Ms Edwards outlined her Pork CRC-supported PhD at the University of New England on early nutrition and the weaning transition, while Dr Downing of the Faculty of Veterinary Science at the University of Sydney discussed his ground-breaking Pork CRC supported work on eliminating the weaning to mating interval.

Feeding for Easy Weaning Transition

above: Megan Edwards outlined her Pork CRC-supported PhD at the University of New England on early nutrition and the weaning transition.
below: Dr Jeff Downing

Ms Edwards conducted four experiments under commercial conditions to assess the influence of various nutritional strategies on the intestinal and immune development, survivability and performance of young pigs in the pre- and post-weaning phases.

The nutritional strategies included extrusion as an alternative milling process, amino acid supplementation, non-nutritional effects of creep feed and the use of two nutraceutical products, spray-dried porcine plasma and a yeast-derived protein meal.

In the latter three experiments, dam parity was considered an influential factor, so comparisons between progeny of primiparous (P0) and multiparous (P2, 3 and 4) sows were examined.

An extruded semi-moist creep feed promoted superior growth performance from day 21 of lactation until weaning (at day 28) compared to a medicated, conventionally milled creep feed. The advantages of the semi-moist extruded creep feed appear to be related to improved palatability. The semi-moist extruded creep feed also appeared to benefit newly weaned pigs by altering digestion (limiting hind-gut fermentation) and by beneficial manipulation of microbial communities along the gastrointestinal tract limiting the proliferation of pathogenic enterotoxigenic Escherichia coli.

The nutritional strategies that enhanced survivability and immune competence in newly weaned pigs included supplemental amino acids at weaning, offering creep diets containing spray-dried porcine plasma and pre-weaning exposure to creep feed. The benefits were more pronounced in progeny of primiparous sows and piglets light-for-age (weighed less than 8kg at 28 days). Reduction in mortality and morbidity through the nursery phase was associated with beneficial manipulation of intestinal microflora and down regulation of the immune system in the acute post-weaning period. An interesting finding was the benefits of the nutritional strategies tested not only influence gastric diseases but also susceptibility of weaners to respiratory diseases.

Providing pigs with creep containing yeast-derived protein meal did not offer the benefits described above but alternatively enhanced growth performance in the second nursery phase and improved the systemic immunity of pigs at day 68. Including a nucleotide-rich nutraceutical appears to have long term, cumulative benefits on the immune robustness of the grower pig. Effects of supplemental amino acids and dietary nucleotides highlight the role protein malnutrition plays in the epidemiology of the post-weaning growth check. Limiting the risk of protein malnutrition was particularly important in pigs at high risk of immunological and physiological challenges.

Of the strategies examined, including spray-dried porcine plasma most effectively maintained post-weaning feed intake and growth performance in the acute post-weaning period. These benefits were reflected in improved intestinal integrity, pancreatic digestive enzyme activity and colonic health.

How creep feed exposure influenced growth performance during the suckling phase depended on a range of inter-dependent factors, including lactation stage and litter size. The non-nutritive benefits were complimentary to subsequent survivability of weaner pigs, with benefits enhanced in progeny of primiparous sows. The importance of creep feed composition becomes more evident during the acute post-weaning phase.

These studies showed that nutrition promises to enhance the intestinal and immune development, survivability and performance of young pigs in pre and post weaning phases.

The results also highlight the nutritive and nonnutritive roles of early nutrition in piglet development. Beyond providing nutrients for growth, early nutrition can promote feed intake, down regulation of the immune system, rapid stabilisation of gastrointestinal microbiota and limit protein malnutrition.

Eliminating the Weaning-to-Mating' Interval

Dr Jeff Downing discussed his Pork CRC-supported work on eliminating the weaning to mating interval. Having provided 'proof-of-concept' in a 2007 Pork CRC-supported study that oestrus could be induced during lactation, using an injection of gonadotrophins (PG 600: Intervet) at 19 to 24 days after parturition, combined with boar exposure and piglet separation for 16 hours each day until mating, Dr Downing and colleague Roger Giles set about testing the concept under commercial conditions in Pork CRC Project 2D113.

They also wanted to test the hypothesis that induction of oestrus during lactation and postponing weaning age to 35 days has no effect on subsequent mating and farrowing performance, compared with a cohort of sows weaned at 20 days after farrowing.

