Scielo RSS <![CDATA[Revista Brasileira de Zootecnia]]> vol. 44 num. 5 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Performance and immunological resistance of Litopenaeus vannamei fed a β-1,3/1,6-glucan-supplemented diet after per os challenge with the Infectious myonecrosis virus (IMNV)]]> This study determined the efficacy of a β-1,3/1,6-glucan source on the survival, growth, and immunological responses of Litopenaeus vannamei challenged with infectious myonecrosis virus (IMNV). The work was conducted in 20 tanks of 500 L with clear water with constant recirculation and aeration. Shrimp weighing 2.6±0.4 g were stocked at 100 animals/m2 and reared for 10 weeks. Viral challenge occurred through oral administration of IMNV positive extract (1.82 £ × 103 copies of IMNV/µL RNA) during three consecutive days, twice a day. One treatment and three controls, with five replicatetanks each, were used, as follows: Com - commercial diet fed to non-challenged shrimp (NCS); Ref - lab-manufactured basal diet, deprived of β-1,3/1,6- glucan fed to NCS; IMNV-Ref - basal diet fed to IMNV-challenged shrimp; and, IMNV-BetG - basal diet with 1,000 mg/kg of a β-1,3/1,6-glucan. Per os challenge began on the 29th day of rearing (4.93-g to 6.92-g shrimp). Shrimp were effectively contaminated with IMNV. Animals were highly susceptible to IMNV four weeks after the first day of infection when mortality peaked. Shrimp in the Com treatment (69.5±12.7%) reached the highest survival, but it did not differ from the Ref group (57.9±9.21%). Shrimp under the IMNV-Ref treatment achieved the lowest survival (23.2±5.76%). Survival for IMNV-BetG (48.1±8.53%) was significantly higher than IMNV-Ref, and similar to the Ref group. Total hemocyte count was significantly affected by treatment and hemolymph sampling time, while serum protein concentration and phenoloxidase activity did not change. Addition of 1,000 mg/kg of β-1,3/1,6-glucan in a diet for L. vannamei enhances shrimp survival when orally exposed to IMNV. No signs of immunological fatigue or detriment in growth are detected when the species is continually exposed to this diet. <![CDATA[Inbreeding on productive and reproductive traits of dairy Gyr cattle]]> The objective of this study was to estimate genetic parameters and to evaluate the effects of inbreeding on productive and reproductive traits of dairy Gyr cattle. Single-trait animal models were used to estimate genetic parameters and solutions for inbreeding coefficients for milk (milk 305-d), fat (fat 305-d), protein (protein 305-d), lactose (lactose 305-d), and total solids (TS 305-d) yield up to 305 days of lactation, days in milk (DIM), age at first calving (AFC) and calving intervals (CI). The mean inbreeding coefficient was 2.82%. The models with linear and quadratic effects of inbreeding coefficients fitted the data better than the models without or with only linear effect of inbreeding coefficient for all traits. The increase in inbreeding coefficient caused several losses in productive and reproductive traits of dairy Gyr cattle. Estimates of heritability for milk 305-d, fat 305-d, protein 305-d, lactose 305-d, TS 305-d, DIM, AFC, and CI were 0.28, 0.27, 0.22, 0.21, 0.22, 0.17, 0.20, and 0.10, respectively. It is possible to achieve genetic progress in productive traits (especially in milk 305-d and fat 305-d) and age at first calving in dairy Gyr cattle through selection. <![CDATA[2,6-Diaminopimelic acid (DAPA) in microbial protein quantification of heifers fed different forage sources]]> The objective of this study was to evaluate the flow of nitrogenous compounds, protein degradability, rumen degradation of total carbohydrate and organic matter and microbial efficiency in heifers subjected to diets containing corn silage, sugarcane or Tifton. For this purpose, the 2,6-diaminopimelic acid (DAPA) technique was adopted and analytical procedures for amino acids by HPLC were adapted. Six rumen-fistulated Holstein-Zebu heifers with 480 kg of initial BW and at 24 months of age kept in individual tie stalls were assigned to two 3 × 3 Latin squares. Omasal digesta dry matter and microbial dry matter flows were determined using the isolated, purified and enriched lignin (LIPE®) and DAPA markers, respectively. Isolated bacteria from rumen showed on average 5.84 g/100 g microbial N, 0.25 g/100 g DAPA in dry matter and 44.61 DAPA:N ratio. The forage sources did not influence the flows of nitrogen compounds, except for total omasal flow and non-ammonia N in relation to N intake for the corn silage diet, for which there was an upward trend compared with the other diets. The degradation of the organic matter and total carbohydrates did not differ, averaging 6.1 kg/day and 5.2 kg/day, respectively. The studied forage sources do not influence the flows of nitrogen compounds, except for total omasal flow and non-ammonia N in relation N intake for the corn silage diet, for which there is an upward trend compared with the other diets. Protein degradability and microbial efficiency are similar between evaluated diets. <![CDATA[Analysis of daily body weight of dairy cows in early lactation and associations withproductive and reproductive performance]]> The objective of this study was to describe daily body weight (BW) changes in the first 100 days of lactation in confined dairy cows and to associate BW loss with productive and reproductive performance. Data included 26,344 daily BW measurements of 372 Holsteins calving between June 2011 and June 2012 in a commercial herd in the South of Brazil. Cows were automatically weighed and were assigned according to parity. Individual measurements were smoothed using cubic splines, generating nadir BW, days to nadir BW and the BW loss (absolute and relative values). This approach used days in milk (DIM) as a single smoothing variable. Body weight at calving differed across parities: 570.5, 653.5, and 699.9 kg, for the 1st, 2nd and 3rd and subsequent parities, respectively. Body weight at nadir also differed across parities: 521.5, 608.8, and 647.3 kg, respectively. Mean days from calving BW to nadir BW and mean loss of BW (kg) from calving to nadir BW did not differ across parities, but relative BW change (kg/100 kg) was larger in animals in first parity (-8.4 kg/100 kg) than second parity (-6.6 kg/100 kg). However, cows in first parity had more chances for good reproduction than cows in third and subsequent parities (44.0% vs. 30.7%, respectively). There was no difference in the probability of adequate reproduction (pregnant until 180 DIM) among cows with low, medium, or high milk yield. Furthermore, cows with low and medium BW loss (below 60 kg of BW change) showed more likelihood to adequate reproduction than cows with high BW loss (above 60 kg of BW): 45.5 and 45.8% vs. 24.4%, respectively. Improvements in fertility of dairy cows should be achieved by minimizing body weight loss in early lactation. <![CDATA[Slow-release urea in diets for lactating crossbred cows]]> 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.