By Dr Pieter Grimbeek, a veterinarian and pig consultant

Newly weaned pigs arriving at weaner pens are the highest – health-risk animals in a production unit.  This makes their initial management and care vitally important. Changes to grower pens and breeder facilities have undergone major renovations in the past ten years, but they pale in comparison to those made to weaner buildings.The industry has rediscovered flat decking both single and multi tiered, plastic flooring, small and big group housing, zone heating, room heating, all in all out systems, environment controlled rooms and interesting feeders.

The drivers behind all this has been the reduction in the weaning age from 35 – 42 days in 1982 to less than 20 days in 2003.  There are vast differences in the basic needs of these two animals.

Producers have successfully managed to compartamentalise their units both by production and financial parameters.  Breeder, weaner and grower facilities and systems are marginilised and measured in their own right.  Standard operating procedures for each section is set, written and enforced.

Newly weaned pigs arriving at weaner pens are the highest – health – risk animals in a production unit.  This makes their initial management and care vitally important.  This paper will attempt to summarise steps to take in the successful transition of vulnerable weaners at 21 – 28 days of age to healthy juveniles of 33 – 35kg at 70 days of age.

Management

•  Before arrival:

Managing weaner pigs begins before their arrival.  The room and all equipment must be properly washed and disinfected.  Ventilation controls should be checked for functionality and properly set, allowing time for the rooms to become warm and dry before the piglets arrive.  Feeders and supplemental heat must be in place and functioning, and waterers should be checked and adjusted to the proper height.  Weaner pigs should have one watering space for each 10 to15 pigs; if using nipple drinkers, the delivery capacity should be 2 or more cups of water per minute.

Feed should be placed in feeders just before piglet arrival, and feeder adjustment should be checked so that approximately 25 to 50 percent of the feeding pan is visible.  After the pigs become more accustomed to the location of the feed and their feeding behaviour adjusts, the amount of feed in the pan should be rapidly decreased to approximately 25 percent coverage.

•  Upon arrival:

Piglets weaned between 21 and 28 days of age generally range in weight from 6 to 9kg.  At arrival, pigs should be sorted according to size and body condition.  Grouping by weight allows to more closely match the pigs’ weight to the diet provided.  This is important because of the expense of these initial diets and the range in the digestive capability of the pigs.

•  First 36 hours after placement:

During the first 36 hours after weaning, pigs need to find the water and feed.  During this period, double-check the water height adjustment to ensure proper access.  Waterer height should be adjusted to approximately shoulder height of the smallest pigs in the pen.  Assure that feed is always available in the feeder, and if comfort mats are used, place small amounts of feed on the mats to encourage feeding behaviour.  Pigs should NOT be limit-fed after arrival.  Feed can be provided several times per day, but fresh feed should always be available.  Pigs should be observed to ensure they have found the water and are beginning to develop feeding behaviour.

•  36 to 60 Hours after placement:

Most pigs will have found the water and will have begun to find the feeders and eat by 36 hours after placement.  However, this is a critical period for identifying pigs that may require extra attention.

Two to 4 percent of pigs will be candidates for individual attention, and identifying them is always the most difficult part of the process.

To identify at-risk pigs while taking a walk-through of the weaner pool, look for:

• mental status — alert versus excited/depressed
• body condition — fat or normal vs thin
• abdominal shape — bloated or gaunt
• skin — sleek versus fuzzy
• appetite — feeding at the feeder versus huddled
• evidence of urination and/or defecation
• signs of dehydration — sunken eyes

Abdominal shape is an especially useful indicator.  Pigs that are eating well will begin to have round abdomens, whereas pigs that have not begun to eat will be gaunt.  The abdomen can be palpatated for evidence of food intake.  Suspected dehydration can be evaluated further by palpatating mucous membranes of the mouth or the tip of the nose.  One other test of dehydration is to pinch a fold of skin just behind the front limb.  If the fold remains elevated for more than a few seconds, it is a sign of dehydration.

When at-risk pigs have been identified, wet a small handful of pellets with water and gently place the softened pellets in each pig’s mouth.  If a large number of pigs require attention, moisten a small bucket of pellets and gently feed individual pigs.  A gruel mixture and a 10ml syringe with the end cut off can be used as a dosing tool.  The moist pellets or gruel sticks to the pig’s tongue, causing a swallowing reflex.  The pig should be carefully placed near the feeder so it associates the food in its mouth with the feed in the feeder.

