Banca de DEFESA: NICOLAS MOREIRA PIEDRAS MONNERAT CAPARELLI

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : NICOLAS MOREIRA PIEDRAS MONNERAT CAPARELLI
DATE: 16/01/2023
TIME: 14:00
LOCAL: Remota - Plataforma GoogleMeet
TITLE:

Effect of the seasons on the pregnancy rate of crossbred dairy cows.

KEY WORDS:

bioclimatology, cattle raising, heat stress, reproduction, conception.

PAGES: 39
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Reprodução Animal
SPECIALTY: Inseminação Artificial Animal
SUMMARY:

The presence of stressors stands out as one of the main elements correlated with the decrease in productive and reproductive performance in cattle. Heat stress has been discussed as one of the main factors impacting livestock due to the increasing change in climatic conditions in the world, in particular the increase in temperature. In dairy cows, heat stress has deleterious effects in several stages of reproductive development, decreasing the fertility of herds in several ways. The temperature and humidity index (THI) has been widely used as an indicator capable of estimating the degree of thermal comfort in the production unit and because it has a positive correlation with physiological parameters indicative of stress and a negative correlation with productive and reproductive aspects. The THI is easy to obtain because it takes into account the ambient temperature and the relative humidity of the air, allowing to quantify the level of exposure to thermal stress. However, studies report a reduction in reproductive performance during the warmer months even in subtropical regions. Therefore, the objective of this study was to compare the pregnancy rates of crossbred dairy cows in the different seasons of the year in the Zona da Mata Mineira region. For that, an observational study was carried out using data from a commercial dairy farm located in Mar de Espanha/MG. The collection of environmental temperature and humidity data was carried out using the INMET base – Instituto Nacional de Meteorologia. The climatic conditions in the period from 2014 to 2022 were evaluated and characterized by the calculation of the THI. The lowest THI was observed during the winter (61.5±3.9) while the highest occurred in the summer (68.4±3.6). The pregnancy rate observed in winter (59.9%) was significantly higher than that observed in summer (48.6%). When comparing the average THIs between pregnant and non-pregnant cows within each of the seasons, no significant difference was observed, as well as no difference was observed in the period of service for any season of the year. Animals with a higher genetic composition of Bos taurus (7/8 and 15/16) showed a reduction in the pregnancy rate during the summer when compared to animals with a lower European composition (30.5% and 62.3%, respectively), showing more sensitive to weather conditions. It is concluded that the subtropical climatic conditions during the summer negatively impacted the pregnancy rate of crossbred bovine females and that this impact occurred more intensely in animals with a higher European genetic composition.

COMMITTEE MEMBERS:
Presidente - 1548043 - MARCO ROBERTO BOURG DE MELLO
Externa ao Programa - 1201559 - VERA LUCIA TEIXEIRA DE JESUS - UFRRJExterno à Instituição - JOAQUIM ESQUERDO FERREIRA - CESVA