Body protein reserves sustained maternal performances in early lactation but dietary protein was necessary to maintain performance and immune responses to Nippostrongylus brasiliensis in lactating rats

Background: It has been shown that dietary protein supplementation during lactation boosts immunity in Nippostrongylus brasiliensis-infected periparturient rats. It is not known whether body protein reserves accumulated during gestation have a similar effect during lactation. Objective: This study aimed to quantify the impact of body protein reserves and dietary protein supplementation on maternal performances and immune responses to N. brasiliensis during lactation. Methods: Multiparous female Sprague-Dawley rats were given a primary infection of N. brasiliensis prior to mating and restrictedly fed either 60 g (Lge) or 210 g (Hge) crude protein (CP) per kg dry matter (DM) until parturition. Parturition onwards, dams were restrictedly fed either 100 g (Lla) or 300 g (Hla) CP per kg DM, generating 4 different dietary treatments. A subset of rats was sampled before parturition; post-parturition, dams were secondary infected with N. brasiliensis and samples were collected at day 5 and 11 post parturition. Results: Maternal performance until parturition, as measured by pup weight, was better in Hge rats compared to Lge (Lge 4.84 g, Hge 6.15 g, S.E.D. 0.19). On day 11, pup weight of dams with reduced protein reserves receiving protein during lactation (Lge-Hla, 20.28 g) was higher compared to their counterparts from Hge-Lla dams (17.88 g, S.E.D. 0.92). Worm counts were significantly different between Lge-Lla (253; 95% CI 124 to 382) and Hge-Hla fed dams (87; 95% CI 22 to 104) on day 11 (P=0.024). Expression of splenic Il13 and Alox15 was significantly higher (P<0.05) in Hge-Hla dams compared to Lge-Lla on day 5. Conclusions: Although protein reserves were adequate to maintain maternal performances in the early stage of lactation in dams infected with N. brasiliensis. they were not adequate to maintain maternal performances and effective immune responses at the later stages. Dietary protein supplementation was required to achieve this.