1. Gilts With Small Litters Tend to Stay That Way
2. Breeding Sows More Than Twice Is a Waste of Money
3. Increasing Lactation Length Improves Sow Performance
4. Background on Increasing Lactation Length
5. Gilt Management with PG600, Matrix and Boar Exposure
6. Split Weaning May Not Work Anymore
7. Skip-Heat Breeding in Parity 1 Sows Is Effective

1. Gilts With Small Litters Tend to Always Have Small Litters

Analysis of a large Chilean pork production system showed that sows tended to have smaller litters in all their farrowings if as a gilt they had a small litter (less than 9 pigs born live). These researchers from Alberta Agriculture decided to see if that was true for herds in the US and Canada. They looked at 33,000 sow histories from three large production systems (two in Canada, one in the US). They found the same thing: gilts with larger litters ended up having more lifetime pigs born live (14.4 more pigs born live in their lifetimes comparing gilts with 6 or less v. 14 or more liveborn). Putting the economics to it, weaned pigs cost more when coming from sows with small gilt litter size (an added cost of $2.50 to about $4.00 per weaned pig).

Clowes E and Bignell D. Gilts with small litters tend to always have small litters. Advances in Pork Production 17: Abstract 18, 2006. (not yet available online) emma.clowes@gov.ab.ca

2. Breeding Sows More Than Twice a Waste of Money

Many production systems inseminate sows more than twice during estrus, basically keep inseminating them as long at they are in standing heat. These researchers decided to evaluate the effectiveness of three v. two inseminations in parity 2 and older sows. Queried the same 33,000 sow history database as above. Results: Sows inseminated 3 times did not produce more total born or live born; in fact, there was a slight drop in litter size associated with 3 inseminations. They figure that the extra insemination ends up adding about $0.18 to $0.25 to the cost of every pig born live in a herd. Discussion: They recommend inseminating twice (AM, AM) rather than 3 times or more in parity 2 and older sows that come in heat within 5 days of weaning. For gilts and parity 1 sows you should continue breeding as you do now because very few of them ever get inseminated more than twice anyway.

Clowes E, Bignell D, and Thompson C. Cost of serving sows multiple times per breeding. Advances in Pork Production 17: Abstract 19, 2006. (not yet available online) emma.clowes@gov.ab.ca

3. Increasing Lactation Length Improves Sow Performance

Same researchers, same 33,000 sow history database. This time they evaluated reproductive performance associated with short (11 to 15 day) v. longer (20 to 21 day) lactations. They stopped at 21 days. Litter size increased progressively by .6 pigs born live as lactation length went from 11 to 21 days. At the same time, more sows came into heat within 7 days of weaning and a higher percentage were bred (at 18-21 days it was 86% in heat within 7 days; at 11-12 days, it was 42%.)

Clowes E, Bignell D, and Thompson C. Increasing lactation length improves sow performance. Advances in Pork Production 17: Abstract 20, 2006. (not yet available online) emma.clowes@gov.ab.ca

My bottom line: The economics are all in favor of moving to longer lactation lengths. See the next article for more.

4. Background on Increasing Lactation Length

Increasing lactation length and piglet weaning age makes you more money. Many of the large-scale producers have already completed building projects that added another room on to their farrowing buildings. Increasing weaning age increases profit by improving follow-on (nursery and finishing) daily gain and reducing follow-on mortality.

Excellent, in-depth article in the National Hog Farmer provides all the detail you need to understand the dynamics and profitability that comes from increased weaning age. The vets from Carthage Vet Clinic do a great job in summarizing and analyzing the research, doing some of their own analysis, and coming to the right conclusions.

The article in Pork magazine highlights research done by Kansas State and includes comments from Bob Goodband. Leave it to Kansas State to do the practical research confirming the value.

K-State (Rodger Main, Steve Dritz, Mike Tokach, etc, etc) did the fundamental research in 2002-2003; Journal of Animal Science published it in May, 2004: Increasing weaning age improves pig performance in a multi-site production system,” Journal of Animal Science, 82:1499-1507. Link to full text article. Then the K-State team created a model to illustrate the economic effects of increasing wean age and presented the results at this past September's Leman Conference in St Paul, MN. [Not much in the Leman Conference proceedings, however, just a one-paragraph description of what they presented.]

The model's details and results were published recently in the Journal of Swine Health and Production: Main RG, Dritz SS, Tokach MD, et al. A partial-budgeting tool to describe the effect of lactation space and lactation-space management on net revenue in a multi-site production system. J Swine Health Prod 2005;13(6):322-332 ( Link to Abstract available to public, full text to members of the American Association of Swine Veterinarians.)

