Are antibiotics needed in high health situations?

Weaning is a stressful time in a piglet’s life. During this time, they are exposed to three major stressors (nutritional, environmental and social). Combined, these can activate the immune response in the piglet, which in turn can have negative impacts on animal performance immediately post-weaning (low or no feed intake, reduced or negative growth rates). In order to help combat the stress/immune response at the time of weaning, piglets are often fed a diet containing a low level of antibiotics. This helps the piglets cope with any potential secondary infections which may be contracted while their immune system is vulnerable.

Canada to phase out in-feed antibiotic use

In April 2015, Health Canada, the country’s government department for public health, announced that the use of in-feed antibiotics will be phased out over the next three years. Health Canada’s measures are dedicated to strengthening regulation and encourage prudent use of anti-microbial drugs used in food-producing animals, particularly drugs considered medically important. To date Health Canada has being working with the pharmaceutical industry in phasing out all growth promotion claims related to medically important drugs by December 2016.

Finding alternate strategies to help piglets cope during weaning is important, and nutritional modulation for this purpose is a growing area of interest. Flaxseed (also known as linseed) is a rich source of omega-3 fatty acids, which are known to have many different health benefits. Omega-3 fatty acids can be easily transferred to piglets via the milk when sows are fed diets containing a good quality source. Perhaps by improving the health of piglets prior to weaning, by allowing them to suckle milk that is high in omega-3 fatty acids they might exhibit growth rates comparable to piglets receiving diets supplemented with antibiotics.

Trial: Omega-3 in sows diets

A total of 103 sows were used for this trial, 52 weaned at four weeks of age and 51 at three weeks of age. Within each weaning group, sows were fed one of two diets (control or with omega-3) throughout lactation. At the time of weaning, ten piglets from each litter were selected, moved to the nursery and housed in two groups of five piglets each (two nursery pens per litter). One half of the litter (1 pen) was fed a starter diet containing antibiotics (LS20, 0.1%), and the other half received the same diet without antibiotics. After one week, all piglets were switched to a common phase 2 diet for the remainder of the study.

Due to the high health status of the facility, prior to weaning nurseries skipped a single wash cycle to increase bacterial exposure; and ensure that each weaning cohort was immunologically challenged. Regardless of weaning age, all piglets completed the trial at 56 days of age. Piglet performance was determined in both the farrowing and nursery rooms. Sow milk was collected during mid-lactation to determine the fatty acid profile of the milk being consumed by the piglets. Piglet health was monitored by collecting blood two days post-weaning and analysing for complete blood cell count (CBC) and chemistry blood panels. A total of 1,181 piglets completed the lactation portion of the trial. Of those, 1,021 piglets were used for the nursery portion.

Results and discussion

There were no effects of diet (with or without omega-3 fatty acids) on sow feed intake, numbers of piglets born, piglet growth or on the number of piglets weaned per litter. As expected, sows fed a diet with added omega-3 fatty acids had significantly more of these fatty acids in their milk relative to control sows.

In the nursery, there was no impact of sow diet on average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (G:F) or final body weight of piglets weaned at three or four weeks of age. For piglets weaned at three weeks of age, ADFI was 20 g/d higher during the fourth week in the nursery for piglets who received no antibiotics in their phase 1 diet; however, ADG and feed conversion ratio were not affected. Feed intake was not affected during any of the other trail weeks for these piglets. For piglets weaned at four weeks of age, ADG tended to be greater in piglets fed diets with antibiotics for week 1 of the trial, which also lead to improved feed conversion ratios during that week.

Growth and feed conversion ratio were unaffected by the inclusion of antibiotics from weeks 2 to 4 in the nursery. Feed intake tended to be higher in antibiotics fed piglets during week 3, and was significantly higher in week 4 relative to piglets who received no antibiotics in the first week post-weaning (930 g/d vs. 900 g/d); however this did not impact grower-finisher. The research team observed no dietary effects (sow diet or nursery diet) on the final body weight of piglets at nursery exit; however, regardless of dietary treatment, piglets weaned at three weeks of age were roughly 1.5 kg heavier than those weaned at four weeks.

No effects were found due to either sow or phase 1 diet on any of the blood measures taken when piglets were weaned at three weeks of age. When piglets were weaned at four weeks of age, piglets weaned from sows fed diets containing omega-3 fatty acids had lower white blood cell counts relative to those weaned from sows fed the control diet. White cell counts were unaffected by phase 1 diet, and neither sow nor phase 1 diet affected any of the other blood parameters measured.

So do piglets need in-feed antibiotics?

This trial was designed to determine if suckling piglets consuming milk enriched with omega-3 fatty acids would have growth rates in the nursery comparable to piglets receiving a diet supplemented with antibiotics.

However, growth rate of piglets was the same, regardless of whether they received antibiotics, omega-3 fatty acids or a diet with neither supplement. The research team therefore is unable to answer the original question. The ‘take-home message’ is that in a high-health herd, even with less than optimal sanitation, piglets can grow well and remain healthy consuming diets that do not contain antibiotics.