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Title: The ability of exogenous growth hormone to maintain milk production during prolonged lactation in the mouse is more evident with reduced nursing frequency

Author
item HADSELL, D - Children'S Nutrition Research Center (CNRC)
item OLEA, W - Children'S Nutrition Research Center (CNRC)
item PARLOW, A - University Of California
item COLLIER, R - University Of Arizona

Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 7/12/2009
Publication Date: 7/12/2009
Citation: Hadsell, D.L., Olea, W., Parlow, A.F., Collier, R.J. 2009. The ability of exogenous growth hormone to maintain milk production during prolonged lactation in the mouse is more evident with reduced nursing frequency [abstract]. Journal of Animal Science. 87(E-Suppl.2):508.

Interpretive Summary:

Technical Abstract: Although growth hormone (GH) increases milk production in dairy animals, the milk production response of lactating rodents to this treatment has been variable. Milk removal frequency in the lactating mouse is about 10-fold higher than that of lactating dairy cows. The hypothesis tested in this study was that the ability of GH to stimulate milk production during prolonged lactation would be greater in mouse dams subjected to reduced nursing frequency than in dams allow to nurse ad-libitum. The growth of 8-day-old crossfoster litters maintained on groups of lactating mice was studied either from day 14 to 21 postpartum, or from day 21 to 27 postpartum using a litter cross-fostering protocol that prevents natural mammary involution. There were four treatments that consisted of ad-libitum (AL) or reduced nursing frequency (4x)in combination with subcutaneous injections of either saline (SAL) or recombinant murine GH (GH). The GH was tested at 2 doses of either 6 or 18 mg/kg/day. Reduced Nursing frequency caused a dramatic decrease in litter gain (P<0.0001) in both SAL- and GH-treated dams. At 6 mg/kg/day, GH failed to significantly increase day 14 to 21 litter gain in either AL or 4x dams (12.4+/-1.4, 15.4±1.2, 24.5+/-1.6 and 25.5+/-0.9 g for 4x-sal, 4x-GH, AL-SAL, and AL-GH, respectively). At a dose of 18 mg/kg/day, GH increased day 14 to 21 litter gain in 4x (P<0.02), but not in AL litters (10.56+/-0.8, 16.03+/-1.4, 30.1+/-1.9, and 30.1+/-0.8 g for 4x-SAL, 4x-GH, AL-SAL, and AL-GH, respectively). Litter gain from day 21 to 27 was increased by GH in both AL (P<0 01) and 4x (P<0.001) litters (2.4+/-1.9, 11.0+/-0.7, 13.5+/-0.5, and 18.8 g for 4x-SAL, 4x-GH, AL-SAL, and AL-GH, respectively). These results support the conclusion that the ability of GH to stimulate milk production in lactating mice is affected both by stage of lactation and the frequency of milk removal.