Effects of increasing dietary levels of microalgae rich in docosahexaenoic acid on dairy cow

Author(s)

Julia Avansi Marques

• Document type: Master's Dissertation
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2019-03-19

Examining board members

Francisco Palma Rennó; Jefferson Rodrigues Gandra; José Esler de Freitas Júnior

• Advisor: Francisco Palma Rennó

Abstract

The objective of this study was to evaluate the effect of increasing levels of microalgae rich in docosahexaenoic acid (DHA) in the diet of dairy cows on dry matter (DM) and nutrients intake and total-tract apparent digestibility (TTAD), milk yield, composition and fatty acids profile, ruminal fermentation, nitrogen and energy balance, ruminal microbial protein synthesis and metabolic profile. Twenty-four (eight of them with ruminal cannulas) Holstein lactating cows [130.3 ± 75.5 DIM and 30.8 ± 2.66 kg/d of milk yield (mean ± SD)] were used in a 4 × 4 Latin square design, to evaluate the following treatments: basal diet with no microalgae; and increasing levels of microalgae (2 g, 4 g, and 6 g/kg DM; All-G Rich™, Alltech®, Nicholasville, KY). Diets were formulated according to NRC (2001), to have the same amounts of energy, protein and lipids. Each experimental period lasted for 21 days, with 14 adaptation days and 7 sampling days. Microalgae inclusion reduced DM, organic matter (OM), crude protein (CP), ether extract (EE) and neutral detergent fiber (NDF) intake. DM, OM, CP and EE TTAD was linearly increased with increasing microalgae level. There was a tendency for a quadratic effect on NDF TTAD, with the highest value of quadratic response estimated at 4.13 g/kg DM microalgae level. Moreover, fat-corrected milk (FCM) and energy-corrected milk (ECM) were quadratically affected, and milk yield tended to be quadratically affected when ALG levels increased. Maximal milk yields were observed at intermediate ALG doses. Milk fat, protein, and lactose contents were diminished, while productive efficiency was improved by the increase of microalgae levels. Microalgae decreased saturated fatty acids proportion, and increased milk polyunsaturated fatty acids proportion. There was low DHA transfer into milk; however, microalgae inclusion decreased C18:0, C18:1 cis-9, C18:2cis-9,12, and C18:3 cis-9,12,15 contents, and increased C18:2 cis-9, trans-11, C18:1 trans-9, and C18:1 trans-11 contents. Gross energy intake was decreased, while there was no effect on digestible, metabolizable, or net energy intake. Microalgae inclusion quadratically affected the microbial protein synthesis, with maximal enhancement estimated at 3.24 g/kg DM dose. Microalgae increased ruminal pH and decreased acetate and total short chain fatty acids concentrations. Therefore, the inclusion of microalgae in diets for midlactating dairy cows decreases feed intake and increases nutrient digestibility, improving productive efficiency and modifying milk fatty acids profile. Estimated intermediate doses (1.22 to 2.90 g/kg DM) of DHA-rich microalgae may be beneficial to milk, FCM, and ECM yields, being recommended for dairy cows. (AU)

• FAPESP's process: 17/12542-3 - Effects of increasing dietary levels of microalgae rich in docosahexanoic acid on lactating dairy cows
• Grantee: Júlia Avansi Marques
• Support Opportunities: Scholarships in Brazil - Master