Effects of fat supplements containing different levels of palmitic and stearic acid on milk production and fatty acid digestibility in lactating dairy cows

Fat supplements based on palmitic acid (PA) or stearic acid (SA) are expected to have different effects on milk production and nutrient metabolism in lactating dairy cows. In this study, the effects of prilled fat supplements containing different levels of PA and SA were tested in 12 high-producing multiparous cows (pretrial milk yield = 53.4 +/- 8.7 kg/d; mean +/- SD) arranged in a 4 & times; 4 Latin square design with 21-d periods. Treatments were control (CON; no supplemental fat), an enriched PA supplement (HP; 91% C16:0), an enriched SA supplement (HS; 92.5% C18:0), and a blend of PA and SA (INT) fed at 1.95% of diet dry matter. All supplements contained oleic acid at approximately 5% of fatty acids. The HP treatment decreased dry matter intake (DMI) by 1.9 kg/d and 1.1 kg/d compared with SA and CON, respectively. Milk yield was not changed by treatment, but INT increased energy-corrected milk by 2.7 kg/d compared with HS. The HP and INT treatments increased milk fat yield by 0.11 and 0.14 kg/d compared with CON, respectively. Additionally, HP decreased yield of <16 carbon fatty acids (FA; de novo synthesized) by 44 g/d and 43 g/d compared with INT and CON, respectively. The HP treatment increased 16-carbon FA (mixed source) by 155 g/d compared with CON and 64 g/d relative to INT. No effect of treatment on apparent total-tract digestibility of dry matter, organic matter, or neutral detergent fiber was detectable. The INT and HS treatments decreased total-tract digestibility of 16-carbon FA by 10.3 and 10.5 percentage units compared with HP, respectively. Total-tract digestibility of 18-carbon FA was lowest in the HS diet and highest with HP. In conclusion, supplementing PA increased milk fat yield compared with control and SA, but supplementing a mixture of PA and SA increased energy-corrected milk without decreasing intake. The FA profile of fat supple ments influences their digestibility and effects on DMI and milk and milk fat synthesis. lactating dairy cows with the goal of increasing energy intake, fertility, or milk and component yields. Feeding saturated FA supplements has little risk of disrupting rumen function, is typically easy to handle on-farm, has less risk of reducing DMI compared with unsaturated FA (Allen, 2000), and increases milk and milk fat and protein yield (Hu et al., 2017). However, saturated FA supplements can differ in their concentration of palmitic acid (PA; C16:0) and stearic acid (SA; C18:0), which may modify responses in intake, production, and

Automated summary

This study investigated the effects of fat supplements containing different levels of palmitic acid (PA) and stearic acid (SA) on milk production and nutrient metabolism in lactating dairy cows. Supplementing PA increased milk fat yield, while a blend of PA and SA increased energy-corrected milk without decreasing intake. The fatty acid profile of fat supplements can influence their digestibility and effects on milk synthesis.