Supplementing Fall-Back Pigs Pays In the Nursery

A number of Michigan pork producers have questioned whether the “rescue decks” really pay off, according to Barbara Straw, Extension veterinarian at Michigan State University (MSU).

Producers are impressed with the way that disadvantaged pigs perform in the decks in the farrowing house, but question whether those pigs will simply fall back again in the nursery.

Jerry May, MSU Extension swine specialist, set up a trial with a 2,000-sow commercial producer who raised this question.

In the past, it's been common procedure on such an operation to provide supplemental care to pigs that demonstrate slow growth in the first 3-5 days of life.

In this herd studied, routine crossfostering occurs at birth to standardize litter sizes. Then at 3-5 days of age, a litter created from 8-11 undersized pigs is collected from a room of 20 litters. The next gilt to farrow (one of the last in the group to farrow) has all of her piglets removed and transferred to the other remaining newborn litters so she can become a nurse sow for an entirely adopted litter of fallbacks.

In an effort to duplicate the success of using foster litters, an automatic milk feeder was installed to accommodate a litter of healthy piglets. These piglets were moved to the milk feeder to free up their dam to nurse fall-back pigs.

While these foster (fall-back) litters thrived in farrowing, it was unknown whether pigs from these litters would do well in the nursery, or whether they would continue to need special care.

Table 1 depicts the fostering process at the farm for challenged 3-5 day-old pigs. At the same time, 18-day-old pigs were being weaned. The protocol at weaning was to commingle pigs that had received supplemental care in lactation with normal pigs to find out if the supplemented pigs could grow on their own.

In four farrowing rooms at the time of weaning, there were 117 pigs that had been small at 3-5 days of age and placed on foster sows. These pigs were ear tagged to identify them as pigs that had received supplemental care during lactation.

At weaning, 88 of the tagged pigs met the target weight of 13 lb. and were moved to the nursery. Eighteen of the remaining 29 pigs that remained in the farrowing room reached the weaning weight requirement one week later at 25 days of age, while the other 11 pigs died.

To reduce handling stress, weights of tagged and routinely handled pigs were collected one week postweaning, when pigs were vaccinated for Mycoplasmal pneumonia. Pigs were weighed again 35 days postweaning, just prior to movement to the finisher (Table 2).

Overall, three of the undersized pigs died in the nursery (3/106=2.8%), compared to the usual herd nursery mortality of 2.0%. A total of 103 of the undersized pigs completed 35 days in the nursery. And their weight going into the finisher of nearly 40 lb. was no different than normally raised pigs.

In sum, pigs that fail to thrive in the first three days of life are capable of performing adequately if provided supplemental care. These pigs can achieve weights at weaning and at the end of the nursery phase comparable to pigs managed without special care.

Fall-back pigs in this study were due to nutritional deficiencies and not disease, which would have required a different outcome.

Researcher: Barbara Straw, DVM, Michigan State University. Contact Straw by phone (517) 432-5199, fax (517) 432-3450 or e-mail

Table 1. Weight and Numbers of Piglets on Sows in Four Farrowing Rooms Involved in the Milk Deck/Foster Management

Sow ID Original litter that was removed and placed in the auto milk feeder Undersized pigs fostered onto the nurse sow
Number of pigs Average wt. Number of pigs Average wt.
16580 11 3.6 10 1.9
105515 10 2.9 10 1.5
105149 11 3.0 11 1.9
16603 9 2.7 8 2.4
92276 11 2.7 11 1.4
106765 9 2.9 10 1.0
92289 11 2.7 11 1.7
Total 72 2.9 71 1.7

Table 2. Weights (LS means ± SE)

Management Weight 7 days postweaning Weight 35 days postweaning
Foster sow 14.5 (n = 88) 38.6 (n = 1031)
Routinely handled n = 74 14.7 39.4
1Includes late-weaned pigs

Dam Parity Influences Litter Performance, Pig Health

University of Nebraska researchers have confirmed earlier work indicating that sow parity affects the health status of her progeny.

The research team evaluated litter performance and the production and passive transfer of immunoglobulins (Ig) {antibodies} in Parity 1 (P1) dams vs. Parity 4 (P4) dams and their progeny.

Immunoglobulin A (IgA) antibodies protect the mucosal surfaces from infection. Immunoglobulin G (IgG) antibodies provide protection against viruses, bacteria and antitoxins and are found in most tissues and plasma.

Researchers found:

Litter weight tended to be greater for P4 progeny compared to P1 progeny.

Dam parity didn't appear to influence circulating Ig in dams during gestation or at farrowing. But IgA concentrations were generally higher for P4 sows than P1 gilts in samples of colostrum and milk. And serum IgG concentrations were greater for P4 progeny compared to P1 progeny across all preweaning samples.

Dams (Large White × Landrace) were first-parity gilts and fourth-parity sows that farrowed over a 22-day period. Dams were housed in stalls during gestation and moved to farrowing crates about five days prior to their expected farrowing date.

All piglets from each litter were weighed on Day 0, 7, 14 and 19 (weaning).

Blood samples were collected from sows during gestation on Day 90 and 114 and a final time after farrowing.

Samples during lactation were obtained at Day 0 (colostrum), Day 7 (mid-lactation) and Day 14 (late-lactation).

Blood samples were collected from six piglets from each litter on Days 1, 7 and 14.

