# Assessment of the relationship between lactation feeding patterns, litter performance, and sow characteristics on sow efficiency metrics

## TL;DR

The study finds that early lactation feed intake, stillbirth rate, and number of piglets nursed affect sow reproductive outcomes, offering targets to improve productivity.

## Contribution

Identifies specific early lactation factors influencing sow efficiency metrics, providing actionable insights for swine producers.

## Key findings

- Low early lactation feed intake increases weaning-to-estrus interval and delays rebreeding.
- High stillbirth rates and large litter sizes reduce subsequent farrowing success and litter size.
- Body condition changes and piglet birth weight correlate with reproductive outcomes.

## Abstract

In U.S. breeding herds, data collection is widespread but often fragmented across systems. While producers rely on performance summaries, integration of these data to improve productivity remains underutilized. This study evaluated sow-level factors associated with sow efficiency, defined as weaning-to-estrus interval (WEI), percentage of sows bred within 7 days post-weaning, subsequent farrowing success, and total piglets born. Data were sourced from six lactation trials on a commercial sow farm, with sows of the same genetics (PIC line 1050), housing, and free of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Porcine Epidemic Diarrhea Virus (PEDV). The dataset contained 4,300 observations, including reproductive performance, daily feed intake, sow and litter weights. Generalized linear regression models were constructed with 23 variables; trial was included as a random effect, and model selection performed through manual stepwise forward selection based on biological plausibility. Pairwise comparisons were made using t-tests with the Tukey-Kramer adjustment at P <0.05 significance. Parity (P < 0.001), nursed piglets (P = 0.01), and average daily feed intake (ADFI0 in the first three days (P = 0.01) were associated with WEI. Sows nursing ≥15 piglets had a 1.3-day increase in WEI (P = 0.01), while ADFI <4.5kgs (10lbs) for the first three days was associated with 1-day increase in WEI (P <0.001). Factors associated with breeding within 7 days included parity (P = 0.05), first-week ADFI (P = 0.01), and nursed piglets (P = 0.009). Subsequent farrowing success was associated with prior litter size (P = 0.02), stillbirth rate (P = 0.01), first-week ADFI (P = 0.01), nursed piglets (P = 0.02), and body weight change (P = 0.01). Sows with ≥1 stillborn piglet had a 7% lower farrowing probability (P = 0.01), and those nursing >15 piglets had a 12% reduction (P = 0.02) in farrowing success. Factors associated with subsequent total born included parity (P < 0.001), previous litter size (P = 0.01), piglet birth weight (P = 0.01), caliper change (P = 0.04), stillbirth rate (P 0.01), and the interaction between body weight change and litter wean weight (P = 0.002). Sows with average litter birth weights <1 kg (2.4lbs) produced two more piglets than those >1.5kgs (3.5lbs). Stillbirth rates >5% reduced subsequent litter size by 2 piglets (P <0.05), and caliper gains >1 unit added 2 piglets compared to sows losing a unit of caliper (P  0.05). Overall, early lactation feed intake, litter size, and body condition were associated with reproductive outcomes. Low early lactation—first week- feed intake and high nursing burden extended WEI, delayed rebreeding, and reduced farrowing success, providing evidence-based targets to improve sow productivity.

Early lactation feed intake, stillbirth rate, and number of piglets suckling are associated with key reproductive outcomes in sows. These factors are linked to longer wean-to-estrus intervals, reduced farrowing success, and smaller subsequent litter, providing evidence-based targets to improve sow management and herd productivity.