RESUMEN

One of the main factors that influences the fertility of cattle in grazing systems in hot tropical climates is heat stress. The objective of this study was to evaluate the effect of season, breed, hormonal and physiological condition on the quantity and quality of cumulus-oocyte complexes (COCs) and embryos produced in vitro, from Romosinuano (RM) and Tropical Milking (TM) donors. Three ovum pick-up and in vitro fertilization (OPU-IVF) were performed, one per season: hot dry (HD; 10, 10), hot humid (HH; 9, 9) and fresh dry (FD; 7, 10) in RM and LT donors. Serum levels of cortisol, insulin and glucose were measured, in addition to heart rate (HR), respiratory rate (RR) and rectal temperature (RT). Effect of season x genotype interaction (p ≤ 0.05) was observed in all COC variables and only in cleavage embryos (CLI) (p ≤ 0.05). Body weight (BW) affected all COC variables (p ≤ 0.01), except unviable (UNV) although affected degenerated embryos (DEG) (p ≤ 0.01) and total blastocysts (BLAST) (p ≤ 0.01). Cow age only affected viable COCs (VIAB) (p ≤ 0.05), code one blastocysts (BC1) and BLAST (p ≤ 0.01). Cortisol affected total COCs (COCsT), VIAB and total matured in vitro (TMIV) (p ≤ 0.01), as well as CLI, BC1 (p ≤ 0.01) and BLAST (p ≤ 0.05). Insulin affected COCsT (p ≤ 0.01), UNV (p ≤ 0.05), denuded oocytes (DE) (p ≤ 0.01), BC1 and code two blastocysts (BC2) (p ≤ 0.01). Glucose affected all COC variables (p ≤ 0.01), except UNV and all embryo variables except BC2. HR affected COCsT, DE, TMIV (p ≤ 0.01), CLI, BLAST and DEG (p ≤ 0.05). RR affected COCsT, UNV, VIAB, CLI (p ≤ 0.05), BC1, BLAST and DEG (p ≤ 0.01). RT only affected DE, VIAB (p ≤ 0.01) and BLAST (p ≤ 0.05). The seasonal climatic year variation of Veracruz and changes in physiological and hormonal variables have diverse effects on the cumulus-oocyte complexes and embryos produced by RM and TM donors.

RESUMEN

The aim of this study was to determine the effect of two energy-level diets on the beef performance of Tropical Milking criollo bulls grouped by weight and age in three periods: initial, middle, and final. Evidence on intensive beef production from Tropical Milking criollo cattle breeds are unknown, and productive alternatives for dairy producers in the hot tropics are needed. Bulls were fed in each period with low (LE, 2.2 Mcal ME/kg DM) and high (HE, 2.9 Mcal ME/kg DM) energy diets and content phase feeding protein of 14.5, 12.0, and 10.3%, respectively. For each period, ten bulls were randomly assigned to diets. In all periods, growth performance for final body weight, average daily gain, feed intake, and feed conversion were all superior in HE (p ≤ 0.05). For the final period, slaughter body, hot and cold carcass weights, and dressing were also superior in HE (p ≤ 0.05); for meat quality traits, differences were observed in muscles Longissimus dorsi, Semimembranosus, Infraspinatus, and Serratus ventralis for pH and tenderness (p ≤ 0.05), although not for diets. For color L*, a*, and b* system, neither diet nor muscle had effect on L* (p > 0.05); however, the diet-muscle interaction was significant for a* (p ≤ 0.05), and only muscle effect was detected for b* (p ≤ 0.05). Tropical Milking bulls responded positively to a high-energy diet, despite not being a beef breed.

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The high climatic variability of hot climates of the intertropical zone reduces cattle fertility. In dairy cows in temperates zones, the THI has been used to evaluate the temperature and relative humidity (RH) joint effect in reproduction, but its use is not recommended in all geographic zones; in hot climates, the maximum temperature (Tmax) can provide more convenient information than THI. The objective of this study was to determine the artificial insemination (AI) service seasons and their joint effect with the maximum temperature and relative humidity of the previous seven days, the service day, and posterior seven days to the AI in the tropical milking criollo (LT) heifer's gestation. Climatic data was used to define three seasons: hot-dry (HD), hot-humid (HH), and fresh-dry (FD), and 313 artificial insemination services from 176 heifers were analyzed over fourteen years. The seasons were determined by cluster analysis. Gestation at first service (GF) was analyzed with a logistic regression model and global gestation (GG) with a mixed linear generalized model. The Tmax of previous seven days insemination [Formula: see text] - 0.20 ± 0.09 (p ≤ 0.02) in HD (p ≤ 0.02) and RH of seven days posterior insemination [Formula: see text]= - 0.08 ± 0.04 (p ≤ 0.04) in HD (p ≤ 0.01) affected GF. No effect of the Tmax and RH on the service day was observed (p > 0.05). The highest GG probabilities were higher than 0.70 in HH and FD, making those seasons the most suitable for inseminating LT heifers.