Small pigs with low body-fat reserves must have a ready source of energy to keep small pigs from starving.  In high-health-status pigs, signs of anorexia, depression, and dullness are more likely to be caused by lack of energy than infectious disease.

•  Remainder of weaner period:

Routine observation during the whole weaner period remains vital for the early observation, identification, and treatment of disease.  Feed and water consumption should be monitored because a reduction in either is a sign of a problem.  Be prepared to act immediately in the event of illness, and train pig handlers to recognise the signs of major diseases and offer the most appropriate treatment.  Necropsies performed on dead pigs to accurately determine the cause of death and the most effective treatment(s) are beneficial.

•  Eating behaviour of pigs and feeder space requirements:

Understanding the eating behaviour of pigs can help producers maximise feed intake and, as a result, promote pig performance.

Dr Harold Gonyou provides some insight into the importance of understanding behaviour and how we can benefit from this.  Daily feed intake is the result of the total duration of eating (expressed as minutes per day) and the rate of eating (expressed as grams per minute).
Because pigs eat multiple meals each day, the duration of eating is composed of a certain number of meals and the average duration of each of these meals.  Any factor influencing the feeding behaviour of pigs can thus influence feed intake and growth performance.

How often pigs eat is related to their age and size.  Finishing pigs eat approximately 7 to 9 meals per day, weaner pigs eat more frequently, and recently weaned pigs eat 15 to 20 meals per day.  Management factors also can influence meal frequency.  For example, individually housed pigs eat more often than pigs housed in groups, and as group size increases, eating frequency decreases.

Eating speed is affected by the body weight of the pig.  Lightweight pigs eat slower than heavy pigs, and eating speed increases linearly as the pig gains weight.  Additionally, pigs fed pelleted feeds eat faster than pigs fed meal diets, and they eat feed in a wet form fastest of all.  Gonyou reported that pigs fed meal diets using wet/dry feeders spend 17 percent less time eating but consumed 5 percent more than pigs fed the same diet using dry feeders.

Group size also affects eating speed.  As expected, larger groups have greater competition, and eating speed increases.  Total duration of eating is also affected by size of the pig.  Heavier pigs eat for a shorter duration than smaller pigs.  From a practical perspective, the number of pigs that can eat from a single feeder space should increase as pig size increases because larger pigs spend less time eating than small pigs.  Pigs adapt their eating behaviour depending on their social interactions (pecking order).  When large groups of pigs are housed together, total eating duration decreases.

Understanding the eating behaviour of pigs will allow us to determine how many pigs we can feed from a single feeder space.  There are three main factors needed in calculating the number of pigs that can be fed from a single feeder:

• The total time per day that the feeder is occupied (feeder occupancy rate)
• The total eating duration
• The addition of water to feed increase eating speed, and, therefore, the number of pigs per feeder space can be increased if pigs are fed from wet/dry feeders.

Note, however, that the optimal number of pigs per feeder should be calculated based on the eating duration of the smallest pig at the feeder.  This is because the total eating duration is greater in small pigs, and, thus, the number of pigs that can be fed from one feeder space will be reduced.

Weaning weights

In general terms the better the weaning weight of a piglet the better the performance in the immediate post-weaning period.  Mahan and Lepine (1991) reported that by improving the weaning weight from an average of 4.5kg to 8.0kg the days to slaughter at 105kg were reduced by over 10 days for sows farrowed indoors and nearly 20 days for outdoor reared sows.  Similar results were reported by Campbell (1989) who demonstrated that an extra 1.8kg at weaning was worth over 5kg at 78 days of age (Table 1).

This work has been substantiated by analysis of data from SCA FEU collected during 1999 using over 6 000 piglets.  As weaning weight increased, the daily liveweight gain in the post weaning period improved, from below 300 grams a day with the lightest pigs to in excess of 500 grams a day for the heaviest piglets (Figure 1), during the 25 days post-weaning.  This resulted in a difference in liveweight of over 13 kilograms in less than 7 weeks of life.

