JOHN GADD ▶▶▶


What the textbooks don’t tell you about... Compensatory growth post-weaning A


s one of the ‘sheltered group’ during Covid-19, I am instruct- ed/advised not to leave the house until this deadly virus has subsided sufficiently. Thus I have more than enough time to think about several controversies in pig production. After


more than 50 years of dealing with post-weaning check problems on perhaps 80 farms over the years, I have a thick file on compensatory growth.


Controversial So what is compensatory growth, and why should it be so controversial? After the usual check to growth rate for a while from being weaned – does the piglet catch up the lost growth by slaughter. Does it happen? “No!,” said the eminent Prof Colin Whittemore, whose knowledge and advice I have always admired, in his book The Science and Practice of Pig Production (1993): “Compensatory growth is the last refuge of pro- ducers who have not managed the pigs properly.” So be it, science has spoken. But what was happening in the field? As I had repeatedly found on over 50 farms that if the post-weaning check is not too severe, say around 5 to 7 days of measurable growth compared to non-checked weaners, these pigs can finish within a day of the less af- fected pigs by slaughter weight.


Weighing on the same day I know because I weighed them all on the same day to check on what my clients were telling me, see Table 1. The equivalent extra value per tonne of feed is £79.50 (€ 87.91) from little or no post-weaning check. Using the MTF figure (Meat per Tonne of Feed fed), which takes account of lean meat deposition rather than FCR, the effect of any check to lean gain is significant in terms of cost effec- tiveness (i.e. econometrically) which rises exponentially the longer the


Table 1 – Average results (8.1-105kg) from 58 farms pigs hardly checked after 27 day weaning compared to those checked between five and seven days.


Feed Conversion Ratio (FCR) Food consumed (kg)


Meat per tonne of feed fed (kg)


Checked for 5 to 8 days 2.91 245 270


Hardly checked, 1 to 2 days 2.51 287 317


check to recovery. These data also confirm the wisdom of using a more expensive starter feed.


Well-known for his writing on pigs across 38 years, John Gadd has writ- ten over 2,600 articles and pa- pers. His speciality is the cost-effectiveness of pig technology. Prior to be- coming an inde- pendent writer and consultant, he had a long ca- reer in the British pig industry, from being a stockman to chief pig advi- sor.


What is right? So who is right? In view of Dr Whittemore’s plangent remarks, this sur- prised me. The answer is that both views are correct. From the figures provided to me by my clients, the pigs did seem to catch up in live- weight terms, but when I applied the MTF figure, the killing out percent of the checked pigs was down between 0.2% to 1.06%, which resulted on average, in some 47kg less lean meat sold (i.e. deadweight not live- weight) for each tonne of food fed, the liveweight measurement includ- ing some carcass contents not required by the consumer. Providing the post-weaning dietary specifications were sufficiently high in nutrient density per tonne of feed fed, then as practical farm nutri- tionist Mick O’Connell has shown (see Table 2), the more expensive high density starter diet wins both in performance and economic terms, but my farm trials suggested that on other hand that lean gain does not catch up by slaughter, as is often the case. And when analysed properly, then both science and practice can largely agree. O’Connell correctly uses a high-density diet to minimise the post-weaning check and dead- weight as his preferred measurement. There are countries in the world where pig producers are still paid on liveweight terms when dead- weight, i.e. lean meat, would be superior from the consumers’ angle. We still have much to learn and apply to record measurements, as I have been saying for over 50 years – see my ‘New Terminology Needed’ in my 3 pig textbooks and 3,000 articles. Getting better, but too slowly, I fear!


Table 2 – The effect of different density postweaning starter feeds on compensatory growth.


Feed intake (g/day) Growth (g/day)


Medium density 387 258


FCR 1.50 Feed cost/kg deadweight Source: O’Connell (2010).


0.5p (€ 0.0056)


High density 405 357 1.15


0.42p (€ 0.0046)


▶PIG PROGRESS | Volume 36, No. 5, 2020


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