Rumen-Reticular Temperature During Estrus and Ovulation Using Automated Activity Monitors in Dairy Cows.

This study aimed to determine changes in rumen-reticular temperature (RRT) at estrus or ovulation and determine if these changes are associated with the intensity of estrous expression. Cows were equipped with an automated activity monitor (AAM) and a rumen-reticular bolus thermometer. A total of 190 estrus episodes were used where physical activity data was recorded using the AAM and ovulation was determined via ultrasonography of the ovaries at alert and twice daily, for a maximum of 60 h. Estrous expression was assessed using the maximum activity and duration in which activity remained above the AAM threshold; both characteristics were categorized using the median. Temperature data was collected for the duration of estrus, as well as for the interval of time where ovulation was determined to occur. Three measures of temperature were calculated: (1) positive area under the curve (AUC), (2) maximum positive temperature change (PTC), (3) maximum negative temperature change (NTC) at estrus (AUCE/ PTCE/ NTCE) and around ovulation (AUCO/PTCO/ NTCO). Both AUC and PTC were greater during estrus than around ovulation (2.7 ± 0.2 and 1.1 ± 0.3°C2 for AUCE and AUCO; 0.55 ± 0.03 and 0.26 ± 0.04°C for PTCE and PTCO, respectively). In contrast, NTC was lower around ovulation than estrus (-0.28 ± 0.05 and -0.60 ± 0.06°C for NTCE and NTCO). Cows with greater estrous expression had greater AUC and PTC during estrus than around ovulation, but cows with lesser estrous expression had similar AUC and PTC. Increases in AUC [High THI (Temperature Humidity Index): High activity: 4.7 ± 0.5, Low activity: 1.5 ± 0.4; Low THI: High activity: 3.1 ± 0.2, Low activity: 1.4 ± 0.2 °C2] and PTC (High THI: High activity: 0.79 ± 0.08, Low activity: 0.36 ± 0.07; Low THI: High activity: 0.60 ± 0.04, Low activity: 0.47 ± 0.04°C) associated with estrous expression were found to be greater on days with higher THI. Alerts created using standard deviations from the mean were unable to detect estrus or ovulation with acceptable precision. Further research is required to determine how changes in RRT can be used successfully to predict estrus and ovulation.

Rumen-protected B vitamin complex supplementation during the transition period and early lactation alters endometrium mRNA expression on day 14 of gestation in lactating dairy cows.

Greater metabolic demands in high-producing dairy cows are believed to be a cause of sub-fertility in these animals. Previously, supplementation with vitamin B complex molecules has shown benefits in improving milk production, health, and reproductive efficiency of dairy cows. The primary aim of this project was to determine the effects of rumen-protected vitamin B complex supplementation of 100 g of Transition VB (Jefo, St. Hyacinthe, QC, Canada) and 4 g of Lactation VB (VB; Jefo), during the transition and early lactation periods, respectively, compared with a control diet containing no supplementation on d 14 endometrial outcomes of pregnancy. In the vitamin B supplemented cows, we expect to see a change in the mark-up of endometrial genes important for embryo survival before implantation. Multiparous Holstein cows were enrolled into the study 3 wk before parturition and were randomly assigned to either the VB or control treatment. Twice-a-week blood samples, weekly milk samples, and daily feed intake were collected. Cows were enrolled onto a double-ovsynch protocol at 33 ± 3 d postpartum and inseminated by timed artificial insemination. Milk production and components, concentrations of BHB, haptoglobin, and progesterone in serum, and ovarian dynamics were also measured, but no treatment effect was observed. The uterus was flushed on d 14 after artificial insemination (around 72 DIM) for conceptus collection, and endometrial samples were collected at the same time. Overall, 42 cows were flushed and 13 embryos were collected. Analysis of mRNA expression of genes related to embryo development, immune system, adhesion, and regulation of vitamin B molecules showed that OXTR, MUC5B, MUC1, IL1B, SPP, TRD, FZD8, and FOLR1 genes were significantly upregulated in the VB group. Vitamin B supplementation had no effect on the size of the embryo and ovulatory follicle or corpus luteum diameter at embryo collection. In conclusion, the benefits of strategic dietary VB supplementation during the transition and early lactation might be directly linked to endometrial functions required for embryo survival during the peri-implantation period.

Effect of estrous expression on timing and failure of ovulation of Holstein dairy cows using automated activity monitors.

