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Le Producteur de Lait Québécois MagazineVolume Number October 14, 2020
Débora SantschiPh.D., Agr.

PROFILab in bulk tank milk: what we’ve learned

PROFILab dans le lait de réservoir: ce qu'on a appris
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In collaboration with Daniel Warner, Innovation and Development, Lactanet

The fatty acid profile of bulk tank milk has been available to Quebec dairy producers since February 2020. Let’s take a look at what we’ve learned so far…

High variability between herds

American studies have reported that herds with higher de novo levels have shown better performances. Quebec data are, to some extent, consistent with that finding, showing a clear relationship between de novo fatty acids and bulk tank fat or protein (Figure 1). In fact, for every tenth of a unit increase in de novo fatty acids (0.10), fat content increases by two tenths (0.20). The link with true protein is also clear: for every 0.10 increase on the de novo scale, true protein increases by 0.12 units.

Figure 1: Each 0.1% increase in de novo fatty acids corresponds to a 0.2% increase in fat
Figure 1: Each 0.1% increase in de novo fatty acids corresponds to a 0.2% increase in fat


Our data for several thousand Quebec herds show, however, that the fatty acid profiles vary widely between farms. Breed is among the factors that have the greatest impact on the fatty acid. As shown in Figure 2, the levels of the different groups of fatty acids are higher in milk from predominantly Jersey herds, especially de novo and mixed fatty acids. More specifically, the de novo fatty acid content for Jersey herds is about 1.3 g/100 g of milk, as compared to around 1.05 g/100 g of milk for Holstein herds, with the other breeds falling in between. It should be noted that the variability between herds is high for all breeds, with the differences largely attributable to ration composition, feeding behaviour and herd management.

Figure 2: Breed influences the fatty acid profiles of Quebec herds
Figure 2: Breed influences the fatty acid profiles of Quebec herds

High performance herds have average levels of de novo fatty acids

There is a common misconception that it is “normal” for high performance herds to have below-average de novo levels, due to a dilution effect related to above-average milk production. This is partly true, but the difference between high performance herds and average herds is minimal. To demonstrate this, Figure 3 shows the distribution of the fatty acid profiles of 3 300 conventional Holstein herds. The herds are categorized by annual production; the red box represents the herds in the bottom 10% for production, the orange box represents the herds that rank between the 10th and 80th percentile (26.6-37.9 kg of milk/cow/day), the green box represents the herds in the top 10% (37.9-40.7 kg of milk), and the blue box represents the top 2% of herds (over 40.7 kg of milk/cow/day). As the values below the graph indicate, the “blue” herds seem to have lower levels of de novo fatty acids in their milk, but the difference is about 0.01 g/100 g of milk on average, which is very close to the average presented in the PROFILab report.

Figure 3: High producing herds (kg/cow/day) make as many de novo fatty acids as the average herd
Figure 3: High producing herds (kg/cow/day) make as many de novo fatty acids as the average herd


If we repeat the exercise but categorize the herds according to their production in kg of fat/cow/day, the result is the same: the best herds have average de novo fatty acid contents (Figure 4). This graph shows that the variation between herds within a same production category is greater than the variation between the different categories. We are currently conducting a study of 100 Quebec herds to gain a better understanding of the factors behind this high variability, specifically those related to feeding, herd management and environment.

Figure 4: High fat producing herds (kg/cow/day) make as many de novo fatty acids as the average herd
High fat producing herds (kg/cow/day) make as many de novo fatty acids as the average herd

How to interpret the boxplot?

A boxplot illustrates the variation within a group of data, in this case a group of herds. In the example below, the blue box represents 50% of herds, that is, all the herds that are “in the middle” of the group. The vertical lines extending below and above the box indicate the herds with the highest and lowest values.

Box-and-whisker plot

More to read: 

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