Resumption of ovarian activity is modified by non-photoperiodic environmental cues in Criollo goats in tropical latitudes

Abstract

The reproductive activity of female goats under tropical latitude is modulated by photoperiod; however other non-photoperiodic cues may play a role in this modulation. We assessed the relationships among circulating concentrations of progesterone and environmental cues (photoperiod, atmospheric pressure, precipitation, absolute humidity, maximum environmental and soil temperatures, and wind speed). For two consecutive years, environmental data were collected every 10min, while 8 female goats, separated from bucks, were individually fed a maintenance diet and were kept under natural conditions of photoperiod and climate (22°N). Female goats were weighed and body mass index (BMI) determined every week and were bled bi-weekly to monitor circulating patterns of progesterone. Environmental data was not similar in both years (P<0.001). Live weight rose from 37.4±1.3kg (mean±SEM) to 53.7±2.2kg, and BMI from 8.3±0.3 to 12.2±0.4 over the course of the experiment. The mean date when resumption of ovarian activity occurred differed between years (17 October vs. 27 September; P<0.001) and it was negatively associated with live weight and BMI (P<0.01). We observed that resumption of ovarian activity occurred when the ambient temperature averaged below 26° C. The concentration of progesterone was positively associated with live weight and BMI (P<0.05), absolute humidity and atmospheric pressure (P<0.001); but it was negatively associated with photoperiod, precipitation, and also maximum environmental and soil temperatures (P<0.001). The concentration of progesterone was not associated with wind speed (P>0.05). In conclusion, criollo goats from the semi-arid region of central-northern Mexico exhibited a clearly defined reproductive seasonality. This reproductive seasonality is not only modulated by photoperiod but also by non-photoperiodic environmental cues which may play an important role on this modulation. Temperature above 28°C affects productivity by causing a decrease of the concentration of progesterone resulting in anoestrus. An understanding of the interactions between climatic variables and the seasonal reproductive activity in goats, may lead environmental manipulations that aid to their reproductive management.