The aim of this study was to determine if estrous expression, as measured by an automated activity monitor (AAM), affects timing and failure of ovulation of lactating Holstein dairy cows. Cows were equipped with 2 AAM, 1 neck-mounted (AAMC) and 1 leg-mounted (AAML), by 10 d postpartum and enrolled into the trial when their activity crossed the alert threshold on the AAMC. A total of 850 episodes of estrus from 293 different cows were used for this study. When cows were enrolled, their ovaries were scanned by transrectal ultrasonography and gait and body condition scored. Ovaries of cows detected in estrus were scanned twice daily for a maximum of 3 d to determine the disappearance of the preovulatory follicle (ovulation) and the interval from estrus to ovulation was calculated. Physical activity data recorded from the AAM were used to determine estrus behavior using 2 traits: (1) peak activity and (2) duration. Peak activity was only available for the AAML. Peak activity was defined as the maximum activity during an estrus episode. Duration of estrus was defined as the time the activity of the cow exceeded threshold values set by the AAM software. The AAMC correctly identified 87.8% of the estrus alerts, with 12.2% false positives. The average (±standard deviation) intervals from activity alert to ovulation were 25.8 ± 10.2 and 24.7 ± 9.3 h for the AAMC and AAML, respectively. Changes in estrous expression were associated with differences in the interval from alert to ovulation. Cows with short intervals to ovulation were found to have less intense estrous expression than cows with medium and long length intervals to ovulation using the AAMC, whereas using the AAML, cows with short intervals to ovulation exhibited less intense estrous expression than cows with medium but the same as those with long intervals to ovulation. Furthermore, irrespective of the AAM, estrus events with less estrous expression had increased odds of having a short interval to ovulation (below the median of 20 h) when compared with those having greater estrous expression (2.6 and 1.9 increased odds for the AAMC and AAML, respectively). Ovulation failure was affected by estrous expression because estrus events with greater peak activity or longer duration had reduced ovulation failure compared with those with less estrous expression (AAMC peak activity: 1.9 ± 1.4 vs. 9.5 ± 1.7%; AAML peak activity: 2.3 ± 1.4 vs. 6.2 ± 1.5%; AAMC duration: 2.1 ± 1.4 vs. 8.9 ± 1.7%). In addition, cows with more estrous expression had greater pregnancy per artificial insemination than those with less estrous expression with both the AAMC (42.3 ± 0.4 vs. 31.7 ± 0.4%) and the AAML (43.1 ± 0.4 vs. 36.3 ± 0.4%). Pregnancy per artificial insemination results were consistent even when removing cows that failed to ovulate. In conclusion, expression of estrus was highly associated with ovulation timing, ovulation failure, and fertility when using 2 different AAM. Cows with greater estrous expression have longer intervals from activity alert to ovulation, experience less ovulation failure, and have greater pregnancy per artificial insemination.

Invited review: Effects of heat stress on dairy cattle welfare.

The effects of high ambient temperatures on production animals, once thought to be limited to tropical areas, has extended into northern latitudes in response to the increasing global temperature. The number of days where the temperature-humidity index (THI) exceeds the comfort threshold (>72) is increasing in the northern United States, Canada, and Europe. Compounded by the increasing number of dairy animals and the intensification of production, heat stress has become one of the most important challenges facing the dairy industry today. The objectives of this review were to present an overview of the effects of heat stress on dairy cattle welfare and highlight important research gaps in the literature. We will also briefly discuss current heat abatement strategies, as well as the sustainability of future heat stress management. Heat stress has negative effects on the health and biological functioning of dairy cows through depressed milk production and reduced reproductive performance. Heat stress can also compromise the affective state of dairy cows by inducing feelings of hunger and thirst, and we have highlighted the need for research efforts to examine the potential relationship between heat stress, frustration, aggression, and pain. Little work has examined how heat stress affects an animal's natural coping behaviors, as well as how the animal's evolutionary adaptations for thermoregulation are managed in modern dairy systems. More research is needed to identify improved comprehensive cow-side measurements that can indicate real-time responses to elevated ambient temperatures and that could be incorporated into heat abatement management decisions.

Association between ambient temperature and humidity, vaginal temperature, and automatic activity monitoring on induced estrus in lactating cows.

