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Life beyond 40 piglets - The “Peter Pan” Factor Dr. Brian Hardy Lost Potential Many farms have a wish to achieve a target of 30 pigs per sow per year. This requires 12 pigs weaned per litter and 2.5 litters per sow per year. However, many farms struggle to do this and most only produce a total of 40 pigs per sow lifetime (10 weaned pigs over 4 litters). An increase in the longevity of the sow and achievement of a greater output of weaned pigs per lifetime is fundamental to increasing sow herd profitability. Spreading the cost of a replacement gilt ($200) over more weaned pigs (one extra litter of 10 pigs) could reduce the overhead cost on each weaned pig by $1.00 per pig. In theory, sows should be capable of producing 60-70 weaned piglets in their lifetime assuming at least 10-12 pigs weaned per litter and production of 5-7 litters. In practice, this is rarely achieved as the sow is removed from the herd after 3-5 litters for one reason or another. We need to look for the “Peter Pan” factor and expect a reproductive life beyond the 4th parity. Decision Making There is a difference between the culling rate and the replacement rate in a herd. The culling rate is normally biologically driven and the typical reasons for sow removal include reproductive failure (30 %), poor performance (9%), feet and leg problems (12%), age (16%) or other ailments (33%). (Adapted from Pig News and Information, June 2004). The average culling rate in the USA is 41.2% and this can range from 21.6% for the top 10% herds to 60.7% for the bottom 10% herds. (Pig Champ, 2003). The replacement rate on the other hand, is normally based on other management decision factors, where the farm manager, often under guidance from his veterinary adviser, will decide to replace all sows after their 4th parity, irrespective of the performance of the individual sow. This policy will normally have been decided based on average performance figures for the herd that may show for instance, a reduction in litter size after 4th parity, an increase in the number of stillborn pigs and problems with the wean to re-breeding interval starting to increase. There may also be an increase in sow mortality and morbidity due to enteric problems, e.g. gastric ulcers or other health issues due to poorer immunity. In the USA, the average replacement rate is 59.5% and the range is 31.1% for the top 10% herds to 89.1% for the bottom 10% herds. (Pig Champ, 2003). In reality, since the only reason to keep the sow is for the ultimate production of pork, the better measure of sow herd efficiency is the total weight of pork produced per sow lifetime and instead of simply counting pigs, we should look at the economic output in terms of total mass (numbers x weight x value). There is normally an incentive to produce a heavier weaned pig as well as more pigs per litter. If the value for a 5 kg weaned pig was $30 and each additional 1 kg was worth an extra $2, then to sell 10 pigs at 5 kg (50 kg) would be worth $300 but to sell 12 pigs at 6 kg (72 kg) would be worth $384, an additional 28% in revenue. The sow has to be able to provide an adequate level of nutrients to meet the needs of the additional 22 kg of piglet mass-produced. If dietary nutrient intake is insufficient then she will use her own body reserves. It is important to understand the reasons for the change in reproductive performance after 4th parity and to look for management and nutritional solutions to correct this lost opportunity for additional profits. Micro nutrition of the sow Most pig production systems around the world now utilize genetically improved, highly prolific breeding stock. These sows tend to have a high lean and low fat body composition, which is often associated with the sow having a low appetite, particularly in lactation. The prolific sow has the ability to produce as much milk expressed on a per unit body weight basis as a high yielding dairy cow, albeit over a shorter period of time. It is the critical balance of dietary nutrient input in relation to the output of nutrients in the production of piglets and milk that will dictate if the sow is in a positive or negative balance for any key nutrient. The sow will mobilize body tissue to make up for any deficit up to a point and thereafter performance will suffer due to an inadequacy of specific nutrients. Loss of body condition in lactation to meet energy, protein and major mineral demands is fairly well recognized and understood, but what is often forgotten is the requirement for trace minerals and vitamins that function within the enzyme and hormonal systems and can have a direct bearing on overall reproductive performance. The relative loss of minerals by the 3rd parity relative to a non-reproductive female of the same age is shown in Figure 1 together with the result of different levels of output in terms of pig litter weaning weight (Mahan and Newton, 1995).
