Supplemental fat sources are utilized in rations for dairy cows as a common method to increase the energy density of the diet to support energy demands for milk synthesis in early lactation (Heravi Moussavi et al, 2007). Although dietary fat supplementation increases the energy density of the diet, data on the relationship between the addition of dietary fat and the performance of lactating dairy cows are inconsistent because the impact of dietary fat is influenced by source of fat, method of processing, amount of fat included in the diet and stage of lactation. Canola seed which contains 40% fat is an excellent source of dietary fat high in unsaturated fatty acids and protein for dairy animals. Canola oil contains 51% oleic, 25% linoleic, and 14% linolenic acids. Fish oil (FO) also contains relatively high concentrations of two polyunsaturated fatty acids of the n-3 family: (EPA, C20:5) and (DHA, C22:6). Combination of fish oil with different plant oils has been studied previously but there are few studies which have examined the inclusion of fish oil in combination with canola oil. The aim of the present study, therefore, was to study the effects of different levels of fish oil and canola oil in early lactating Holstein cows.

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