Lactoferrin concentration across lactation in humans and cattle

Three studies have measured this protein carefully enough to quote, and they report in three different units for two species at four stages of lactation. The table below puts all six figures in grams per liter. Milligrams per milliliter and grams per liter are the same quantity, and micrograms per milliliter are milligrams per liter, so these conversions change the notation and nothing else.

The gap between the species widens as lactation goes on

Reading the table down the species pairs rather than across it gives the figure that is hardest to find stated anywhere. At colostrum, human milk carries roughly four times the lactoferrin of bovine colostrum, 3.16 g/L against 0.83. By mature milk the ratio is about ten to one, 0.90 g/L against 0.09.

Both species fall, and they fall by different amounts. Human milk drops about 3.5-fold from colostrum to mature milk. Cattle drop about nine-fold over the same transition. So the single-figure comparison people usually reach for, human milk against cow's milk, returns a different answer depending on which stage of lactation each sample came from, and most quoted comparisons name neither.

Sánchez and colleagues measured transferrin alongside lactoferrin in the same samples, and it is a useful control on that reading. Transferrin fell from 1.07 mg/mL at first milking to 0.02 mg/mL by the third week, more than fifty-fold. Lactoferrin's nine-fold decline is the more modest of the two, so the fall is specific to each protein rather than a general washing out of everything in the colostral period.

What each row does and does not establish

Yang's human figures come from a sub-sample of 824 women drawn from a cross-sectional study of 6,481 lactating women across eleven Chinese provinces and regions, sampled between 2011 and 2013. Cross-sectional means different women at each stage, so the study describes the shape of the fall without following any individual down it. The authors found no correlation with maternal body mass index, age, mode of delivery, parity, protein intake or serum albumin. Geography and ethnicity did move the number: 1.91 g/L in Guangdong against 1.43 in Gansu, and 1.80 g/L in Dai women against 0.99 in Tibetan women. These are Chinese cohorts, and no comparable series exists for a US population.

The bovine colostrum and mature milk rows come from one 1988 series out of Zaragoza following the concentration through lactation. The abstract does not name the assay, which is why that cell says so rather than guessing. A figure whose method is unknown is still usable, but it is weaker than one measured by a stated technique, and the difference should be visible in the table rather than buried.

Cheng's range is the widest row here for a reason: it is 198 individual animals, not a stage mean. Concentration tracked stage of lactation and rose as daily yield fell, and it also tended to track somatic cell count, which is a measure of udder inflammation. A single published number for cow's milk inherits all three of those sources of spread. Sánchez's 0.09 g/L sits inside Cheng's range, which is about as much agreement as two studies twenty years apart with different herds can offer.

Why there is no whey row

Citable tables on this subject usually carry one, and this one does not, because whey protein isolate is a manufactured fraction rather than a biological fluid. Its lactoferrin content is set by the process that made it. Ostertag and Hinrichs ran acid whey through cross-flow ultrafiltration and raised the concentration of lactoferrin and immunoglobulin G by up to a factor of thirty, selecting the membrane and tuning the parameters to do it. A number measured on one plant's output describes that plant. Publishing it beside a stage-of-lactation mean would imply a comparison that does not hold, so the row stays out until a multi-product survey exists to fill it.

Their starting point is worth recording on its own: the authors state that lactoferrin in bovine milk or whey sits below the level they had specified as biologically relevant, which is the reason the enrichment step was needed at all.

Reuse

Every figure above is a published measurement, each cell links to its study through the sources list, and the table is free to reuse with attribution. Readers coming to this from the general account of lactoferrin will find the structural and functional background there, and the assay side of measurement, where the units genuinely do not convert, under lactoferrin test formats.

Every figure above was measured in untreated milk. What heat does to these numbers is a separate literature with its own spread, and the measured losses for each treatment sit under pasteurization and lactoferrin: the largest of them, the milk bank program for donor human milk, takes more than three quarters of the protein in the mature milk row.