Introduction
The growing-finishing stage of pig production can significantly impact a farm's efficiency and profitability. In addition, the economic importance of pigs becomes deceptive when it is realized that more than 50% of production cost relies on feed cost. Therefore, several industries and animal nutritionists were encouraged to explore strategies to improve animal growth performance by reducing feed costs. Besides feed cost, the feed structure (particle size) and feed form (mash, pellet, extrusion, and crumble) of the swine diet have become the most critical factor in determining the efficiency of feed utilization (Ball et al., 2015). Feed processing may change feedstuff's physical and chemical properties and improve the feed's nutritional value through various mechanisms (Kim et al., 2015; Muniyappan et al., 2022). Such processed diets have been extensively used in commercial feed production. Compared to the mash form diet, an expanded crumble diet has decreased the feed cost per kg weight gain by 15% (Yang et al., 2001). Usually, young piglets were offered to have mash from feed, while growing pigs were fed with pelleted feed (Vukmirović et al., 2017). Previously many researchers (Al-Rabadi et al., 2009; Rojas and Stein, 2015; Bao et al., 2016) reported that decreasing the particle size of main diet components could improve the performance of pigs. However, Goodband and Hines (1988) said that fine particle size of the diet has negatively affected pigs’ gastrointestinal (GIT) health. However, Wondra et al. (1995) observed decreased average daily feed intake (ADFI) in pigs fed mash diets containing finer particles of corn size from 800 to 400 μm. Stark et al. (1993) reported that pellet diet improves the feed efficiency of nursery and finishing pigs. Likewise, Wondra et al. (1995) stated that pigs fed pellet diets via conventional dry feeders showed an increased gain-to-feed ratio (G : F) compared to a mash-form diet. Early literature has addressed that compared to the mash diet, pellet-form diets showed better growth efficacy in pigs (Skoch et al., 1983). In addition, Yang et al. (2001) study showed that feed cost per kg weight gain was the lowest in the expanded crumble group regardless of feeding methods. Crumble feed has recently become popular in broiler production due to its convenience (Nguyen et al., 2017). Moreover, Reece et al. (1984) have observed that pigs fed with a crumble form of feed with high energy levels and protein profiles have the best feed conversion. Furthermore, Jahan et al. (2006) reported that the highest body weight gain was seen in the crumble feed group compared with the mash and pellet feed groups. However, data concerning the potential benefits of crumble and mash form feed in growing-finishing pigs are still rare. Therefore, this study aimed to determine the effect of a mash and/or crumble diet on growth performance, nutrient digestibility, and backfat thickness of growing-finishing pigs.
Materials and methods
Ethics
Before starting this trial, the experimental protocol (No: DK-2-2121) was revised and approved by the Institutional Animal Care and Use Committee of Dankook University.
Trial design, animals, and diets
A total of 120 ([Landrace × Yorkshire] × Duroc) growing pigs with an average initial body weight of 26.65 ± 3.54 kg were randomly allotted to 2 experimental diets based on initial BW, with 12 replicate pens per treatment and five pigs per pen (2 barrows and three gilts). This trial lasted about 16 weeks, and the pigs were fed the following diets.
1. CON- Mash diet
2. TRT- (Mash [50%] + Crumble [50%] form diets)
The mash-and-crumble diet was formulated to meet or exceed NRC (2012) nutrient requirements (Table 1). All pigs were moved to the growing chamber and housed in an environmentally controlled slatted plastic floor facility. The room temperature was stably sustained at approximately 24℃. Each pen was equipped with a self-feeder and a nipple drinker to allow pigs to access unlimited feed and water throughout the experimental period. Both Mash and crumbled form diets contain corn-soybean meal-based basal diet (grower phase 1: 37.57% of corn and 19.00% soybean meal [SBM]; grower phase 2: 37.98% corn and 24.00% of SBM, and finisher phase: 36.15% of corn and 29.00% of SBM.
Sampling and analysis
Individual pig BW and the feed consumption (per pen) were recorded at the end of weeks 1,6,11,16, and the overall experimental period to calculate the average daily gain (ADG), average feed intake (ADFI), and gain to feed ratio (G : F). Seven days before fecal collection, 0.5% of chromium oxide (Cr2O3) as an indigestible marker was added to pigs’ diet to determine the nutrient digestibility of dry matter, nitrogen, and gross energy. At the end of weeks 1, 6, 11, and 16, fresh fecal samples were collected from at least 2 pigs·pen-1 (1 barrow and 1 gilt) by rectal palpation. The collected samples were taken to the laboratory within 1 hr and placed in a hot air-drying oven 60℃ for 72 hours, then pulverized well and sieved using a 1 mm screen sieve. Following the guidelines of AOAC (2005), dry matter (DM) and nitrogen (N) were analyzed. The chromium absorption in feed and fecal samples were identified using UV-1201 spectrophotometry (Shimadzu, Kyoto, Japan). The protein content (N) in feed and the fecal samples was analyzed using a TecatorTM Kjeltec8400 analyzer (Höganäs, Scania, Sweden). The GE was determined by measuring the heat of combustion in the samples, using a bomb calorimeter (Parr 6400; Parr Instrument Co., Moline, IL, USA). The nutrient digestibility was calculated using ND = [1 - {(Nf × Cd)/ (Nd × Cf)}], where Nf = nutrient concentration in feces, Nd = nutrient concentration in diets, (Cf = chromium concentration in feces, and Cd = chromium concentration in diets. At initial and end of weeks 1, 6, 11, and 16, all pigs’ back-fat thickness (BFT) was measured using a real-time ultrasound instrument (Piglog 105; SFK Technology, Herlev, Denmark). The mean value of BFT was recorded for statistical analysis.
