Temperament is fundamental to animal production due to its direct influence on the animal-herdsman relationship. When compared to calm animals, the aggressive, anxious or fearful ones exhibit less weight gain, lower reproductive efficiency, decreased milk production and higher herd maintenance costs, all of which contribute to reduced profits. However, temperament is a trait that is complex and difficult to assess. Recently, a new quantitative system, REATEST®, for assessing reactivity, a phenotype of temperament, was developed. Herein, we describe the results of a Genome-wide association study for reactivity, assessed using REATEST® with a sample of 754 females from five dual-purpose (milk and meat production) Guzerat (Bos indicus) herds. Genotyping was performed using a 50k SNP chip and a two-step mixed model approach (Grammar-Gamma) with a one-by-one marker regression was used to identify QTLs. QTLs for reactivity were identified on chromosomes BTA1, BTA5, BTA14, and BTA25. Five intronic and two intergenic markers were significantly associated with reactivity. POU1F1, DRD3, VWA3A, ZBTB20, EPHA6, SNRPF and NTN4 were identified as candidate genes. Previous QTL reports for temperament traits, covering areas surrounding the SNPs/genes identified here, further corroborate these associations. The seven genes identified in the present study explain 20.5% of reactivity variance and give a better understanding of temperament biology.

RESUMO -Objetivando determinar a melhor idade para a inclusão do farelo de girassol (FG) e o seu melhor nível nas rações de frangos de corte, bem como, avaliar a viabilidade econômica desta inclusão, 480 pintos de corte com 3 dias de idade, metade de cada sexo, foram distribuídos em um delineamento inteiramente ao acaso. Os tratamentos experimentais consistiram de uma combinação de níveis de FG nas rações (0, 4, 8 e 12%) e idades de fornecimento destas (I1= 3-21, I2= 22-35 e I3= 36-42 dias), sendo: T1= 0% de inclusão de FG nas rações nas idades I1, I2 e I3; T2= 4% nas idades I1, I2 e I3; T3= 8% nas idades I1, I2 e I3; T4= 12% nas idades I1, I2 e I3; T5= 0% na idade I1 e 4% nas I2 e I3; T6= 0% na I1 e 8% nas I2 e I3, T7= 0% na I1 e 12% nas I2 e I3; T8= 0% nas I1 e I2 e 4% na I3; T9= 0% nas I1 e I2 e 8% na I3; e T10= 0% nas I1 e I2 e 12% na I3. As análises estatísticas foram realizadas em arranjos fatoriais 4x2, 7x2 e 10x2, para as características ganho de peso, consumo de ração e conversão alimentar dos 3-21, 3-35 e 3-42 dias, respectivamente. Não houve efeito dos níveis de FG sobre o ganho de peso e consumo de ração nas idades estudadas. Dos 3-35 dias de idade, os tratamentos T1 e T7 proporcionaram, respectivamente, a melhor e a pior média para conversão alimentar. Aos 42 dias de idade o menor custo de produção foi obtido para o T8.Palavras-chave: eficiência alimentar, fibra, nutrição Sunflower Meal in Different Phases of Broiler DevelopmentABSTRACT -The aims of this work were to know the best age to feed poultry with sunflower meal (SM), to determine the best percentage of SM to feed animals in different ages and to evaluate economicall viability of SM as a feeding for poultry ration. In this experiment 480 three days old chicks were distributed in a randomized design. The experimental treatments consisted in rations with different percentages of SM (0, 4, 8 and 12%) and birds with different ages (I1= 3-21 days, I2=21-35 days and I3= 36-42 days of age). The treatments were: T1= 0% of SM inclusion on the rations at ages I1, I2 and I3; T2= 4% at ages I1, I2 and I3; T3= 8% at ages I1, I2 and I3, T4= 12% at ages I1, I2 and I3, T5=0% at age I1 and 4% at ages I2 and I3, T6=0% at age I1 and 8% at ages I2 and I3 ; T7= 0% at age I1 and 12% at ages I2 and I3, T8= 0% at ages I1, I2 and 4% at age I3, T9= 0% at ages I1, I2 and 8% at age I3; e T10= 0% at ages I1, I2 and 12% at age I3. Statistical analyses were carried out in factorial schemes 4x2, 7x2 and 10x2 to evaluate characteristic weight gain, feed intake and feed conversion rate at 3-21, 3-35 and 3-42 days, respectively. There were no treatments effects on weight gain and on feed intake in the birds age. At 3-35 days of age, treatments T1 and T7 provided respectively the best and the worst feed conversion rate. The lowest production cost was obtained when the animals were fed at treatment T8.

The Brazilian Guzerá population originated from a few founders introduced from India. These animals adapted well to the harsh environments in Brazil, were selected for beef, milk, or dual-purpose (beef and milk), and were extensively used to produce crossbred animals. Here, the impact of these historical events with regard to the population structure and genetic diversity in a Guzerá meta-population was evaluated. DNA samples of 744 animals (one dairy, nine dual-purpose, and five beef herds) were genotyped for 21 microsatellite loci. Ho, He, PIC, Fis, Fit, and Fst estimates were obtained considering either farms or lineages as subpopulations. Mean Ho (0.73) and PIC (0.75) suggest that genetic diversity was efficiently conserved. Fit, Fis and Fst values (95% CI) pointed to a low fixation index, and large genetic diversity: Fit (Farms = 0.021–0.100; lineages = 0.021–0.100), Fis (Farms = –0.007–0.076; lineages = −0.014–0.070), and Fst (Farms = 0.0237–0.032; lineages = 0.029–0.038). The dual-purpose herds/selection lines are the most uniform subpopulation, while the beef one preserved larger amounts of genetic diversity among herds. In addition, the dairy herd showed to be genetically distant from other herds. Taken together, these results suggest that this Guzerá meta-population has high genetic diversity, a low degree of population subdivision, and a low inbreeding level.

