Abstract
Neonatal harbour seal pups (Phoca vitulina) admitted to rehabilitation facilities are typically fed via gastric gavage until weaning. The gavage method facilitates feeding numerous animals while ensuring that adequate food volumes are delivered to each individual; however, it involves restraint and forced insertion of the tube into the esophagus and stomach. Early physiological research showed that the anticipation of eating triggers the digestive processes of salivation and secretion of stomach acids, but a stress-producing event can bring these processes to an abrupt halt.1 Gavage is a stressful event for most pups, and could inhibit pups' digestion. A more natural feeding system in which pups could feed naturally from a nipple might contribute to greater assimilation of the formulas and possibly increased weight gain. Currently, there are no adequate alternatives to gavage for rearing seal pups. Techniques such as bottle-feeding may further increase handling time and the risk of pups bonding with caregivers. Additionally, it can be difficult and time-consuming to induce pups to drink from nipples. However, the lack of successful nipple feeding may be, in part, due to the use of artificial nipples that are not appropriate for young seals. Work with lambs has demonstrated that if a nipple is of inappropriate size, hardness, and/or length it will deter the animal from sucking.2
In 2007, a variety of nipple designs were introduced to 16 unweaned pups to determine which, if any, elicited a sucking response. Based on these observations, a prototype nipple-feeder was designed that allowed pups to drink formula without being handled. The nipple-feeder consisted of a human baby bottle (Playtex® Drop-Ins System Original Nurser with a NaturaLatchTM Latex Nipple) fitted to a 10 cm PVC pipe with an elbow joint. The apparatus was fastened to the side of pups' enclosures so that the bottle was horizontal and 15 cm from the bottom of tub in order to approximate the natural nursing position.
In 2008, at the Vancouver Aquarium Marine Mammal Rescue Centre, two unweaned harbour seal pups (<10 days of age) were fed from admittance until weaning using the prototype nipple-feeder. Pups were fed an artificial milk-replacer (Zoologic® 30/55 Milk Matrix, PetAg, USA) 5 times per day at volumes of 80-140 ml/kg/day (~11% of pups' body weight). Forty-six pups were fed the same formula via gavage. Both pups were successfully drinking from the feeder within 1 to 3 exposures. Meal size was between 170 ml and 250 ml per feed, and pups took 45 to 240 seconds to consume each meal. Both pups gained weight at approximately the same rate as animals fed the same diet via gavage (123g/day) and were weaned at 28 and 31 days, which was within the range (8-36 days) for gavage-fed animals. The development of an alternative feeding method to gavage has the potential to allow for the efficient feeding of pups with the benefit of reduced handling and restraint. Additionally, the capacity to deliver milk-replacer ad libitum would enable pups to control meal frequency and possibly increase their daily intake.
Acknowledgements
We thank the staff and volunteers of the Vancouver Aquarium Marine Mammal Rescue Centre for their hard work and dedication, particularly Lindsaye Ackhurst, Karyn MacDonald, Shanie Fradette, Kerry Leonard, Victoria Chang, Jeong-hoon Kim, and Meghann Cant.
References
1. Canon WB. 1915. Bodily Changes in Pain, Hunger, Fear and Rage, second edition. Harper & Row Publishers Inc., New York.
2. Fraser D. 1987. Suckling behaviour of artificially-reared lambs: What kind of teat elicits spontaneous sucking? Appl Anim Behav Sci 19: 99-109.