Heat decreases production and profitability of US animal agriculture by billions of dollars each year. The heat-induced decrease in feed intake (hypophagia) fully explains the depressed growth in heat exposed animals. Yet, it only explains 40% of the acute depression in milk production (hypogalactia). We hypothesized that a mouse model of heat exposure (35°C; 50% humidity) would recapitulate the heat-induced hypophagia, acute hypogalactia, and depressed mammary gland development observed in the dairy cow. We first established that heat robustly depressed feed intake relative to mice at 22°C (>50% reduction; P < 0.05). We next showed that heat exposure from d 5–11 of lactation (21-d lactation) depressed dam weight, litter mass gain, and milk production (P < 0.05). By pair feeding (equivalent to the ad libitum feed intake of heat stressed animals) during that same period, we showed that approximately 40% of the decrease in cumulative milk production and litter mass gain was independent of feed intake. Thus, the relative role of hypophagia in acute heat induced hypogalactia is similar in lactating mice and cows. In the cow, heat exposure during the dry period suppresses mammary gland development, decreasing mammary gland size and milk production throughout the entire lactation. We tested the effect of heat exposure on mouse mammary gland development, by heat exposing throughout the final 5 d of pregnancy (last 1/4 of parturition). Heat stress during this time decreased cumulative dam weight gain (21%; P < 0.05), feed intake (28%; P < 0.05), pup weight at parturition (14%; P < 0.05), and total mammary gland weight at parturition (21.5%; P < 0.05). Pair-feeding decreased cumulative dam weight gain (30%), pup weight at parturition (10%) and mammary gland weight (21.5%) relative to thermoneutral control mice (P < 0.05). Thus, the heat-induced decrease in mammary gland development is completely attributed to hypophagia. Together these studies propose that the mouse may serve as an ideal model of heat stress hypophagia and hypogalactia. Using the genetic tools unique to the mouse will expand our mechanistic understanding and encourage informed treatments to alleviate the production losses resulting from heat exposure.