The most efficient way of feeding the piglet to optimise weaning weight is to feed and water the sow correctly in order to maximise milk production.  However, even when sows are milking well, milk intake and hence nutrient supply can vary from piglet-to-piglet depending upon which teat they suck (Hoy and Puppe 1992).

This variation can be eliminated somewhat by the practice of creep feeding, which provides a direct supply of nutrients and acclimatises the piglet to solid food before weaning, so helping to optimise weaning weight and post-weaning performance.From the analysis of the data, of the 6 000 piglets produced at the SCA FEU, a positive correlation was found between the quantity of creep consumed and weaning weight (Figure 2).

Piglets that consumed less than 400 grams of creep feed before weaning were weaned some 400 grams lighter at approximately 7.8 kg compared to piglets that had consumed 600 grams of creep feed that were weaned at about 8.3 kg.

Furthermore, the data clearly showed that piglets which received creep feed prior to weaning had a markedly better growth rate in the immediate post-weaning period (Figure 3).Post-weaning gain in the first seven days post-weaning was increased from 180 grams per day to 240 grams per day as a result of increasing creep feed intake from 400 to 600 grams a day.

Piglets that received creep feed prior to weaning, not only had increased weaning weights that directly led to better post-weaning performance, but also had enhanced post-weaning performance due to the enhanced development of their digestive system.  Piglets that have had experience of creep feed are not so challenged by the process of weaning.  They are familiar with the smell and taste of the post-weaning diet and have better development of the enzymes needed to digest solid food.

Practical application of nutrition concepts

•  Immaturity of the digestive function

The earlier the pigs are weaned the more the alternative feed should emulate the composition of sows milk.  The 20% of solids in sows milk is made up roughly of 8% fat, 6% protein, 5% lactose, 1% minerals and other components, and is completely digestible.

Each piglet commonly receives around 1 000 grams of milk/day (approximately 200 grams of milk solids) and converts this at better than 1:1.  So the suckling pig is attuned to utilising milk fat and lactose for energy and milk proteins for its amino acid supply.

Consequently diets for the early weaned piglet (10 to16 days) enjoy most success when they contain a significant quantity (30 to 40%) of milk solids (skim milk, whole milk, butter milk, whey powder and/or lactose), and digestible fat sources.  The young pig handles short chain and unsaturated fatty acids better than the long chain and saturated fatty acids, and for this reason finds vegetable oils more digestible than animal fats such as tallow.

Alternative energy sources such as starch and sugars can also be employed but should be in a readily digestible form and within the bounds of the piglets enzymic competence.  Cooked cereals can be readily accommodated but raw starch and some sugars such as sucrose can prove a challenge at high inclusion rates.  With the use of supplementary enzymes raw starches and other ingredients are more readily used.

•  Marginal acid secretion:

The gastric acid secretion of piglets is at best marginal and in the presence of high acid binding feedstuffs can prove inadequate.  In this situation gastric pH rises, the pH barrier to indigested bacteria (especially E coli) is relaxed, the activation of pepsinogen to pepsin is compromised and the digestive efficiency is impaired allowing more undigested material to flow to the lower gut.  This combination results in bacterial proliferation, diarrhoea, dehydration, enterotoxaemia and possibly death.

By providing supplementary organic acids via the feed or water the gastric pH barrier is maintained, digestion is more complete, and the lower pH levels in combination with lactose promote the proliferation of favourable gram positive bacteria (lactobacillus and streptococcus spp.) which colonise the gut and resist E coli by preferential exclusion.

The need to provide supplementary acid insurance increases with the acid binding capacity of the feed.  A range of single organic and inorganic acids have been employed with variable success (eg lactic, citric, fumaric, formic, phosphoric, acetic, etc).  These are normally added to the feed or in their water soluble form to the drinking water.

•  Feed intake:

When we consider that sow’s milk has a digestible energy value of around 25 MJ/kg dry matter, is provided in frequent (hourly) small serves and is rapidly digested, it is not difficult to understand why the shift to dry feed post weaning results in net reduction in nutrient intake.

The key to the successful transition to post weaning diets is the combination of high nutrient density, high digestibility and factors that promote intake (eg palatability, physical form of the feed, frequent feeding, prior experience of feed, familiarity with the drinker nipples, minimal stress, etc).

