Westpac has taken its covered bond issuance to date to approximately A$13 billion. The bank sold US$2.0 billion (A$1.90 billion) of covered bonds on the US s144A market on Tuesday night. The issue was well received by investors, with a US$3 billion order book built from 100 investors, despite the issue being marketed at 50 basis points over swap. The covered bonds have a five-year term to maturity and were priced at 61.9 bps over US Treasury bonds to yield just 1.252 per cent per annum.Westpac has sought to develop covered bond yield curves in euros, as well as in US and Australian dollars, to ensure strong investor demand and diversity for future issuance. The bank has the capacity to issue A$35 billion to A$45 billion of covered bonds under the regulatory limit of eight per cent of Australian assets.Last week, NAB sold €1.0 billion (A$1.24 billion) of 10-year covered bonds priced at 37 bps over mid-swaps. The sale takes NAB's covered bond issuance total to approximately A$7 billion.While credit spreads on covered bonds have narrowed considerably since the start of this year, issuance by the major banks may moderate from now on. The banks are expected to implement a spread of maturities and hold some capacity in reserve for use when wholesale market conditions again deteriorate.(Covered bonds are debt securities backed by specific assets on the borrower's balance sheet, such as pools of home loans.)Meanwhile, FirstMac upsized its mortgage-backed bond sale to A$440 million from $300 million yesterday.FirstMac said 11 real money accounts accounted for 78 per cent of the funds. The Australian Office of Financial Management did not invest in the bonds.The class A-1 top tranche was priced at 145 basis points over one-month swap, down from a spread of 160 bps on the previous FirstMac RMBS bonds sold in August.