INTRODUCTION

Failure to properly develop and follow feed budgets can easily increase the cost of production by $1 per pig or more, if excessive quantities of Phase 1 or 2 diets are fed; alternatively, poor performance resulting from feeding insufficient amounts of the early diets can reduce nursery exit weights, which in turn lowers market weights.

Failure to manage the nursery properly may cause any number of problems, including increased mortality, lower nursery exit weights, increased labour to manage “pulls” and increased medication to handle individual and group health problems. Perhaps the most critical is the reduction in exit weights. Everyone knows that small pigs eat less feed and grow slower; therefore, improved nursery management, resulting in higher exit weights, will improve growout performance as well. We have found that for every 1 kg increase in nursery exit weights, market weights will increase by 2 kg. The exact ratio between exit weights and market weights will vary among farms. The only circumstances in which increased nursery exit weights will not increase growout weights exist when extraordinary actions are taken to improve nursery performance, such that the increased growth is not sustainable by the pig.

The following topics represents issues covered in research at the Prairie Swine Centre over the past few years. While certainly not exhaustive, we hope these topics represent issues of interest as producers seek to operate their nurseries to achieve peak performance and animal well-being.

HOUSING MANAGEMENT

Thermal Environment
Recent studies on temperature preference by newly weaned piglets suggest that current recommendations are higher than required. The experiment involved pigs weaned at 12 to 14 days of age and weighing an average of 3.5 kg; average daily gain during the experiment was 325 g/d. Given the opportunity to choose their own temperature settings through the use of pressure switches, 17-day old piglets selected an average daily temperature of 26.3ºC, 24-day old piglets selected 25.7ºC and 29-day old piglets selected 25.2ºC. These temperatures are somewhat lower than typically recommended, especially for the youngest age group (Figure 1).

It should be noted that the temperature selected by different groups of pigs ranged from a low of 22.9ºC to a high of 29.8ºC. It should also be noted that the rooms in which this work was conducted were ventilated in a manner typical of that used in the commercial industry: preheated hallway (9ºC), recirculation ducts and unit heaters within the nursery room.

These results were supported by quite different experiments by Harmon et al. (1997a,b) who measured performance and heat production in pigs housed in environmental chambers. For pigs weaned between 13 and 16 days of age, weighing an average of 4.4 kg and on test for 3 weeks, growing at 370 g/d and consuming about 500 g/d, their data supports initial nursery temperatures between 27ºC and 29ºC. They reduced the nursery temperature by 1.1ºC per 14 days.

Many factors would increase the thermal requirement of the newly-weaned pig, such as drafts or damp conditions. The temperature would have to be elevated when feed intake is very low, such as the first few days after weaning. However, excessively warm temperatures will reduce feed intake. It would appear that, with all other factors being equal, current recommendations (Dee, 1999) tend to keep our nurseries slightly warmer than necessary, resulting in lowered feed intakes and poorer growth.

Finally, in the Prairie Swine Centre study, it is interesting to note that the piglets preferred cooler temperatures at night. Between 10:00 pm and 6:00 am, the piglets selected temperatures that were about 3ºC to 4ºC lower than during the daytime (Figure 2).

Floor Space Allowance
According to the Code of Practice for Swine, the recommended floor space allowance for pigs is 0.035m2/kg BW0.667 (to convert m2/pig to ft2/pig, multiple by 10.76); this represents 2.8 ft2 for 20 kg pigs and 3.6 ft2 for 30 kg pigs. We conducted an experiment investigating three floor space allowances/group sizes – 2.5, 3.0 and 3.5 ft2/pig – against 5 feeder adjustments (see results of feeder adjustment component below). The three floor space allowances were achieved by increasing the number of pigs/pen from 16 to 20 to 24. Feeder access was kept constant by blocking part of the feeder when there were fewer than 24 pigs in the pen; this provided a constant 4 pigs/feeder space in all treatments.

There was a linear response to reducing group size/density, such that 3.0 ft2/pig increased nursery exit weight by 4.9% (1.4 kg) and 2.5 ft2/pig provided a further small (1%; 0.6 kg) improvement. There also tended to be a slight increase in uniformity as group size/density declined (Table 1).

Assuming nursery housing floor space costs $40/ft2, providing 3.0 ft2/pig instead of 2.5ft2/pig would increase housing capital costs by $20 per pig capacity; amortized over 15 years, assuming 6.5 turns/year and seeking 15% return on capital costs, the increased housing cost per pig would be $0.67. Further assuming the 1.4 kg increase in nursery exit weight translates into 2.8 kg additional market weight, in a $1.50/kg pig market, the additional weight would increase income over feed cost by $1.70 per pig. The advantage of additional floor space in the nursery is clear.

Completing the same analysis for increasing nursery floor space from 3.0 to 3.5 ft2/pig, housing costs increase by another $0.67/pig. Net income over feed increases by $0.37/pig; this would not be sufficient to cover the additional housing cost. Obviously, many assumptions went into these calculations; individual situations may differ. Nonetheless, one should be able to conclude that floor space allowance in the nursery deserves attention, due to its impact both in the nursery and later in the production cycle.

