG in promoting growth in preovulatory follicles and elevating the PR in Nellore cows with a moderate BCS subjected to a progesterone-based FTAI protocol with EC. <![CDATA[Effect of low or high stress in pre-slaughter handling on pig carcass and meat quality]]> The objective of this study was to evaluate the consequences of low or high stress during pre-slaughter handling of pigs on their carcass and meat quality. Forty-four animals of a commercial lineage, with an average weight of 107.23±5.23 kg, were used. At lairage the animals were randomly divided into two groups, the least and the most stressed. At slaughter, during bleeding, blood samples were collected for later cortisol and lactate tests. Forty-five minutes after slaughter the initial pH of th carcasses was measured and samples of the semitendinosus muscle were collected for R-value calculation. After 24 hours of cooling, the final pH was measured, damage scores were assessed and samples of the longissimus dorsi muscle were collected to evaluate drip loss, liquid loss from defrosting and cooking, shear force, lipid oxidation, and color. The results were evaluated by analysis of variance and the means were compared by Tukey´s test. It was found that cortisol, lactate and R-value were lower and initial pH was higher for the least stressed animals, whereas the other parameters were not significantly affected. Thus, low stress in the pre-slaughter handling of pigs is effective in reducing stress and carcass damage, but has no effect on meat quality. <![CDATA[Effect of supplementing finishing pigs with different sources of chromium on performance and meat quality]]> The objective was to evaluate the dietary supplementation of different sources of chromium (inorganic: chromium sulfate and chelated: chromium-methionine) during the finishing period of pigs to obtain improvements in the animal performance, and carcass and meat quality. The statistical design was randomized blocks, where 44 barrows, with an initial weight 60.49±5.12 kg, were divided into four blocks (heavier, heavy, light and lighter) according to initial weight. The experimental diets were isoenergetic and isonutrient, except for the chromium level. The treatments were divided as follows: control (without chromium), control + 200 ppb of inorganic chromium (chromium sulfate), and control + 200 ppb of chelated chromium (chromium-methionine). In the performance measures, the stall was considered the experimental unit and in the blood parameters, carcass and meat evaluations each animal constituted the experimental unit. Animals were slaughtered when they reached the final average weight of 107.23±5.23 kg. Blood samples were collected and tested for blood parameters (cholesterol, triglycerides and glucose) as well as carcass quality (hot and cold weights, yield, loin-eye area, muscle depth and backfat thickness) and meat quality (initial and final pH, drip loss, color, chemical composition and lipid oxidation) parameters. Chromium-methionine supplementation provides a greater daily weight gain only compared with the animals that are not supplemented with chromium, because feed conversion is better as compared with the other treatments. After 24 hours of storage, the meat from pigs supplemented either with chromium-methionine or with chromium sulfate presents lower lipid oxidation than that from non-supplemented animals. However, after three days of storage, only chromim-methionine is effective in reducing lipid oxidation. <![CDATA[Effects of dietary brown propolis on nutrient intake and digestibility in feedlot lambs]]> The present study tested brown propolis in crude or extract form as a feed supplement for feedlot lambs to identify the type that most improves in vivo nutrient digestibility. Digestibility was assessed by both total fecal collection and internal markers and the results obtained by these techniques were compared. The completely randomized design was used to compare feed intake and nutrient digestibility of 24 male lambs aged seven months among four dietary treatments (crude brown propolis, propolis ethanol extract, monensin sodium, and control). Methods of feces collection were compared using a completely randomized split-plot design, with experimental diets corresponding to the main factor and the methods to estimate fecal production as the sub-factor. The diets had a roughage:concentrate ratio of 50:50, with Tifton-85 bermudagrass hay (Cynodon spp.) as roughage, and ground corn, soybean meal and minerals as concentrate. The lambs fed diets with crude propolis had higher feed intake than those fed diets containing monensin sodium. The different diets did not affect dry matter, organic matter, crude protein, neutral detergent fiber, or acid detergent fiber digestibility, but crude propolis supplementation provided higher ether extract digestibility than monensin sodium. Nutrient digestibility, as indicated by indigestible neutral detergent fiber, indigestible acid detergent fiber and sequentially-determined indigestible acid detergent fiber, was lower than that found with the fecal collection method. The addition of brown propolis has the same effect as monensin, but neither maximized nutrient availability in the diet of feedlot lambs at 7 months of age. Digestibility assessment using the internal markers indigestible neutral detergent fiber, indigestible acid detergent fiber and sequentially-determined indigestible acid detergent fiber is not an efficient method compared with total feces collection. <![CDATA[Economic viability of the use of crude glycerin supplements in diets for grazing crossbred calves]]> The objective of this study was to evaluate the economic returns of crossbred calves grazing on pastures formed by Urochloa brizantha fed crude glycerin as a supplement. Thirty-six crossbred calves with initial average weight of 301.5 kg were distributed in a completely randomized design with four treatments and nine replicates per treatment. The animals were maintained on rotational grazing production of Urochloa brizantha cv. Marandu. The tested treatments were 0.0, 3.33, 6.66 and 9.99% inclusion of crude glycerin in the total dry matter as a substitute for corn. The production of meat was not altered by the inclusion of glycerin in the diet. The inclusion of glycerin caused a reduction of up to 14.93% in the price of the concentrate. There was a significant increase in the total balance, which rose from 3.76 to 91.89 R$/ha with the inclusion of glycerin. The inclusion of crude glycerin in the supplement was capable of raising the net present value and the internal rate of return, proving to be an alternative to reduce the cost of production of supplemented pastured animals. <![CDATA[Efficiency of calf production of cows from two genetic groups]]> The objective was to evaluate the effect of weight, age and production efficiency of cows from genetic groups based on the calf weight at calving and at weaning. For a period of five years, data of 120 cows (60 Angus-Nellore (AN) and 60 Simmental-Nellore (SN)) at four to nine-years of age were evaluated. All cows were maintained on Brachiaria decumbens pastures, with two forage availability levels (high and low), distributed in a randomized-block design. The cows were placed together with Canchim bulls to generate the crossbred calves. A supplement, consisting of 200 g/kg crude protein and 820 g/kg of total digestible nutrients, was provided to the calves in creep feeding until 210 days-old (weaning). Supplement had a significant effect on the weight of the cow at calving and weaning. The average weights of the Angus-Nellore cows were 529.19 and 514.23 kg at calving and on the weaning day, respectively. These values were higher for Simmental-Nellore cows, which presented 569.60 and 542.59 kg, respectively. The male-calf weight at weaning was 254.69 kg, which was higher than the females (237.70 kg). Genetic group had no effect on weaning weight. The average weight for Canchim × Angus-Nellore calves was 243.41 kg and for Canchim × Simmental-Nellore it was 248.98 kg. Cow age affected weaning weight, promoting a linear increase of 0.804 kg in the weaning weight each year. Younger and smaller cows (Angus-Nellore) are more efficient for calf production.