Milk Collection in the Rat Using Capillary Tubes and Estimation of Milk Fat Content by Creamatocrit

Abstract

Milk, as the sole source of nutrition for the newborn mammal, provides the necessary nutrients and energy for offspring growth and development. It also contains a vast number of bioactive compounds that greatly affect the development of the neonate. The analysis of milk components will help elucidate key factors that link maternal metabolism and health with offspring growth and development. The laboratory rat represents a popular model organism for maternal studies, and rat milk can be used to examine the effect of various maternal physiological, nutritional, and pharmacological interventions on milk components, which may then impact offspring health. Here a simple method of manually collecting milk from the lactating rat that can be performed by a single investigator, does not require specialized vacuum or suction equipment, and provides sufficient milk for subsequent downstream analysis is described. A method for estimating the fat content of milk by measuring the percentage of cream within the milk sample, known as the creamatocrit, is also presented. These methods can ultimately be used to increase insight into maternal-child health and to elucidate maternal factors that are involved in proper growth and development of offspring. Video LinkThe video component of this article can be found at

Maternal waterpipe tobacco smoke exposure during lactation induces hormonal and biochemical changes in rat dams and offspring

“…Lactating dams were separated from the pups for 2 hours before milk collection, and oxytocin injection (5 UI/mL S.C) 23 was given. The rats received anaesthetic dose of ketamine (40‐100 mg/kg, IP) and xylazine (5‐13 mg/kg, IP) for 60‐80 minutes 24 before manually collecting the milk from all teats as described previously 25 . The collected milk from all teats was pooled, the volume was measured, and it was saved at −80°C until further analysis.…”

Got Milk? Maternal immune activation during the mid-lactational period affects nutritional milk quality and adolescent offspring sensory processing in male and female rats

“…At the time of milk collection, ∼20 ul of sample was collected into a microhematocrit tube, which was then sealed and placed into a hematocrit spinner (2 minutes at 13, 700 g; StatSpin CritSpin Microhematocrit Centrifuge, Beckman Coulter, Inc). Measurements were taken to calculate percent (%) creamatocrit by evaluating the sample separation into each of the cream and clear layers by following the procedures outlined in Paul et al (2015). The remaining milk that was collected (∼500 ul per animal) was aliquoted across microcentrifuge tubes and stored at - 80°C until further processing.…”

Milking it for all it’s worth: The effects of environmental enrichment on maternal nurturance, lactation quality, and offspring social behavior

“…The milk procedure was adapted from a published procedure (Paul et al, 2015 ) . Immediately following the separation period, dams were lightly anesthetized with isoflurane in O2, followed by the administration of 0.2 mL of oxytocin (20 USP/mL i.p).…”

“…The dataset was not powered to evaluate sex-differences so male and female animals were evaluated separately (Ordoñes Sanchez et al, 2021). Two-way repeated measure ANOVAs (Housing x Time) were used to compare P1 and P10 milk levels of creamatocrit, which is linearly related to the fat concentration and energy content of milk (Lucas et al, 1978; Paul et al, 2015). This statistical analysis was also used to compare the total time the dam spent on the nest (P1-P4, P10) across the light and dark phases of the circadian cycle.…”