Nutritional composition of basal rations
The nutritional composition of the basal rations is presented in Table 2. The estimated CP (%) and calculated energy value (Kcal ME/kg) of the rations were as per standard and CF (%) was below 6% (on DM basis) in all the rations. The calculated lysine (%) and methionine (%) were also within the recommended levels of
NRC (2012) for grower-finisher pigs.
The average DM% of Liquid feed, FLF was estimated at weekly interval as back-slopping was done for 7 days. The FLF DM (%) of T
3 varied from 24.02-28.93% (average-26.57%) and of T
4 varied from 24.27-28.08% (average-26.71%). The DM% of liquid feed varied from 26.48%-29.26% (average-27.92%).
Feed consumption
Feed intake has direct relationship with the efficiency of pork production. It is influenced by many factors and the way feed is delivered is one of the important factors which significantly influences feed consumption in pigs
(Choct et al., 2004; NRC 1998). There was no significant effect of FLF on feed consumption during growing phase; however, an increasing trend was noticed for T
3 and T
4 (Fig 1). In finishing phase, feed consumption was significantly high in T
3 and T
4 (Fig 2). Total average feed consumption, however, was non-significant, but showed increasing trend (T
1<T
2<T
3 <T
4) (Table 3).
Improvement of feed consumption in T
3 and T
4 might be for fermentation of feed as it causes physical and chemical changes of feed in favourable way (
Brooks 2003;
Choi et al., 2011). It might also be for enhanced acceptability due to liquid nature of feed without dustiness. Fermentation of feed is also known to control pathogens in feed and pig’s gut excluding enteropathogens like
E. coli and
Salmonella and improves foregut barrier function against pathogens
(Engberg et al., 2006). Inhibition or prevention of pathogens in the gut and enhancement of intestinal mucosal immunity
(Pasca et al., 2009; Rauch and Lynch 2010) might also be related with more feed consumption in T
3 and T
4.
Macasait et al., (2021) reported significantly higher cumulative feed intake in pigs fed wet and fermented feed with different levels of wood vinegar and
Xin et al., (2021) also observed positive tendency in feed intakes in pigs fed fermented liquid feed.
Growth performance
Sustainable growth indicates optimal feed efficiency and is also one of the indications of sound gut health and immunity. As feeding cost accounts nearly 2/3
rd of total production, supply of quality feed and feeding method is important for efficient utilization of feed in pigs. The body weight gain was significantly (P<0.05) high in T
3 in the growing phase. In the finishing phase, significantly (P<0.01) higher gain was recorded in T
4. The total average body weight gain was significantly high in T
3 and T
4 than T
1 and T
2 (Table 3). In growing phase, improvement in body weight gain was 22.34% and 13.64%, respectively in T
3 and T
4 than T
1 and was 15.58% and 6.85%, respectively than T
2. Similar records for T
3 and T
4 in finishing phase were 14.59% and 20.49% than T1; and 7.66% and 13.20% than T
2, respectively. As a whole, improvement of 17.76% and 17.71%; and 10.86% and 9.76% were recorded for T
3 and T
4, respectively than T
1 and T
2.
Xin et al., (2021) also reported significantly increased final body weight and average daily gain in pigs fed fermented liquid feed. Similar findings were also reported by
Jiang et al., (2019), Xu et al., (2020) and
Hao et al., (2020). Significant improvement in growth for FLF might be for improvement of feed consumption and nutrient digestibility for improved villus height enhancing nutrient digestibility and favourable effect on intestinal microbiota supporting gut health (
Canibe and Jensen 2012).
