EFFECT OF CHITOSAN AND LIPID SOURCE COMBINATION ON ENERGY INTAKE AND MILK YIELD AND COMPOSITION OF DAIRY COWS
The aim of this study was to evaluate the effects of chitosan and soybean oil in the dairy cow's diets, on energy intake and milk yield. Twenty-four Holstein averaging 174.7 ± 53.1 DIM, were randomly assigned in six Latin Square design with a two by two factorial arrangement of treatments. The diets contained chitosan (150 mg.kg-1 of body weight) and/or soybean oil (3.3% of the diet DM). Each experiment period had a 14 d adaptation period and an seven for collection data. Sampling of milk was done on days 16, 17 and 18 of each period to evaluate the composition. The net energy intake (NEI), energy requirement for maintenance (NEm) and lactation (NEL) were obtained from the equations of NRC (2001). NEI was decrease with the use of chitosan in the diets without supplementation of soybean oil, but has no difference between diets containing soybean oil as well as the dry matter intake. The NEL was decrease by addition of soybean oil in the diet, regardless of the addition of chitosan. This occurred due to the reduction of on average 5.0 g.kg-1 the synthesis of fat in milk of animals fed soybean oil. Although the animals receiving chitosan and soybean oil had less milk yield (31.26 kg) compared with animals receiving only the soybean oil (32.86 kg) and in this diet decrease fat concentration was only 3.7g.kg-1, making fat corrected milk unchanged. Milk yield did not differ between cows fed chitosan diet (33.87 kg) and control diet (32.85 kg).The net energy balance was decrease on chitosan diet (2.97 Mcal) compared with control diet (5.33 Mcal) and was not influenced by the addition of chitosan on diets containing soybean oil (5.0 Mcal). The efficiency of use of energy, measured by the ration between the NEL and digestibility energy intake, was decrease by the addition of chitosan in diets with soybean oil and increased in diets without oil. Chitosan increases energy efficiency in dairy cows, provided that the diet has a low level of ether extract.
Keywords: Fat, feed additive, milk energy.