INTRODUCTION: THE KEY PERFORMANCE INDICATORS FOR BREEDING HERD PERFORMANCE
Pork producers are acutely aware of the importance of the breeding herd in overall profitability. Most producers invest in herd recording systems of varying descriptions that allow themselves or their consultants to summarise and diagnose problems in performance based on Key Performance Indicators. These Key Performance Indicators are breeder efficiency targets such as conception and farrowing rates, litters per sow per year and litter sizes born and weaned. These are often related to targets based on experimental or on-farm studies.
The large commercial producer also heavily relies on volume-driven targets, such as the number of matings per week, farrowing crate occupation, and weaners produced per week. These are much more farm-specific and are influenced by season, unexpected and subclinical disease outbreaks, and management issues (human and physical) in the piggery. If we are to optimise reproductive performance, then we need to consider the impact on both efficiency and volume-based targets. Over a number of years the performance of the breeding herd has come into focus due to the lack of advancement in Key Performance Indicators (KPIs). Whilst some producers are progressing ahead with breeder performance, the overall industry trends show little improvement. Figures in Table 1 are derived from the Australian survey of the same 30 farms each year as a reference study group. Herd size ranged from 185 to 4,700 sows, and the farms are located all over Australia. Even the best producers in the group have shown little improvement despite a decade of genetic selection, the introduction of artificial insemination and advances in breeder nutrition (Table 2).
Premature culling of sows due to poor reproductive performance and locomotor attributes will increase the sow replacement rate and reduce the average parity of the herd. To date, it has generally been accepted that sow productivity increases to parity 3 (3rd litter) and remains relatively constant until parity 6-8 (Jalvingh et al., 1992; Dhuyvetter, 2000; Lucia et al., 2000). However, optimal parity distribution is a complex issue affected by the productivity of sows as influenced by lactation length, feed costs and sow management. Xue et al. (1996) reported that litter size was affected differently depending on genetic lines and parities.
Studies at QAF Meats have shown that older sows in segregated early weaned (SEW) systems have a poorer farrowing rate and litter size than sows of the same parity when pigs are weaned at 25 days (BTB) (Figure 1). There are also generally more deaths in older parity sow herds (Koketsu, 2000).
Genetic selection for leanness often bears the blame for low reproductive performance. Gaughan et al. (1995) analysed sow records by correlating sow leanness and weight and lifetime performance. They found that sow lifetime productivity was not highly correlated with carcass fatness or weight at selection (21 weeks of age), however when sows were grouped into lean, medium or fat categories, sows that were lean at selection produced significantly fewer pigs over their breeding lives. In his review, Whittemore (1996) recommended that gilts be bred at a minimum live weight of 125 kg and a P2 of 13 mm. However lean genetic lines can be just as productive as fatter maternal lines if managed correctly. In a large study conducted by the National Pork Producers Council in the US, a number of maternal lines were evaluated side by side for reproductive performance (Johnson et al., 2000; Moeller, 2000). The evaluations confirmed the research by Xue et al. (1996) in that there were genetic x parity interactions for performance and
that each parity must be managed, not simply gilts and sows. In Australia, Tholen et al. (1996) reported that longevity was unfavourably correlated with backfat, though there were genetic differences between the two herds studied. Their results also suggested that not all herds that maximise first litter size will have a longer breeding life. There were strong negative correlations in one herd between the litter size born alive in the first litter and ‘stayability’ between parities 1 and 4.
SOW WASTAGE IN COMMERCIAL HERDS
Worldwide interest has re-focused on setting the gilt and sow on the right course for lifetime productivity. The slow rate of reproductive improvement, and in some cases the continued decline in Key Performance Indicators, tells us that commercially we need to change the way the gilt and sow are currently managed. The first step in dealing with a decline in productivity is to make sure that all the recommendations from research studies are implemented, or at least tested on-farm. As simple as this may sound, many aspects of gilt stimulation, feeding and mating management are overlooked in the interests of time, capital and labour constraints in the commercial environment. A Quality Assurance approach to reproduction has been adopted by some farms, including our own, which has resulted in at least an awareness of what strategies have been implemented, if not in improvements in Key Performance Indicators. Industry information packages and training sessions such as the Alltech Pig Program have been of great assistance in reinforcing management techniques.
