Nutrition: Can weaner diets affect long-term performance?
Tuesday, August 4, 2009
U.K. research suggests that feeding high-protein and high-quality diets for two weeks post-weaning enhanced performance during that period but had no lasting effect on lifetime performance
by JANICE MURPHY
Feeding pigs at weaning is an art as much as a science. At one of the most stressful times in its life, the weaned pig must adjust to leaving the sow, moving to a new environment, and adapting to a completely different diet in both form and composition. Gone is the security of the sow's udder, along with the essential nutrients it provides, and in its place is a dry diet.
As a result, piglets face many challenges as they adapt. While producers do their best to meet the changing needs of a rapidly growing animal, the nutritionist's goal is to get them eating a carefully balanced ration in order to achieve optimum growth and minimize the potential for post-weaning health problems and mortality.
Recent research has focused on the potential to reduce protein content of weaner pig diets in order to decrease the risk of post-weaning diarrhea. The assumption is that this approach will reduce protein availability to gut pathogens and limit production of predisposition factors that arise from protein fermentation. The downside is that low protein diets may also lead to a lag in post-weaning growth, although this may be short-lived.
The benefit of a higher quality diet is a reduced risk of post-weaning diarrhea, resulting in improved post-weaning growth rate and the ability to reach slaughter weight more quickly. These improvements are the direct results of an improved amino acid profile, as well as increased digestibility of animal proteins and the starch in processed cereals. However, you get what you pay for, so higher quality diets tend to be pricey.
Researchers in the United Kingdom recently investigated the long-term impact of improving diet quality in weaner diets on pig health and performance. The aim of the study was to investigate the combined effects of manipulating protein content and diet quality for two weeks post-weaning on the performance of pigs from weaning to slaughter under commercial conditions similar to those seen on high-health pig units.
Four hundred pigs, weaned at an average of 29 days and 10 kilograms of body weight, were removed from the sow and randomly assigned to the four experimental treatments based on body weight and sex. The diets consisted of four combinations (Table 1) of protein content – high (230 grams of protein per kilogram) versus low (170 grams of protein) – and diet quality (high-quality versus low-quality).
The high-quality diets contained cooked cereals (micronized wheat, micronized maize and cooked dehulled oats) and animal protein sources (fish meal and dried skimmed milk powder), whereas the low-quality diets contained raw cereals (wheat, maize and dehulled oats) and plant protein sources (soybean meal and full fat soybean). From day 14 post-weaning to slaughter at 104 kilograms, all pigs were fed the same series of standard commercial diets, based on wheat, barley and soybean meal.
The results
The experiment suggested that high-quality diets did promote gut health. Pigs consuming these diets had fewer coliforms and enterotoxigenic E. coli than pigs on the low-quality diets. And they tended to have increased lactobacilli numbers in fecal samples taken at the end of the treatment period. As a result, pigs on the high-quality diets had an increased ratio of fecal lactobacilli to coliform compared with pigs on the low-quality diets.
There was, however, no effect of protein content on any of these parameters, even though pigs on the high-protein diets exhibited higher counts of lactobacilli than pigs on the low-protein diets.
Improved diet quality and higher protein content both increased average daily gain during the 14 day post-weaning period, resulting in heavier pigs on day 14 (Table 2). However, this improvement was not carried forward to finishing and slaughter. Pigs on the high-quality diets also had greater average daily feed intake than pigs on the low-quality diets during the 14 days post-weaning.
Meanwhile, pigs consuming the high protein diets had greater feed gain:feed than pigs on the low protein diets over the treatment period. Despite these differences, the researchers found no difference in the number of days pigs needed to reach the end of the weaner phase (average 49 days) or slaughter weight (average 128 days), regardless of treatment.
In assessing carcass characteristics, the researchers found that diet quality and protein content did not significantly affect backfat thickness or calculated percentage lean at slaughter. However, pigs consuming the high-protein and high-quality diet had the heaviest hot and cold carcass weights, whereas pigs receiving the low-protein and low-quality diet had the least.
In an attempt to apply some economics to their results, the researchers used U.K. ingredient prices to calculate diet costs as of June 1, 2006, the date of diet manufacturing (Table 3). As expected, the high-protein and high-quality diet was the most expensive compared to the low-protein and low-quality diet, which was the least expensive per ton.
When the cost was calculated per kilogram of pig body weight gain, the high-protein and high-quality diet remained the most expensive, but the high-protein and low-quality diet turned out to be the most economical over the 14-day experiment. Regardless of treatment, however, there was no effect of weaner diet on the cost per kilogram of body weight gain from weaning to slaughter, a reflection of the small amount (estimated to be less than 2.5 per cent) that the treatment diet contributed to lifetime intake.
The researchers were quick to point out, however, that although the high-protein and low-quality diet was the most cost effective per kilogram of body weight gain during the weaner phase of this particular study, this may not be the case for pigs exposed to disease pressures. Under disease challenges, increased protein levels and decreased diet quality have been shown to increase susceptibility to post-weaning diarrhea, which will affect the bottom line. The researchers caution that producers in that situation will struggle to decrease their weaner diet cost without a loss of both performance and margin.
Based on the results of this experiment, the researchers concluded that feeding high-protein and high-quality diets for two weeks post-weaning enhanced performance during that period but had no effect on lifetime performance.
They suggested, as a result, that it may be possible to use the less expensive, lower quality weaner diets without any adverse effects on lifetime performance when weaning later, weaning heavier piglets, and where health status, environment, and management are all maintained at a high standard.
Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.
Source: I. J. Wellock, J. G. M. Houdijk, A. C. Miller, B. P. Gill and I. Kyriazakis. 2009. The effect of weaner diet protein content and diet quality on the long-term performance of pigs to slaughter. J Anim Sci 87:1261-1269.