Abstract
Prediction models for estimating voluntary feed intake (VFI) or metabolizable energy intake (MEI) of pigs are available in the literature. During the recent 2 decades, quite a few data have been reported to address the influence of heat stress on feed intake of pigs. The present study aimed to validate the accuracy of previous prediction equations for estimating VFI and MEI of pigs using data from heat stress experiments in the literature. Additionally, novel equations for estimating MEI of pigs under neutral or high ambient temperature (T) were developed based on body weight (BW) and ambient T. A total of 146 mean values from 30 research papers measuring the effects of heat stress on VFI of pigs published between 2001 and 2024 were used for the validation of the previous equations and development of novel equations. In the 30 papers, the thermoneutral T ranged from 17 to 25 °C, the heat stress T ranged from 21 to 35 °C, and the BW of pigs ranged from 19 to 119 kg. Based on the validation of the previous equation for VFI, the intercept representing a mean bias was 118 g/d (standard error = 31; P < 0.001). The validation of the previous equation for estimating the fraction of MEI using lower critical T and ambient T indicated that the intercept representing a mean bias was 834 kcal/d (standard error = 72; P < 0.001). The validation of equation for the fraction of MEI under high T showed a linear bias (slope = 0.196; standard error = 0.072; P = 0.008). Novel equations for estimating MEI and a fraction of MEI under neutral or high ambient T were developed. Taken together, previously published equations underestimate feed intake and MEI of pigs based on the present validation study. Additionally, novel equations for estimating MEI under neutral or high ambient T have been developed.