Nutrient digestibility
No significant (P>0.05) difference observed for apparent nutrient digestibility in growing phase. However, positive effect was prominent as shown by higher digestibility of nutrients in T
3 and T
4 than T
1 and T
2. In the finishing phase, CP digestibility was significant (P<0.05) high in T
3. However, nutrient digestibility in other groups were comparable without any significant differences (Fig 3 and 4). Insignificant but improvement of nutrient digestibility for feeding of fermented liquid feed in pigs were also reported by
Lin et al., (2017) and
Xin et al., (2021). Improvement of nutrient digestibility in T
3 and T
4 might be for enhancement of substrate availability for offering feed in liquid form, entero-pathogen removing effect of FLF and improvement in gut structures. Low pH of FLF might help in digestion of protein in starter pigs and maintain condition of cell wall inside small intestine which might lead to better absorption of nutrients
(Sayan et al., 2018). Improved nutrient digestibility might also be for production of antimicrobial substances, such as organic acids and bacteriocins, which functions as natural antimicrobial, decreases the intestinal pH, inhibits the growth of pathogenic bacteria, such as
Salmonella spp. or
E. coli, also reported by
Cernauskiene et al., (2011) and
Giang et al., (2010).
Effects of FLF on carcass traits and sensory qualities of pork
The carcass length was significantly more in T
3 and T
4 than T
1 and T
2. Dressing percentage was also significantly better in T
3 and T
4. However, no significant difference was observed for other wholesale cuts. There was no significant (P>0.05) difference in average pre-slaughter weights of the pigs. However, due to variability of body weight and hence the size, body length of the animals was not the same and this might contribute to the significantly (P<0.05) different carcass length. Significant (P<0.05) higher dressing percentage in T
3 and T
4 might be for differences in live and visceral organ weights as negative correlation exists between live weight and weights of the visceral organs. Carcass weight and back-fat thickness have been reported to affect carcass grading and properties
(Park et al., 2009). A strong positive correlation exists between carcass weight and back-fat thickness and meat quality grade (
Kim and Kim 2017). Comparatively higher body weights of the pigs might contribute to higher backfat thickness in pigs of T
3 and T
4. The leaf fat of pigs is positively correlated with body weight. Comparatively higher leaf fat weight in T
3 and T
4 might be related to higher final body weight than T
1 and T
2 (Table 4).
The quality indicators of raw meat that can predict the yield of the processed meat are especially the pH and water holding capacity. pH was found to be below 6.0 in all the groups indicating that feeding of FLF did not have any adverse effect on meat quality, particularly tenderness and juiciness. There was no significant (P>0.05) difference in tyrosine value among the pigs which is used to monitor the meat quality to indicate proteolysis and to measure the amino acids (tyrosine and tryptophan) present in non-polar extract of meat. Water holding capacity was comparatively higher in T
3 and T
4 than T
1 and T
2 and might be related to higher pH estimated in them. The thiobarbituric acid value was lesser than 0.02 in all the groups without any significant (P>0.05) difference. Higher extract release volume in T
2, T
3 and T
4 might be associated with significantly higher water holding capacity as both are positively correlated (Table 5).
Hao et al., (2020) also reported improved carcass performance and meat quality parameters in pigs fed fermented mixed feed.
No significant difference was observed between the groups for proximate principles of pork, which might be the indication that feeding of FLF might not have any effect on the proximate composition.
No significant difference (P>0.05) was recorded for different sensory attributes of pork between the treatment groups. Sensory evaluation of pork is important to judge meat quality because meat should be acceptable to the both consumers and the meat processors. Comparatively higher scores given by the panellists might be the indication of some favourable effect of liquid and FLF on pork flavour. Comparatively higher perception of juiciness by panellists for T
3 and T
4 might be for higher intramuscular fat as indicated by higher ether extract content of meat than T
1 and T
2.
Effect on economic parameters
Amongst many factors, feed form is one of the external factors which can be manipulated for improvement of feed efficiency in pigs. The feed conversion ratio (FCR) was significantly better in T
3 and T
4 than T
1 and T
2, both in the growing and finishing phase (Table 6). This improvement might be for better nutrient digestibility and growth rate for favourable effect of FLF. The feeding cost/kg gain in body weight were calculated as ₹ 128.36, ₹ 120.43, ₹ 112.87 and ₹ 115.51 in T
1, T
2, T
3 and T
4, respectively based on the prices of feed ingredients at Aizawl, Mizoram, India during 2017-2018.