Average litter size on pig farms in Canada has increased from approximately 12.3 to 13.7 piglets in the last five years. Further improvement is expected and is an important determinant of the competitiveness of the industry in Western Canada.

However, research conducted at the Prairie Swine Centre showed that, as litter size increased from 8.4 to 15.4 pigs born alive, average birth weight decreased by approximately 250g or almost 40g per additional pig. The number of pigs less than 850g increased from 0.2 per litter in the small (five to 12 piglets) litters to almost one pig per litter in the largest litters, i.e. 16 or more born alive.

It is apparent that, as litter size continues to increase, it is crucial that these small pigs survive and go to market or the benefits of larger litters will not be realised.

The period immediately post-weaning is characterised by problems such as low feed consumption, poor growth rate and increased incidence of diarrhoea in the piglets. Reducing the interval between weaning and resumption of feed consumption can mitigate these issues, thus the piglet must be encouraged to begin consuming solid feed upon entering the nursery. Traditionally, the feed offered immediately post-weaning is very high quality, containing animal by-products, providing the piglet with 'extra-nutritional' benefits including appetite stimulation. This feed, however, is very expensive and producers are questioning if it is necessary for all piglets.

This experiment was designed to determine if the requirement for a complex dense feed immediately post-weaning is dependent on the weaning weight of the pig. The authors hypothesised that the light-weight pigs at weaning would show a greater response to the higher quality fed. They also studied whether the provision of creep feed was beneficial. This creep feed data and that pertaining specifically to weaning weight were described in the Fall 2011 issue of Centred on Swine.

Fifteen nursery fills were studied. Each nursery (32 pens; four to five pigs per pen) was filled with the piglets from one week's farrowing. Only 12 pens - six for the lightest and six for the heaviest pigs - from the weaning group were used. Within each bodyweight grouping, these six pens were then assigned to one of three treatments (Table 1).

Thus, within each nursery, there were two pens per treatment, per bodyweight grouping. Pens were mixed gender and contained at least two pigs of one gender. Farrowing groups 1 to 8 received creep feed (a non-medicated phase 1 starter) for one week prior to weaning. Groups 9 to 15 received no creep feed. A previous report of this trial showed that creep feeding did not improve average litter weaning weights.

Diets (Table 2) were formulated to meet or exceed amino acid, energy, vitamin and mineral requirements for pigs of this age and bodyweight (NRC, 1998).

The 'complete' diet used corn instead of corn DDGS and contained whey, plasma, blood meal and fish meal, while the 'simple' diet met requirements using wheat, soybean meal, canola meal and corn DDGS. The simple diet would be cheaper to manufacture. While both diets met all the nutrient requirements for piglets of this age and weight, ingredients in the complex diet should supply additional benefits such as improved palatability and aiding the immune system. The authors hypothesised that the complex diet would be especially beneficial for lightweight piglets and those that had not received creep in the farrowing room. As shown in Table 2, based on August 2012 ingredient prices, the complex diet cost C$906 per tonne or $400 more than the simple diet.

The three treatments were A: the complex diet only on day 1; B, the complex diet on the first four days followed by the simple diet and piglets on treatment C only received the simple diet.

Surprisingly, dietary regime had no effect of piglet performance during the first 14 days in the nursery (Table 3; bodyweight on day 14, average daily gain, average daily feed intake and feed conversion efficiency days 0 to 14 all P>0.05). The provision of the complex feed improved feed intake and prevented some bodyweight loss during the first 24 hours post-weaning, however, this benefit was not maintained.

There was an interaction between diet and bodyweight category of growth rate immediately post-weaning (Figure 1). Piglets that were heavier at weaning lost weight during the first day post-weaning, regardless of diet complexity. In contrast, piglets that were lighter and received the complex diet maintained their body weight (bodyweight group by diet, day 0 and 1, P=0.01).

Figure 1. Interaction between bodyweight and feeding regime on the growth of piglets day 0 and 1 post-weaning.
Treatment A and B piglets received the complex diet and treatment C piglets the simple diet during this period.

The hypothesis that light-weight pigs would respond more to a higher quality diet was proven correct for the first 24 hours post-weaning. However, overall, this response appears to be of little importance as there were no interactions of birthweight and feeding regime after this time (data not shown).

In this experiment, feeding a simple diet formulated to meet an nutrient requirements did not reduce growth of piglets compared to a complex diet fed for one or four days post-weaning.

Switching for a complex diet to a simple diet after one day reduced feed intake to a greater extent than switching four days post-weaning.

Feeding the complex diet for the initial four days in the nursery would cost about $0.50 more per pig than the simpler, cheaper diet throughout. The results indicate that these savings would accrue regardless of piglet birthweight.

It is important to note that these studies were designed specifically to investigate the response to the diets and these pigs were raised under ideal, non-stressful conditions. The authors are presently conducting experiments to determine if these results will be maintained under more commercial conditions.

In a similar experiment, however, Levesque and co-workers (2012) at the University of Guelph showed that although pigs fed a simple diet post-weaning did have decreased growth and feed intake relative to their cohorts receiving a complex diet, they compensated for this reduction during the grower-finisher phase and thus there was no overall effect on performance but overall, a decrease in lifetime diet cost.

Bottom Line

Producers may be able to save money by feeding simpler stage 1 diets. However, this study and one conducted at the University of Guelph indicates that further research is required to determine if these simpler, cheaper diets affect the ability of the young pig to respond to disease or environmental stressors.

March 2013