Background We have previously reported higher protein and zinc levels in the milk of ewes delivered prematurely when compared with reference data for term ewe milk. We did not know, however, whether these differences would still be evident when compared with milk obtained from a contemporary cohort of ewes delivered at term.
Purpose To compare protein, lactose, fat, and total energy content of preterm (PT) to term (T) ewe milk.
Design Daily milk samples were obtained between 0 and 21 days postpartum from healthy ewes delivered preterm (131-133 days' gestation) by cesarean section (PT, n = 7) and ewes allowed to deliver naturally at term (≈145 days, T, n = 8). Aliquots were taken from 24-hour collections with fresh samples used to determine total lipid content by the crematocrit technique. The crematocrit was performed in triplicate and averaged. The remaining samples were frozen at −70°C until analysis. Total protein and lactose (g/dL) values were determined at days 1 to 7, 10, 14, 17, and 21 by colorimetric assay and spectometry, respectively. Total energy (kcal/dL) was estimated from the sum of protein and lactose (4 kcal/g) and fat (9 kcal/g). Differences between PT and T ewe milk were determined by ANOVA with p ≤ .05.
Results Overall, PT ewe milk had higher mean values for protein, lactose, fat, and energy (Table 1). Total protein levels were 1.5 to 3.0 times greater in PT milk from days 1 to 21, with the largest differences observed from days 1 to 10 (p = .001). Lactose, fat, and energy levels were 16%, 55%, and 50% higher, respectively, in PT versus T milk from days 2 to 17 (p ≤ .01).
Conclusions Our findings confirm that premature delivery alters the nutrient composition of ewe milk during early lactation as evidenced by up to a threefold increase in total protein, fat, and, subsequently, total energy. Future work to determine whether greater protein and fat benefit PT lamb growth and overall nutrition status is needed.
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