The objective of this study was to determine the association between ambient temperature and humidity, vaginal temperature, and automated activity monitoring in synchronized cows. Lactating Holstein cows (n = 641; 41.5 ± 9.4 kg of milk/d) were fitted with leg-mounted pedometers, resulting in 843 evaluated activity episodes of estrus. Vaginal temperature was monitored using thermometers attached to an intravaginal device as part of a timed artificial insemination (TAI) protocol; vaginal temperature was recorded every 10 min for 3 d. Ambient temperature and relative humidity were monitored using an external thermometer placed in the center of each pen. Milk production and body condition score (BCS) data were collected at the time of thermometer insertion. All statistical analysis was performed in R (https://www.r-project.org/) using Pearson correlation, analysis of variance, and logistic regression. Heat stress was calculated based on the percentage of time the cow spent with a vaginal temperature ≥39.1°C (PCT39) 9 to 11 d before TAI, and was classified as high (≥22.9%) or low (<22.9%). The mean vaginal temperature was 38.9 ± 0.2°C, and the mean maximum and minimum vaginal temperatures were 39.7 ± 0.5°C and 38.0 ± 0.8°C, respectively, with an average amplitude of 1.71 ± 0.9°C. Mean relative increase (RI) of estrus walking activity was 237.0 ± 160%. Animals with low BCS had a lower RI compared with cows with medium BCS (260.31 ± 17.45% vs. 296.42 ± 6.62%). Cows in early lactation showed lower RI compared with mid- and late-lactation animals (265.40 ± 9.90% vs. 288.36 ± 11.58% vs. 295.75 ± 11.29% for early, mid, and late lactation, respectively). Temperature-humidity index (THI) conditions categorized as low (THI ≤65) were associated with greater RI compared with medium (>65 to <70) and high THI (≥70). We detected no significant effect of PCT39 or milk production on RI, whereas parity exhibited a tendency. Cows that displayed greater RI at estrus had greater pregnancies per artificial insemination (P/AI) than cows with low RI (27 vs. 20%) or no RI (27 vs. 12%). Primiparous cows had greater P/AI than multiparous cows (27 vs. 20%), and cows in early and mid lactation had improved P/AI than those in late lactation (26 vs. 22 vs. 16% for early, mid, and late lactation, respectively). An interaction was observed between PCT39 and THI on P/AI, where a subpopulation of cows with high PCT39 had decreased P/AI under high THI conditions, but no differences in P/AI were observed for high PCT39 cows under medium or low THI conditions (13 vs. 24 vs. 26%). Future research should aim to refine variables related to hyperthermia and to understand the effects of body temperature on estrus expression and pregnancy rates.

Automated and visual measurements of estrous behavior and their sources of variation in Holstein heifers. II: Standing and lying patterns.

Lying (LY) and standing (ST) behavior of Holstein heifers (n = 57) was studied from Day -7 to Day +2 relative to estrus (Day 0) using leg-mounted accelerometers. A total of 269 estrus episodes were studied. The objectives were to quantify the effects of estrus on ST and LY patterns, identify sources of variation, and provide insight into new approaches for the use of sensors in estrus detection. The sensors were used to obtain ST bout frequency (bouts per day), total daily ST time, and mean bout duration and duration of the longest bout for ST and LY on a daily basis. Estrus episodes were identified using walking activity peaks and validated by ovarian ultrasonography. Repeated-measures ANOVA was used to analyze the effects of estrus order (pubertal vs. second and greater), season, time of estrus onset, category of baseline walking activity, and number of heifers simultaneously in estrus on ST and LY variables. Overall, ST bout frequency was lower, whereas mean ST bout duration, duration of the longest ST bout, and total daily ST time were longer on Day 0 (P < 0.05). The longest ST bout increased from 232 ± 5 minutes on Day -7 to 488 ± 16 minutes on Day 0 (P < 0.05), and on Day 0, it started within -2 to 4 hours of time of estrus onset. Measurements of ST bouts varied the most on Day 0 (coefficient of variation = 21.5%-52.8%). The pubertal estrus was characterized by smaller increase in mean ST bout duration, longest ST bout duration, and total daily ST time (P < 0.05) compared to the second and greater episodes. Second and greater episodes had greater longest LY bout on Day +1, but on Day 0 it was not different from other nonestrus days (P < 0.01). The longest ST bout on Day 0 was longer for heifers with high baseline walking activity and for episodes occurring during the cold season (P < 0.05). The effect of estrus on ST variables for morning-onset episodes was observed only on Day 0. Episodes with afternoon and night onset showed the effect of estrus spread over Days -1 and 0, resulting in a smaller change between Day -7 and Day 0. The number of heifers simultaneously in estrus did not affect the studied variables (P > 0.05). Measurements of ST and LY changed during estrus and were correlated to walking activity. The large increase in duration of the longest ST bout and its occurrence in proximity of estrus onset suggest potential for automation. Incorporating measurements of ST and LY corrected for sources of variation could improve estrus detection systems.