Heat Treatment of Bovine Milk Influences Gastric Emptying of Lactose but not its Apparent Small Intestinal Disappearance in the Growing Pig as a Model for the Adult Human

Heat treatment influences gastric emptying of proteins and lipids in bovine milk. Whether heat treatment influences lactose gastric emptying and small intestinal lactose disappearance remains unknown. This study aimed to determine the gastric emptying of lactose and its disappearance from the small intestine of the growing pig as a model for the adult human. After 10 d of adaptation, fasted 9-wk-old pigs (n = 48) consumed 500 mL of pasteurized or ultra-high-temperature (UHT) bovine milk before being killed at 20, 60, 120, or 180 min post-feeding. Gastric, small, and large intestinal contents were collected to determine the gastric emptying of lactose, its apparent small intestinal disappearance, and its release into the large intestine. Portal vein blood samples were also collected to measure galactose concentration over time. Data were analyzed using nonlinear and polynomial models. The gastric emptying of lactose was faster for pigs fed pasteurized milk than those fed UHT milk (P ≤ 0.05). For example, 14 ± 2.9% and 24 ± 2.2% (mean ± standard error) of lactose, respectively, were retained in the stomach at 60 min post-feeding. The apparent small intestinal disappearance of lactose increased to 88 ± 2.4% over time, but it did not differ between milk types. Similarly, the plasma galactose concentration in the portal vein increased during the first post-feeding hour but did not differ between milk types. Lactose reached the large intestine during the first 20 min post-feeding, and the amount of lactose released into the large intestine did not change over time (523 μmol on average across post-feeding times after back transformation of 6.26 ± 0.37) or between milk types. Heat treatment influenced the gastric emptying of lactose but did not impact subsequent small intestinal apparent disappearance and portal blood plasma galactose appearance.