Animal plasma’s memory effect on young broilers

With increased attention towards antibiotic-free rearing of livestock and a stronger focus on growth performance of starting broilers, spray-dried plasma (SDP) can offer a key feed ingredient in successfully achieving both goals. In the last decade, trials with broilers and turkeys show superior technical performance at better economics and increased resilience of young animals when SDP is introduced at low inclusion levels in starter diets.

SDP is a blend of highly functional proteins

Animal plasma is derived from porcine (or bovine, outside of EU) blood. After collection at the slaughterhouse from approved and inspected healthy animals, the blood is fractionated by centrifugation into red cells and the liquid plasma phase. After a concentration step the plasma is spray-dried and marketed as a creamy-white powder with a protein content of up to 80%. The protein fraction in SDP is known to be a highly versatile blend of functional molecules, with over 1,400 types of different proteins identified. Most important protein fractions are immunoglobulins, albumin and fibrinogen, next to smaller fractions of growth factors, enzymes and peptides.

SDP protein is highly digestible and has a high biological value as about 45% is composed of essential amino acids. It has been established, however, that apart from the nutritional value of SDP its main value is in its functional component.

Well documented beneficial effects

For over 20 years the beneficial effects of plasma in young piglets have been well documented: enhanced feed intake, improved weight gain and more efficient feed conversion observed especially in the first week post-weaning. The highly functional ingredient has a positive effect on gut barrier integrity, can bind to pathogens thanks to its immunoglobulin (IgG) component and can modulate a strong pro-inflammatory immune response after infection or artificially imposed antigen challenge. Effects are maximised in sub-optimal hygienic conditions. Research on plasma performance in poultry is limited but similar effects can be expected based on the suspected modes of action.

Some historical broiler trials with SDP

At the start of the millennium, several trials in the United States have been performed with SDP on broilers at different state universities, see Table 1. All of these trials have in common SDP is administered to the young animals during the complete growth period (21 to 42 days) at inclusion levels between 0.5 and 2%.

Some trials keep inclusion level constant over the complete period, others start with higher concentrations during starter phase and decrease the inclusion levels during grower and finisher phases. Both bovine and porcine SDP are used in different trials. Often animals are microbiologically challenged by using the same litter of a previous batch of animals. Results of these trials all conclude more or less the same: inclusion of SDP increases daily feed intake (DFI) and average daily gain (ADG) and often improves feed conversion ratio (FCR). Animals fed with SDP show better survival and performance figures, especially in challenging conditions with sub-standard hygiene and higher microbial loads. Both bovine and porcine SDP show effects, indicating the SDP functionality seems to be species-independent. These results are very much in line with the richly documented inclusion of SDP in piglet (pre-)starter diets.

SDP inclusion in starter feed

Piglets fed with pre-starters containing SDP suffer less effects from the infamous weaning dip. This seems to give the animals a boost from which they profit their complete life cycle, even when their starter and grower diets no longer contain SDP. For economic reasons it would be preferable if a similar ‘memory’ effect of SDP inclusion exclusively in the starter phase could also be demonstrated in broilers.

Recently, the University of New England, Australia, published a trial performed on broilers in which the addition of 0.5% or 1% of bovine or porcine plasma was tested. Only during the first ten days pullets were fed diets containing 0 to 1% of plasma powder. Next, all groups switched to a commercial diet without SDP and were monitored for a total of 35 days. Feed conversion rate of groups fed with plasma improved several points during the first ten days. More importantly, the positive effects on FCR were maintained during the complete trial period of 35 days, see Figure 1, even when all trial groups shared the same commercial diet for the remaining 25 days. From this trial it can be understood that an inclusion of 0.5% of either porcine or bovine plasma to a broiler starter diet can reduce the FCR by 10 to 14 points as obtained over the total growth period of 35 days. A series of follow-up trials at the same research institute confirmed the above findings.

Detailed financial calculations comparing the different groups in these trials show the initial investment in a starter containing 1% of SDP is quickly recuperated because of higher weight gain and improved FCR. Actually, costs of feed per kg of meat were found to be lower in the feeds with SDP. This is excluding the reduction of indirect costs because of reduced medication use, higher resilience of the pullets and reduced mortality in the population.

A bright future for SDP in broiler starter feeds

Animal trials and performance economics seem to indicate SDP is a valid ingredient in broiler starter diets. Yet, more studies are required to uncover the full potential of SDP in broiler populations. Next to the increased resilience in SDP-fed pullets there are indications the overall health in the complete flock is increased, resulting in more homogeneous groups of animals with less variation in bodyweight. A better understanding of the working mechanisms of SDP in broiler health could further improve its enhancing effects on the performance of the animals, offering feeding specialists a natural alternative to antibiotics.

References are available from the author: louisvandeun@sonac.biz