Many questions, however, remain unanswered. There is often a lack of response under commercial production to ‘tried and true’ recommendations. There may be a difference in the responsiveness of the breeder herd to nutrition and breeding practices in the modern lean genotype used in commercial units today, as much of the research was conducted on old genotypes. On commercial breeding units we are generally seeing:
1. An increase in both reproductive and structural problems resulting in high culling rates (mainly in early parities);
2. A parity-related reduction in sow performance that is occurring much earlier (parity 4-5) than has been traditionally assumed (see Figure 1).
A stable commercial unit at QAF Meats in Corowa, NSW, Australia was surveyed over a 12 month period. All sows were stalled throughout gestation and pigs were weaned between 22 and 26 days of age. The results supported those of other studies in that the major cause of sow turnover was due to reproductive failure or low reproductive performance (Table 3). Reproductive failure was mostly a result of post-weaning anoestrus (26%) and a failure to conceive (20%). There was also a high percentage of sows that became pregnant but then failed to farrow (36%). This was due to either abortion, irregular returns, culling for infectious discharge and not-in-pig due to other reasons. The number of sow culls/destructions due to leg weakness was 12% of all culls (including cull for age) and was not dissimilar to numbers reported in other studies (Dijkhuizen et al., 1989; Hughes and Smits, 2002). Sows that left the herd were significantly lighter and leaner than the sow population remaining in the herd (Table 4). For those sows culled or destroyed for locomotor difficulties, there was a large difference in live weight and P2 compared to the general herd (Table 5).
The data from our study showed that live weight was more related to litter size than fatness within any weight category (Table 6). In an earlier study at QAF Meats, we showed that litter size tended to increase in the first and second litters following a high level of feeding during the gilt’s first gestation (Table 7). Either the rate of protein deposition prior to puberty (Edwards, 1998) or the amount of protein and fat reserves as a total live weight mass (Hughes and Smits, unpublished) may be more important targets for nutritional management in the future. The commercial study we conducted at QAF also highlighted that we are far from the ‘ideal recommendations’ of target live weight and P2 in the breeding herd population at the commencement of each reproductive cycle. The need to correctly manage the gilt from a young age as a breeder and then adjust nutritional management as the sow becomes older is a challenge commercial producers must meet if we are to increase sow productivity.
NUTRITIONAL MANAGEMENT FOR MODERN GENOTYPES
There is no doubt that changes in the genetic basis of the breeding herd has made us re-think how we manage the modern genotype for reproductive productivity. Macronutrition in terms of dietary energy and protein has been well researched in the past, though nutrient requirements for leaner genotypes are now being re-examined. In a study at QAF Meats, we found that increasing the protein concentration of the gestation diet fed to mated gilts had no effect on first litter size or subsequent litter size (Table 8). Conversely, Cia et al. (1998) restricted protein accretion in an effort to produce fat gilts at puberty with negative effects on fertility (Table 9).
Nutrition has a large impact on reproductive performance and sow longevity. Since the late 1980s investigations into the requirements for energy, protein, amino acid, mineral and vitamin requirements for the modern lean genotypes have been comprehensively reviewed (SCA, 1987; Verstagen et al., 1987; NRC, 1988; Mahan, 1990; AFRC, 1990; Close and Cole, 2000). The importance of minerals, fatty acids and vitamins is being highlighted as an integral part of the breeder herd management as well as the more traditional focus on energy and protein. In the past, diets have been formulated with vitamin and mineral levels on the basis of preventing acute deficiency symptoms and yet many of these micronutrients are essential for reproductive metabolism and optimum fertility (Figure 2).