Revisiting Weaning Age Trends, Dynamics by Joseph F. Connor, DVM; William L. Hollis, DVM; and Keith R. Erlandson, DVM (National Hog Farmer / Oct 15, 2005)

Weaning Age: Finding the Payoff By Roger Stevens (Pork Magazine / December 1, 2005)

5. Boar exposure, PG600, and Matrix: Components in Effective Gilt Development Unit Management

In their own words: "This study provides 'proof-of-principle' that the three essential components of effective GDU management (boar exposure area, PG600 and Matrix) are effective in meeting breeding targets, synchronizing breeding weeks, and helping focus staff at the time of breeding to maximize Parity 1 farrowing rates, litter size and lactation length."

Patterson J, Wilson W, Francisco C, Williams N, Spronk G, Beltranena E, and Foxcroft G. BEAR, PG600 & Matrix Use: Components in Effective Gilt Development Unit Management. Advances in Pork Production 17: Abstract 21, 2006. (not yet available online) george.foxcroft@ualberta.ca

Basically this abstract lays out a very condensed version of the Foxcroft team's process of intensely managing gilt development and breeding.

You can find much more information in the following recent publications. (I'll bet the authors or your friendly Intervet tech sales rep would be happy to send you copies of the articles.)

Foxcroft G, Beltranena E, Patterson J, and Williams N. Recognizing the Characteristics of Our New Dam Lines. Proceedings, Allen D Leman Swine Conference 32: pp 130-138, 2005.

Spronk GD and Pizarro G. Successful and Unsuccessful Puberty Induction in Gilts: A Case Study. Proceedings, Allen D Leman Swine Conference 32: pp 139-141, 2005.

Patterson J, Wilson W, Francisco C, Williams N, Spronk G, and Foxcroft G. Application of MATRIX as a Component of Effective Gilt Development Unit (GDU) Management. Proceedings, Annual Meeting of the American Association of Swine Veterinarians 36: pp 177-180, 2005.

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6. Split Weaning May Not Work Anymore

George Foxcroft's research team presented two abstracts on a controlled study they did to research the effects of split weaning on sow reproductive performance. They allocated first- and second-parity sows to either a control group (all pigs weaned at 19 days) or a split-weaned treatment group (the heaviest pigs weaned at day 16, the 5 lightest pigs weaned on day 19). They did a 96-hr hormonal sampling phase and then looked at the follow-on reproductive performance for the two groups. Bottom line: Split-weaning had no impact on weaning-to-estrus interval (WEI), pregnancy rate, ovulation rate, or embryo survival rate.

Of course, the big deal here is that producers moved to split weaning specifically to counter the detrimental effects of early weaning especially in Parity 1 sows. And studies years ago showed that it could be effective in mitigating the negative effect of early weaning on WEI. In other words, split weaning was suppposed to prevent the longer WEI associated with early weaning age.

They did see a predictable hormonal response to split weaning: plasma prolactin was lower, plasma FSH was higher, LH concentration was higher, and the number of LH episodes during lactation was higher in split-wean sows. But there was no effect on sow fertility.

Their bottom line: "needs further study" and "the response of modern sows to this technique has changed dramatically."

Wellen A, Degenstein K, Zimmerman P, O'Donoghue R, Patterson J, Dyck M, and Foxcroft G. Effects of split weaning on fertility following lactation. Advances in Pork Production 17: Abstract 22, 2006.

Degenstein K, Wellen A, Zimmerman P, Shostak S, Patterson J, Dyck M, and Foxcroft G. Effect of split weaning on hormone release in lactating sows. Advances in Pork Production 17: Abstract 23, 2006.

7. Skip-Heat Breeding in Parity 1 Sows Is Effective

Skipping the first heat and breeding on the second heat after weaning in first-parity sows erases the second-parity dip in litter size. This is well-known and good research has been published on it (Clowes et al., Journal of Animal Science 72: 283, 1994). However, it does cost money in terms of non-productive days. These researchers decided to take another look and see if it truly remains an effective process (much like they took another look at split-weaning). Controlling for weaning-to-estrus interval, they allocated pairs of first-parity sows to be bred at either their first or second heat after weaning. Turned out that the percentage bred, the ovulation rate, and the conception rate were the same between the two groups. But the sows bred on their second heat had higher embryo survival and more total embryos at gestation day 30 (15.2 v. 12.9). They didn't present farrowing results, but assuming similar fetal survival rates past day 30, this would increase litter size by 2.3 pigs in skip-heat females, which is consistent with previous research on this topic.

Bottom line: Skip-heat breeding in first-parity sows works, it increases litter size by 2+ pigs, takes away the second-parity dip, and does it by increasing embryonic survival rate.

Patterson J, Zimmerman P, Dyck M, and Foxcroft G. Effect of skip-a-heat breeding on subsequent reproductive performance in 1st parity sows. Advances in Pork Production 17: Abstract 24, 2006.

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