Herd Health and Management Extending Weaning Age Boosts Finishing Efficiency, Pounds Sold

Producers have shortened weaning age to improve pig health and growth performance. Kansas State University (KSU) studies document the impact of earlier weaning age, and show that increasing weaning age up to 21 days improves grow-finish throughput within a three-site system.

In two trials, wean-to-finish average daily gain, mortality rate, average pig gain/days postweaning and pounds sold/pig weaned improved as weaning age increased.

The improvements in growth and livability largely occurred in the 42-day postweaning period. There were also some gains in growth during finishing.

KSU researchers stress that the growth rate improvement as weaning age rises is fairly predictable within a given production system. But the level of improvement in mortality rates is somewhat dependent on baseline nursery mortality rates, pig flow, site or system-specific challenges.

For this study, weaned pigs were derived from a 7,300-sow, three-site farm with single-source weaned pigs flowing into all-in, all-out nursery and finishing sites.

In trial 1, litters of pigs were weaned at 12, 15, 18 or 21 days of age. In trial 2, litters were weaned at 15, 16, 18, 19, 21 or 22 days of age. For trial 2, researchers averaged weaning ages to study: 15.5, 18.5 and 21.5 days of age.

Each trial had four blocks, and each block had four replications or pens on test. Blocks remained intact as pigs were moved from nursery to finishing sites.

Each 8 × 12-ft., wired-floored nursery pen in trial 1 contained an equal number of barrows and gilts. Each pen contained 36 pigs/pen, except for the first block in trial 1 which had 34 pigs/pen. Pigs were placed on a three-phase nursery feed budget. Trial 2 pigs were housed in similar conditions and placed on a nursery feed budget that was more or less complex.

For finishing in trial 1, each 7.5 × 22-ft. pen housed 10 barrows and 10 gilts. For trial 2, 13 gilts and 12 barrows were confined in 9.5 × 22-ft. pens. Finishing pens had partially slotted flooring (2/3 solid, 1/3 slotted).

