Ashley Graham breastfeeds her baby while giving his twin formula in new combo feeding campaign

Breast, bottle, whatever: How You Feed is a shame-free series on how babies eat.

Ashley Graham has never shied away from sharing photos of herself nursing her three boys, first with Isaac, now 2 1/2, and now with 8-month-old twins Malachi and Roman. But the supermodel mom hasn't been relying on breast milk alone to keep her babies nourished. In new billboards for the organic infant formula company Bobbie, Graham is shown breastfeeding one twin while feeding the other a bottle filled with formula.

According to a press release from Bobbie, Graham is the first parent to be featured combo feeding — as in, using both breast milk and formula — on billboards, which will be going up across the United States. The campaign is intended to draw attention to the 70% of formula-feeding parents who give their babies both breast milk and formula.

Graham, who joined Bobbie's MotherBoard this summer, also opened up about her experience with feeding, including the moment she panicked to her mom about her fears about nursing twins. After nursing firstborn Isaac for 13 months, she turned to combo feeding to keep up with the demands of her two youngest boys for the first six months of their lives. She has since transitioned to formula only.

"Feeding your babies is as personal as it gets," the 34-year-old shares in a press statement. "After solely breastfeeding my first son for 13 months, I thought I was going to need a different plan for my twins. When the time came I knew combo feeding would be best for us. That worked really well for six months and now I’m exclusively formula feeding and it’s fantastic. For many parents, there's often a series of decisions that play out over the course of your feeding experience — and no matter where you are on that journey, there is no wrong choice.

In an Instagram post, Graham also spoke out about the "shame culture" that casts judgment on how parents feed their babies.

"After becoming a mom, I recognized the shame culture surrounding parents' decisions to feed their children," she wrote. "Every day I am amazed and grateful for all that my body is capable of, but I constantly remind myself that it doesn’t have to do it all. That it's OK to feel exhausted raising three children under 3, that it’s OK to live in a postpartum body, that it's OK to ask for help and support, that it's OK to formula feed when I can't breastfeed. That my best is best, no matter what it looks like."

Graham recently spoke to Yahoo Life about her experience with breastfeeding, and realizing she would need to supplement with formula after she and husband Justin Ervin welcomed their twin boys.

"We do breast milk and we do formula," she told Yahoo Life. "We do both because, just as one human being, I cannot keep up with two very savage babies."

Graham will be sharing more of her feeding journey with the Bobbie community through the month of September. The female-led brand — founded by mom of three Laura Modi — will also be hosting educational events on combo feeding this month as part of its efforts to destigmatize using formula.

Read more about baby feeding here:

• Why is there so much shame surrounding formula and breastfeeding?

• A history of breastfeeding and formula shaming: How did we get here?

• How does breastfeeding actually work? Experts explain

• When is a child too old to breastfeed? Experts weigh in

• Celebrities sound off on breastfeeding and formula shaming: 'There should be no judgment'

• Here's what the data says about the breastfeeding vs. formula feeding debate

• This mom launched the U.S.'s first female-led infant formula brand after feeling 'riddled with guilt.' Now she's shaking up the industry.

• Mom who breastfed 4-year-old on iconic 'Time' magazine cover looks back: 'I didn't like the photo'

• The nuances of breastfeeding as a Black mother

• I breastfed for almost 2 years — but I still got a guilt trip when I tried to wean

• Why 'breast is best' can send a harmful message: 'If your baby needs more, they need more'

• What is baby-led weaning and when is the best time to start?

• Is nipple confusion real? What experts say about your baby's feeding preferences

• What to know about mastitis, the breastfeeding complication that sent ‘Bachelor’ alum Lauren Burnham to the hospital

• The fascinating — and controversial — history of baby formula

• Mom praised for sharing TikTok of her 2-year-old respecting her boundaries while breastfeeding

• Emily Ratajkowski says she is 'always' breastfeeding. Here's why nursing takes so much time.

• 5 reasons why breastfeeding isn’t the solution to the formula shortage

• The controversial history of wet-nursing and what the 'informal,' 'underground' practice looks like today