**2. Materials and Methods**

#### *2.1. Animals*

Male Sprague-Dawley rats and C57Bl mice (all weaned on day 21) used in these studies were single-housed in a temperature-controlled (22 ◦C) animal facility with a 12:12-h LD cycle (lights on at 07:00). Standard chow (Diet 86, Sharpes Stock Feed, Wairarapa, New Zealand) and water were available ad libitum unless indicated otherwise. The University of Waikato animal ethics committee had approved the procedures (ethics approval numbers: 1020, 1043, and 1057), and they are compliant with the NIH Guide for the Care and Use of Laboratory Animals (NIH Publ., no. 80–23, rev. 1996). Feeding experiments were performed in separate cohorts of animals unless specified otherwise. The age of animals included in the adolescent (5–6 weeks), adult (3–5 months), and aged (25–27 months) categories was based on previous publications pertaining to the aging process in rodents [25]. It should be noted that despite poor digestibility of lactose post-weaning, we did not observe any signs of gastrointestinal discomfort or sickness, which is in line with previous studies showing that rats fed as much as 30% lactose in their daily diet (thus, more than given here) for several weeks displayed good tolerance of the carbohydrate [24].