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Importation of livestock genetic resources from industrialized countries for introgression of specific traits and other forms of crossbreeding is often indicative of a shift in production systems toward greater intensification and specialization. In developing countries, imported genetic resources are regarded as both a solution to improve the performance of local livestock and as one of the main threats to local populations. Using international databases, censuses and technical reports, we investigate ongoing trends and consequences of these two phenomena in 40 countries from Africa, Asia and Latin America. In these countries, the share of locally adapted breeds within species has decreased by an average of 0.76% per year over the last 20 years. The corresponding increase has been distributed between pure exotic breeds and crossbred animals, with differences across regions. In several countries, increased utilization of exotic cattle breeds and crossbreeding has been accompanied by a trend in increased milk yield per cow. The shift from local genetic resources to crossbred and exotic animals must be considered in the context of challenges such as food security, erosion of agrobiodiversity, interactions with other agricultural production, reduction of poverty and provision of ecosystem services, as well as resilience to and mitigation of climate change.

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Crossbreeding represents an important technique to improve growth, beef quality and adaptability in beef production systems in tropical countries. The aim of this study was to evaluate sire and dam breed effects on performance and carcass traits of crossbred cattle produced in a tropical environment. Heifers and steers were evaluated during the pre-weaning, the post-weaning (n = 173) and the finishing phase (n = 123). Animals were produced by mating Nellore (N_N), Angus × Nellore (A_N) and Caracu × Nellore (C_N) dams with Braford, Charbray and Caracu sires. After weaning, animals were raised grazing on Marandu grass for 12 months; thereafter they were housed in individual pens and finished in a feedlot, receiving a total mixed ration. Ultrasound carcass evaluations were performed to determine ribeye area (R_A), backfat thickness (B_T) and rump fat thickness (R_T). A_N progeny were heavier at birth than N_N (P < 0.05), and Braford progeny had greater birth BW than Caracu (P < 0.05). Greater weaning BW was observed in the A_N and C_N offspring compared to N_N (P < 0.01). Greater average daily gain during the post-weaning period was verified in the N_N progeny compared to C_N (P < 0.05). No dam or sire breed effects were observed for BW at the end of the post-weaning period (P > 0.05). Progeny of N_N cows had greater B_T (P < 0.05) and R_T (P < 0.01) at the end of the post-weaning period in relation to C_N. Greater R_A was observed in the Caracu progeny than in the Braford (P < 0.05), which showed greater R_T than the Charbray progeny at the end of the post-weaning period (P < 0.05). No dam or sire breed effects were verified for final BW at the feedlot or for feed efficiency traits (P > 0.05). A_N progeny were superior in final B_T compared to C_N (P < 0.01), and Braford progeny had greater R_T at the end of finishing than Charbray (P = 0.05). The use of crossbred dams allows an increase in productivity until weaning, but this is not maintained in the post-weaning and finishing periods. The use of Braford sires produces similar growth performance in the different stages of the production system to those seen with Charbray and Caracu sires but generates animals with higher fat thickness at the end of finishing, which may improve carcass quality and commercial value.

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Abstract The first horses were brought to Brazil by the colonizers after 1534. Over the centuries, these animals evolved and adapted to local environmental conditions usually unsuitable for exotic breeds, thereby originating locally adapted Brazilian breeds. The present work represents the first description of maternal genetic diversity in these horse breeds based on D-loop sequences. A D-Loop HSV-I fragment of 252 bp, from 141 horses belonging to ten Brazilian breeds / genetic groups (locally adapted and specialized breeds) were analysed. Thirty-five different haplotypes belonging to 18 haplogroups were identified with 33 polymorphic sites. Haplotype diversity (varying from 0.20 to 0.96) and nucleotide diversity (varying from 0.0039 to 0.0239) was lower for locally adapted than for specialized breeds, with the same pattern observed for FST values. Haplogroups identified in Brazilian breeds are in agreement with previous findings in South American samples. The low variability observed mainly in locally adapted breeds, indicates that, to ensure conservation of these breeds, careful reproductive management is needed. Additional genetic characterization studies are required to support accurate decision-making.

