Different dietary forage sources regulate health-promoting fatty acids (HPFAs), such as conjugated linoleic acids (CLAs) and omega-3 polyunsaturated fatty acids (n-3 PUFAs), in the milk of lactating cows. However, the overall mechanism of forages regulating lipid metabolism from the gastrointestinal tract to the mammary glands (MGs) is not clear. Three isocaloric diets that contained (1) 46% corn silage (CS), (2) a mixture of 23% corn silage and 14% grass hays (MIX), and (3) 28% grass hays (GH) as the forage sources and six cannulated (rumen, proximal duodenum, and terminal ileum) lactating cows were assigned to a double 3 × 3 Latin square design. Our results show that a higher proportion of grass hay in the diets increased the relative contents of short-chain fatty acids (SCFAs), CLAs, and n-3 PUFAs. The lower relative content of SCFA in the milk of CS was predominantly due to the reduction in acetate production in the rumen and arteriovenous differences in the MG, indicating that the de novo synthesis pathways were inhibited. The elevated relative contents of total CLA and n-3 PUFA in the milk of GH were attributed to the increases in apparent intestinal digestion and arteriovenous differences in total CLA and n-3 PUFA, together with the higher Δ⁹-desaturase activity in the MG. In conclusion, this study provides an overall mechanism of dietary forages regulating HPFA status in the milk of dairy cows.

This study investigated the effect of moderate risk level (8 µg/kg) AFB₁ in diet supplemented with or without adsorbents on lactation performance, serum parameters, milk AFM₁ content of healthy lactating cows and the AFM₁ residue exposure risk in different human age groups. Forty late healthy lactating Holstein cows (270 ± 22 d in milk; daily milk yield 21 ± 3.1 kg/d) were randomly assigned to four treatments: control diet without AFB₁ and adsorbents (CON), CON with 8 μg/kg AFB₁ (dry matter basis, AF), AF + 15 g/d adsorbent 1 (AD1), AF + 15 g/d adsorbent 2 (AD2). The experiment lasted for 19 days, including an AFB₁-challenge phase (day 1 to 14) and an AFB₁-withdraw phase (day 15 to 19). Results showed that both AFB₁ and adsorbents treatments had no significant effects on the DMI, milk yield, 3.5% FCM yield, milk components and serum parameters. Compared with the AF, AD1 and AD2 had significantly lower milk AFM₁ concentrations (93 ng/L vs. 46 ng/L vs. 51 ng/L) and transfer rates of dietary AFB₁ into milk AFM₁ (1.16% vs. 0.57% vs. 0.63%) (p < 0.05). Children aged 2–4 years old had the highest exposure risk to AFM₁ in milk in AF, with an EDI of 1.02 ng/kg bw/day and a HI of 5.11 (HI > 1 indicates a potential risk for liver cancer). Both AD1 and AD2 had obviously reductions in EDI and HI for all population groups, whereas, the EDI (≥0.25 ng/kg bw/day) and HI (≥1.23) of children aged 2–11 years old were still higher than the suggested tolerable daily intake (TDI) of 0.20 ng/kg bw/day and 1.00 (HI). In conclusion, moderate risk level AFB₁ in the diet of healthy lactating cows could cause a public health hazard and adding adsorbents in the dairy diet is an effective measure to remit AFM₁ residue in milk and its exposure risk for humans.

(Objectives) The objectives of this study were to evaluate the effect of half-replacement of the supplementary sulfate sources of Cu, Mn, and Zn with methionine-hydroxy-analog-chelated (MHAC) mineral or amino-acid-complexed (AAC) mineral forms in diets on the mineral status, blood immune biomarkers, and lameness of lactating cows. (Methods) Sixty multiparous Holstein cows (158 ± 26 days in milk; body weight: 665 ± 52 kg; milk yield: 32 ± 7 kg/day) were randomly assigned into one of three dietary treatments (n = 20 per group): (1) MHAC: 50% replacement of sulfate minerals with MHAC forms. (2) AAC: 50% replacement of sulfate minerals with AAC forms. (3) S: 100% sulfate minerals (control). Their Cu, Mn, and Zn concentrations, blood immune biomarkers, and lameness were measured monthly. Repeated-measure mixed models were used to evaluate the effects on trace mineral status over time. As the responses with the MHAC and AAC forms were similar, the treatments were also analyzed as organic trace minerals (OTMs, combining the MHAC and AAC groups, n = 40) versus inorganic trace minerals (ITMs, the S group, n = 20). (Results) Cows supplemented with OTMs had higher concentrations of Cu and Mn in their serum (p ≤ 0.05), a higher hoof hardness (p ≤ 0.05), and a lower incidence of lameness compared to those with ITMs on d 90. There were no statistical differences (p > 0.10) in the concentrations of IgA, IgG, or ceruloplasmin, but there were significant differences (p = 0.03) in the concentrations of IgM in the serum as fixed effects of the diet treatments during the whole trial. On d 30 and 90, the serum IgA concentrations of the cows supplemented with OTMs tended to be higher (0.05 < p ≤ 0.10) than those in the cows supplemented with ITMs. (Conclusions) The half-replacement strategy showed that the MHAC and AAC sources of Cu, Mn, and Zn additives had similar effects on the production performance, blood immune biomarkers, and lameness of the lactating cows. The long-term replacement strategy with OTMs led to the enhancement of the trace mineral concentrations in their body fluids, blood immune biomarkers, and hoof health.