The accuracy and precision of pig subsampling methods can determine the swine
producer’s ability to sell pigs at optimal market BW and reduce economic discounts.
The first objective of this experiment was to determine the time required to weigh pigs
for different sampling methods used to estimate the mean and SD of a population.
The second objective was to define the optimal sampling method considering the time
required to weigh pigs as well as the precision and accuracy of each sampling method.
A total of 68 pens of pigs (359 × 1050, PIC, Hendersonville, TN; 169.8 lb BW) in 2
commercial finishing facilities with 20 to 35 pigs per pen were used. Pens of pigs were
blocked by location within barn and randomly allotted to 1 of 4 treatments with 17
pens per treatment. The 4 treatments included (1) selecting and weighing the heaviest
and lightest pig per pen; and (2), (3), and (4) weighing the first 5, 10, and 15 pigs out
of the pen, respectively. The time required for 2 people to complete each treatment was
recorded. To determine the total barn time required to conduct a specific sample, the
time required to weigh the specific number of pigs per pen was multiplied by n pens.
The accuracy and precision for estimating the mean BW and SD for each sampling
method was determined by using datasets A and C reported in Paulk (20144). The
precision was determined by calculating a 95% confidence interval (CI) for the sample
means and SD. The time taken to select and weigh the heaviest and lightest pigs in a pen
(Treatment 1) did not differ from weighing 5 pigs per pen (Treatment 2). Increasing
the number of pigs weighed per pen (Treatments 3 and 4) increased (P < 0.05) the
amount of time to weigh a single pen. Based on these results, the number of pens for
each treatment that can be weighed without influencing weighing time was determined
to be 15 pens (30 pigs), 15 pens (75 pigs), 9 pens (90 pigs), and 6 pens (90 pigs) from
Treatments 1, 2, 3, and 4, respectively. For dataset A, these 4 sampling methods had a
similar CI range for estimating the mean BW and SD. For dataset C, Treatments 1
(30 pigs) and 2 (75 pigs) had a reduced CI range for estimating the mean BW compared
with Treatments 3 (90 pigs) and 4 (90 pigs); however, Treatments 2 (75 pigs) and 3
(90 pigs) had a reduced CI range for estimating the SD compared with Treatments 1
(30 pigs) and 4 (90 pigs). Therefore, we conclude that swine producers should weigh 5
pigs from 15 pens to estimate the mean BW and SD within a barn.
