The objectives of this study were to investigate the effects of incremental hydrogenated palm oil (HPO) and yellow grease (YG) on in situ nutrients disappearance and dairy cows performance, digestibility, blood parameters and chewing behavior when whole cotton seed containing alfalfa based diets with different forage to concentrate (F:C) ratios were fed. In this study eight early lactating Holstein cows (55 d in milk in a replicated 4×4 Latin square design with 21-d periods) and two Holstein dairy bulls fitted with ruminally and duodenally cannulas were used. Treatments were 1) 0% fat with 34:66 F:C ratio (Control), 2) 2% HPO with 34:66 F:C ratio (HPO), 3) 2% YG with 34:66 F:C ratio (YG) and 4) 2% YG with 45:55 F:C ratio (YGHF). Cows were allowed to ad libitum consumption of diets fed twice daily as total mixed ration. Feeding fat had no effect on dry matter intake (DMI), but DMI was reduced in high forage diet significantly (P 0.001). Diets including fat did not affect milk yield, but relative to Control, HPO and YGHF diets, YG ration increased milk yield. Feeding fat tend (P 0.06) to increase milk fat but increased milk fat yield significantly (P 0.04). High forage ration did not influence milk fat percent and yield compared with YG diet. Feeding fat had not affected milk protein percent and yield, however comparing with HPO and YGHF diets, YG increased milk protein percent and content. Total tract digestibility of DM was higher (P 0.04) in YG diet than HPO, however it was not affected by fat. Yellow grease tend (P 0.06) to decrease DM digestibility in high forage diet. Total tract digestibility of CP and fiber constitutes were not affected by treatments, but fat and it’s sources increased total fatty acid digestibility. Compared with third treatment, high forage ration had lower digestibility of total fatty acids significantly (P 0.05). Pre feeding blood concentration of non-esterified fatty acids was higher and lower in fat and high forage diets, respectively. Eating, ruminating and total chewing time, were not affected in first three diets with same F:C ratio, but high F:C diet influenced those activities. Feeding fat tend (P 0.06) to decrease in situ DM digestibility, however HPO diet significantly (P 0.05) decreased in situ DM digestibility. Digestibility of crude protein, NDF, ADF, and total fatty acid were not affected by feeding and source of fat and ratio of F:C, with exception of cellulose digestibility that significantly (P 0.04) increased with increasing amount of the forage in diet. Results of current study suggest that the use of yellow grease in alfalfa hay based diets did not cause milk fat depression and increased production responses compared with other treatments. Chewing behavior were not affected by fat and source of fat supplementat