S000006639 [Member] Investment Strategy - Loomis Sayles Securitized Asset Fund

Sep. 30, 2025

Prospectus [Line Items]

Strategy [Heading]

INVESTMENTS, RISKS AND PERFORMANCE Principal Investment Strategies

Strategy Narrative [Text Block]

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in a diversified portfolio of securitized assets, such as mortgage-backed and other asset-backed securities. The Fund may invest in asset-backed securities of any type, including residential and commercial asset-backed securities, asset-backed securities related to automobiles, credit cards, home equity loans, manufactured housing, utilities, and other miscellaneous asset-backed securities. The Fund may only buy securities that are rated investment-grade at the time of purchase by at least one of the three major rating agencies (Moody’s Investors Service, Inc., Fitch Investor Services, Inc. or S&P Global Ratings) or, if unrated, are determined by Loomis Sayles to be of comparable quality. It is expected that a majority of the Fund’s securities will have credit quality equal to the credit rating of the U.S. Government’s

long-term debt by at least one of the rating agencies at the time of purchase. The Fund may continue to hold securities that are downgraded in credit rating subsequent to their purchase if Loomis Sayles believes it would be advantageous to do so.

The Fund may, without limitation, seek to obtain market exposure to the securities in which it primarily invests by entering into a series of purchase and sale contracts (including on a “to be announced” basis) or by using investment techniques such as buybacks and dollar rolls.

Loomis Sayles uses a bottom-up, fundamental research process to select individual securities for the Fund. The decision to buy or sell a particular security is largely driven by Loomis Sayles’ view of the fundamentals of the issue compared to the prevailing market valuation, which may be higher (suggesting a potential sell decision) or lower (suggesting a potential buy decision). Loomis Sayles also may seek to construct a portfolio with risk characteristics similar, but not identical to, certain of the securities in the Bloomberg U.S. Securitized Bond Index (the “Index”). Examples of typical risk characteristics that Loomis Sayles might consider include average life, credit quality, effective duration, yield curve exposure and sector exposure. The portfolio will not necessarily exhibit similarities with the Index for some or all risk characteristics. It is currently anticipated that the Fund’s effective duration will be within +/- 1 year of the effective duration of the Index.

In deciding which securities to buy and sell, Loomis Sayles will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, Loomis Sayles’ expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with Loomis Sayles’ expectations concerning the potential return of those investments.

The Fund’s investments may also include, among other things, the following: fixed and floating-rate instruments, mortgage pass-through securities issued or guaranteed by agencies or instrumentalities of the U.S. government, collateralized mortgage obligations, commercial mortgage-backed securities, mortgage-related asset-backed securities, other collateralized asset-backed securities, securities issued pursuant to Rule 144A under the Securities Act of 1933 (“Rule 144A Securities”), other privately placed investments such as private credit instruments, U.S. government securities, corporate debt securities, zero-coupon securities, step coupon securities, commercial paper, structured notes, other mortgage-related securities (including adjustable rate mortgage securities, stripped mortgage-backed securities and mortgage dollar rolls), when-issued securities and repurchase agreements. The Fund may also invest in options, futures and swaps (including credit default swaps, in which one party agrees to make periodic payments to a counterparty in exchange for the right to receive a payment in the event of a default of the underlying reference security).

The Fund may also engage in active and frequent trading of securities. Frequent trading may produce a high level of taxable gains, including short-term capital gains taxable as ordinary income, as well as increased trading costs, which may lower the Fund’s return.