Table 1. Influence of Weaning Age on Nursery Performance (Trial 1)a
Weaning Age, Days
Item 12 15 18 21
Allotment weight, lb.b 7.6 9.4 10.8 12.7
Regressed weaning weight, lb.c 9.3 10.9 12.6 14.3
Average daily gain, lb.d,e .66 .81 .90 1.05
Average daily feed intake, lb.d,e .94 1.13 1.25 1.44
Feed:gaind,e 1.42 1.39 1.38 1.38
Mortality, % 5.25 2.82 2.11 .54
42-day weight postweaning, lb. 37.3 44.7 49.8 56.9
a2,272 pigs with 34 or 36 pigs/pen (50% barrows, 50% gilts) and 16 pens/treatment or a total of 64 pens on test.
bAllotment weights were taken on all pigs three days prior to weaning.
cPredicted treatment mean weaning weights were calculated by regressing the three-day preweaning weights on a pen basis.
dAllotment weights were used for all growth and efficiency calculations.
eAverage daily gain, average daily feed intake and feed:gain are all calculated with allotted pen weight, 42-day pen weight and pen space days postweaning.
Table 2. Influence of Weaning Age on Finishing Performance (Trial 1)a
Weaning Age, Days
Item 12 15 18 21
Allotment weight, lb. 37.3 44.9 49.9 57.0
Average daily gain, lb.b 1.59 1.60 1.62 1.69
Mortality, % 4.38 5.21 4.79 3.13
Off-test weight, lb. 229 240 247 259
Off-test weight/day of age, lb.c 1.36 1.40 1.42 1.46
Carcass weight, lb.d 197 197 195 202
Yield, % 75.9 75.5 75.6 75.8
10th-rib fat depth, in.e .70 .69 .70 .66
Loin depth, in.e 2.53 2.52 2.57 2.55
Lean, %e 54.6 54.6 54.7 55.0
a1,920 pigs with 20 pigs (10 barrows, 10 gilts)/pen and 24 pens/treatment, or 96 pens on test.
bAverage daily gain = (off-test pen - allotment pen weight ÷ (no. of pig spaces × no. of days on test).
cOff-test weight per day of age = off-test weight ÷ pig age.
dDue to extended transfer to slaughter strategy, comparing carcass weights between treatments was not of interest.
e10th-rib backfat, loin depth and lean percentage measures are all adjusted to a common carcass weight utilizing carcass weight as a covariate.
Table 3. Influence of Weaning Age on Wean-to-Finish Performance (Trial 1)a
Weaning Age, Days
Item 12 15 18 21
Allotment weight, lb. 7.5 9.4 10.8 12.7
Off-test weight, lb. 229 241 247 259
Average daily gain, lb.b 1.28 1.36 1.40 1.51
Mortality, %c 9.39 7.88 6.80 3.68
Average pig gain/days postweaning, lb.d 1.42 1.48 1.51 1.57
Pounds sold/pig weanede 208 222 230 249
aLinking nursery allotment weights and nursery mortality data within treatment and block to respective finisher pen to quantify wean-to-finish performance.
bAverage daily gain = (finisher pen weight sold - (nursery allotment weight × no. of weaned pigs required to place finishing pen)) ÷ (no. of weaned pigs required to place finishing pen × no. of days postweaning).
cMortality = (1 - (finishing pen inventory weighed off-test ÷ no. of weaned pigs to place finishing pen)) × 100.
dAverage pig gain ÷ days postweaning = (off-test weight - allotment weight) ÷ no. of days postweaning.
ePounds sold/pig weaned = off-test pen weight ÷ no. of weaned pigs required to place finishing pen.
Table 4. Influence of Weaning Age and Nursery Feed Budget Complexity on Wean-to-Finish Performance (Trial 2)a
Less Complex Nursery Budget More Complex Nursery Budget
Weaning Age, Days
Item 15.5 18.5 21.5 15.5 18.5 21.5
Allotment weight, lb. 9.0 10.5 12.4 9.0 10.5 12.5
Off-test weight, lb. 246 255 263 248 254 262
Average daily gain, lb.b 1.50 1.53 1.60 1.48 1.54 1.58
Mortality, %c 2.89 3.86 2.20 4.95 2.99 2.77
Average pig gain/days postweaning, lb.d 1.54 1.60 1.64 1.56 1.59 1.63
Pounds sold/pig weaned, lb.e 239 246 257 236 246 255
aLinking nursery allotment weights and nursery mortality data within treatment and block to respective finisher pen to quantify wean-to-finish performance.
bAverage daily gain = (finisher pen weight sold - (nursery allotment weight × no. of wean pigs required to place finishing pen)) ÷ (no. of wean pigs required to place finishing pen × no. of days postweaning).
cMortality = (1 - (finishing pen inventory weighed off-test ÷ no. of wean pigs required to place finishing pen)) × 100.
dAverage pig gain ÷ days postweaning = (off-test weight - allotment) ÷ no. of days postweaning.
ePounds sold ÷ pigs weaned = off-test pen weight ÷ no. of wean pigs required to place finishing pen.

Pen identity was maintained from birth through the packing plant in both trials.

In the nursery phase of trial 1 (Table 1), allotment or starting weights increased as weaning ages increased, and the variation in those weights dropped as weaning age rose. The most weight variation was seen in pigs weaned at 12 days of age.

Nursery performance and 42-day postweaning weight improved significantly as weaning age climbed from 12 days to 21 days. Performance was the poorest in 12-day-old weaned pigs.

Average daily gain, off-test weight variation and off-test weight/day of age during finishing in trial 1 also improved as weaning age increased from 12 to 21 days of age (Table 2).

Table 3 depicts how weaning age also influenced performance for the wean-to-finish period. Increasing weaning age from 12 to 21 days resulted in improved average daily gain, mortality, average pig gain/days postweaning and pounds sold/pig weaned.

Similar results were seen in trial 2 in performance gains and in 42-day postweaning weights as weaning age increased from 15.5 to 21.5 days (Table 4).

During wean-to-finish in trial 2, average daily gain, average pig gain/days postweaning and pounds sold/pig weaned all improved as weaning age rose.

