Effects of Season, Maximum Temperature and Relative Humidity on the Gestation of Tropical Milking Criollo Cows

Abstract

The season of the year (ES), maximum temperature (Tmax) and relative humidity (RH) affect gestation success of Tropical Milking criollo (TM) heifers, but their effects on the gestation of TM cows are not completely known. The study aimed to determine the effects of environmental factors along with artificial insemination (AI) service and calving on the gestation success of TM cows. Data were collected during 14 years, 959 records of AI of 155 cows in three seasons: hot-dry (HD), hot-humid (HH) and fresh-dry (FD). The response variables were gestation success of cows at first service after first calving (GF), first calving first to fifth service (GS) and global gestation success (GG). Model effects were ES, Tmax and RH seven days before the AI (PRAI), the day of the service (DAI) and seven days after (POAI); and days open (DO), cumulative milk production (MP), number of service (NS) and calving number (CN). GF was analyzed with logistic regression, and GS and GG with generalized linear models. Over 50 % of estrus occurred in the HH season. Tmax affected GF b1 = -0.13 ± 0.07 (p ≤ 0.05) and GG b1 = -0.08 ± 0.04 (p ≤ 0.05) in PRAI. There were no effects of ES, RH, NS or MP on GF, GS and GG for PRAI, DAI and POAI (p > 0.05). DO affected GG in PRAI, DAI and POAI b2 = -0.005 ± 0.002 (p ≤ 0.01). GG were as close to 52.0 % for the three seasons. Although with no statistical differences in multiparous cows (p > 0.05), for NS maximum gestation were 60 % at first and third, and minimum 40 % at fourth services; for CN they were 60 % at fourth, and 40 % at sixth and seventh calving, respectively. TM cows are adapted to a hot tropical Climate and their seasonal changes, showing similar pregnancy frequencies among seasons.

<em>In vitro</em> embryos of Romosinuano and Tropical Milking cattle during three seasons in Veracruz, Mexico

“…The criollo breeds Romosinuano and Tropical Milking are Bos taurus naturalized to hot climates of the tropical region, with populations established in different countries of the Americas, although relatively small of thousands of individuals [22][23][24]. Studies have been carried out to determine the effect of Tmax and RH on the fertility of TM heifers and cows,it was found that the lowest pregnancy, less than 50%, occur in the hot dry season with Tmax greater than 27 °C and RH of 85% for heifers [18], but no season effect was observed in cows [25]. When comparing, Brahman and Angus breeds to determine the effect of heat shock on oocytes cultured in vitro at 41°C, oocytes had greater cleavage, with embryos of more than eight cells four days after IVF [26].…”