Does garlic change the taste of cow milk when fed as a feed supplement?

Flies and other parasites are commonly known pests for cows. Garlic (Allium sativum) might be a solution for the reduction of flies as it is included for its function as insect repellent in equine supplements. Until now it is unknown if consumers could taste a difference of cow milk when cows get garlic as a feed supplement. This study was conducted to answer this question. Nine Simmental cows where divided into a control group (n=4) and a test group (n=5). The test group received 10 g of a garlic supplement per cow per day in experiment 1 (T1) and 50 g garlic supplement in experiment 2 (T2). After an adaption period of 7 days for each experiment, the milk of every cow was collected individually. The milk was blended to reach the equal fat content in control group and test group. Then the milk was homogenized and pasteurized. A sensory difference test (triangle test based on ISO 4120:2004) was conducted to identify whether consumers could taste a difference between the milk samples (test set up: one sample is different and two are equal; H0: There is no perceptible difference between the samples). The test was carried out with 56 consumers (T1) and 55 consumers (T2), respectively. They were asked to identify the different milk sample (with or without garlic taste). The minimum correct responses for a perceptible difference are calculated with x=(n/3)+z*√(2*n/9) with a z-value of 1.64 for p=0.05. If the correct responses are greater than or equal to the calculated value there is a rejection of the assumption of ‘no difference’. The calculated value was 25 for both tests. Therefore, 25 correct answers are needed to conclude there is a statistically significant difference between the two milk samples. 27 (T1) and 26 (T2) consumers did correctly detect the different sample during the sensory test (p<0.05). Based on this study, consumers recognized a difference between the milk of cows fed with garlic, independent of the garlic concentration in the feed. Further research is required to identify different garlic substances for feed which might not result in a taste difference of milk.