Summary

The number of piglets born alive per litter has increased by 1.5 in the past 10 years, from 10.8 in 2001 to 12.3 in 2011 (Teagasc PIGSYS, 2011). This trend is set to continue. Interpig (2011) showed that in 2011 the number born alive per litter was 14.8, 13.6 and 13.2 for Denmark, The Netherlands and France, respectively.

As we approach these levels of productivity, the importance of lactation feed intake for sows will increase even more than heretofore. Estimates of the nutritional requirement of lactating sows must consider the body weight of the sow (maintenance component), the yield and composition of milk, loss in body weight (mobilisation of body tissue) during lactation and the litter's intake of creep feed.

This paper looks at these the factors that determine the optimum lactation feed intake for sows and in particular it looks at the sows' requirement for energy (digestible energy) and lysine during lactation.

Energy Requirement

1. Sow weight (Maintenance energy requirement)

The empty weight of the sow after farrowing can be used to determine the maintenance energy requirement for the sow. This is calculated as 0.492MJ digestible energy (DE) per kg body weight^0.75 per day.

Table 1 shows the Maintenance Energy requirement for sows varying in weight from 180 to 250kg. It can be seen from this that maintenance energy requirement is low relative to the total energy requirement of sows during lactation. Every 10kg increase in sow weight above 180kg increases daily maintenance energy requirement by 1MJ.

2. Milk production

The energy requirement for milk production can be calculated from litter weight gain by assuming that 1kg of piglet weight gain during lactation requires a maternal intake of 30.4MJ DE. It depends on a number of factors such as piglet weaning weight, number of piglets weaned per litter and creep feed intake per litter. For this and all subsequent calculations, the authors assume a lactation length of 28 days.

2.1. Piglet weaning weight

The effect of piglet weight at weaning on the energy requirement for milk production is shown in Table 2. It can be seen that for every 0.5kg increase in the average pig weight at weaning above 7.0kg, there is an increase in the energy requirement for milk production of 5.4MJ DE per day.

2.2. Number weaned per litter

The effect of the number of pigs weaned per litter on the energy requirement for milk production is shown in Table 3. It can be seen that for every extra pig weaned per litter above 10, there is an increase in the energy requirement for milk production of 7MJ DE per day.

2.3. Creep feed intake

The effect of the creep feed intake per litter on the sow's energy requirement for milk production is shown in Table 4. It can be seen that for every 1kg in creep feed consumed per litter there is a reduction in the sow feed energy requirement for milk production of 1.1MJ DE per day.

3. Sow weight loss

Each 1kg of body weight loss will contribute 12.5MJ DE to the energy requirements of the sow over an entire lactation. It can be seen from Table 5 that for every 10kg weight loss in a sow during lactation, there is reduction in the sow feed energy requirement of around 4.5MJ DE per day.

This is an important source of energy for the lactating sow, however, it is important that weight loss in sows is not excessive during lactation. Thaker and Bilkei (2005) found that weight loss during lactation should not be greater than five per cent (around 10kg) for first parity sows and 10 per cent (around 22kg) for older parities if early return to oestrus, high farrowing rate and a high subsequent litter size are to be achieved. Gilts are most affected by lactation weight loss because of their inherent drive to achieve their target lean body mass and therefore, even after weaning, they continue to mobilise body fat to sustain lean tissue deposition (Foxcroft et al., 1997). This leads to an unfavourable endocrine and metabolic state in these young sows which impacts negatively on their fertility.

Example

Sows or gilts weaning 11 pigs will need a mean lactation feed intake in excess of 94MJ DE per day to avoid excessive weight loss during lactation. This is the equivalent of 6.6kg of a diet containing 14.2MJ DE per kg. Roughly 25 per cent of this is required for the maintenance of the sow while 75 per cent is required for milk production and litter growth.

Lysine Requirement

1. Sow weight (Maintenance lysine requirement)

The empty weight of the sow after farrowing can be used to determine the maintenance lysine requirement for the sow. This is calculated as 40mg total lysine per kg body weight^0.75 per day.

Table 7 shows the maintenance lysine requirement for sows varying in weight from 180 to 250kg. It can be seen from this that maintenance lysine requirement is very low relative to the total lysine requirement of sows during lactation. Every 10kg increase in sow weight above 180kg increases daily maintenance lysine requirement by approximately 0.1g.

2. Milk production

The lysine requirement for milk production depends on a number of factors such as piglet weaning weight, number of piglets weaned per litter and creep feed intake per litter. It can be calculated from litter weight gain by assuming that 1kg of piglet weight gain during lactation requires 4kg of sow's milk. The yield of sow’s milk can then be used in the following equation to calculate the daily lysine requirement for milk production:

Lysine requirement for milk yield (g/day) = milk yield (ml/day) × 0.056 × 0.076 ÷ 0.8 ÷ 0.9
OR
Lysine requirement for milk yield (g/day) = milk yield (ml/day) × 0.0059

2.1. Piglet weaning weight

The effect of piglet weight at weaning on the lysine requirement for milk production is shown in Table 8. It can be seen that for every 0.5kg increase in the average piglet weight at weaning above 7.0kg, there is an increase in the total lysine requirement for milk production of around 4.2g per day.

2.2. Number weaned per litter

The effect of the number of pigs weaned per litter on the total lysine requirement (g/day) for milk production is shown in Table 9. It can be seen that for every extra pig weaned per litter above 10 there is an increase in the total lysine requirement for milk production of around 5.5g per day.

