A trial was conducted during the anestrous period in female goats to determine: (a) whether estrus can be induced in anestrous goats by administration of equine chorionic gonadotropic hormone (eCG) and PGF2α under pen conditions and (b) whether these sexually active female goats can elicit sexual arousal in sexually inactive bucks. One hundred and fifteen pluriparous, nonlactating mixed-breed female goats were randomly assigned to one of four treatment groups: (1) administration of a single dose of 240 IU of eCG, 50 μg PGF2α i.m., and 25 mg progesterone (P4) (eCG; n=30); (2) administration of P4 and exposure to female goats treated with eCG-PGF2α (P4; n=39); (3) administration of 0.5 ml saline and P4 (Sal; n=23); and (4) P4 plus exposure to female goats treated with saline (Con; n=23). After hormone administration, all goats were put together with adult sexually inactive bucks for 15 days. The percentage of goats in estrus during these 15 days was similar in eCG-treated animals and untreated animals exposed to the eCG animals (97 and 95%). Pregnancy rate was also similar (63 vs. 64%) between these two groups. eCG-treated goats exhibited estrus earlier (P<0.05) than the treated goats in contact with the eCG goats. Furthermore, eCG-treated goats had larger litters (1.9 ± 0.2 vs. 1.6 ± 0.1, P<0.05) than the untreated goats in contact with the eCG goats. These results show that fertile estrus can be induced in anestrous female goats by exposing them to female goats induced to estrus with eCG. This female-female interaction triggers the stimulation cycle leading to the sexual arousal of bucks.

This study characterized the environmental–climatic trends occurring in the largest dairy cattle intensive production cluster under arid land conditions in northern Mexico. The study was based on the Temperature Humidity Index (THI); it aimed to identify the number of days with THI values ≥68 as a bio-marker of heat stress (HS) and evaluate the possible HS effect upon the milk production of dairy cows. Climate data were obtained every 10 min in five farms across years (i.e., 2015–2020). THI was divided into four HS subclasses, 68–71, 72–76, 77–79, and ≥80, according to the circadian HS occurrence (i.e., 1, 4, 8, 12, 16, 20, 24 h), and analyzed across seasons–years. Thus, a total of 1,475,319 THI across different time-scale subclasses was analyzed. The observed results supported our working hypothesis in that yearling-average periods with more than 300 d, HS was confirmed. A yearly average of 31.2 d with THI ≥ 80 with similar (p > 0.05) trends across dairy farms and a slight annual variation (p < 0.05) were also witnessed. Moreover, the highest days with THI levels ≥68 occurred in summer and autumn (p < 0.05), while the in the subclasses 68–71, 72–76, and 77–79, THI occurred in any hour-scale subclass (i.e., 1, 4, 8, and 12 h). Furthermore, a trend to observe THI-HS increases either among years or within an hour-scale basis were also observed. On average, HS engendered a reduction of up to 11.8% in milk production. These research outcomes highlight the need to identify and quantify the negative impacts that HS may generate at a productive and reproductive level in order to delineate mitigation strategies that may lessen the environmental impact upon the dairy cattle industry.

No abstract

The Temperature Humidity Index (THI) is the most used to identify the risk of heat stress for dairy cattle, which is based on the environmental temperature (ºC) and humidity (%), and of which they are currently considered 68 points as the threshold for high producing dairy cows. In the Comarca Lagunera, located in north central Mexico, 21% of the Mexican dairy production is generated annually, despite its environmental conditions characterized by temperatures up to 41.5 ° C in the summer, low relative humidity and high solar radiation. The objective was to identify the average number of days in which a THI ≥68 is reached per month in each season of the year with 1, 8 and 16 h of exposure in dairy farms of the region, for which, the information recorded every 10 min was analyzed daily in five farms for 6 years (2015–2020), using the DiGiTH ™ application (DiGiTH Technologies, Mexico) and through ANOVA (proc GLM; SAS Inst. Inc., Cary, NC, USA), to identify differences seasonal for this variable. The attached table shows that spring and summer were the seasons in which the highest number of average days per month were recorded, and winter in which the fewest days were recorded. Regarding the hours of exposure, it is observed that spring and summer are very similar in 1 and 8 hours of exposure, while for autumn and winter a clearer decrease is observed according to the hours of exposure for these seasons. These results indicate a very marked seasonal variability and in terms of the hours of exposure, which should be considered in order to adopt the measures to reduce the negative effects for the dairy cattle of the region.

The Lagunera region, located in north central Mexico (24° 01′-26° 48 ‘LN and 101° 52′-101° 52′ 104° 40′ LO), produce the 21% of the national Mexican cow’s milk despite its climatic conditions (temperatures that fluctuate between 12.7 °C in January and 28.5 °C in June, with extremes of -5 °C and 41.5 °C, in addition to high solar radiation). The Temperature Humidity Index (THI) is the most useful indicator to define if there are heat stress conditions. To identify whether the days in which THI ≥68 (considering the threshold for signs of heat stress to appear in high-producing lactating cows) are increasingly reached at least one hour a day, the information of this indicator was recorded every 10 min daily, from 5 cow farms for 6 years (2015–2020), using the DiGiTH™ application (DiGiTH Technologies, Mexico), and regressions were run to identify if there is a relationship between the years of study and the THI levels. At any level of THI (≥68), there is a tendency to increase the number of days (10.05 d per year; R2 0.37); Disaggregating the data by THI level, this trend is also observed for levels 68 to 71 and 72 to 76 THI, registering an increase of 11.33 d (R2 0.45) and 9.03 d per year (R2 0.45) respectively. At the 77 - 79 THI level there is no trend, while at the ≥80 THI level, a decrease of 5.66 d per year was registered (R2 0.79). The results suggest that in this region, the days of heat stress are increasing, except for the level ≥80 THI, which indicates that palliative measures for heat stress should be intensified, and it is necessary to identify the reason for the decrease in heat stress days at the most dangerous level for livestock.