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Objetivou-se avaliar o efeito da estação do ano sobre a qualidade do sêmen fresco e criopreservado de reprodutores Pantaneiros (Bos taurus) criados em condições tropicais. Foram utilizados 7 touros Pantaneiros e 3 Nelores (controle), dos quais foi aferido circunferência escrotal, consistência testicular e após a coleta e congelamento do sêmen realizada análise de motilidade, vigor, defeitos menores, maiores e totais, concentração, integridade de membrana plasmática e acrossomal para sêmen fresco e além destas, estresse oxidativo para sêmen criopreservado. O experimento foi conduzido em delineamento inteiramente casualizado, e arranjo fatorial 2x2 (2 raças e 2 estações do ano). A raça, estação do ano ou a interação entre eles, não alteraram significativamente as médias de circunferência escrotal, consistência testicular, motilidade, vigor, concentração, integridade de membrana acrossomal e porcentagem de defeitos menores. A integridade da membrana plasmática no sêmen fresco sofreu efeito da estação do ano e foi menor no inverno em ambas raças (95,76 ± 1,77% vs. 87,07 ± 4,78% P=0,03). A estação do inverno aumentou a porcentagem de defeitos maiores (29,15% vs. 16,44%, P<0,01) e totais (17,49% vs. 30,45%, P<0,01). Os parâmetros do sêmen congelado não foram influenciados pela raça, estação do ano ou interação entre elas. Portanto, nas condições edafoclimáticas estudadas, os reprodutores Pantaneiros apresentaram redução na sua qualidade seminal na estação do inverno.

The aim of the present study was to evaluate the effect of seasonality on the quality of fresh and cryopreserved semen of Pantaneiro breed (Bos taurus) bulls raised under tropical conditions. Scrotal circumference and testicular consistency were performed in seven Pantaneiro and three Nellore (control) bulls. Sperm motility, vigor, minor, major and total defects, concentration, plasma and acrosomal membrane integrity were assessed in fresh and post-thawed semen. Additionally, oxidative stress was determined in post-thawed semen samples. The experiment was done in a complete randomized design, with a 2x2 factorial arrangement (2 breeds and 2 seasons). Breed, season of the year or the interaction of both did not alter scrotal circumference, testicular consistency, motility, vigor, concentration, acrosomal membrane integrity and percentage of minor defects (P<0.05). Plasma membrane integrity of fresh semen was affected by the season and was smaller in winter in both breeds (95.76 ± 1.77% vs 87.07 ± 4.78%, P=0.03). Nevertheless, also in the winter there was an increase in the percentage of major (29.15% vs 16.44%, P<0.01) and total defects (17.49% vs. 30.45%, P<0.01) in fresh semen samples. Breed, season or interaction of both did not influence the sperm parameters of cryopreserved semen. Thus, in the studied climatic conditions, the Pantaneiro breed bulls present decrease in semen quality mainly in the winter season

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The objective of this study was to compare physiological and thermographic responses to heat stress in three breeds of cattle. Fifteen animals of each of the Nelore, Pantaneiro and Curraleiro Pe-Duro breeds, of approximately two years of age, were evaluated. Heart and respiratory rates, rectal and surface temperature of animals as well as soil temperature were recorded at 8:30 and 15:30 on six days. Variance, correlation, principal factors and canonical analyses were carried out. There were significant differences in the rectal temperature, heart and respiratory rate between breeds (p < 0.001). Nelore and Pantaneiro breeds had the highest rectal temperatures and the lowest respiratory rate (p < 0.001). Breed was also significant for surface temperatures (p < 0.05) showing that this factor significantly affected the response of the animal to heat tolerance in different ways. The Curraleiro Pe-Duro breed had the lowest surface temperatures independent of the period evaluated, with fewer animals that suffered with the climatic conditions, so this may be considered the best adapted when heat challenged under the experimental conditions. Thermography data showed a good correlation with the physiological indexes, and body area, neck and rump were the main points.