The mineral requirements for sows of modern genotypes have attracted more attention in recent years. Existing mineral requirements of sows based on the recommendations for deficiency symptoms (eg. NRC, 1988) were highlighted as a major concern by Mahan and Newton (1995). These authors investigated the mineral status of sows after three parities compared to sows of a similar age that had not reproduced. There was a substantial reduction in the mineral content of sows that were high producers (>60 kg litter weights) compared to the unbred (non-reproducing) sows of similar age (Table 10) when fed the same diets. The demand for minerals by reproducing sows is high and often results in de-mineralisation of their bones and tissues (Fehse and Close, 2000).
The availability of some microminerals has also been identified as a problem if formulated in diets at marginal levels. Organic sources of trace elements have been developed that bind the element with an organic ligand such as an amino acid or peptide. Alltech refers to these organic complexes as ‘Bio- Plex™’, and include copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn). Selenium can also be provided in organic form. Sel-Plex™ is derived from yeast, which produce selenomethionine. Chromium can also exist in organic forms such as chromium picolinate and chromium nicotinate. Bio- Chrome™ is an organic form of chromium derived from yeast, which forms the ‘glucose tolerance factor’.
The use of organic forms of minerals was studied in a high-productivity sow herd (Fehse and Close, 2000). The addition of Zn, Mn, Fe, Cu, Cr and Se with yucca extract (De-Odorase™) to the standard diet increased most elements by 20-30%. The trial was conducted over 2 years such that all sows on the organic supplement (‘Sow Pak’) had elevated supplementation levels over a number of litters.
There was trend toward improved reproductive performance when the organic supplement was used (Table 11). The authors also noted that there were proportionately more sows in the total herd still being fed the Sow Pak after parity 4 compared to the controls (57% vs 20%).
In a study conducted at QAF Meats, we evaluated addition of 200 ppb of organic chromium
(Cr) (chromium picolinate) to breeder diets fed in both gestation and lactation. Chromium has a role in regulating the insulin response in sows and consequently its effect on follicular growth and development and ovulation, and embryo survival due to increased progesterone (Tilton, 2000). We recorded a trend toward improved farrowing rate and a better litter size (Table 12).
CONSEQUENCES OF CHANGES TO THE NUTRITIONAL PROGRAM
Given concerns about environmental quality and sustainable agriculture, it is important to consider the impact of diet formulation on nutrient output. Increasing the protein levels and concentrations of phosphorus (P) and other minerals in diets is not only an increased feed cost but could result in an unwanted increase in nutrient loading to the environment. Diets are now routinely formulated on the basis of available amino acids and available phosphorus at QAF Meats. We have demonstrated in grower pigs that we can reduce excretion of nitrogen (N) and P by using recommended amino acid and P levels designed for our genotype when formulating to animal requirements as a phasefeeding strategy (Table 13).
Although the breeder diets represent only 20% of all feed costs, it is necessary to feed sows to nutrient requirements so that there is maximum nutrient retention and minimal excretion. Mineral requirements for the sow are generally less than those for growing pigs (with the exception of iodine) on a dietary concentration basis (Close and Cole, 2000). Nevertheless, all aspects of the nutritional program have an environmental impact. Advances in the knowledge and application of phytase and bioavailable minerals are being evaluated from a nutrient load viewpoint in grower pigs (Smits and Henman, 2000; Carlson, 2001; Wu et al., 2001). So far there have been no reports on the impact of using more bioavailable trace minerals or phytase on nutrient excretion in breeders. Improving the retention rates of minerals and the use of phytase in breeder diets will soon become important areas of research to demonstrate industry commitment to the environment.
