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Later weaning can significantly boost piglet performance during the immediate post-weaning period, but it will not improve clinical health status. That was the finding of a study – the AGEWEAN programme – to investigate the effects of weaning age in both an indoor- and outdoor-lactation environment on the biological and economic efficiency of production where diets contain no antibiotic growth promotors (AGPs) and include lower levels of copper and zinc.
The immediate post-weaning period in pigs is often characterised by a reduced and variable food intake, digestive disorders and poor growth and development. Weaning pigs at a later age has been suggested as an approach to reduce the potentially negative effects of the AGP ban on the national herd.
The results of the research were presented to delegates at the British Society of Animal Science’s annual conference by Newcastle University’s Helen Edge.
Involving piglets at six separate experimental sites in the UK, the three weaning age treatments were four weeks, six weeks and eight weeks. All progeny were monitored to weaning, at least 50% were monitored to 30kg live weight and at least 25% were monitored through to slaughter weight.
“And there were significant differences between the three weaning age treatments in terms of daily live weight gain (DLWG), feed intake and feed conversion efficiency (FCR) during the immediate post-weaning period. Pigs weaned at eight weeks of age had significantly higher DLWG and feed intakes. But their FCR was poorer, possibly due to them being offered a lower quality diet appropriate to their age,” explained Dr Edge.
Conversely, from 30kg to the point of slaughter, pigs weaned at four weeks of age had significantly higher DLWG and feed intake than pigs weaned at either six or eight weeks of age. There was no significant difference in FCR.
There were significant effects of weaning age on the back-fat thickness of the pigs at the point of slaughter. And in terms of overall lifetime performance, pigs weaned at four weeks of age had a significantly higher DLWG when calculated from birth to slaughter.
“While there was no effect of weaning age on the number of pigs requiring veterinary treatments from weaning to slaughter, there was a significant increase in the number of four week weaned pigs being removed from trial during this period,” added Dr Edge.
“Overall, when physical performance was considered over the period from birth to slaughter, there were no benefits of later weaning.”
Breeding could be the key to improved piglet pre-weaning survival in alternative farrowing systems to the crate. A recent study, carried out by the SAC, Newcastle University and Grampian Country Food Group, has shown that there is potential to breed for high survival in alternative farrowing systems.
“Recent estimates of total pre-weaning piglet mortality range between 16% and 19%,” the SAC’s Emma Baxter told delegates at this year’s British Society of Animal Science annual conference. “A different approach to effectively address piglet survival is needed. Genetic breeding programmes implemented in alternative farrowing systems could prove a viable option,” she said.
To test this theory, behavioural and physiological indicators of pre-weaning piglet survival were measured on both gilts and their piglets in a genetic selection group bred for high (postnatal) survival (HS) and a control group (C) farrowing in indoor loose-housed and outdoor farrowing systems in a two-by-two design. The gilts were offspring from a previous generation selected for survival traits and bred under outdoor conditions.
In the outdoor environment total mortality tended to be higher in the control litters than the high survival litters – 18% compared to 12% – and this tendency was even lower in live-born mortality at 13% compared to 10%. In the indoor environment there were no significant differences in either total mortality or live born mortality.
Regardless of environment or genotype, important indicators of prenatal survival were body shape and size, farrowing birth order, and placental efficiency. Birth weight and behavioural development were the most important indicators of postnatal survival and, although indicators were independent of environment, there were genotype interactions with temperature and time to udder as survival determinants.
Gilt behaviour affected piglet postnatal survival. Piglets that died had mothers that were more careless with their posture changes, crushed more and were more aggressive. When comparing survival indicators at a litter level, regardless of environment, the control gilts showed more crushing incidents – both fatal and non fatal. In the indoor environment, high survival gilts were more aggressive towards their offspring and were the only genotype to show savaging – 40% of the high survival indoor gilts mouthed or bit piglets.
“The mortality results in the indoor environment illustrate the genotype by environment interactions and the potential to further improve survival,” explained Miss Baxter. “Indicators of prenatal survival were generic across systems, with piglet shape being the most important survival indicator.
“Postnatal survival indicators included birth weight and behavioural development,” she added. “In both systems, control gilts showed more crushing behaviour than high survival gilts. However, there are potential undesirable side-effects of selecting for high survival gilts in the indoor system, as they showed heightened aggression towards their piglets.”
Less ‘active’ sows were more prone to crushing their piglets in a recent trial that looked at the link between sow behaviour and their history of piglet crushing. That was just one of the unexpected findings of a study, carried out at Writtle College in Essex, that compared the behaviour immediately post-farrowing of sows with a history of piglet crushing and those without a single recorded mortality due to crushing.