Feed intake in gestation is not very different across parities, the normal range being 1.8-2.25 kg per day, and yet the mature sow can be about 60% heavier than the replacement gilt (210 kg and 130 kg respectively). The type and amount of sow vitamin-trace mineral (VTM) premix included in sow feeds is normally the same for all reproducing animals in the breeding herd. The amount of VTM intake per unit of body weight can therefore diminish by 40% from 1st to 5th parity (Figure 2) and there is less VTM available for development of each litter and for production of milk with successive parities. This level may be below some biological threshold.
After Boyd, D.R. (2004) The cumulative effect of a greater level of nutrient output relative to nutrient input becomes obvious by the end of the 3rd parity. An insufficient supply of these key micro-nutrients can then have an adverse effect on the reproductive parameters, such as, wean to breed interval, ovulation rate and litter size, conception rate and number of repeat breeding sows, farrowing rate, milk yield and weaning weight. This increases the likelihood for the sow to be culled due to poor performance. It seems highly probable that this may account for why sows do not appear to perform very well after 3rd-4th parity. Some trial work from The Hanor Company (Dr. Dean Boyd, Prince AgriProducts Nutritional conference, 2004) has demonstrated that when sows are fed a constant amount of vitamins and trace minerals relative to body weight, performance can be enhanced and sows have larger litter sizes well beyond the 4th parity (Fig. 3). Sources of Trace Minerals In the case of inorganic trace minerals, the amount retained in the body is inversely related to the amount added to the diet. This is the same as the “law of diminishing returns”; the more that is added the lesser proportion that is retained for productive purposes. If the objective is to increase the retention of trace minerals per unit of body weight, then trace minerals in a more bioavailable form should be considered. Some trace minerals in organic forms have been proven to have bioavailability values that can be 20-40% higher than the respective inorganic sulphate forms. However, not all sources of organic trace minerals are of equal bioavailability. (Cao et al., 2000 and Cao et al., 2002). If the older sow responds to an extra 40% inorganic trace mineral and gave a significant improvement to number of pigs born and weaned in the Hanor Company trial, then a lower addition of organic trace minerals should have a similar or better effect. The PIC USA Nutrient Specifications (2002) give the following values for trace minerals in gestation and lactation and an additional 40% of inorganic trace minerals are shown in brackets; Zinc 125 ppm (175), iron 100 ppm (140), manganese 35 ppm (49) and copper 15 ppm (21). If organic trace minerals that had a 40% better biological availability were used instead of inorganic minerals to meet this need, then the additional amounts would be zinc 35 ppm, iron 28 ppm, manganese10 ppm and copper 4 ppm. Data presented in a previous Pig International article (February 2003) - “ A window of opportunity” described the benefits to sow performance by using additions of organic trace minerals. All trace minerals should be considered when reviewing the need of the older sow, including chromium and selenium. Both are available in organic forms. The legislation controlling the levels of inclusion in feed varies from country to country and can be different according to the individual product licence. It has been shown that chromium can increase pigs born by up to 2.0 pigs per litter. Research data indicates that up to 600 ppb chromium is most beneficial for maximal retention and response. Whilst the highest permitted dose should be fed, consideration should still be given to the level of active or bioavailable chromium and not simply the total amount added. Organic selenium in the form of selenium yeast also has higher bioavailable selenium content than sodium selenite. Fed at the permitted maximum of 0.3ppm it will appear to give a response similar to 0.5 ppm of selenium fed in the inorganic selenite form.It would appear that to maximize sow longevity and lifetime productivity and in turn reduce the sow replacement rate, higher levels of trace minerals will be required in the later parities and that this need will best be provided for by the use of organic trace minerals as partial replacements for inorganic trace minerals.
After Boyd, D.R (2004)
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