Freddie Mac: Investment Portfolio Grew  NEW YORK (Reuters) - Freddie Mac &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=FRE.N target=/stocks/quickinfo/fullquote"&gt;FRE.N&lt;/A&gt; said on Thursday  its mortgage investments, or retained portfolio, grew at an  annualized rate of 20.8 percent in July, compared with a 19.4  percent increase in June.