The crushing of piglets by the sow is the main cause of pre-weaning mortality and has been reported to be responsible for up to 80% of piglet deaths. Studies have identified that sows maintain some stable behavioural traits over parities, for example response to a piglet scream test, and sows with a history of crushing piglets are more likely to stay inside a farrowing hut while housed outdoors.
“However, there is little information available regarding previous piglet-crushing history and its association with the behaviour of sows housed in farrowing crates,” said Writtle College’s Jonathan Amory, when he presented the findings of the trial to delegates at this year’s British Society of Animal Science’s annual conference.
“Sows with a history of piglet crushing showed different behaviour patterns to those that had never crushed a piglet,” he explained. “And contrary to expectations, the latter group of sows made more transitions between sitting/lying and standing than the sows with a history of piglet crushing.”
He said that this had previously been suggested to be the point at which piglets were most at risk from crushing. “But we now know that this may depend on other factors, such as how calm the sow is. In our study, sows with a history of crushing were more restless while lying compared with sows without a ‘crushing’ history. In fact, sitting up from a lying position was responsible for 24% of piglet trappings, which is higher than recorded by other researchers.”
Although the sow’s reactions to her piglets has previously been suggested to be an important factor in piglet survival there was very little attention paid by ‘crushing’ and ‘non-crushing’ sows to their litter before or after posture changes, regardless of whether a piglet had been trapped.
“This might suggest that piglet behaviour might play a more important role in influencing the incidence of piglet crushing,” added Dr Amory.
How water is supplied to growing pigs has no effect on their performance, but it can make a difference when it comes to waste and slurry volume – up to an additional 32 tanker loads, according to a trial recently completed at Hillsborough’s Agri-Food and Biosciences Institute and led by Elizabeth Magowan.
“Neither drinker design or position had any effect on pig performance. However, significantly more water was used with the Halfman Bite and Jalmarsen Bite Ball drinkers compared to the Drik-O-Mat Bowl and Verba Nipple drinkers we used in the trial,” she told delegates at this year’s British Society of Animal Science annual conference.
Inadequate water intake is associated with reduced feed intake, poor daily gain, poor feed conversion, scour problems and lower digestibility of feed in pigs. And factors that can reduce water intake include contamination, high mineral content of water, low temperature, low flow rate from drinker, too few drinkers or poor drinker/nipple position. “But there is a lack of information on the effect of drinker design on water intake and performance,” said Dr Magowan.
“Three designs of drinker commonly used are nipple drinkers, bite drinkers and bowl drinkers. And the aim of our study was to investigate the effect of drinker design and position on performance and water usage of growing pigs,” she added.
A total of 720 pigs were split into groups of 20 and randomly allocated to one of six treatments. Two drinkers were placed in each pen of 20 pigs. Pigs were offered water from four drinker designs, two of which were in different positions. Daily feed intake, daily live weight gain, feed conversion ratio and water usage were determined from weaning to seven and 10 weeks of age.
“And we found that the design or position of drinker had no effect on growth performance, feed intake or feed conversion efficiency of pigs,” said Dr Magowan.
Flow rates were measured as 250ml/minute, 600ml/minute, 700ml/minute and 1,200ml/minute for the Drik-O-Mat bowl, Verba Nipple, Halfman Bite and Jalmarsen Bite Ball drinkers respectively. Compared to the Drik-O-Mat bowl and Verba nipple drinkers, water usage tended to increase from four to 10 weeks of age, when the Halfman bite drinker was used and was significantly greater when the Bite Ball drinker was used.
“It is likely that the majority of the extra water used was wasted and, therefore, potentially increased slurry volume, resulting in an additional 17 and 32 tanker loads (6.82 m3) of slurry produced per year on a 200-sow unit using either the Halfman Bite or Jalmarsen Bite Ball drinkers respectively,” added Dr Magowan. “And this would have major implications on the dry matter of slurry and slurry storage requirements on pig farms.”
Weaner piglets prefer zinc oxide-free feed because the palatability of feed is reduced by adding the mineral. These were just two of the findings of a trial, carried out by scientists at the University of Leeds, to test the hypothesis that weaned piglets would avoid a diet high in zinc oxide (ZnO) when given the choice, and to investigate the resultant performance and choice feeding behaviour of individual piglets in the immediate post weaning period.
“A nominal amount was still eaten in our trial, suggesting the piglets consumed a small amount in ‘continuous sampling behaviour’, albeit insufficient to benefit the piglet,” