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Abstract Maximizing growth performance and feed intake for nursery pig diets is an ongoing challenge in the US swine industry. Using sensory feed additives is one strategy to optimize feed intake and growth rates of pigs. Weanling pigs (n = 416; average age = 19.8 d) were used to test the effects of sensory feed additive (SA; Luctamax Piglet, Lucta, Mahwah, NJ) addition to control (CON) and low crude protein (LCP; decreased 4% CP) nursery diets in a 2 x 2 factorial design (CON, CON+SA, LCP, LCP+SA). Decreased dietary CP was achieved by removing or decreasing fish meal and soy concentrate in phases 1 and 2 and reducing soybean meal in phase 3 and adding synthetic amino acids to maintain amino acid ratios (NRC 2012). Nursery treatments were fed in three phases; phase 1 (PH1, d 0-7, 0.10% SA), phase 2 (PH2, d 7-21, 0.10% SA), and phase 3 (PH3, d 21-36, 0.05% SA). Pigs were blocked by initial body weight (BW), sex, ancestry, and housed at 6 or 7 pigs/pen with 15 pens/treatment. Weekly pig BW and feed intake were used to calculate pen average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F). Data were analyzed using GLM procedure of SAS 9.4. During PH1 pigs receiving the CON diets tended (P = 0.065) to have a greater G:F compared with pigs receiving LCP diets. For the remainder of this study there were consistent interactions between dietary CP and SA. When SA was added to the LCP diet ADFI increased but when SA was added to CON diet ADFI decreased and these changes in feed intake often led to similar dietary interactions in ADG. During PH2, pigs fed CON or LCP+SA diets had greater ADFI (P = 0.032) and tended to have a greater ADG (P = 0.094) but reduced G:F (P = 0.100) compared with pigs fed CON+SA or LCP diets. In PH3, pigs fed CON or LCP+SA diets had a greater ADG (P = 0.027) and ADFI (P = 0.011) compared with CON+SA or LCP diets. Pigs fed LCP diets had greater ADFI (P = 0.001) but reduced G:F (P = 0.0001) than pigs fed CON diets. Overall, pigs fed CON or LCP+SA diets had greater ADFI (P = 0.016) and tended to have a greater ADG (P = 0.059) but reduced G:F (P = 0.067) compared with pigs fed CON+SA or LCP diets. Pigs fed CON diets had a greater G:F (P 0.001) compared with pigs fed LCP diets, while LCP pigs tended to have a greater ADFI (P = 0.054) compared with CON pigs. Inclusion of SA to LCP diet mitigated the adverse impact of replacing whole dietary proteins with high inclusion of synthetic amino acids. Careful consideration is needed when using sensory feed additives so as not to impede growth performance in diets containing traditionally greater levels of crude protein.
Pound et al. (Wed,) studied this question.