This study aimed to assess iron deficiency anaemia in new-born lambs and goat kids and was carried out in two parts: (1) Twenty blood samples were taken from one-month-old lambs and kids under different systems and were tested for haemoglobin. Three groups of lambs were compared: indoor reared on maternal milk, indoor reared on milk replacer, and outdoor reared on maternal milk. Indoor-reared kids were compared: those fed on maternal milk and fed on milk replacer. Indoor-reared kids and lambs on maternal milk showed significantly lower haemoglobin levels than those on milk replacer or reared outdoors. (2) On farms with indoor-reared lambs or goat kids on maternal milk, an intervention trial was carried out: animals were randomly assigned at 1–8 days of age to either receive 300 mg (lambs) or 150 mg iron (goat kids) as intramuscular iron dextran, and growth rates were compared after one and two months. Haemoglobin levels at one month were also compared in randomly selected animals from both groups. Treated lambs and kids showed higher haemoglobin levels at one month of age and a numerically increased growth rate that was statistically significant for twin lambs. Iron dextran improves haemoglobin levels in these animals and may lead to higher growth rates, especially in twin lambs.