Production, milk iodine, and nutrient utilization in Jersey cows supplemented with the brown seaweed Ascophyllum nodosum (kelp meal) during the grazing season

摘要

Kelp meal (KM) is a supplement made from thebrown seaweed Ascophyllum nodosum, known to bioaccumulateiodine (I) and to be the richest source ofphlorotannins, which can inhibit ruminal proteolysisand microbial growth. The objective of this studywas to investigate the effects of KM on production,milk I, concentrations of blood metabolites, apparenttotal-tract digestibility of nutrients, and CH_4 emissionsin grazing dairy cows. Eight multiparous Jersey cowsaveraging (mean ± SD) 175 ± 60 d in milk and 12primiparous Jersey cows averaging 142 ± 47 d in milkat the beginning of the study were assigned to either0 g/d of KM (control diet, CTRL) or 113 g/d of KM(brown seaweed diet, BSW) in a randomized completeblock design. Diets were formulated to yield a 70:30forage-to-concentrate ratio and consisted of (dry matterbasis): 48% cool-season perennial herbage and 52%partial TMR (pTMR). Each experimental period (n =3) lasted 28 d, with data and sample collection takingplace during the last 7 d of each period. Cows hadapproximately 16.5 h of access to pasture daily. Herbagedry matter intake increased, and total dry matterintake tended to increase in cows fed BSW versus theCTRL diet. Milk yield and concentrations and yields ofmilk components were not affected by diets. Similarly,blood concentrations of cortisol, glucose, fatty acids,and thyroxine did not change with feeding CTRL orBSW. However, a diet × period interaction was observedfor milk I concentration; cows offered the BSWdiet had greater milk I concentration during periods 1,2, and 3, but the largest difference between BSW andCTRL was observed in period 2 (579 vs. 111 μg/L,respectively). Except for period 2, the concentrationof milk I in cows fed KM did not exceed the 500 μg/Lthreshold recommended for human consumption. Diet× period interactions were also found for serum triiodothyronineconcentration, total-tract digestibilities ofcrude protein and acid detergent fiber, CH_4 production,and urinary excretion of purine derivatives. Overall, thelack of KM effects on milk yield and concentrations andyields of milk components indicate that dairy producersshould consider costs before making KM supplementationdecisions during the grazing season. Futureresearch is needed to evaluate the concentration of I inretail organic milk because of the high prevalence ofKM supplementation in northeastern and midwesternUS organic dairies and possibly in other regions of thecountry.