What Effect Does Sorghum-based Feeding Have on Cheese Quality?

Climate change is compelling producers to find alternatives to the usual fodders. Sorghum is one alternative. When used in dairy-cattle feed, how does it affect the quality of hard cheeses?

In recent years, regions producing milk for Swiss Gruyere PDO have had to contend with a dry climate. If they are to meet the requirement that 70% of the feed ration come from the farm itself, producers will need to find solutions. Consequently, they are turning to water-efficient crops such as sorghum. This plant can be grazed by dairy cows to compensate for the shortage of fodder from July to September. But does feeding cows with sorghum affect the quality of Swiss Gruyere PDO?

Grazing on either grass or sorghum

As part of a joint Agroscope / Grangeneuve project, experts examined the quality of hard cheeses made from the milk of cows consuming either sorghum or grass. For the three days of the experiment, cows grazing on sorghum were treated separately from those grazing on grass, and the milk from the two groups was used in cheesemaking. The cheeses were made according to the recipe for hard cheeses used at the Agroscope Liebefeld research dairy. Once ripened, the six cheeses produced underwent a tasting.

Analyses

Several analyses were conducted as part of the experiment. In particular, a method was developed to analyse the concentration of thiocyanate (a highly toxic component of hydrogen cyanide) in the feed, blood and milk of the cows. The results revealed that when the cows began grazing on sorghum this had caused a slight increase in thiocyanate levels in their blood, but without knock-on effects for the milk.

The milk analyses showed that rather than negatively affecting protein content, the consumption of sorghum appeared to be beneficial.

Lastly, other analyses were conducted on the cheeses at 24 hours and at nine months of age. Analyses of the ripened cheeses revealed that the type of feed used affected the levels of certain amino acids, but that these differences did not influence cheese quality.

Sensory evaluation of the cheeses

The sensory evaluation of the cheeses was carried out by a panel comprising employees of Agroscope Posieux and Grangeneuve, together with a panel of experts consisting of individuals trained at Liebefeld.

The panel of employees did not perceive a significant difference in the comparisons. The panel of experts showed the same tendency as the panel of employees.

Neither panel was able to observe a clear-cut trend whereby a specific characteristic was “responsible” for the perceived difference. This demonstrates that the addition of sorghum to cow feed is not perceptible from a sensory perspective in hard cheeses.

In terms of appearance, the cheeses exhibited no major visual defects.