This book features four peer-reviewed reviews on the development of alternative sources of protein as feed for pigs. The first chapter summarises the nutritional attributes of macroalgae in terms of macro and micronutrients as a source of protein and other compounds in pig nutrition. The chapter also discusses the benefits of macroalgae or macroalgal derived extracts in feed. The second chapter considers the application of corn fermented protein in feed formulations for pigs. The chapter reviews the challenges in producing corn fermented protein and includes a selection of case studies which detail the effects of adding corn fermented protein into the diets of pigs. The third chapter provides an overview of the current state of insect production for pig feed globally and reviews the nutritional, economic and environmental benefits of using insects as feed. The chapter also summarises current research on insects as antimicrobials and life cycle assessments of their rearing. The final chapter discusses the use of black soldier fly (BSF) as an alternative protein source to conventional proteins, such as soya bean meal or fishmeal, in the diets of pigs. The chapter also reviews the benefits and challenges of using BSF in pig diets and highlights what data is still lacking for widespread use of this novel protein.