Another hypothesis to test was that postponing weaning to 35 days after farrowing will increase piglet weight at weaning and increase growth at 70 days of age when compared to a cohort of piglets weaned at 20 days after farrowing.

The study was conducted at QAF (now Rivalea), Corowa, New South Wales, with 46 multiparous sows in conventional farrowing crates and housed in the same room. At 20 days after parturition, the sows were treated with an injection of PG 600, combined with boar exposure and piglet separation from 16:00hr to 08:00hr each day until mating by AI; or sows were weaned into dry-sow stalls, combined with boar exposure each day until mating by AI. Piglet separation on induced sows ceased after AI. The piglets remained on each induced sow until weaning at 35 days after farrowing.

At 35 days after farrowing, all sows were housed as one group in straw-based accommodation. Pregnancy was confirmed at 40 days after mating by ultrasound. All pregnant sows were farrowed subsequently as one group in the same room. Project outcomes were:

• The study confirmed that the previous findings by Downing et al. (2007) were repeatable under commercial conditions
• Induction of oestrus at 24 to 25 days after farrowing and postponing weaning age to 35 days had no effect on subsequent mating and farrowing performance
• Of 23 sows allocated to each treatment, 87 per cent of sows were mated within a mean of 4.3 days resulting in a subsequent farrowing rate of 65 per cent and an average of 11.3 piglets born alive per sow
• Although postponing weaning age to 35 days increased mean piglet weight by 0.9 kg, this weight advantage was not maintained to 70 days of age.

Implications of this project for the Australian pig industry are:

• This new sow strategy uncouples weaning from reproduction in the sow, transfers mating activity to the farrowing crate and allows weaning age to be increased without compromising subsequent farrowing performance
• This new sow strategy can be used to induce oestrus at 20 to 21 days after farrowing with the potential to reduce non-productive sow days and provide an additional two piglets per sow per year
• Ease of adoption by industry is likely to be 60 per cent because of the commercial availability of PG 600, the minor change required to farrowing accommodation to enable piglet separation for four to six days and the application of AI to sows housed in farrowing crates.

Dr Downing said: "We now know oestrus can be induced during lactation at 24 to 25 days after farrowing, with no effect on subsequent farrowing performance and recommend a further study to see if it's possible to induce oestrus at 20-21 days after farrowing to further reduce non-productive sow days."

An opportunity now exists to see if it is possible to inject PG 600 earlier than 20 days after parturition.

He continued: "We are confident oestrus can be induced during lactation at 20-21 days post-partum. The deliverable will be a reduction in non-productive period by 10 days per reproductive cycle for sows weaned at 26 days post-partum; and seven days for sows weaned at 23 days after farrowing.

"Potential benefits include an additional two piglets per sow per year. We estimate this benefit alone will increase industry profitability by 10 per cent.

"This new sow strategy allows for flexibility in when to wean without compromising the number of litters per sow per year."

However, it appears from the current study that piglet separation for 16 hours per day for four to five days only from injection of PG 600 until mating was insufficient to increase creep feed intake and reduce the growth check following weaning at 35 days of age.

Recent research conducted in the Netherlands (Berkeveld et al., 2007) suggests that piglet separation is required each day from day 20 until weaning at day 35 (or later) to increase creep feed intake and limit the growth check following weaning.

Despite a reduction in weaning growth check, Berkeveld and co-workers found that postponing weaning and subjecting piglets to a prolonged period of intermittent suckling did not improve subsequent piglet growth compared to conventional weaning.

This conclusion is similar to the findings from the current study. However, Berkeveld et al. suggest that an intermittent suckling regime will reduce the potential risk of post-weaning diarrhea and the need to treat piglets with antibiotics.

"This new sow strategy has the potential to reduce non-productive days in the breeding herd and we are confident oestrus can be induced during lactation at 20 to 21 days post-partum resulting in an additional two piglets per sow per year," Dr Downing concluded.

At the WA Pork CRC/APL Roadshow at Technology Park, Perth, were veterinarian Dr Barb Frey of Consistent Pork, producer Annette Howard of Wannamal, WA, Pork CRC Commercialisation and Adoption manager Dr Rob Wilson and producer Sharon Martin of Wannamal.

At the WA PorkCRC/APL Roadshow were Dr Yvette Miller, Portec Australia, Dr Jeff Downing, University of Sydney, Dr Mike Brumm, USA, Emalyn Loudon, APL and Steve Lyneham, producer from Popanyinning, WA.