born in parity 1 decrease by 0.6 pigs at their subsequent parity, whereas for pregnant gilts the decreases are only 0.2 pigs. In parity 2 or higher sows, the decrease was 0.4 pigs. So, parity 1 sows are three times more sensitive to high temperature for total number of pigs born than pregnant gilts. Again, this type of sensitivity in par- ity 1 sows appears to be related to low feed intake of parity 1 sows during lactation. Delayed first-mating of gilts born in winter and spring increases the total number of pigs born alive. There is, however, only a small increase of at most 0.4 pigs, even when the gilt age increased from 200 to 300 days. So the benefit of increasing the gilt age is limited for increasing PBA. Also, no association was found between the ages and PBA for gilts born from summer to autumn. A typical approximately 240 days of age at first-mating has been practiced to increase body weights and more body reserves of replacement gilts to be first-mated. Additionally, PBA in parity 1 is a predictor that can help produc- ers to identify high prolific sows (super sows) at an early stage. Sows that have a high PBA in parity 1 typically produce high PBA throughout all the subsequent parities. These high prolific sows also have high lifetime reproductive performance. Gilt develop- ment is critical to have more super sows. Also, foot care for long toes or claw lesions is a good idea to keep good sows.


Pre-weaning mortality In this decade, the number of pigs born alive has increased in many countries. Genetic improvement is a driver for increasing PBA. However, increased PBA also increases preweaning mor- tality. Using herd level records, risk factors are farrowing more PBA, higher parity at farrowing, summer or winter farrowing, ages of 0-1 days of lactation and longer lactation length. Trauma and low variability account for 80% of reason records for death. Recommendations for sow management are assisted-farrowing following careful management and supplemental heaters in early lactation.


Birth weight and pre-weaning growth rate Birth weight and pre-weaning growth are not in the productivity tree. Both measurements indicate quality of piglets, and affect post weaning growth performance of piglets and subsequent reproduc- tive performance of sows. Pre-weaning growth is affected by sow milk production, whereas lighter birth weights are associated with more pigs born in the litter. Pre-weaning growth can be increased by genetics and management tools such as use of a milk replacer and two-step nursing.


Lifetime performance The PWSY is not the best measurement for sow lifetime perfor- mance. The lifetime performance of sows should be measured to maximise sow reproductive potentials and save resources. Lifetime performance contains parity at removal (i.e. longevity), lifetime PBA and lifetime NPD. The lifetime NPD includes reser- vice interval and removal intervals which account for 70% of NPD. Also, increased mortality decreases longevity and lifetime PBA, and increases death interval and lifetime NPD. As an integrated lifetime performance of sows, the research team has been using annualised lifetime PBA which is defined as the number of lifetime PBA divided by reproductive herd life days of the sow. The reproductive herd life days is defined as the period


8 PIG PROGRESS VOLUME 32, No. 6,2016


Figure 2 - Increased outside temperature reduces farrowing rate (%) – especially during parity 1.


(n = 264,057) 90 Parity 2-3 Parity 4-5


80


Parity 0 (gilts)


Parity 1 70 10 15 20 25 21-day pre-service mean daily temperature (˚C) 30


between the date of first mating and the date of removal of the sow. The annualised PBA indicates reproductive efficiency per year of the sow.


Mortality of gilts and sows Increased mortality occurrences increase non-productive days and decreased numbers of pigs born alive. Farrowing is a major risk factor for sows in all parities and seasons. Approximately 68% sow deaths occurred in a six-week peripartum period. As the parity number increases, the mortality risk for sows also increases. So, parity 6 or higher sows in the peri-partum period are at the high- est risk of dying. Increased care of maternal health in the peri-par- tum period in the farrowing barns would decrease the number of deaths of females. In subtropical climate zones, mortality in low parity sows increas- es during summer, whereas in aged sows it increases during win- ter. For example, mortality in parity 0 and 1 sows increased 0.3% in summer, as outside high temperature increased 10°C. Also, mortality in parity 6 or higher sows increased 1% in winter as low temperature decreased 10°C.


Longevity Longevity is typically measured as number of parity at removal. Lower longevity in sows increases costs for replacement gilts and subpopulations of parity 0 and 1 sows which have low immune status for diseases. Also, both high efficiency and longevity can be achieved in breeding herds. In herd measurements, a lower per- centage of re-serviced female pigs is associated with both higher PWSY and higher parity at removal. Increasing the farrowing rate and decreasing the number of re-serviced females is the way to go.


Need for close monitoring It is recommended that producers closely monitor the high risk female groups to reduce non-productive days and pre-weaning mortality, and increase the number of pigs born alive to improve herd productivity. Also, in most cases, reproductive performances are influenced by a set of sow factors, management factors, envi- ronment and nutritional factors depending on farms. In short – data analysis is important for each farm.


References are available on request.


Farrowing rate (%)


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