Aplicações da intensidade do estro de novilhas holandesas determinada por monitoramento automatizado

Abstract

Detection of estrus in dairy cattle is challenging, in part due to poor expression of behavioral estrus. The automated activity monitors allow the quantification of estrus expression based on the restlessness and its different intensities. The main objectives of this thesis were to evaluate the influence of estrus expression intensity on the duration of estrus events and characteristics; on ovarian dynamics and progesterone concentrations in Holstein heifers. A total of 62 estrus events from 41 heifers were evaluated. Heifers were monitored continuously by an automated activity monitor. Counting steps, and relative increase of activity (HI) were collected each hour during an estrus event. Two groups were formed considering the relative increase on estrus peak; High intensity (HIGH; >300 HI) and Low intensity (LOW; <300 HI). In first study, lying behavior and duration of events were recorded hourly and analyzed. Ovulation was checked using ultrasonography monitoring. Heifers classified as HIGH had greater duration at Peak-End (11.3±0.9 vs 6.4±0.9; P = 0.01) and estrus time (21.3±1 vs. 14.1±0.1; P = 0.01) than heifers LOW. Estrus intensity showed on peak was positively correlated to duration (r=0.48, P = 0.01). The longest rest per bout at the day after of estrus was different when comparing high intensity and low intensity (59.3±4.4 vs 71.1±4.2, respectively; P<0.05). Intensity of estrus did not impact at ovulation timing. However, impacted estrus duration. Measurements such as lying behavior provided important insights on how rest time measurements could be used for further improve estrus detection and timing. In second study, blood samples were harvested and determined the concentrations of progesterone, and preovulatory follicles and CL diameters. Heifers classified as high intensity had greater P4 levels at L3 (0.84±0.07 vs 0.64±0.04; P = 0.02) than heifers with low intensity. Weak correlations were observed between estrus intensity to progesterone concentration at PGF day and L3 day (r=0.11, r=0.20; P<0.05, respectively). Also, P4 levels was weakly correlated to estrus duration at PGF day and HT day (r=0.19, r=0.08; P<0.05, respectively). Intensity of estrus activity did not change ovarian parameters and P4 concentration. However, impacted progesterone levels at third day after estrus. The results suggest a potential in the application of the classification of estrus expression intensity from activity automatized monitors as part of decision making to increase reproductive performance of Holstein heifers.