In addition to environmental sustainability, definitions of sow welfare are changing. Sow
welfare guidelines differ around the world, however the one thing that is the same is the attention of welfare activists on the use of sow stalls. In Australia, Canada and the US there is no legislative requirement to loose-house sows, and many producers house sows in stalls either throughout gestation or for a period of time (4-6 weeks). In Australia, the industry Code of Practice designates a minimum stall length and width (2.0 m x 0.6 m clear space). In some states in Australia this recommendation is now mandatory. Since reproductive performance and live weight (see Table 6) even in older sows is correlated, when we change feeding strategies, sows become much larger and stall sizes become more of an issue. It is proposed that reproductive potential is now achieved at a heavier live weight because the mature body size of the sow has increased with genetic selection for leanness (Edwards, 1998). This could be an advantage in a nutritional policy that adds more weight to sows in that the income received from cull sales will be increased if sold on a carcass weight basis. It is important that we remain aware of the interactions between nutrition, feeding management and commercial management issues such as how we house breeders.
NATURAL ADDITIVES FOR IMPROVED PERFORMANCE
Alternatives to antibiotics in animal feeds are increasingly demanded by both the consumer and the feed industry. The use of the mannan oligosaccharide product, Bio-Mos™, to improve the growth performance of weaner and grower pigs was reviewed by Pettigrew (2000). Bio-Mos™utilises the mannan oligosaccharide fraction of the cell wall of yeast. Its mode of action involves both prevention of pathogen colonization in the intestine and enhanced immune response. Effects of Bio- Mos™ on sow reproductive performance were reported by Funderburke in 2001. When added to the gestation (2 kg/tonne) and lactation diets (1 kg/ tonne) in a mixed parity herd weaning at 21 days, an increase in birth weight, a decrease in preweaning mortality, increased pre-weaning growth
rate and a quicker return to oestrus were noted (Table 14). The study also showed a significant increase in the immunoglobulin levels in the colostrum.
HIGH SOW TURNOVER – BREAKING DOWN OR SLOWING DOWN?
We found that about 12% of all sow removals were due to physical locomotor problems in our herd survey over 12 months on a 5,400-sow unit. By far the most common cause of removal was for reproductive failure or low productivity. This result was similar to those from other studies. The notion that high sow turnover in commercial units is due to sows having more locomotor problems because of leanness is not well supported by these studies. Current studies at our facility and in other locations are looking at ways to increase sow longevity by increasing calcium and phosphorus levels and supplying organic minerals. It is hoped that these studies will provide more information as to sow mineral status during her lifetime, but more importantly, ameliorate low reproductive performance.
In order to maintain our minimal disease status, QAF have largely converted production units to breeder units that early wean and segregate progeny. These progeny are then grown out in segregated all-in-allout deep litter ecosheds (hoops). This production system is favoured by our export customers in Japan and has allowed medication to be removed from the feed. However, there has been a reduction in the average litter size born in these early-weaned units that has not been compensated by more litters per sow per year. The impact of changes in nutrition on numbers of pigs weaned per sow per year is more heavily weighted toward Key Performance Indicators for litter size and pre-weaning mortality than any reduction in culls, deaths or destructions due to locomotor problems (Table 15).
CONCLUSIONS
Improvements in the reproductive performance of commercial herds will rely on how well we manage the modern genotype. Improved genetic lines to produce leaner progeny are not the downfall of breeder productivity. The use of mating technologies such as artificial insemination, embryo transfer and genetic markers to target fecundity genes should provide plenty of opportunities for substantial advances in productivity. However, we must recognise that these gilts and sows have different nutrient requirements than their forebears in the 1980s and probably even the early 1990s. There have been advances made in the nutrition of the sow in recent years. There is a growing acceptance that the gilt as well as sows of different parities need to be managed differently. Live weight and probably protein mass are likely to be more important for optimal reproductive performance than simply making the gilt or sow fatter. Most of the high sow turnover in a commercial unit is due to reproductive failure and low fecundity rather than skeletal failure and breakdown. The attention to mineral nutrition and improvements in bioavailable trace elements will provide a better foundation on which to build sow longevity, as well as reduce impact of the breeder herd on the environment.
Finally, the alternative to in-feed medication by the use of Bio-Mos™ should be encouraged as breeder herd health is a substantial limitation to consistently breaking through the 25 pigs weaned/sow/year Key Performance Indicator.
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