Effects of calcium montmorillonite clay and aflatoxin exposure on dry matter intake, milk production, and milk composition.

Fifteen primiparous crossbred dairy cows that were 114±14d in milk and weighed 533±56kg were used in a replicated 5×5 Latin square to test the efficacy of a calcium montmorillonite clay, NovaSil Plus (NSP; BASF Corp., Ludwigshaven, Germany), for the reduction of aflatoxin (AF) metabolite (AFM1) in milk and the effect of NSP on milk composition. Cows were housed in a freestall barn, fed once a day and milked twice a day. The experiment consisted of five 14-d periods: d 1 through 7 were considered for data collection, and d 8 through 14 were considered a wash-out phase. In each period, cows were randomly assigned to 1 of 5 dietary treatments: (1) control (CON), consisting of a basal total mixed ration (TMR); (2) high-dose NSP diet (NSP-1%), consisting of TMR plus 230 g of NSP; (3) aflatoxin diet (AFD), consisting of the TMR plus AF challenge; (4) low-dose NSP with AF (NSP-0.5%+AFD), composed of TMR plus 115 g of NSP and AF challenge; and (5) high-dose NSP with AF (NSP-1%+AFD), consisting of TMR plus 230 g of NSP and AF challenge. The AF challenge consisted of top dressing a daily dose of 100 µg/kg estimated dry matter intake (DMI); similarly, NSP was fed at 1.0 or 0.5% of estimated DMI. Milk yield and DMI were similar across treatments averaging 21.1±1.33 kg/d and 19.7±0.56 kg/d, respectively. Concentration of milk fat, protein, and lactose were similar across treatments with averages of 4.91±0.20%, 3.85±0.10%, and 4.70±0.06%, respectively. Concentration of vitamin A averaged 0.28±0.03 µg/mL and riboflavin concentration averaged 1.57±0.13 µg/mL across treatments. The concentration of minerals in milk were similar for all treatments. Cows fed CON and NSP-1% yielded the lowest concentration of AFM1 in milk with 0.03 and 0.01±0.06 µg/L. Addition of NSP reduced milk AFM1 from 1.10±0.06 µg/L with the AF diet to 0.58 and 0.32±0.06 µg/L with the NSP-0.5%+AF and NSP-1%+AF diets, respectively. Excretion of AFM1 was reduced by NSP; mean values were 24.38, 11.86, 7.38, 0.64, and 0.23, ± 1.71 µg/d, for AFD, NSP-0.5%+AFD, NSP-1%+AFD, NSP-1%, and CON, respectively. More specifically, 1.07±0.08% of the daily AF intake was transferred to the milk of cows consuming the AFD, whereas the AF transfer rates in milk from cows that consumed the NSP-0.5%+AFD and NSP-1%+AFD were 0.52 and 0.32±0.08%. Results from this research demonstrate that feeding NSP to lactating cows is an effective method to reduce the transfer and excretion of AFM1 in milk with no negative effects on dry matter intake, milk production, and composition.