Impact of DDGS feeding on the composition of milk and baby Swiss cheese

Late blowing in Swiss cheese, a result of unwanted gas production during ripening, isunacceptable to consumers, and causes economic loss to manufacturers. Cheese processorshave raised concerns that feeding dried distillers’ grains with soluble (DDGS) to cows leadsto this defect, in part, because of Clostridial spores. In this study, the effect of feeding DDGSto lactating dairy cows on composition and quality of milk and baby Swiss cheese wasexamined. Thirty healthy multiparous and mid-lactation Holstein cows were assignedrandomly to one of three dietary treatment groups (10 cows per treatment group): (1) totalmixed ration (TMR) with no DDGS, (2) TMR with 10% DDGS by dietary DM, and (3) TMRwith 20% DDGS by dietary DM in a 3 × 3 Latin square with repeated measures. Onecomplete milking from all cows within a treatment was collected and pooled for cheese-making trials, twice within each month of the three-month study. Additionally, individualmilk samples from three milkings of a day were collected weekly, and proximate analysiswas carried out on pooled individual milk samples. Milk used for cheese production wasstandardized to 0.88 fat:protein, and pasteurized before making baby Swiss cheese. The ~3.5 31kg cheese blocks were vacuum packed and allowed to ripen (10C, 7 days; then 22C, 21days), then cooled (4C, 60 days). Milk, cheese, TMR, DDGS and manure were analyzed forgas formation by Clostridial spores. Within 48 hours incubation in modified reinforcedclostridium lactate medium, tubes containing milk, cheese, TMR, or manure showed gasformation. Conversely, DDGS used in our study was not a source of gas-producing spores.Feeding 10% and 20% DDGS decreased milk fat content (P < 0.0001) and increased thesolids nonfat (P < 0.005), protein (P < 0.05), and lactose concentration of milk (P < 0.05) when compared with the milk from cows fed the control diet. After 60 days ripening, babySwiss cheese had typical propionic acid Swiss cheese aroma. Regardless of diet treatment,pinholes, slits, and cracks were seen throughout most cheeses. Feeding of DDGS increasedthe amount of long-chain unsaturated fatty acids and decreased short-chain and mostmedium-chain fatty acids in the baby Swiss cheese. Although feeding cows with DDGS,modified milk composition and subsequently the cheese composition, DDGS could not be blamed as a source for gas-producing spores or for quality defects in Swiss cheese, but,rather, the gas-producing spores likely originate from the cow herself or the environment.