Altering nursery feed budgets in trial 2 based on weaning age did not affect wean-to-finish growth performance.

Overall, the trials did not clearly show that either weaning age or nursery feed budgets affected carcass parameters measured.

An economic evaluation indicated that for each one-day increase in weaning weight, cost of production was reduced by 30¢/cwt. and income over costs increased by 94¢/pig weaned. Thus, increasing average weaning age from 15 to 20 days was projected to increase income over costs by $4.70/weaned pig.

This calculation assumes limited finishing capacity, and that since the pigs weaned at a younger age grew slower, they would be sold at a lighter weight. If younger pigs were allowed to grow more days to achieve a similar market weight as the faster-growing, older pigs, the cost/cwt. was reduced by 18¢ and income over costs increased by 53¢/pig weaned.

Researchers: R.G. Main, DVM; S. S. Dritz, DVM; M.D. Tokach, R.D. Goodband and J.L. Nelssen of Kansas State University. Phone Nelssen at (785) 532-1251; fax (785) 532-7059; or e-mail jnelssen@ksu.edu.

Finishing Performance Improved by Sorting Off Heaviest 25%

Removing 25% of the heaviest market hogs from a finishing barn pen provided the most improvement in growth performance and total live weight produced, according to University of Illinois researchers. Sorting off 50% of the heaviest pigs from a pen did not provide additional benefits, they found.

The study involved 1,456 crossbred pigs housed 52/pen in a wean-to-finish, tunnel-ventilated barn. Pigs were placed on test 22 weeks postweaning and remained on test for 19 days.

Four treatment groups were studied:

Group 1 (control group) had no pigs removed, with 52 pigs/pen at 7 sq. ft./ pig.

Group 2 had 25% of the heaviest pigs removed, leaving 39 pigs/pen at 9.4 sq. ft./pig.

Group 3 had 50% of the heaviest pigs removed, leaving 26 pigs/pen and floor space unadjusted at 14 sq. ft./pig.

Group 4 had 50% of the heaviest pigs removed from the pen, leaving 26 pigs/pen, with floor space adjusted to that of the control group at 7 sq. ft./pig.

Removing a proportion of the heaviest pigs from the finishing pens boosted growth performance. Compared to the control group, removing 25% and 50% of the pigs from the group (with no adjustment of floor space) increased feed intake 10.8% and 8.0%, respectively; average daily gain increased 20.6% and 21.0%, respectively; and gain:feed ratio improved 7.7% and 14.3%, respectively.

Table 1. Effect of Removal Strategy at Slaughter on Growth Performance
Removal treatment
Item Control 25% 50% 50% adjusted space, Significant effect of treatments
Weight before removal, lb. 249 251 250 251 No
Weight after removal, lb. 249 244 233 235 Yes
Final weight, lb. 278 279 269 268 Yes
Daily weight gain, lb. 1.45 1.83 1.84 1.66 Yes
Daily feed intake, lb. 6.16 6.91 6.69 6.30 Yes
Gain:feed 0.24 0.26 0.28 0.26 Yes
Total live weight produced, lb. 14,412 14,457 13,968 13,902 Yes

Floor space allowance had an effect on growth performance. Group 4, which had 50% of the heaviest pigs removed and floor space adjusted to 7 sq. ft./pig, had lower feed intake (0.4 lb/day) and grew slower (0.2 lb/day) than Group 3 pigs, which had 50% of the heaviest pigs removed, but floor space unadjusted at 14 sq. ft./pig. Group 4 pigs did grow faster (0.2 lb/day) than the control group (Table 1).

The Illinois scientists concluded that only part of the improvement in growth rate following the removal of pigs from a group was due to the increase in floor space. They suggested that part is due to other factors, such as change in social order and dynamics within the group.

Carcass composition and pigs pulled due to poor health were similar for all treatment regimens.

The four pens of 52 pigs produced total live weight of 14,412 lb., 14,457 lb., 13,968 lb. and 13,902 lb. for treatments 1, 2, 3 and 4, respectively.

