Earlier this week, as she prepared for Passover, Shannon Gessner suddenly remembered her dog, Marcy.

“This is our first Passover together,” says the 32-year-old account manager who lives on the Upper West Side with her 3-year-old mini-schnauzer. An observant “modern Orthodox” Jewish woman, Gessner has had the stray rescue since July and didn’t know what to do about her pup’s food for the upcoming holy festival, which starts Monday and lasts eight days.

“I e-mailed my rabbi about how to prepare for Passover when you have a dog,” says Gessner.

When it comes to the annual celebration, some observant pet owners don’t only avoid eating grains and leavened breads, known as chametz, themselves; they also have Fido and Fluffy abide by the dietary restrictions to keep their homes holy.

For the past 20 years, Star-K, a kosher certification agency, has been publishing an annual list of Passover-friendly pet foods. The brands on the list aren’t necessarily kosher, but they are Passover-friendly in that they are free of wheat and rice.

This year’s list was posted in early March, since many pet owners make the food transitions slowly so their pets have time to get used to the new foods.

“It’s not soon enough,” jokes Rabbi Zvi Goldberg with Star-K. “We get calls about Passover even in January.”

Rebecca Singer Walker, the 30-year-old director of the Israeliness Community at the 92Y, doesn’t look to the Star-K list for her 8-year-old Yorkie, Miles. She just feeds him what she eats.

“I’m going to be cooking beef or chicken or fish,” says Walker, a Riverdale resident.

For some, tweaking their pets’ diet is too much hassle, and they go for other options.

“Depending on how strict you are, some people might board their pet for a week,” says Rabbi Ayelet S. Cohen, the director of the Center for Jewish Living at the Jewish Community Center on the Upper West Side.

Others ceremoniously “sell” their pet’s food to a nonobservant friend for Passover. That way, Cohen explains, “the food doesn’t belong to you, it just lives in your house.”

That’s what Rikki Davidson, 29, plans to do. Davidson, who lives on the Upper West side with her husband, her son and her 7-year-old Maltese, Zoe, doesn’t want to be wasteful, so she plans to sell Zoe’s favorite treat, Nutri Dent, to a nonobserver and keep it in their house. After the holiday, she’ll buy it back. The dog’s regular kibble isn’t an issue.

“Zoe happens to be on a grain-free dog food,” Davidson explains.

Things aren’t so convenient for Gessner and Marcy.

“I was hoping I would get away with feeding her dog food, but [my rabbi] wants to err on the side of caution, so we’re going to be cooking for her,” says Gessner.

She plans to feed Marcy “human food,” which will include organic kosher meat and apples, instead of her typical diet of Orijen kibble. The pup will also have to forego her favorite treats, Wagatha’s biscuits and chewy bully sticks.

“It’s going to be hard, though, because she loves to chew,” says Gessner. “But I’m handmaking her breakfast and dinner, so she’ll survive.”