https://www.selleckchem.com/products/icrt14.html Heat-stressed dairy animals increase their reliance on glucose. This elevated glucose demand is partially met by increasing the conversion of glucogenic amino acids (AA) in the liver. Propylene glycol (PG) is a glucogenic precursor and was not tested in dairy goats under thermoneutral (TN) and heat stress (HS) conditions simultaneously. We hypothesize that if HS-goats are fed with PG, they would get more glucose and consequently spare more glucogenic AA for milk protein synthesis rather than gluconeogenesis. Eight multiparous dairy goats (40.8 ± 1.1 kg body weight; 84 ± 1 days in milk) were used in a replicated 4 × 4 Latin square design of 4 periods; 21 d each (14 d adaptation, 5 d for measurements, and 2 d of transition). Goats were allocated to one of 4 treatments in a 2 × 2 factorial arrangement. Factors were control (CO) without PG or 5% of PG, and thermoneutral (TN; 15 to 20 °C) or heat stress (HS; 12 h/d at 37 °C and 12 h/d at 30 °C) conditions. Feed intake, rectal temperature, respiratory rate, milk yield, milk composition, and blood metabolites were measured. Compared to TN, HS goats had lower (p less then 0.01) feed intake (-34%), fat-corrected milk (-15%), and milk fat (-15%). Heat-stressed goats also tended (p less then 0.10) to produce milk with lower protein (-11%) and lactose (-4%) contents. Propylene glycol increased blood glucose (+7%; p less then 0.05), blood insulin (+37%; p less then 0.10), and body weight gain (+68%; p less then 0.05), but decreased feed intake (-9%; p less then 0.10) and milk fat content (-23%; p less then 0.01). Furthermore, blood non-esterified fatty acids (-49%) and β-hydroxybutyrate (-32%) decreased (p less then 0.05) by PG. In conclusion, supplementation of heat-stressed dairy goats with propylene glycol caused milk fat depression syndrome, but reduced body weight loss that is typically observed under HS conditions. Supplementation with lower doses of PG would avoid the reduc