Researchers: Jacob M. DeDecker and Mike Ellis, University of Illinois. Phone Ellis at (217) 333-6455; fax (217) 333-7861; or e-mail mellis7@uiuc.edu.

Better Gilt Programs Can Boost Sow Reproductive Efficiency

Improving gilt management programs will result in reduced sow replacement rates, improved sow fitness, increased labor efficiency and better space utilization.

To achieve that success, reduce annual replacement rates while still meeting breeding targets. Annual replacement rates on swine operations average 62.9% in the U.S. and 58.7% in Canada, according to PigCHAMP data.

Recent research points to three key elements in good gilt management programs:

  • Implementing a strict selection program that identifies the most fertile animals;

  • Achieving appropriate weights at first breeding to prolong lifetime sow performance; and

  • Minimizing non-productive days (NPD) in the gilt pool.

A selection program must identify the 75-80% of pre-pubertal gilts that best respond to boar stimuli.

Based on earlier research at the Swine Research and Technology Centre, and a current study at Prairie Swine Centre, Saskatoon, the link between age at boar-induced puberty and lifetime performance is being examined in Camborough 22 and L42 gilts. Gilts are exposed to vasectomized boars for 20 minutes daily starting at 140 days of age. Gilts achieving puberty by 180 days of age are named “select” gilts and classified as Early (EP), Intermediate (IP) or Late (LP) for first standing estrus. EP gilts have a recorded heat within 140 to 155 days, IP gilts within 155 to 170 days and LP gilts within 170 to 180 days. Gilts are classified “non-select” (NP) if puberty is not reached by 180 days of age.

“Select” gilts are bred at third estrus regardless of age or weight. To meet breeding targets, most NP gilts are bred with the aid of PG600.

Table 1. Breeding Herd Efficiency Measured as Cumulative Non-Productive Days to Day 30 of Gestation in Parity 2*
Early Puberty Intermediate Puberty Late Puberty Non-Select (No Estrus)
NPD Actual1,2 50.5 58.5 75.5 71.1
NPD Predicted3 41.2 41.4 49.2 69.2
Reduction in NPD 9.3 17.1 26.5 -----
Expected Savings4 $18/60 $34.20 $53.00 -----
*Inclusive in estimated non-productive days (NPD) for each gilt category are days-to-service as gilts, wean-to-service interval, days to culling for gilts not bred or not farrowing, and non-productive days (NPD) for sows culled after weaning their first litter (Prairie Swine Centre and University of Alberta, Swine Research and Technology Centre, unpublished data, 2003).
1NPD calculated from 170 days (days to reach slaughter weight of 264 lb. with an average growth rate of 1.6 lb./day).
2Actual number of NPDs accumulated to Day 30 of gestation of parity 2.
3Predicted number of NPDs if gilts bred at 297 lb. body weight or third estrus.
4Example of a 600-sow unit × 45% replacement = 270 gilts × 120% to meet requirements = 324 gilts × (average of $18.60 + $34.20 + $53.00 = $11,426 (savings/year)).

These breeding results have shown that pregnancy rate, farrowing rate, weaning rate and the percent of gilts rebred after weaning the first litter were lower for NP gilts than for EP, IP or LP gilts (Figure 1, on page 15).

First-litter sows need to weigh 385-396 lb. to protect them from adverse affects of first lactation on subsequent fertility, according to recent research.

This data also suggests that instead of following the conventional wisdom of using age to determine time of breeding, ad libitum-fed gilts should be bred based on weight (297-330 lb.)

If gilts are also “select” (recorded standing heat within a set number of days of direct contact with mature boars), and an upper limit of third estrus for breeding is also required, the number of non-productive days (NPD) will dramatically drop (Table 1).

If one NPD is worth $2/day, University of Alberta data says efficient gilt management strategies on a 600-sow unit will produce savings of $11,426 due to reduced NPDs (Table 1).

Researcher: George Foxcroft, University of Alberta. Contact Foxcroft by phone (780) 492-7661; fax (780) 492-4265 or e-mail george.foxcroft@ualberta.ca.