2.3. Creep feed intake

The effect of creep feed intake per litter on the sow's total lysine requirement (g/day) for milk production is shown in Table 10. It can be seen that for every 1kg of creep feed consumed per litter, there is a reduction in the total lysine requirement for milk production of around 0.9g per day.

3. Sow weight loss

Total lysine contribution associated with weight loss in sows during lactation as presented in Table 11 is calculated using the following equation

Total lysine contribution from weight loss = Sow weight loss (g/day) × 0.175 × 0.85 × 0.07
or
Total lysine contribution from weight loss = Sow weight loss (g/day) × 0.0104

For every 10kg weight loss in a sow during lactation there is reduction in the sow feed total lysine requirement of around 3.7g per day. This can also be an important source of lysine for the sow during lactation. However, excessive weight loss must be avoided at all costs for the reasons already stated.

Example

Gilts and sows weaning 11 pigs will need a minimum mean lactation intake in excess of 56.5g and 53.1g total lysine per day, respectively. This is the equivalent of 6.2kg for gilts and 5.8kg of feed per day for sows when fed a diet containing 9.1g total lysine per kg. Roughly 3.5 to 4.5 per cent of this is required for maintenance while the remainder is required for milk production/litter growth.

Feeding Lactating Sows

An average yielding dairy cow (5,000 litres per year) with a 260-day lactation has an average milk yield of 19.2 litres of milk per day or 2.4kg solids (12.5 per cent solids content). The litter of a sow weaning 11 pigs at 8kg has a mean growth rate over 28 days of 2.55kg per day, which is the equivalent of 10.2 litres per day of sow’s milk. Sow's milk has a solids content of 21 per cent, so this sow is producing 2.14kg solids, which is not that far off that of the dairy cow.

What is even more important is that the energy value of the milk produced by the sow is even higher than that of a dairy cow due to its significantly higher fat content. The daily production of fat would be 740g per day for the dairy cow while it is 1020g day for the lactating sow. These high-producing sows must be fed appropriately to support this level of production.

Increasing Lactation Feed Intake

• Do not inadvertently restrict feed intake by feeding less than sows can eat
• Over-feeding sows in gestation will reduce lactation feed intake
• Maintain farrowing rooms at 18-20°C. High farrowing house temperatures depress feed intake
• The intake of wet fed sows (2× per day) is higher (12 per cent) than that of ad-libitum dry fed sows
• Ad-libitum wet dry feeding is a good alternative to wet feeding to promote increased feed intake
• Dry feed is eaten more readily in pelleted than meal form
• The higher the energy density of the sows diet the greater the energy intake of the sow will be
• Feed lactating sows at least twice but preferably 3 times daily to encourage increased feed intake.
• Ensure that the feed in front of the sow is fresh
• Ensure that supplementary water is provided to match the sow's needs. Wet fed sows may not be getting sufficient water from the feed mix in the days after farrowing but depending on water to meal ratio excess water in the mix may limit intake late in lactation.
• Increasing gestation feed intake (+1kg) in the last few weeks before farrowing can help encourage higher feed intakes in the days following farrowing
• High feed intake in the first two weeks of lactation is very important if high average lactation feed intakes are to be realised
• Suggested target mean daily intakes are 4.1kg (58 MJ DE) in week 1, 6.4kg (91 MJ DE) in week 2, 7.8kg (111 MJ DE) in week 3 and 8.4kg (119 MJ DE) in week 4.
• Ensure that there is sufficient capacity in troughs. This is particularly important when wet feeding sows at high feed allocation levels to prevent wastage while feeding.

Summary

Modern sows can produce quantities of milk solids similar to that of dairy cows. To maximise this potential to produce milk, without excessive weight loss during lactation, sow feed intake must be maximised.

Pre-weaning growth rate in pigs is directly proportional to the sow's milk yield (4:1 conversion).

The requirement for feed will be determined principally by the number of piglets reared by the sow and their weaning weight (i.e. milk production of the sow). On average, sows and gilts weaning 11 pigs at 8kg will have an average daily feed intake requirement of more than 6.6kg of a standard lactation diet (14.2 MJ DE/kg and 9.1g/kg lysine) to satisfy their energy and lysine requirements.

Each unit should check the lactation intakes of their sows against their piglet performance. Where necessary feed intake should be increased.

References

Close, W.H. and Cole, D.J.A. 2000. Nutrition of Sows and Boars. Nottingham University Press, Nottingham, UK. 377pp.

Foxcroft, G.H., Zak, L., Aherne, F.X., Kirkwood, R.N. 1997. Management of the early weaned sow. In: Proceedings of the Banff Pork Seminar, Advances in Pork Production, 8:117-135.

Lynch, P.B. 1989. Voluntary food intake of sows and gilts. In: The Voluntary Food Intake of pigs. An occasional publication of the British Society of Animal Production. No.13 71-77.

Teagasc. 2011. PigSys National Pig Herd Performance Report 2011. Teagasc, Oak Park, Carlow, Ireland. 24pp.

Thaker, M.Y.C. and Bilkei, G. 2005. Lactation weight loss influences subsequent reproductive performance of sows. Animal Reproduction Science, 88:309-318.

Further Reading You can view other papers from this TEAGASC conference by clicking here.