Gross profit
Gross profit of $69.1 million for the three months ended December 31, 2019, increased $0.5 million, or 1%, as compared to the three months ended December 31, 2018. Gross profit increased to 32.3% of net sales for the three months ended December 31, 2019, as compared to 31.5% for the three months ended December 31, 2018.
Animal Health gross profit increased $1.1 million due to volume growth in nutritional specialty and vaccine products, partially offset by lower volume in MFAs and other. Mineral Nutrition gross profit decreased $0.5 million, as the decline in average selling prices and unfavorable product mix more than offset lower raw material costs. Performance Products gross profit decreased $0.1 million due to decreased volume, partially offset by favorable product mix.
Selling, general and administrative expenses
Selling, general and administrative expenses (“SG&A”) of $49.5 million for the three months ended December 31, 2019, increased $6.6 million, or 15%, as compared to the three months ended December 31, 2018. SG&A for the three months ended December 31, 2019, included $0.6 million of stock-based compensation and $0.2 million of other acquisition-related costs. SG&A for the three months ended December 31, 2018, included $0.6 million of stock-based compensation and a $1.5 million benefit from the cancellation of a certain business arrangement. Excluding the effects of these costs, SG&A increased $4.9 million, or 11%.
Animal Health SG&A increased $4.4 million, including increased investments in product development and the effect of the Osprey acquisition. Mineral Nutrition and Performance Products SG&A were comparable to the prior year. Corporate expenses increased $0.5 million due to increased costs of strategic initiatives and public company costs. Stock-based compensation, other acquisition-related costs and the benefit in the prior year from the cancellation of a certain business arrangement resulted in a net $1.7 million increase to SG&A.
Interest expense, net
Interest expense, net of $3.4 million for the three months ended December 31, 2019, increased $0.4 million, or 14%, as compared to the three months ended December 31, 2018. The increase in interest expense was primarily driven by the increase in outstanding borrowings on the Revolver. Interest income from short-term investments was comparable to the prior year.
Foreign currency (gains) losses, net
Foreign currency (gains) losses, net for the three months ended December 31, 2019, amounted to net gains of $0.7 million, as compared to $2.6 million in net losses for the three months ended December 31, 2018. Foreign currency gains and losses primarily arose from intercompany balances.
Provision for income taxes
The provision for income taxes was $5.0 million and $5.3 million for the three months ended December 31, 2019 and 2018, respectively. The effective income tax rate was 29.6% and 26.5% for the three months ended December 31, 2019 and 2018, respectively. The provision for income taxes during the three months ended December 31, 2018, included a $0.7 million benefit from an adjustment to the previously recorded mandatory toll charge on deemed repatriation of undistributed earnings of foreign subsidiaries and a $0.1 million benefit from the exercise of employee stock options. The effective income tax rate, without these benefits, would have been 30.5% for the three months ended December 31, 2018.
Net income
Net income of $11.9 million for the three months ended December 31, 2019, decreased $2.9 million, as compared to net income of $14.8 million for the three months ended December 31, 2018. The decrease was primarily due to a $6.1 million decline in operating income and increased interest expense of $0.4 million, partially offset by favorable foreign currency movements of $3.3 million and lower income