Seasonal fluctuations in feed supply often result in serious under-nutrition of dairy cattle. We investigated the effects of impairments and improvements of feeding levels on milk production, weight changes, and the plasma level of IGF-1 in the third lactation of 27 Boran (Bos indicus) and Holstein-Boran crossbred cows. Results showed that Boran cows responded to changes in feed supply with weight changes and crossbreds predominantly with changes in milk yield. Milk yield was generally higher in crossbred cows; however, cows previously well fed showed higher milk production levels. IGF-1 was highest in Boran cows. Also crossbreds, well fed after previous undernutrition, showed high plasma levels of IGF-1, suggesting that these cows replenish first their body reserves at the expenses of milk production.