A sustainable increase in livestock productivity cannot be achieved without the use of sustainable animal feed. Due to the growing awareness of the long-term benefits of sustainability, there is an increasing interest in replacing traditional feed resources with the most sustainable feedstuffs in pig production. Rye production is relatively sustainable compared to wheat. This farm study investigated whether the newborn body weight as well as antibody transfer in piglets (serum immunoglobulin immunocrit) are affected by feeding rye instead of wheat grain to transition sows. A total of 237 sows and their piglets (n = 711) from three farms located in northern Germany participated in this study. During the transition period, the sows were fed either a wheat-based diet used as the control diet (CON) or a 30% rye diet (RYE) for 7 days before the calculated farrowing date. On the day of farrowing, piglet body weights within 24 h post-natal (PN) were recorded, and blood samples were taken from the lightest, medium, and heaviest piglets in each litter to determine the quantification of immunoglobulins in the piglets. Feeding rye-based diets to the sows showed no differences in the body weight of the newborns (within 24 h) compared to the CON group in all body weight categories, except on Farm C in light and medium piglets, where high BW were observed in the CON group. The immunocrit ratio did not show any differences between both feeding groups. A relationship between newborn body weight and immunocrit ratios in the CON and the RYE groups was observed only on farm A. Overall, this study showed that including amounts of rye up to 30% in sows’ diets during the transition period had no negative effects on newborn piglet body weight or on antibody transfer and therefore can be considered an adequate replacement for wheat (up to 30%) in diets for transition sows. However, future research is needed to determine whether a higher proportion of rye may be used.