Garcia-Peña, Juan C.

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    Evaluación de la capacidad termoregulatoria de la vaca criolla lechera de la República Dominicana
    (2015) Garcia-Peña, Juan C.; Sánchez-Rodríguez, Héctor L.; College of Agricultural Sciences; Santana Nieves, Carmen; Cabrera Cabrera, Carlos J.; Pagán Morales, Melvin; Latorre, José R.; Department of Animal Science; Gélica, Jocelyn A.
    The Criollo cattle from the Caribbean have been suggested as an alternative highly adapted to difficult environmental conditions. However, to our knowledge, there has not been extensive research about its thermoregulatory capacity. The present study aimed to evaluate the effect exerted by the air temperature, relative humidity, thermal humidity index, solar radiation, wind speed, and gust speed over the vaginal temperature of 13 lactating Criollo dairy cows from the Dominican Republic. The environmental conditions and the vaginal temperature were recorded every 5 minutes for 6 consecutive days. The GLIMMIX and CORR procedures of SAS were used to analyze the data (averaged by hour). Because the environmental conditions were greater during the last three days of the study (P<0.0001), the study was separated in two periods: COOL (days 1, 2, and 3) and HOT (days 4, 5, and 6). Period and time (hour of the day) interacted to affect the environmental temperature (P<0.0001), the relative humidity (P=0.0334), the thermal humidity index (P=0.0002), the solar radiation (P<0.0001), the wind speed (P<0.0001), and the gust speed (P=0.0003). These interactions were the result differences mostly observed during the afternoon time with air temperature, thermal humidity index, solar radiation, wind speed, and gust speed presenting 4.72°C, 5.17, 284.68W/m2 , 0.89 m/s y 2.37 m/s greater during the HOT than during the COOL period, respectively. Also during the afternoon hours the relative humidity was 14.83% lower during the HOT than during the COOL period. Similarly, cows presented greater vaginal temperatures during the HOT than during the COOL period (P<0.0001) from 1400-1800h (38.96±0.03 vs. 38.75±0.02°C, respectively). However, this trend was inverted during the morning hours. Greater vaginal temperature values (P<0.0001) were observed during the COOL than during the HOT period from 0200-0400h (38.37±0.02 vs. 38.21±0.02°C) and 0800-1100h (38.60±0.02 vs. 38.44±0.01°C). On average, daily vaginal temperature ranges of 38.38 - 38.79°C and 38.19 - 39.09°C were observed during the COOL and HOT periods, respectively. There was also a smaller asociation between vaginal temperature and air temperature (r=0.46; P<0.0001 vs. r=0.65; P<0.0001), thermal humidity index (r=0.47; P<0.0001 vs. r=0.60; P< 0.0001), solar radiation (r=0.34; P<0.0001 vs. r=0.50; P<0.0001), wind speed (r=0.35; P<0.0001 vs. r=0.54; P<0.0001), and gust speed (r=0.38; P<0.0001 vs. r=0.51; P<0.0001) during the COOL than during the HOT periods, respectively. Otherwise, the association between the relative humidity and the vaginal temperature was greater during the HOT than during the COOL period (r=-0.56; P<0.0001 vs. r=-0.46; P<0.0001). Even with the difficult environmental conditions present in this study, the observed daily vaginal temperature range and the inversion in the vaginal temperature trends suggested that these Criollo cows were highly adapted to these conditions. Future studies should be directed to compare this genotype with the european breeds comonly used for milk production in the tropics.