God instituted 3 Feast days each year where all members of the House of Israel and all nations were called to appear before the Lord in the temple. These festival days of commemoration and remembrance are Pesach or Passover, Shavuot or Pentacost, and Sukkot or Tabernacles. While most people (even non-Jews) have heard of Passover or even participated in a Seder Service, many people may not be aware of Pesach Sheni (Chain'-ee) or Second Passover.
Appearing in the temple for Passover requires ritual purity. However, because there are so many ways to become ritually unclean according to the Law of Moses, there was likely a good number of persons not able to participate in Passover because they could have simply been in the same room as a person who has died. Accordingly, God established Second Passover a month later so any person's who could not observe the First Passover could observe the Second (Numbers 9:9-13).
I am an ER doctor, and am routinely in the same room as someone who has died, even if they are not my patient. In reality, when it came to First Passover, I was working every day. So, when I heard about Second Passover, I decided to put on a simple Seder meal for my family and talk about Passover and Pesach Sheni.
Followers of Christ observe Passover by participating in the Lord's Supper each week. Jesus Christ gave and fulfilled the Law of Moses and observed Passover Himself. However, before His crucifixion and during the Last Supper, Christ instucted His disciples that they were to remember Him by breaking and blessing bread and blessing and drinking wine in His name. The Lord's Supper is the Christian Passover. But, it is still significant and fun to observe the original Passover and point out all the wonderful symbolism that points to Jesus/Yeshua as the promised Messiah and remember God's deliverance of the whole House of Israel from Egyptian bondage.
You will note that we do use lamb in our Seder. Some would question this as the lamb has not been ritually purified and sanctified in the temple by an authorized priest of Aaron. But if we were really worried about ritual purity (tumah and taharah), could we observe any part of Passover at all? Also, LDS believe our homes are next to the temple in holiness and all worthy makes are ordained to the Aaronic and Melchizedek priesthoods. But most importantly, the Passover lamb is the most important symbol of Jesus Christ and I wouldn't feel right substituting chicken or anything else.
By the way, I seasoned the Lamb with fresh rosemary and parsley from my garden together with cumin, garlic, salt and pepper and it was perfectly tender, moist and delicious.