Advances in low-protein diets for swine

Abstract

Recent years have witnessed the great advantages of reducing dietary crude protein (CP) with free amino acids (AA) supplementation for sustainable swine industry, including saving protein ingredients, reducing nitrogen excretion, feed costs and the risk of gut disorders without impairing growth performance compared to traditional diets. However, a tendency toward increased fatness is a matter of concern when pigs are fed low-protein (LP) diets. In response, the use of the net energy system and balanced AA for formulation of LP diets has been proposed as a solution. Moreover, the extent to which dietary CP can be reduced is complicated. Meanwhile, the requirements for the first five limiting AA (lysine, threonine, sulfur-containing AA, tryptophan, and valine) that growing-finishing pigs fed LP diets were higher than pigs fed traditional diets, because the need for nitrogen for endogenous synthesis of non-essential AA to support protein synthesis may be increased when dietary CP is lowered. Overall, to address these concerns and give a better understanding of this nutritional strategy, this paper reviews recent advances in the study of LP diets for swine and provides some insights into future research directions.

Effects of Different Protein Levels on the Nitrogen Balance, Performance and Slaughtering Traits of Cinta Senese Growing Pigs

“…It can be assumed that they have an adequate enzymatic profile to degrade dietary formulations up to CP18, but once AAs are adsorbed and the genetic upper limit for protein deposition is reached, AAs are used in catabolic processes. The poor efficiency of protein catabolism is widely known [1,11,28], and the negative effects of this pathway affect overall animal performance.…”

“…The opportunity for further lowering the dietary CP for Cinta Senese growing pigs cannot be excluded, but the linear increase in fat gain observed from CP12 to CP18 animals might indicate that we reached the lower limit of protein to energy supply below which, lacking the AAs required for protein deposition, the energy in excess is used for fat deposition. Indeed, diets excessively poor in protein enhance the genetic predisposition to fat deposition in local breeds, leading to carcasses that are extremely fat [11], with a worse slaughtering yield and a lower consumer acceptability of meat when compared with those of leaner pigs.…”

“…Applying feeding models based upon the performance of lean genotypes to Cinta Senese might lead to a protein surplus in feed, which cannot be used for protein synthesis, and is excreted through the urine, leading to an energetic cost for animals and an economic loss for farmers. In addition to cost effectiveness, defining the optimal balance between protein and energy intakes for Cinta Senese pigs would also have positive consequences on the environment, lowering the nitrogenous excretions of pig farms [10,11]. This is particularly important for this breed, and for local breeds in general, that are traditionally reared outdoors in systems where animal excretions are more exposed to nitrogen leaching [12][13][14].…”

Overcoming nature’s paradox in skeletal muscle to optimise animal production

“…Therefore, plant-based protein diets require higher crude protein intake or supplementation with an animal protein source (derived from meat/fish and diary processing) or specific amino acids (Beski et al 2015). There are considerable advantages of reducing dietary crude protein with supplementation of free amino acids for sustainable livestock production, including saving on protein ingredients, reducing nitrogen excretion, feed costs and the risk of gut disorders, without impairing growth performance compared with traditional diets (Wang et al 2018). Some amino acids with beneficial effects on skeletal muscle growth will now be discussed in detail.…”

Effects of different protein sources completely replacing fish meal in low‐protein diet on growth performance, intestinal digestive physiology, and nitrogen digestion and metabolism in nursery pigs

“…It, therefore, is urgently required nutritionists to develop nutrition strategies to save protein resources and reduce nitrogen excretion. Low‐protein, AA‐supplemented diets based on an ideal protein pattern have been successfully applied in piglet production without affecting performance via maintaining gut health and reducing diarrhea (Nyachoti, Omogbenigun, Rademacher, & Blank, ; Wang et al, ; Yue & Qiao, ).…”