Effect of rearing cross-fostered piglets in litters of either uniform or mixed birth weights on preweaning growth and mortality

Abstract

Cross-fostering is a practice commonly used in the swine industry to equalize litter sizes, however, there is limited understanding of the optimum cross-fostering methods that will maximize piglet pre-weaning growth and survival. This study evaluated the effects of within-litter variation in birth weight after cross-fostering on piglet pre-weaning mortality (PWM) and weaning weight (WW) using litters of 15 piglets. A hierarchical incomplete block design was used (blocking factors: day of farrowing and sow parity, body condition score, and number of functional teats) with a 3 by 2 factorial arrangement of treatments: 1) Birth Weight Category (BWC): Light (< 1.0 kg), Medium (1.0 to 1.5 kg), or Heavy (1.5 to 2.0 kg); 2) Litter Composition: UNIFORM (all 15 piglets in each litter of the same BWC), or MIXED (5 piglets in each litter from each BWC; i.e., 5 Light, 5 Medium, and 5 Heavy piglets). At 24 h after birth, piglets were weighed and randomly allotted to Litter Composition treatments from within BWC. The experimental unit was five piglets of the same BWC; there were three experimental units within each Litter Composition treatment litter. There were 17 blocks, each of six litters (one UNIFORM litter of each BWC; three MIXED litters) and 51 replicates (three replicates per block of six litters) for a total of 102 cross-fostered litters and 1,530 piglets. Piglets were weaned at 19.7 ± 0.46 d of age; WW and PWM were measured. PROC GLIMMIX and MIXED of SAS were used to analyze PWM and WW, respectively. Models included BWC, Litter Composition, the interaction, and replicate within block. There were BWC by Litter Composition treatment interactions (P ≤ 0.05) for PWM and WW. Pre-weaning mortality was greater (P ≤ 0.05) for Light piglets in MIXED than UNIFORM litters. In contrast, for Heavy piglets PWM was greater (P ≤ 0.05) and WW was lower (P ≤ 0.05) in UNIFORM than MIXED litters. Medium piglets had similar (P > 0.05) PWM and WW in UNIFORM and MIXED litters. The results of this study, which involved large litter sizes typical of current commercial production, suggested that for piglet survival to weaning, using cross-fostering to form litters of piglets of similar birth weight was beneficial for Light piglets, detrimental for Heavy piglets, and neutral for Medium piglets.

Effect of rearing cross-fostered piglets in litters of differing size relative to sow functional teat number on preweaning growth and mortality

“…In the present study, there were no differences between BWC for the causes or timing of PWM, or the age of piglets at death. These results are at variance with the results of two cross-fostering studies that were carried out in the same facilities and using the same BWC as the current experiment ( Vande Pol et al, 2021a , 2021b ). However, the effects of birth weight on PWM in these two studies were inconsistent.…”

“…A summary of sow parameters for each of the Litter Size treatments is presented in Table 1 . The parity, body condition score, and teat number of sows were similar ( P > 0.05) across treatments, and were comparable to those reported in studies carried out with commercial populations ( Maes et al, 2004 ; Vande Pol et al, 2021a , 2021b ). Recent studies have reported similar teat numbers to those found in the current study.…”

“…However, the effects of birth weight on PWM in these two studies were inconsistent. Vande Pol et al (2021a) found that age at death generally increased with birth weight and that Medium piglets had greater mortality due to crushing than the other two BWC. In contrast, Vande Pol et al (2021b) found that age at death was greater for Medium than Light and Heavy birth weight piglets, and that mortality due to crushing was similar for the three BWC.…”

“…Recent studies have reported similar teat numbers to those found in the current study. For example, Kim et al (2005) showed that the total number of teats for Landrace and Yorkshire gilts averaged 14.9 and 13.7, respectively, and Vande Pol et al (2021a , 2021b ) reported that total teat numbers of commercial sows were between 14.4 and 14.7. Using the same teat functionality scoring system as in the current study, Vande Pol et al (2021a) reported that 78.5%, 21.5%, and 2.8% of teats had functionality scores of 1, 2, and 3, respectively, and Vande Pol et al (2021b) reported values of 84.3%, 13.8%, and 2.0%, respectively.…”

“…Currently, the number of piglets born to sows averages between 14 and 17 per litter ( SEGES, 2017 ; PigChamp, 2019; Agriculture and Horticulture Development Board, 2020 ). In contrast, commercial sows generally have, on average, between 13 and 15 functional teats ( Kim et al, 2005 ; Rothe, 2011 ; Vande Pol et al, 2021a , 2021b ). As a result, it is increasingly common for the total number of piglets born alive within a litter to exceed the number of functional teats on the sow.…”