Abstract #W157

# W157
Effect of kelp meal on milk yield, methane emission, and thyroid hormones in Jersey cows.
M. Ghelichkhan*1, R. C. R. Tinini2, J. G. Dessbesell2, H. A. Whitesel1, Y. Zang1, L. H. P. Silva1, M. A. Zambom2, A. F. Brito1, 1University of New Hampshire, Durham, NH, 2Universidade Estadual do Oeste do Paraná, Marechal Cándido Rondon, PR, Brazil.

Kelp meal (KM) is a supplement made from the brown seaweed Ascophyllum nodosum known to bioaccumulate iodine (I) in addition to be the richest of phlorotannins (PT). Previous research revealed that up to 5% of KM in the diet DM decreased CH4 emission in vitro and inhibited ruminal archaea in vivo with these responses likely modulated by PT. However, feeding ≥2% of KM is challenging because high intake of I may negatively affect thyroid health. We designed a study in which 2% of KM (400 g/d) was fed during 3 wk (high phase) followed by 0.5% of the diet DM (100 g/d) for another 3 wk (stepdown phase) and complete removal during the last 3 wk of the experiment (withdraw phase). Our goal was to investigate the effect of KM on yields of milk and milk components, CH4 emission, and thyroid hormones. Twenty Jersey cows (102 ± 52 DIM) were assigned to treatments in a randomized complete block design. Cows were fed (DM basis) 60% alfalfa hay and 40% concentrate. Milk and blood samples were collected on wk 3, 6, and 9. The GreenFeed system was used to measure CH4 emission throughout the study. Data were analyzed using the MIXED procedure of SAS with repeated measures over time. Iodine intake from KM averaged 240 mg/d (high phase) and 60 mg/d (stepdown phase). This resulted in I intake 34- (high phase) and 8.5-fold (stepdown phase) greater than required (i.e., 7.1 g/d). No treatment by wk interactions were observed for any variable tested. Likewise, treatments did not affect DMI (mean = 20.4 kg/d) and milk yield (mean = 24 kg/d). Concentrations and yields of milk fat and true protein, as well as CH4 production were also unchanged. Specifically, CH4 production averaged 389 g/d (high phase), 394 g/d (stepdown phase), and 380 g/d (withdraw phase). Treatments did not affect plasma concentrations of thyroid stimulating hormone (mean = 0.445 µIU/mL), free triiodothyronine (mean = 4.43 ng/mL), free thyroxine (mean = 0.74 ng/mL), and cortisol (mean = 31 ng/mL). Overall, dietary inclusion of up to 2% KM did not affect CH4 production or thyroid health, suggesting that greater levels of KM may be required to depress methanogenesis and thyroid function.

Key Words: iodine, methane, seaweed