Effects of added fat on growth performance of finishing pigs sorted by initial weight1

Abstract

Two studies were conducted to determine whether dietary fat fed to pigs of different weight categories differentially influences growth performance. Both experiments were conducted in a 2 × 3 factorial arrangement with main effects of dietary fat addition (0 or 6% choice white grease) and sort weight category (HEAVY, LIGHT, or MIXED). In experiment 1, 1,032 pigs (initially 30.7 kg) were individually weighed and sorted into two body weight (BW) groups with one group consisting of pigs greater than median BW and the other group less than median BW. Pens were then formed by randomly selecting pigs: 1) only from heavy group (HEAVY), 2) only from light group (LIGHT), or 3) from both heavy and light groups to create a normal distribution around barn BW mean (simulation of unsorted pigs; MIXED). In experiment 2, 1,176 pigs (initially 35.1 kg) were visually sorted into BW groups and assigned to HEAVY, LIGHT, and MIXED pen weight categories. Overall in experiment 1, adding 6% dietary fat increased average daily gain (ADG) of LIGHT pigs, but not HEAVY pigs (HEAVY vs. LIGHT × fat interaction, P = 0.03), but increased (P < 0.05) ADG regardless of sort category in experiment 2. In both experiments, HEAVY pigs had greater (P < 0.05) overall ADG and average daily feed intake (ADFI), but decreased (P < 0.05) G:F compared with LIGHT pigs. However, when HEAVY and LIGHT treatment groups were combined, growth performance and carcass characteristics were similar to MIXED pigs. Sorting decreased coefficient of variation (CV) of final BW but did not affect CV of ADG. In conclusion, because adding fat to the diets of lightweight pigs improved ADG in both experiments, dietary fat could be used selectively in the barn to increase the weight of the lightest 50% of the pigs. However, the sorting pigs into light and heavy weight groups did not improve growth performance or carcass characteristics.

Increasing Dietary Lysine Impacts Differently Growth Performance of Growing Pigs Sorted by Body Weight

“…Furthermore, a lightweight at the end of the nursery has been related with reduced ADG during the grow-finishing [ 2 ], but some degree of compensatory growth might be expected by those pigs if sufficient nutrients are provided [ 44 ]. Thus, worthwhile strategies to avoid increasing the differences in BW between Lp and Sp pigs might focus on maximizing ADG of low BW pigs [ 28 , 45 ].…”

“…Consequently, most nutritional studies have focused on feeding high density diets, by increasing amino acid or energy concentrations during the nursery phase, as they considered that early interventions might be more effective [ 12 , 24 , 25 , 26 ]. However, other studies have also reported positive effects of dietary interventions during the grow-finishing phase [ 17 , 27 , 28 ], and others reported no advantage [ 29 , 30 ]. Finally, modelling approaches also support the idea that low BW pigs would require a greater lysine concentration in the diets compared to heavier pigs [ 6 , 31 ].…”

A Meta-Analysis to Understand the Relationship between Pig Body Weight and Variation from Birth to Market

“…The addition of dietary fat has been observed to improve the gain of light-weight pigs. Hastad [21] sorted pigs by light, mixed, and heavy BW categories at the beginning of the growing-finishing period (approximately 30 to 120 kg) and fed pigs a diet with or without added fat (i.e., 0 or 6%). While heavy pigs had greater ADG and ADFI when compared with the light pigs, the average combined growth performance of these groups was similar to that of mixed BW pigs.…”

Limiting Dietary Lysine Increases Body Weight Variability by Restricting Growth Potential of the Lightest Growing Pigs

“…Numerous strategies such as prolonging lactation [ 10 ], using complex diets at weaning [ 11 ], increasing amino acid density [ 12 , 13 ], energy density [ 14 ], or sorting by BW [ 15 ] have already been proved as useful in some conditions to increase BW of the lightest pigs. Nevertheless, the impact of some of those strategies, especially the nutritional ones, on BW variability still remains unclear.…”