Early vs. Late Maturing Sire Lines

An examination of the growth curve, post-weaning stress and creep-feeding factors.

by Jamil Faccin

Imagine if in the same barn you had two groups with opposing genetic selection goals.

The first group is modern genotype pigs with growth peaking late in finishing, and the second group of pigs are selected for earlier maturation.

How similar would their growth curve be? Which one would be more feed efficient? How differently would they react to weaning stress? How would they respond to different management strategies, like creep-feeding? I will try to answer these questions in this article for Benchmark magazine.

A notorious fact of current swine production is, as genetic companies have selected for improved finishing performance, getting pigs started on feed right after weaning has become more challenging.

This highlights how a pig’s genetics can influence the stress in the early nursery stage and, subsequently, growth performance. Another typical discussion between swine professionals is related to practices that are often adopted, but fall out of favor over the years.

For example, I personally have had lots of conversations with people who love creep feeding and people who do not believe that farrowing house creep-feeding provides enough value for the work involved.

Dr. Madie Wensley, nutritionist at Pipestone Swine Nutrition Services in Pipestone, Minnesota and former PhD student from our group, was responsible for this exciting trial conducted from breeding to marketing at the K-State (Kansas State) University Swine Teaching and Research Center farm.

While there is no “pig’s time machine” available on Amazon, we designed a trial with early and late maturing Duroc sire lines, intending to determine how different maturation patterns affect their growth curves, outcomes of creep feeding, and stress response.

To achieve the study purpose, we bred sows with two different sources of semen from Duroc sires with the highest index of early growth in the nursery or highest index for late finishing growth (Early or Late maturing, respectively).

During the farrowing house portion of the trial, half of the litters within each sire line had access to creep-feed starting 14 days prior to weaning. The creep feed diet was the same phase 1 diet used as the first diet in the nursery. The weaning happened at 21 days of age, and pigs were placed in pens based on sire line (Early or Late maturing) and creep feeding treatment (with or without).

To check the stress response immediately after weaning, we bled a sample of pigs one day prior and 30 minutes post-weaning and tested the cortisol concentrations.

Talking about post-weaning growth check, a pig producer once told me: “There is nothing better than the pig growth rate in the first days in the nursery to express their level of adaptation after weaning”.

It means that if a group of weaned pigs had many individuals losing weight in the first days, they struggled to adapt. I liked that, and we were able to illustrate it very well in this trial.

Early maturing pigs are indeed more precocious, and in our study, at 72 hours post-weaning, only 5.4 percent of them were lighter than at weaning compared to the 39.5 percent of the Late maturing pigs.

In addition, the Late maturing pigs presented higher blood cortisol concentrations than Early pigs. This fact might explain the struggle that the Late maturing sire line has when trying to get off to a good start in the nursery. So, it makes sense that stressed pigs will hesitate to eat and consequently be at a higher risk of losing body weight.

Even with the treatment names already indicating just how fast the maturation of the two sire lines were, we were able to measure and model their growth rate curves.

Figure 1 shows an advantage in favor of the Early maturing pigs until approximately 120 days of age.

graph showing effect of sire line on average daily gain in pigs
Figure 1. Effect of sire line (Early or Late maturing Duroc sire) on the modeled average daily gain of pigs from birth to market (Wensley et al. 2022)

After that, however, the maximum average daily gain for Late maturing pigs reached a higher and 10-day later peak than the Early maturing pigs. The pigs responded just as expected.

Interestingly, the feed efficiency curve (Figure 2) in the nursery and finishing periods expressed the effect of the post-weaning stress and the growth performance downstream in a single graph.

graph showing effect of sire line on feed efficiency iof pigs
Figure 2. Effect of sire line (Early or Late maturing Duroc sire) on feed efficiency of nursery and finishing pigs (Wensley et al. 2022).

Because of their rapid adaptation after weaning, Early maturing pigs had improved feed conversion up to 25 days in the nursery. After that, the Late maturing pigs recovered from weaning stress and, expressing one of the main characteristics of the modern genotypes, had better feed efficiency in the later nursery period and throughout the finishing phase.

At this point, you might think I should have discussed the creep-feeding piece of the study. Actually, I saved it to the end.

From day 67 of age until marketing at day 170, Late maturing creep-fed pigs were heavier than those from the same sire line not fed creep. The impact was tremendous in Late maturing pigs.

Curiously, the Early maturing pigs did not exhibit any creep-feed advantage. They seem to be tough guys, very well adapted to the farrowing house-to-nursery transition.

Thus, creep-feeding effects (on improved gut health and adaptation to the nursery’s solid feed) allow us to understand why Late maturing sire lines can benefit in the long term whereas early maturing pigs may not.

Finally, we should be patient and not make decisions too quickly while looking for creep-feeding effects. As in many other trials, creep-fed pigs’ weaning weight and early-nursery growth performance were not greatly affected.

In genetic improvement, unfortunately one cannot improve all traits at the same time.

Improving a characteristic of interest may harm some other traits. It is a matter of priorities, in other words, of the industry demands.

Postponing the timing of maximum weight gain and improving feed efficiency from mid-nursery until marketing caused pigs to struggle more right after weaning and have a greater negative response to stress.

On the other hand, the reward is at the same final body weight, where pigs needed approximately six percent less feed.

Wensley, Madie R.; Woodworth, Jason C.; Tokach, Mike D.; Goodband, Robert D.; DeRouchey, Joel M.; and Gebhardt, Jordan T. (2022) “Effect of Early vs. Late Maturing Sire Lines and Creep Feeding on the Stress Response, Intestinal Permeability, and Growth Performance of Nursery and Finishing Pigs,” Kansas Agricultural Experiment Station Research Reports: Vol. 8: Iss. 10. https://doi.org/10.4148/ 2378-5977.8358

Researchers: Jamil Faccin, Mike Tokach, Joel DeRouchey, Jordan Gebhardt, Robert Goodband, and Jason Woodworth.

Jamil Faccin, DVM, PHD

Jamil is a post-doctoral researcher on the Applied Swine Nutrition team at K-State. In 2011, he obtained his degree in Veterinary Medicine and worked in technical services at BRF - Brasil Foods from 2011 to 2015. Jamil received his PhD in Brazil in 2020. Today, at K-State, Jamil is engaged in all aspects of nutrition/feed management research, industry partnerships, and graduate student mentorship.