Effects of calving season on the voluntary waiting period and reproductive performance of Holstein cows in the tropical savannah

The effects of calving season [rainy (RS) and dry (DS)] on the voluntary waiting period (VWP) of 58 Holstein cows raised in the tropical savannah were investigated using data of temperature humidity index (THI), total antioxidant status (TAS), respiratory rate (RR), rectal temperature (RT), glucose, total cholesterol (TC), triglycerides (TG), velocity of uterine regression, and subsequent reproductive performance. Blood samples and clinical data were taken once every week, from calving until the sixth postpartum week. Reproductive data were collected until 180 days postpartum. THI differed between seasons (P < 0.05], as well as TAS (P < 0.001), RR (P < 0.001), RT (P < 0.01), glucose (P < 0.001), TC, and TG (P < 0.05), with higher values in RS. Although the velocity of uterine regression showed to be slower (P < 0.001) during RS, no differences were present regarding uterine health. Days open increased in RS (P < 0.001), but the number of services/conception was similar (P = 0.33). The results suggested cows under heat stress during the rainy season in the tropical savannah are more susceptible to a decline in the reproductive performance due to oxidative, metabolic, and uterine health problems.     

Fasting heat production of Saanen and Anglo Nubian goats measured using open‐circuit facemask respirometry

This study aimed to establish the heat production (HP) of Saanen and Anglo Nubian goats at absorptive (feeding) and at post‐absorptive (fasting) statuses to determine the adequate period of fasting required for the measurement of basal metabolism. Gas exchange was recorded via open‐circuit facemask respirometry. Six non‐lactating and non‐pregnant goats of each breed, Saanen (49.2 ± 3.2 kg of body weight, BW) and Anglo Nubian (64.0 ± 3.0 kg BW), were placed in individual pens with ad libitum access to the same total mixed ration. After a 3‐day feeding period, the animals were subjected to fasting (no feed), and the gas exchange measurement was performed for 30 min at 0, 12, 20, 36, 44, 60 and 68 h after fasting. The daily HP of the Saanen and Anglo Nubian goats averaged 557.4 ± 38.7 and 357.1 ± 35.3 kJ/kg^0.75 BW day respectively. During fasting, the methane production decreased exponentially in both breeds, and the critical time when methane production was statistically equal to zero was at 31 h of fasting for the Saanen goats and at 40 h for the Anglo Nubian goats. The daily HP and respiratory exchange rate during fasting decreased up to 60 h. Taken together, our results suggest that the ideal period to measure fasting heat production (FHP) for goats fed at maintenance levels should be between 40 h and 60 h of fasting. Consequently, the daily FHP, after 60 h of fasting, of Saanen and Anglo Nubian goats was 183.3 ± 16.3 and 211.1 ± 11.5 kJ/kg^0.75 BW day respectively. The results presented herein are relevant for future studies of energy metabolism in goats.     

Characterization of antixenosis to Dichelops melacanthus (Hemiptera: Pentatomidae) in soybean genotypes

Soybeans are of great importance in the world agricultural landscape, and their productive potential is significantly reduced by attacks from insect pests. Factors such as the expansion of national agricultural regions, together with no-tillage management and “off-season” maize cultivation, have favored the increase of secondary species such as Dichelops melacanthus (Dallas) (Hemiptera: Pentatomidae), intensifying the damage caused by the soybean stink bug complex. The use of resistant genotypes may be a valuable strategy as an alternative to the excessive use of chemical control in crops. This study evaluated the attractiveness and feeding preferences of the green-belly stink bug in 17 soybean genotypes in different maturity groups (early, semiearly, and late) to characterize the expression of antixenosis resistance. To this end, free-choice tests of attractiveness and food preference were performed under laboratory conditions. The early genotypes PI 171451 and D 75-10169, the semiearly genotypes IAC 78-2318, “IAC 100”, IAC 74-2832, PI 227687, and “IAC 24” and the late genotypes PI 274454, PI 274453, and L 1-1-01 expressed significant levels of antixenosis against adult D. melacanthus. These results will be useful for soybean breeding programs focusing on the stink bug resistance complex.     

Efficiency of methods for genetic progress estimation in common bean breeding using database information

The final field trials to evaluate elite lines developed by the Embrapa national common bean breeding program generated a phenotypic database composed by agronomic traits of 84 elite lines and nine cultivars over a 16-year period (1993–2008) and 450 environments in all Brazilian growing areas. The main goal of this study was to use this database as a model to compare the consistency of the results obtained from indirect methods for genetic progress estimation for grain yield in common bean breeding, using the direct method as a reference. Three indirect methods for genetic progress estimation were evaluated: (1) linear regression with unadjusted averages, (2) linear regression with averages adjusted by the mixed models, and (3) linear regression with averages adjusted by a fixed effects model with the error exception. The genetic progress estimated by the direct method was 31.3 kg ha^?1 per year (1.34%**). This value was considered as the reference estimate, since it was calculated using the grain yield data from final field trials with all common bean lines evaluated under the same environmental conditions. The estimate obtained using the regression with unadjusted averages of the three best lines by cycle was 25.66 kg ha^?1 per year (1.26%*), similar to the result obtained by the direct method. Considering both methods using fixed and mixed models, the genetic gain estimates were statistically null (0.42% and 0.45%, respectively). Therefore, the regression method with unadjusted means was more informative than the other indirect methods.