Effects of changing the essential and functional fatty acid intake of dairy calves.

There is limited information on the effects and requirements of specific fatty acids for dairy calves. The starter diet based on corn and soybean meal, which is typical in the United States, is low in C(18:3), and the ratio of C(18:2) to C(18:3) is quite high relative to recommendations for human infants. Additionally, other functional fatty acids (C(20:4), C(20:5), C(22:6)) elongated from C(18:2) and C(18:3) have proven benefits in monogastric species. Thus, the effect of adding Ca salts of flax oil (high in C(18:3)) or fish oil (high in C(20:4), C(20:5), C(22:6)) to the starter diet of calves less than 3 mo old was investigated. In trial 1, 48 Holstein bull calves [43.2 +/- 1.4 kg of body weight (BW); 12/treatment] that were 2 to 3 d of age were fed 1 of 4 starter treatments containing A) no flax or fish oil (control), B) 0.125% Ca salt of flax oil, C) 0.250% Ca salt of flax oil, or D) 0.250% Ca salt of fish oil. Starters and water were fed free-choice to calves. During the first 56 d, calves were individually penned. From arrival until d 28, calves were fed a 26% crude protein, 17% fat milk replacer. From 56 to 84 d, calves were penned in groups of 6 and maintained on their same starter blended with 5% chopped grass hay. Trial 2 used 96 Holstein steer calves (66.3 +/- 3.11 kg of BW; 24/treatment) that were 59 to 60 d old in a 28-d trial. These calves had been managed for their first 56 d in the same way as the calves from trial 1 before starting trial 2. Trial 2 evaluated increasing concentrations of Ca salt of flax oil within a starter blended with 5% chopped grass hay and fed with water free-choice. The 4 treatments were A) 0%, B) 0.083%, C) 0.167%, and D) 0.250% Ca salt of flax oil. In trial 1, there were no differences among calves fed the control diet and calves fed the diet supplemented with flax oil. In trial 1, average daily gain (ADG) increased linearly as flax oil increased in the starter from d 0 to 56 and from d 56 to 84, and hip width change increased linearly as flax oil increased in the starter. Serum urea nitrogen and serum glucose concentrations decreased as flax oil increased in the diet. In trial 2, ADG and feed efficiency increased linearly as flax oil increased in the starter. Serum alkaline phosphatase concentrations increased as flax oil increased in the diet. Supplementing a Ca salt of fish oil had no effect on any variables measured. Supplementing C(18:3) (linolenic acid) as a Ca salt of flax oil to the corn and soybean meal-based diet of dairy calves less than 3 mo old resulted in increased ADG and feed efficiency.