Swine barns are often filled with multiple groups of pigs over a period of numerous days. However, there is little research available to know if the second or subsequent group entering the facility have different performance than the first fill group, according to Haley K. Schwecke, Kansas State University, in a poster presented at the 2022 Leman Swine Conference.

A binomial regression analysis was conducted to determine the influence of barn fill rate on nursery pig’s exit weights by Schwecke and colleagues at Kansas State.

The datasets used were an accumulation of 20 trials conducted from 2017 to 2019 with a total of 37,539 nursery pigs. An excel-based spreadsheet was used to compile, visualize, and descriptively compare growth performance data across trials.

Fill time ranged from one to eight days with barns filled with up to four groups of pigs across four commercial research facilities located in central Minnesota.

The following data were collected per trial at the pen-level: Fill rate including fill group (range of one to four groups and days between entry), starting body weight (BW), final BW, average daily gain (ADG), average daily feed intake (ADFI), mortality rate, feed to gain ratio (F/G), starting head count, and final head count.

An equation, “AdjFinalWt,” was generated to adjust final BW of pens to a common number of days on feed using growth rate during the last period of each experiment. Two linear mixed models were fit using a forward selection process to determine significant factors influencing adjusted final weight (AdjFinalWt; model one) and actual end BW (exit weight; model two).

Data were analyzed with the GLIMMIX procedure of SAS (v. 9.4) and results considered significant at P < 0.05.

Results

In model one, the following factors were significant (P < 0.001): Starting BW, source, fill group, and days on feed.

In model two, the following factors were significant (P < 0.001): Days on feed, starting BW, source, days after barn began filling, and fill group.

Both models revealed a difference in pig exit BW due to their fill group. Final BW of pigs in the first two fill groups were 3.5 and 3.3 pounds heavier, respectively, than pigs in the fourth fill group, with pigs in the third fill group being intermediate — 2.0 pounds heavier than the fourth fill group.

Similarly, when days on feed was included in model 2, fill group had a similar magnitude of impact with pigs in fill group 4 being 3.8, 3.5 and 1.7 pounds lighter than pigs in the first, second, and third fill groups, respectively.

Both models support heavier exit weights of nursery pigs when two or fewer groups enter a facility and lower final BW for the third and fourth groups placed in the facility, regardless of days between entry.

These results can help producers determine the economic impact of filling nursery barns with fewer weaning groups, according to the researchers.