Cold and heat climatic variations reduce indigenous goat birth weight and enhance pre-weaning mortality in subtropical monsoon region of China.

The subtropical monsoon climate characterized by high or low temperature and humidity can induce cold and heat stress for newborn animals, which results in adverse effect on birth weight and even pre-weaning mortality. However, this early growth performance on indigenous goats is affected by cold and heat climatic environments and is still unclear in subtropical climate. In this study, we continuously measured (July 2011 to June 2016) the birth weight and mortality of an indigenous goat species (n = 530), and collected temperature, humidity, temperature-humidity index (THI) in original farming area, Chongqing, southwest China. As the result, the mean birth weights in cold months (January and February, mean temperature < 10 °C and THI < 56) and heat months (July and August, mean temperature > 29 °C and THI > 76) were significantly lower (P < 0.05) compared to the other months (June and October, mean temperature = 16~25 °C and THI = 61~75). Meanwhile, the birth weight was positively correlated (P < 0.01) with gestational THI from November to May, and was negatively correlated (P < 0.01) with those parameters from June to October, respectively. The maximum pre-weaning mortality, occurring in the 1st month after birth, is 16.17 ± 2.56%. However, when the birth weight was 20% lower than annual average (2.09 ± 0.54 kg), the mortality was significantly enhanced (P < 0.01) to 46%. In addition, cold and heat climates respectively enhanced mortality in the 1st month and 2nd~4th months after birth. In conclusion, annually chronic heat and cold climates could play important roles in lowering birth weight and their survival in subtropical monsoon region. Low birth weight and cold temperature play critical role to contribute the advent of higher mortality after birth. Our results potentially provide the appropriate ranges of temperature (16~26 °C) and THI (61~75) as pregnant goat and kids raising condition to avoid these negative influences.