On- Versus Off-Site
Research over the past 5 years has demonstrated a growth advantage when piglets are weaned to an off-site nursery (Figure 3), when compared to a conventional on-site nursery (Patience et al., 2000). We have studied weaning from 12 to 21 days of age and the impact tended to be greatest with younger weaning ages. Indeed, with 21 day weaning, the benefit of off-site weaning was observed only in the lightest piglets (Figures 4 and 5).

Since the experiment protocols always required that great care being directed at removing any confounding effects due to stockperson, nutrition, genetics or housing, the only uncontrolled variable was “site”; this in turn was assumed to most likely reflect background pathogen loads. Consequently, the research suggests that even when single-site production is employed, cleanliness is even more important than previously assumed. The control “on-site” nursery was power washed and disinfected between groups, and all-in-all-out housing by room was employed. The herd of origin of the piglets had a reasonably high health status as well. Given the benefit observed with moving pigs to an off-site nursery, we can reasonably conclude that any efforts to minimize pathogen load in a single-site production system would also be beneficial.

FEEDING AND NUTRITION

Nutrition: Amino Acids
There have been literally dozens of experiments conducted to define the lysine requirement of the weanling pig. Interestingly, the results of these experiments have been widely divergent. There are great difficulties in defining the amino acid requirement for a given herd under a given set of conditions, the most significant of which is expected growth rates and daily feed intake. One way to address this issue is to determine amino acid requirements in a factorial manner, that is to define the amino acids required for daily body maintenance plus that required for growth. For example, based on recent research (Williams et al., 1997, Oresanya et el, unpublished results), one can estimate the lysine requirement of young weanling pigs to be 36 mg/kg BW0.75 for maintenance plus an allowance for protein gain in the body.

Few studies measure actual protein deposition in the young pig. Based on the literature, a reasonable average of 15.5 to 16.0% protein in the whole body can be used to estimate protein deposition. Furthermore, one can estimate the total (as opposed to digestible) lysine required per unit of protein deposited to be in the range of 0.14 mg/g (Beltranena and Patience, 1997). In other words, for every gram of protein deposited per day, the piglet must consume 0.14 mg of total lysine daily. The maintenance requirement adds another 0.3 g/d.

Therefore, one can estimate that for weanling pigs gaining 500 g/d, the daily lysine requirement will be about 11.2 g/d. Assuming typical feed intakes of 800 g/d, this would correspond to 1.4% total lysine in the diet. In general terms, at least, this approach is supported by research from various institutions conducted under diverse conditions (Beltranena and Patience, 1997; NRC, 1998; Williams et al., 1997). This approach has the advantage of tailoring diet nutrient composition to a given set of performance circumstances.

Other amino acids can be formulated as a ratio to lysine using the concept of ideal protein ratios. This has been commonly practiced by the industry for the past decade, and although it has some drawbacks, it is convenient and sufficiently precise, given our current level of knowledge.

Nutrition: Energy
Selecting appropriate energy concentrations for starter diets has received considerably less attention than other nutrients. As a consequence, much less is know about the response of the young pig to increasing increments of energy concentration; this is surprising, not only because energy is the most expensive nutrient in the diet, but also because it is generally accepted that energy intake drives growth.

Recent research has shown that previous assumptions about energy concentration may be incorrect. Although it is generally assumed that gut capacity is limiting performance in the young pig and that increasing energy concentration will increase performance, we have not found this to be true experimentally. Two experiments have failed to demonstrate increase rate of gain when energy density of the diet is increased; feed efficiency tended to follow energy concentration, but growth rate did not (Table 2). Further research is underway to determine why no growth response was observed. One possibility is that factors others than energy are placing a limit on growth (health, genetics, other nutrients or even the source of energy employed). Another possibility is that the stressors commonly observed in commercial conditions were not present for the pigs on these studies, and thus the response to energy concentration was somehow masked. Further research is planned in this important area.

Feeder Management
There are widely divergent recommendations with respect to feeder management in the nursery. Some suggest keeping the feeder trough full of feed, in order to maximize intake, while others recommend a tighter adjustment, to avoid wasting expensive feed. To apply some science to the recommendation, we recently completed a study of various adjustments and determined that a minimum of 40% of the floor of the feeder should be covered with feed, to maximize feed intake and nursery exit weights. Less coverage resulted in poorer growth and slower eating, while greater trough coverage provided no benefit in terms of performance, but increased the risk of wastage (Table 1).

Feed Budgets
Feed budgets are not a new concept, having been around for many years. Nonetheless, the importance of feed budgets is often underestimated and many farms operate either without them, or do not track them on a regular basis. Recently, a summary of commercial nursery closeout data revealed to us the importance of tracking feed budgets. For a period of 12 weeks of close outs, insufficient Phase 1 starter was being fed; instead of feeding 2 kg/pig as prescribed, only 0.4 kg was fed. Feeding the proper amount of Phase 1 starter, and increasing Phase 2 intake slightly as well, increased nursery exit weights from an average of 30.5 kg to an average of 34.2 kg (Table 3). This would increase return over feed cost for this (600 sow farrow-to-finish) farm by about $25,000 per year!

