Throughput is important for maximized production. Faster growth rates do not hinder the quality of the pork produced. The relationship between growth rate, feed intake, and feed conversion contributes to the overall growth rate. Pigs gain muscle mass with increased protein in the diet as long as sufficient energy is available. It has been estimated that only about one-third of the protein consumed in the diet will be retained in the body as protein. Minerals, protein, and energy are all needed for growth. Excess protein will be used for energy, and excess energy will be deposited as fat. Genetics have allowed for different options when purchasing breeding stock. Current genetic improvements have resulted in an increase in the lean growth rate of up to 3% per year. As the lean content of the pig increases, feed efficiency improves. In order to support this increased growth, the supply of nutrients must also increase, through either increased feed intake or the use of more nutrient dense diets. Environmentally, pigs need to be in their thermal comfort zone to maximize feed intake without hindering growth rate. Heat emission from basic pig metabolism should be taken into account so that pigs do not get too hot in warm temperatures. The environment should successfully balance the heat loss with the heat production of the pigs. Newly weaned pigs should be in a room with a slightly higher temperature to make up for pigs that are not eating and losing heat. Typically, lower average daily gains and higher feed intake occurs among pigs in a cold environment. As a thumb rule, one can estimate that for every degree C below the thermal comfort zone, growth rate will decline by 10 to 22 g/d. While crowding is known to reduce growth rate and feed intake, increasing the density of the diet to achieve equivalent daily nutrient intake is not successful in returning the performance of crowded pigs to that achieved by non-crowded pigs. A healthy animal is important because the immune system requires energy to operate. Diet composition must be adequate (not too dense yet not too thin). Particle size is important for maximizing feed intake and efficiency, and research is still going on to determine the optimal particle size.