Is the ileo-caecal Peyer's patch in ruminants a mammalian "bursa-equivalent"?

The ileo-caecal Peyer's patch (IPP) in young ruminants shows prenatal maturation and involution in young age, mainly like the thymus (1, 7, 8). In an examination of three-week-old calves IPP had features compatible with an essentially thymus-independent, primary function, different from that of jejunal patches. Features of IPP included very high lymphoblastic activity despite scarcity of coronal cells and few high endothelial venules in the interfollicular tissue.