Response of laying hens to dietary saturated and unsaturated fatty acids in the presence of varying dietary calcium levels

The response of 33-week-old White Leghorn laying hens to dietary palmitic, oleic, or a 50/50 mixture of oleic and palmitic acids at an 8% inclusion level in the presence of 3, 3.6, or 4.2% dietary calcium was investigated over a 7-week period. There was no significant effect of treatments on egg production and egg weight. Although birds on diets supplemented with oleic acid consumed less feed (P less than .01) than those on diets supplemented with palmitic acid (102 g vs. 114 g), they gained more weight (P less than .01) than birds on diets supplemented with palmitic acid (+105 g vs. -32 g) over the 7-week period. There was no significant effect of the fatty acid treatment on shell quality as estimated by shell deformation. However, increasing the calcium content of the diets reduced feed intake and weight gain (P less than .05) and improved egg shell quality (P less than .05). The fat content of diets supplemented with oleic acid was better utilized than that from diets with an oleic/palmitic mixture, which, in turn, was better utilized than fat from diets supplemented with palmitic acid (P less than .01). Metabolizable energy values of diets followed a trend similar to fat retention and were independent of dietary calcium levels. There were no significant effects of fatty acid supplementation on calcium and magnesium retention, although increasing the calcium content of the diet resulted in a decreased (P less than .01) percentage of calcium retention.