Piglet Management
While environmental management and proper nutrition are critical to success in the nursery, I suspect everyone here today would agree that piglet management is the most important of all. Following is an abbreviated list of key management practices to achieve success in piglet management.

1. The room, including all equipment, must be thoroughly cleaned and disinfected. This includes fans and blades, air inlets and recirculation ducts, feeders, penning and, as much as possible, slats. Any attention paid to proper cleaning is likely to pay significant dividends in piglet performance and health after placement.
   
   

2. Prior to arrival, the room air and all equipment in the room should be warmed to receiving temperature. The recommended receiving temperature will depend on piglet size and initial feed intake, but an average of 28ºC is a reasonable starting point. Piglet behaviour will reveal if the temperature is too high or too low. The temperature can be dropped by 0.5ºC per day, until 26ºC is reached, at which time the temperature should drop 1 to 2ºC per week. Because individual pig preference appears to be quite wide, defining an absolute temperature regime for all fills – though convenient and practical - is risky.
   
   

3. Adjust feeder gate so that about 40% of the feed tray is covered with feed. Anything less than this will impair pig performance, and greater coverage provides no benefit but increases the risk of wastage. Check all drinkers to ensure they are functioning correctly. If nipple drinkers are used, they should be adjusted so they are at shoulder height of the smallest pig in the pen.
   
   

4. Pigs should be placed in pens according to bodyweight; this is not to improve uniformity of growth (because it will not!), but because it facilitates more effective feeding and water management. In other words, the pens of smaller piglets will probably require more attention than the pens of larger pigs. Additional waterers are recommended for the smaller pens, to ensure dehydration does not occur.
   
   

5. Feed mats or trays are often used in conjunction with early weaning. However, only very small amounts of feed should be placed on the trays, and feed should always be readily available in the feeder (Figure 6). Otherwise, the pigs depend on the feed trays and because feed wastage on trays is so high, total feed intake may suffer (Dritz et al., 1999).
   
   

6. By about 36 hours postweaning, piglets not eating or drinking can generally be easily identified. The management of such pigs will depend on individual units, but hand feeding, offering a gruel or other personal attention will reduce mortality and “pulls.” If weaning has occurred on Thursday, unfortunately this critical time will fall on Friday night or Saturday morning, a time when labour could be in short supply. Nonetheless, this is the time when potential non-viables can be turned into healthy productive animals.

Implications
Nursery feeding and management remain more “art than science” than any other phase of production. Development of standard protocols that apply to all pigs must always recognize the unique needs of different sub-groups within the total weekly weaning. Nonetheless, as more research on critical topics such as the thermal environment, housing and feed management and nutrition, advances can be made. Clearly, improvements achieved in nursery management will pay big dividends in terms of overall performance, including that in growout.

References

Beltranena, E. and J.F. Patience. 1997. Defining the response of early-weaned piglets to dietary lysine:energy ratios. 1997 Annual Research Report, Prairie Swine Centre Inc., Saskatoon, SK. pp. 22-25.

Dee, S. 1999. Nursery pig nutrition and environmental management. Food Animal Comp. 21(3):S92-S96. Dritz, S.S., M.D. Tokach, R.D. Goodband and J.L. Nelssen. 1999. Feeding management of nursery pigs. Large Anim. Pract., Nov/Dec. pp. 28-31.

Harmon, J.D., H. Xin and J. shao. 1997a. Thermal needs of the early weaned pig. Livestock Environmen 5. Proc. 5th Int’l Symp. pp. 482-488.

Harmon, J.D., H. Xin and J. shao. 1997b. Energetics of segregated early weaned pigs. Trans. A.S.A.E. 40:1693-1698.

Levesque, C., J.F. Patience, E. Beltranena and R.T. Zijlstra. 2001. Effect of site of weaning and diet digestible energy content on weanling pig performance. Proc. Amer. Soc. Anim. Sci. Midwest Section, Des Moines, IA. p. 55

NRC. 1998. Nutrient Requirements of Swine (10th Ed.). National Academy of Sciences, Washington, DC.

Patience, J.F., H.W. Gonyou, D.L. Whittington, E. Beltranena, C.S. Rhodes and A. Van Kessel. 2000. Evaluation of site and age of weaning on piglet growth performance. J. Anim. Sci. 78:1726-1731.

Smith, L., J.F. Patience, H.W. Gonyou, A.D. Beaulieu and R.D. Boyd. 2001. Impact of nursery feeder adjustment and group size/density on the performance of pigs from 4 to 10 weeks of age. Monograph No. 01-01. Prairie Swine Centre Inc., Saskatoon, Canada. 25 pp.

Williams, N.H., T.S. Stahly and D.R Zimmerman. 1997. Effect of chronic immune system activation on the rate, efficiency and composition of growth and lysine needs of pigs fed from 6 to 27 kg. J. Anim. Sci. 75:2463-2471.

Source - Prairie Swine Centre - March 2004