Chromium supplementation improves glucose metabolism and vaginal temperature regulation in Girolando cows under heat stress conditions in a climatic chamber.

This study aimed to evaluate chromium supplementation on productive, reproductive, and metabolic parameters at lactating Girolando cows subjected to heat stress conditions in a climatic chamber. Thirty-six lactating Girolando cows were subjected to two sequential trials. In trial 1 (thermoneutral environment), the effect of chromium supplementation was evaluated (0 vs. 0.50 mg/kg of dry matter). In trial 2, the cows were fed the same diets, but they were divided into three environmental conditions: heat stress conditions in climatic chamber, fed ad libitum (HS); thermoneutral environment, fed ad libitum (TN); and thermoneutral environment, pair-fed (PF). In thermoneutral conditions, chromium supplementation did not affect productive or metabolic parameters, although supplemented cows had lower viability of oocytes (65.11 ± 0.08% vs. 76.86 ± 0.08%). During heat stress, chromium supplementation lowered plasma glucose levels (61.17 ± 1.90 vs. 67.11 ± 1.90 mg/dL), and increased the insulin:glucose ratio (0.39 ± 0.04 vs. 0.27 ± 0.04). Cows fed the control diet in the HS group had higher vaginal temperature values (39.40 ± 0.10 °C) than the cows in the TN group and PF group (38.89 ± 0.10 °C and 38.85 ± 0.11 °C, respectively). However, supplemented cows heat-stressed maintained the same vaginal temperature as cows in thermoneutral conditions. In conclusion, chromium supplementation improved glucose metabolism and prevented body temperature increases under heat stress conditions.

Identification of Candidate Genes for Reactivity in Guzerat (Bos indicus) Cattle: A Genome-Wide Association Study.

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.

Estrus behavior in Guzera (Bos taurus indicus) breed cows / Comportamento estral de vacas da raça Guzerá (Bos taurus indicus)

The estrus behavior was evaluated during an induced and natural subsequent estrus in twelve Guzera breed cows, in the winter and summer seasons in two consecutive years. The proportion of cows that responded to estrus synchronization was 84.8 percent. The effect of the interaction season x year of experiment on estrous cycle length was observed. Pro-estrus was longer in the summer (57.69±4.72h) and in the natural estrus (74.23±4.41h) than in the winter (38.95±4.02h) and in the induced estrus (22.40±4.36h). Estrus length was similar in the winter (11.48±0.70h) and in the summer seasons (13.40±0.82h) as well as among cows with induced (12.47±0.75h) and natural estrus (12.41±0.76h). The number of mounts accepted during estrus and the number of mounts accepted/ hour in estrus were similar in winter (29.17±2.86 and 2.59±0.22, respectively) and summer (31.45±3.36 and 2.42±0.26, respectively) as well as between induced (30.23±3.10 and 2.54±0.24, respectively) and natural estrus (30.40±3.14 and 2.47±0.24, respectively). The length and intensity of estrus were not influenced by synchronization or season of the year. Longer period of pro-estrus in summer may favor the identification of sexually active animals in this season.

A manifestação do comportamento estral foi avaliada durante um estro induzido e o estro subseqüente, em 12 vacas da raça Guzerá, no inverno e no verão em dois anos consecutivos. A proporção de vacas que respondeu à sincronização de estros foi de 84,8 por cento. Observou-se efeito de interação entre estação e ano sobre a duração do ciclo estral. O proestro foi maior no verão (57,69±4,72h) e no estro natural (74,23±4,41h), que no inverno (38,95±4,02h) e no estro induzido (22,40±4,36h). A duração do estro foi similar no inverno (11,48±0,70h) e no verão (13,40±0,82h), assim como entre as vacas com estro induzido (12,47±0,75h) e natural (12,41±0,76h). O número de montas recebidas durante o estro e o número de montas recebidas/hora em estro foram similares no inverno (29,17±2,86 e 2,59±0,22, respectivamente) e no verão (31,45±3,36 e 2,42±0,26, respectivamente), assim como entre o estro induzido (30,23±3,10 e 2,54±0,24, respectivamente) e o natural (30,40±3,14 e 2,47±0,24, respectivamente). A duração e a intensidade do estro não foram influenciadas pela sincronização ou pela estação do ano. O maior período de proestro no verão pode favorecer a identificação dos animais sexualmente ativos.

Variações sazonais no comportamento de vacas holandesas estabuladas em sistema free stall / Seasonal variation in the behavior of holstein cows housed in a free stall barn

O efeito da estação (verão e inverno) sobre o comportamento alimentar e postural de 19 vacas holandesas em lactação, confinadas em free stall, foi avaliado durante 11 dias nos meses de verão (janeiro, fevereiro e março), e 14 dias, nos meses de inverno (junho, julho e agosto), nos anos de 1993 a 1995. A temperatura ambiente (TA) e a umidade relativa do ar (UR), foram monitoradas diariamente, durante o período citado. As atividades referentes a alimentação, ruminação e ócio, bem como a posição dos animais (em pé ou deitada) foram anotadas a cada 10 minutos durante 24h. A estação do ano influenciou todas as variáveis relacionadas ao comportamento. No verão, as vacas diminuíram o tempo de alimentação e de ruminação e ficaram mais tempo em pé, enquanto no inverno, permaneceram mais tempo no ócio e na posição deitada. A produção de leite afetou o tempo de ruminação e a postura corporal dos animais mostrando que vacas no estágio inicial da lactação e de maior produção reduzem o tempo de ruminação e ficam mais tempo de pé. A mudança de comportamento entre as estações reflete a tentativa dos animais de evitar o estresse calórico [AU]