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The present study evaluated the heat stress response pattern of dual‐purpose Guzerá cattle for test‐day (TD) milk yield records of first lactation and estimated genetic parameters and trends related to heat stress. A total of 31,435 TD records from 4,486 first lactations of Guzerá cows, collected between 1986 and 2012, were analysed. Two random regression models considered days in milk (DIM) and/or temperature × humidity‐dependent (THI) covariate. Impacts of −0.037, −0.019 and −0.006 kg/day/THI for initial and intermediate stages of lactation were observed when considering the mean maximum daily temperature and humidity to calculate THI. Heritability estimates ranged from 0.16 to 0.35 throughout lactation and THI values, suggesting the possibility to expect gains from selection for such trait. The variable trajectory of breeding values for dual‐purpose Guzerá sires in response to changes in THI values confirms that the genotype × environment interaction due to heat stress can have some effect on TD milk yield. Despite the high dairy performance of Guzerá cattle under heat stress, estimated genetic trends showed a progressive reduction in heat tolerance. Therefore, new strategies should be adopted to prevent negative impacts of heat stress over milk production in Guzerá animals in future.

Four models for in vitro embryo production traits in Guzerá cattle were compared: Gaussian (untransformed variable - LIN and transformed in logarithmic scale - LOG), Poisson (POI) and zero-inflated Poisson (ZIP). Data consisted of 5716 ovum pick-up and in vitro fertilization records performed in 1205 cows from distinct regions of Brazil. Analyzed count traits were the number of viable oocytes (NOV), number of grade I oocytes (NGI), number of degenerated oocytes (NDG), number of cleaved embryos (NCLV) and number of viable produced embryos (NEMB). Heritability varied from 0.17 (LIN) to 0.25 (POI) for NOV; 0.08 (LOG) to 0.18 (ZIP) for NGI; 0.12 (LIN) to 0.20 (POI) for NDG; 0.13 (LIN) to 0.19 (POI) for NCLV; 0.10 (LIN) to 0.20 (POI) for NEMB depending on the considered model. The estimated repeatability varied from 0.53 (LOG) to 0.63 (POI) for NOV; 0.22 (LOG) to 0.39 (ZIP) for NGI; 0.29 (LIN) to 0.42 (ZIP) for NDG; 0.42 (LIN) to 0.59 (POI) for NCLV; 0.36 (LIN) to 0.51 (POI) for NEMB. The goodness of fit, measured by deviance information criterion and mean squared residuals, suggested superiority of POI and ZIP over Gaussian models. Estimated breeding values (EBV) obtained by different models were highly correlated, varying from 0.92 for NOV (between LIN-POI) and 0.99 for NGI (between POI-ZIP). The number of coincident animals on the 10% top EBV showed lower similarities. We recommend POI and ZIP models as the most adequate for genetic analysis of in vitro embryo production traits in Guzerá cattle.

Inbreeding has been associated with the impairment of reproductive performance in many cattle breeds. Although the usage of reproductive biotechnologies has been increasing in bovine populations, not much attention has been given to the impact of inbreeding over cow's performance on artificial reproduction. The objective of this study was to estimate the impact of inbreeding on in vitro embryo production in a Guzerá breed population. The inbreeding coefficient (F), calculated as half of the co-ancestry of the individual's parents, was used as an estimate of inbreeding. The inbreeding coefficients of the donor, sire (used on in vitro fertilization) and of the embryos were included, separately, in the proposed models either as classificatory or continuous variables (linear and quadratic effects). The percentage of non-inbred individuals (or embryos) and mean F of donors, embryos and sires were 29.38%; 35.76%; 42.86% and 1.98±2.68; 1.32±3.13; 2.08±2.79, respectively. Two different models were considered, one for oocyte production traits and other for embryo production traits. The increase of F of the donor significantly (P<0.05) impaired the number of viable oocytes (N OV), number of grade I oocytes (N GI) and number of cleaved embryos (N CLV). Moreover, the donor's F influenced the percentage of grade I oocytes (P GI), percentage of viable embryos (P EMB) and percentage of cleaved embryos that turned into embryos (P CXE). No significant (P>0.05) effects were observed for the sire (father of the embryos) inbreeding coefficient over the traits analysed. Embryo's F influenced (P<0.05) the number of viable embryos (N EMB), percentage of viable embryos (P EMB) and percentage of cleaved embryos that turn into embryos (P CXE). Results suggested that an increase in the inbreeding coefficient might impair the embryos ability to survive through challenges imposed by the in vitro environment. Submitting highly inbred Guzerá female donors to in vitro embryo production may, in the long-term, have negative implications on the number of embryos obtained per cow and increase the relative costs of the improvement programmes based on this technology. High levels of inbreeding should be avoided when selecting Guzerá female donors and planning in vitro fertilization mating.

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