Predominant in all these factors is digestibility.  Whittemore (1991) suggested that digestibility is the prime determinant of intake and proposed the following relationship:

Voluntary feed intake = 0.013 liveweight/1 – digestibility.

So for a 10kg pig which has passed the immediate stress of weaning, this would imply the following effects of digestibility on appetite.

Materials which are digested quickly and completely move out of the gut quicker than materials of lower digestibility and this helps to overcome the volumetric ingestive limits of the pigs stomach.

There is good evidence to suggest that exposure to solid feed pre-weaning not only educates piglets to recognise this as food but also stimulates gastric acid and protease secretion capacity.

The physical form of the feed does influence the voluntary intake rate.  Fineness of grind promotes digestibilty by increasing the surface area accessible by enzymes but dustiness can detract from intake or increase wastage.  Feeding mash feeds as a wet gruel in either milk, whey or water can improve intake and performance but requires greater management to maintain freshness and hygiene and can become a net negative if poorly managed.

Supplemetary feeding of suckers and weaners with cow’s milk has been shown to be most beneficial but the economic feasibility depends on the cost of the milk.  Other dairy by-products such as whey solids, yoghurt, icecream, cheese are also utilised very effectively by weaner pigs when fed in a balanced nutritional program.

Apart from the first week post weaning when feed intake is usually quite modest while the piglet adapts to the stresses and changed circumstances of weaning, a reasonable intake target for weaners is 4% of their bodyweight, eg 320 grams/day for an 8 kg piglet – with an expected feed conversion ratio of 1.1 : 1 this would produce a respectable growth rate of around 290 grams/day.

The cost of the diet

This is important to appreciate because there is an investment to consider when we put together management and nutrition programs in the post-weaning period.  In order to maximise post-weaning gain, high quality diets have to be used.  These are never the cheapest feeds but in the lifetime of the pig they are the most cost effective.  If we consider that only a very small percentage, of the total feed consumed in a pig’s lifetime is eaten in the immediate post-weaning period, but this can affect the daily gain to slaughter by up to 30%, the investment in the highest quality starter diet is clearly a very good investment.  The feed inputs to a bacon pig are illustrated in the following table. (Table attached at the end of the article).

Modern diets

Poultry producers feed up to 5 diets in a 40 day broiler program.  AIAO facilities with modernised feed delivery systems offer pork producers similar opportunities.  The provision of phase diets and packages to spread the load both nutritionally and financially are the starting point to reduce the burden.

Todays diets offer extremely well balanced, palatable feeds.  New words like iso-energetic, iso-nitrogenous, milk and whey powders, pre and pro-biotics, plasma proteins, starch gelatinisation, palatants, extrusion, micronisation, expansion, fractionated fibres and acid oils are all terms used for products that make up the modern diet.  An enormous amount of time and research has gone into the new Meadow pig feeds.

Health and welfare

Most pigs in South Africa are reared in conventional farrow to finish operations, housed on one site.  Farrowings are continuous, some weaners may be all-in all-out but often grower / finisher house are continuous flow, multi aged, single diet systems.  Such systems provide maximum opportunity for disease to spread from the sow to the litter, through the weaner and grower phases.  There is both lateral and vertical spread of disease.

Important points to remember in the restriction of disease are:

• The ability of the newborn piglet to resist infection by consuming adequate amounts of colostrum
• The “infective dose” required to cause disease
• The effect of the housing and environment.

Producers should ensure that sows are well immunised, that piglets consume ample colostrum, that cross fostering has been completed by 48 hrs post farrowing and that environments are clean and that temperature requirements catered for.

Summary

In summary the successful weaning process offers the producer a “window of opportunity” to really add value to the lifetime performance of the pig.  He should concentrate on:

Weaning pigs as heavy as possible within his production unit – this entails feeding and watering the sow correctly and improving on pre-weaning creep intakes. The first 5 days in the weaner pool (this always occurs over the weekend).  Temperature control, feed quality, supply and intake and management are paramount.

Continously monitoring and checking and benchmarking and seeking ways to improve. Evaluating diets in a scientific manner and remembering the added advantages of additional early improved mass for down the track performance.