Save a datagrid column in the database

Question

I need to get the value of the discount column from mine datagrid and save in my database, will I get, it is calculated when I record consumption according to quantity, follows below the code:

foreach (var leitura in leituras)
{
    totalConsumo += leitura.Consumo;
    totalDesconto += leitura.Desconto;
}

dgv[0, dgv.Rows.Count - 1].Value = "Total";
dgv[1, dgv.Rows.Count - 1].Value = totalConsumo.ToString();
dgv[2, dgv.Rows.Count - 1].Value = totalDesconto.ToString();
lblResultado.Text = "Total consumo com desconto: " + (totalConsumo - totalDesconto).ToString();

Persistence code

    CONEXAO.Open(); 
    MySqlCommand INSERT = new MySqlCommand("INSERT INTO consumo (casa, consumo)" + "VALUES ('" + casa + "','" + consumo + "')", CONEXAO);
    INSERT.Parameters.AddWithValue(casa, txtCasa.Text); 
    INSERT.Parameters.AddWithValue(consumo, txtConsumo.Text); 
    INSERT.ExecuteNonQuery(); 
    MessageBox.Show("O registro foi inserido com sucesso !");