Dam and litter performance are illustrated in Table 1. Data shows parity had no effect on number of pigs/litter or on litter weaning weights.

But P4 dams tended to have pigs with heavier bodyweights compared to P1 dams, and P4 dams had less preweaning mortality and heavier litter weaning weights.

Figure 1 depicts progeny bodyweights of gilts (P1) and Parity 4 (P4) sows. The P4 progeny had heavier bodyweights among all time points from farrowing to weaning than P1 progeny.

Researchers acknowledged that they expected to observe greater differences in dam and litter performance, but based on previous work, it's possible that the greatest differences in performance occurs between P1 and P2 or P3 dams.

IgG and IgA antibodies in P1 and P4 dams during gestation and after farrowing are represented in Figure 2. While IgA increased as the dams approached farrowing, IgG levels declined over time, with the lowest concentrations observed at farrowing. Researchers suggest this result may contribute to the higher levels of IgA in mid- and late-lactation milk as compared to IgG.

IgG and IgA antibodies in colostrum and milk during lactation are shown in Figure 3. IgG concentrations were unaffected by parity. But IgG antibodies averaged among both parities were greater for colostrum than mid- and late-lactation samples. For IgA, concentrations tended to be greater in P4 dams than P1 dams, and again the greatest concentrations were observed during early lactation (colostrum).

There were no parity-by-time interactions for IgG or IgA antibodies in serum from P1 and P4 progeny (Figure 4). However, among all time points, piglets from P4 dams had greater circulating IgG than P1 dams. Parity had no effect on IgA levels in P1 and P4 progeny, but P1 progeny had lower (numerically) IgA levels compared to P4 progeny at Days 1 and 7.

In conclusion, it appears that mature dams (P3+) may provide their progeny with performance advantages due to their contributions of passive immunity. However, future research is needed to determine if these observations are consistent throughout the sow's reproductive lifetime.

Researchers: Erin Carney, Huyen Tran, Justin Bundy, Roman Moreno, Matthew Anderson, Jeffrey Perkins, Phillip Miller and Thomas Burkey, all of the University of Nebraska. Contact Burkey by phone (402) 472-6423, fax (402) 472-6362 or e-mail

Table 1. Treatment Effects of Sow Parity on Litter and Pig Measurements

Item Parity
1 4
Number of sows 19 24
Total born 12.79 12.79
Born live 12.00 11.50
Stillbirths 0.63 1.13
Mummified fetuses 0.16 0.21
Mortality (preweaning) 2.68 1.83
Weaned 10.16 10.13
Litter weight, lb.
Birth (Day 0) 15.73 17.89
Weaning (Day 19) 55.14 58.07

Experimental Vaccine Is Effective Against PRRS

A modified-live-virus (MLV) vaccine, propagated in an innovative porcine alveolar macrophage cell line, designated ZMAC, was effective in protecting pigs from porcine reproductive and respiratory syndrome (PRRS) virus.

Use of the ZMAC-grown, MLV vaccine prevented the weight loss observed in non-immunized animals within seven days after exposure to a highly virulent strain of PRRS virus.

“Remarkably, analyses of the virus load in serum and lung samples from PRRS virus-immunized and challenged animals revealed that the vaccine virus grown in ZMAC cells was significantly more effective at reducing the extent of viremia (the presence of virus in the blood) at seven days post-challenge, and also at eliminating virulent virus from their lungs by 10 days post-challenge,” says Federico A. Zuckermann, professor of immunology at the University of Illinois College of Veterinary Medicine.

The researcher says the degree of protection afforded by this vaccine “against a genetically divergent and highly virulent PRRS virus has important implications for the prospect of developing an effective vaccine against this pathogen.

“Namely, the results of this study suggest that the effectiveness of a PRRS MLV vaccine can be improved, and that it is not, as it is commonly believed, only determined by its genetic similarity to the challenge virus, but is also influenced by how it is produced.

“The results of this study provide great hope that an effective MLV vaccine against PRRS virus can be developed,” says Zuckermann.

The goals of this project, funded by the National Pork Board, were to use an innovative porcine cell line to produce a PRRS MLV vaccine, and to compare this virus' efficacy to that of vaccine made traditionally in the simian MARC-145 cell line, the only other type of cell line known to support the growth of PRRS virus.

To evaluate the vaccine potential of the ZMAC-grown virus, a standard immunization test was conducted. Six, 8-week-old pigs were injected with the Prime Pac commercial vaccine (Schering-Plough Animal Health) propagated in either ZMAC or MARC-145 cells, while two groups of three animals were not immunized and served as controls.

Four weeks later, all vaccinated pigs and one of the PRRS naïve groups were challenged with an “atypical PRRS abortion storm” virus.

The result was that the Prime Pac vaccine grown in either cell line proved equally effective at preventing weight loss by pigs exposed to virulent virus seven days earlier. (See Figure 1, where weight changes of non-immunized and vaccinated pigs at seven days after challenge with atypical PRRS virus are depicted.)

The vaccine virus grown in ZMAC cells, however, was much more effective than the one generated in MARC-145 cells at reducing the extent of infection and also at eliminating virus from the lungs at 7 or 10 days post-challenge.

Researcher: Federico Zuckermann, University of Illinois. Contact Zuckermann by phone (217) 333-7767, fax (217) 244-7421 or e-mail