Statistical analysis
Experimental data were analyzed in a complete randomized block design using the GLM procedure of SAS (version 9.2 SAS Institute, Cary, NC, USA) with a pen as an experimental unit. Growth performance and nutrient digestibility analysis were performed using GraphPad Prism statistical software version 5.0. The significant differences among treatments were identified and separated using a t-test. A probability value <0.05 was considered statistically significant, and <0.10 was considered as a trend.
Results and Discussion
The physical form of feed (mash and/or pellet) is an important factor in meat production. Mash is a form of complete feed that is finely ground and mixed so animals cannot separate ingredients; each mouthful provides a well-balanced diet (Sureshkumar and Kim, 2021). Moreover, it gives better unification of growth and less death loss and is more economical. Crumble is a feed prepared at the mill by pelleting the mixed ingredients and then crushing the pellet to a consistency coarser than mash (Sureshkumar and Kim, 2021). This feed form has recently become popular in broiler production due to its convenience. Mash is the cheapest feed compared to crumble, and it requires less processing time. This form of form feed can provide a balanced diet, and they are specially made for starter pigs to rapidly build muscle tissues and other organs. Additionally, it contains high-quality proteins and high levels of amino acids, also it could support pigs’ rapid growth and development. Recently much interest has been shown in extruding/expanding the technology for manufacturing swine feeds, and it has been widely accepted that pelleting of diets could improve ADG and FCR in pigs (Kim et al., 2015). Previously, Ohh (1991) reported that pigs fed a pelleted form diet had improved their growth performance by 3 - 4% compared to those fed a mashed diet. Similarly, Wondra et al. (1995) stated that pelleting could increase ADG while reducing pelleting and particle size could improve FCR. Previous studies have dealt with crumble and mash form feed in pigs’ diets, but the combination of 50 : 50 mash and crumble in a growing-finishing pig diet is still limited. In this study, growing-finishing pigs fed mash and/or crumble feed did not affect body weight, daily gain, and daily feed intake throughout the trial (Fig. 1A - C), and this finding was not constant with Nguyen et al. (2017) who found increased ADFI and ADG in growing-finishing pigs. But, G : F ratio was significantly increased at the end of week 1 (p < 0.025) and tended to increase at the end of week 16 (p <0.078) (Fig. 1D) in the TRT group pigs, which was not agreed with Nguyen et al. (2017) who found increased G : F ratio in pigs fed crumble diet. Previously, several studies (Baird, 1973; Braude and Rowell, 1996; Sampath et al., 2021) addressed that crumble feed could increase the ADG and FCR in pigs. For instance, Pettersson and Bjórklund (1976) have found that piglets fed a crumble diet increased ADG and FCR by 20%, and 7%, respectively. Moreover, Jahan et al. (2006) also observed better BW, ADG, and feed consumption in the broiler (21 - 56 days) fed crumble diet and concluded that the crumbled form of feed is better than mash or pellet form for broiler productivity. However, Sinha et al. (1994) and Reece et al. (1985) reported that broilers fed mash form diet showed significantly lower body weight gain than the crumbled form feed. The probable reason for improvements in the above studies might be due to a better farm environment, while the lack of growth performance in this current research might be due to the difference in animals, feed structure or manufacturing technology. The effect of mash vs crumble form feed on the nutrient digestibility of growing-finishing pigs is shown in Fig. 2A - D. No significant difference was observed in the nutrient digestibility of DM, N, and GE of pigs until end of the trial. However, Owsley et al. (1981) reported that a reduction in particle size of sorghum from 1,262 μm to 802 μm to 471 μm has improved the apparent digestibility of DM, starch, N, and GE measured at the terminal ileum of the total digestive tract of growing pigs. Also, Wan et al. (2021) stated that the apparent digestibility of P% (phosphorus) and Ca% (calcium) was higher in Hy-Line brown hens fed pellet form diet. So far, very less literature has been published on animals fed mash or crumble form diets that enhance the nutrient digestibility parameter, and thus sufficient comparison could. We speculate that no effect on growth parameters is probably due to the lack of nutrient digestibility, while the exact cause is currently unknown, thus it needs further investigation. In this study, no significant difference was observed in back-fat thickness (Table 2), which was constant with the findings of Nguyen et al. (2017). Moreover, Pettersson and Bjórklund (1976) reported no significant differences in carcass quality in pigs fed crumble feed.
In conclusion, our study demonstrates that growing-finishing pigs fed 50% mash + 50% crumble form diet significantly enhanced G : F only at week 1 compared to those fed only mash form feed, and there was no adverse effect observed on the growth performance, nutrient digestibility, and back-fact thickness. Based on the current outcome, we infer that feeding growing-finishing pigs with a combined (mashed and crumble) form diet instead of having only mashed feed would be better to enhance their performance. Moreover, our research team has planned to conduct future investigations to find a better feed structure that could enhance animal production by dropping the feed cost.
