Complex sentence: Peak lactation is the most energetically demanding stage of the animal's life and occurs around the 3 rd and 4 th weeks, at which point the lactating queen will not be able to maintain her body weight and will require the maximum amount of energy.
Split into simpler sentences: Peak lactation is the most energetically demanding stage of the animal's life and occurs around the 3 rd and 4 th weeks of lactation. At this point the lactating queen will not be able to maintain her body weight and will require the maximum amount of energy.