Macauba (Acrocomia aculeata) pulp as an alternative feedstuff in growing-finishing pig nutrition

Abstract

Traditional feed grains have historically formed the basis of pig diets. However, their limitations in terms of resource availability, cost volatility, and environmental impact have fueled a growing interest in alternative feed sources. In this pursuit, macauba pulp (Acrocomia aculeata), a coproduct of biodiesel production, emerges as a promising candidate that warrants thorough investigation for its potential to revolutionize pig nutrition and production. Thus, our study sought to optimize pig nutrition by strategically incorporating macauba pulp into their diets. Two studies were designed to guide our investigation. In study I, we aimed to evaluate the balance and digestibility of dry matter (DM), crude protein (CP), nitrogen (N), and energy of macauba pulp in finishing pig diets. By understanding the nutritional interaction between this feedstuff and pig digestive processes, we intend to provide valuable insights so that macauba pulp can be used as an alternative ingredient in pig diets. In study II, we investigated the effects of partially replacing corn with macauba pulp on the growth performance, carcass characteristics and pork quality of growing-finishing pigs; and whether differences in residual feed intake breeding values could influence pigs’ growth responses to macauba pulp dietary inclusion. We intended to uncover whether certain genetic backgrounds may synergize more effectively with macauba pulp, potentially opening new avenues for precision feeding strategies. In study I, twenty-four finishing barrows (66.3 ± 0.7 kg BW) were individually housed in suspended metabolism crates allotted in two climatic-controlled rooms. The digestibility assay was conducted in a randomized complete block design, comprising two blocks (climatic-controlled rooms), four dietary treatments, and six replicates per treatment. The reference diet (RD) was a complete corn-soybean meal diet formulated to meet or exceed the nutritional requirements of finishing barrows with high genetic potential with regular- medium performance, while the test diets varied in proportions of RD and macauba pulp: 950 g/kg of RD and 50 g/kg (MAC50), 900 g/kg of RD and 100 g/kg (MAC100), and 850 g/kg of RD and 150 g/kg (MAC150). The 12-day experimental period consisted of a 7-day adaptation period followed by a 5-day quantitative collection period. Urine and fecal materials were collected using the marker-to-marker approach. In study II, a total of 282 (34.8 ± 4.40 kg) pigs (barrows and gilts), progeny of sires with high (HRFI) or low (LRFI) breeding value for residual feed intake, were pair-housed in a 2 × 2 × 2 factorial design based on sex, breeding value, and initial BW. Diets with 50 g/kg of macauba pulp inclusion (macauba) or without (control) were randomly assigned to experimental pens. Thus, eight treatment groups were formed: HRFI barrows fed the control diet; HRFI barrows fed the macauba diet; LRFI barrows fed the control diet; LRFI barrows fed the macauba diet; HRFI female pigs fed the control diet; HRFI female pigs fed the macauba diet; LRFI female pigs fed the control diet; and LRFI female pigs fed the macauba diet. The trial, lasting 90 days, comprised four phases: growing phase 1 (G1), growing phase 2 (G2), finishing phase 1 (F1), and finishing phase 2 (F2). In study I, pigs fed RD had lower (p < 0.01) fecal excretion of DM and CP compared to pigs fed MAC100 and MAC150. Fecal energy excretion was higher (p < 0.01) in macauba fed pigs than in pigs fed RD. Digestible and metabolizable energies in RD were higher (p < 0.01) than in MAC100 and MAC150. The apparent total tract digestibility (ATTD) of dry matter and gross energy was lower (p < 0.01) in MAC50, MAC100, and MAC150 than in RD. The ATTD of protein in pigs fed RD was higher (p < 0.01) than in pigs fed MAC100 and MAC150, although not differing from pigs fed MAC50. Pigs fed RD had lower (p < 0.01) fecal N excretion than pigs fed MAC100 and MAC150 but did not differ from MAC50. The ATTD of N in RD was higher (p < 0.01) than in MAC100 and MAC150 and did not differ from MAC50. The present study indicates that up to 50g/kg macauba pulp can be used in the diets of finishing pigs without affecting the energy partitioning, ATTD of protein, and N utilization. In addition, including macauba pulp in corn-soybean meal based diets lowers the urinary-to-fecal N excretion ratio. In study II, there was no interaction between sex, breeding value, and diet for performance, carcass, and pork traits. Barrows outperformed female pigs in feed intake (ADFI), daily gain (ADG), feed conversion rate (FCR), and final body weight. The breeding value had no effect on performance measurements. The inclusion of macauba pulp in pig diets did not affect any growth parameter during G1, G2 and F1 phases. However, reduced ADFI and improved FCR were observed in F2. Female pigs had lower backfat thickness (BF) and higher loin eye area (LEA) than barrows. HRFI pigs had higher hot carcass weight, LEA, and lower BF than LRFI pigs. There was no effect of macauba pulp inclusion on carcass traits. Pork from barrows presented lower Warner–Bratzler shear force and higher fat content than pork from females. There was no effect of breeding value on pork traits. Pork from pigs fed the macauba diet showed lower moisture content and water-holding capacity but tenderness and color was not affected by this substitution. In conclusion, the inclusion of 50 g/kg of macauba pulp in the pigs’ diets did not affect any growth parameter during G1, G2 and F1 phases. However, reduced average daily feed intake and improved feed conversion rate were observed in F2. Regardless of sex and breeding value for RFI, pigs responded similarly to macauba pulp inclusion in their diets. Keywords: Swine; Biofuels coproducts; Feed efficiency; Palm; Alternative feedstuff.