Animal Welfare Performance, Welfare in Stalls Comparable to Group Sow Housing

The performance and welfare of sows in stalls was comparable to that of two other group sow housing systems in a pork checkoff-funded study conducted by the University of Minnesota.

A research team led by Leena Anil, post-doctoral associate at the University's Swine Center, concluded that the stall system provided comparable benefits to sows. But stalls do limit space. Further, as sows grow larger, there is greater potential for injury in the limited space they provide, warns the team.

Group sow housing with electronic sow feeder (ESF) offers great potential for providing proper animal welfare provided changes can be made to reduce injuries inherent in the system.

Table 1: Median and Range of Total Injury Scores and Mean ± Standard Error of Cortisol Concentration (ng/ml.) of Sows at Different Stages of Gestation in Pens with Electronic Sow Feeding (ESF) and in Stalls*
Preweaning Day 5 Mixing-1 Mixing-2 Day 28 Day 56 Day 84 Day 108
Total injury scores (pens with ESF) 4(1-11)a 25(9-41)b 22(10-40)bc 21(9-38)cd 18(7-34)e 19(7-39)de 20(7-38)cd
Total injury scores (stalls) 5(1-11)a 5(1-16)a 5(1-14)a 4.5(2-14)a 5(2-13)a 6(2-13)b
Cortisol (pens with ESF) 0.5399 ± 0.087a 4.1227 ± 0.535b 3.1404 ± 0.419bc 2.4883 ± 0.233c 2.1117 ± 0.248c 3.1271 ± 0.477bc 4.2388 ± 0.576b
Cortisol (stalls) 1.2109 ± 0.1230a 1.0166 ± 0.1501a 0.4442 ± 0.06651b 0.4518 ± 0.1291b 0.5258 ± 0.06651b 0.9515 ± 0.1216a
a,b,c,d Within each row, values with different superscripts are significantly (P<0.05) different.
*The injury scores were based on frequency and severity of wound on different body locations (ranging from 0 to 3; no injury, mild, obvious and severe, respectively) and the scores were totaled. A higher cortisol concentration is suggestive of increased stress compared to the lower concentration, though there is no base level.

The third sow housing system tested, hoops with deep-litter bedding, holds promise. But in the small group system tested (15 head/pen), sow handling becomes more labor intensive in terms of management and manure removal, according to the Minnesota team.

The first study compared sows housed in stalls with sows housed in pens with ESF. Welfare status of the group-housed sows in terms of number and severity of injuries and salivary stress hormone (cortisol) concentrations were consistently lower than that of the stall-housed sows. Results are shown in Table 1. Overall production performance was better for sows in stalls than for sows group-housed with ESF.

In the first study, researchers compared 206 Parity 1-4 pregnant sows grouped-housed with ESF in pens 43 ft. long and 22.5 ft. wide on fully slotted floors, with 176 pregnant sows of Parity 1-5 in conventional sow stalls.

Group sows with ESF were housed 38-39/pen. To achieve this size, sows were added to the pen twice, two weeks apart. Sow welfare was assessed four days before weaning and at different stages of gestation. Sows in pens were assessed on Days 5, 19 (both mixing days), 28, 56, 84 and 108 of gestation. Sows in stalls were assessed on Days 5, 28, 56, 84 and Day 108 of gestation.

The concentration of stress hormone in saliva and injury levels in sows housed in pens with ESF was lowest prior to weaning and highest during mixing days. After mixing, both injury levels and stress hormone levels gradually declined before increasing during late gestation. More injuries were observed on the neck, shoulder, chest, croup and limbs. The same trends were observed in stall-housed sows. Most of the injuries were at the back, limbs and udder area.

Injuries and stress levels were lower at all stages of gestation for sows housed in stalls. As parities increased, the chance for injury rose in stalls and declined in group sows with ESF.

Stalled sows enjoyed higher farrowing rates and lower culling rates than sows housed in groups with ESF. Litter size, born alive and stillborns were the same for both groups. Stall-housed sows had fewer mummies, while sows in pens with ESF had fewer piglet deaths and lower preweaning mortality. Lameness was the most common cause of removal in sows housed in pens with ESF.

The Minnesota team states the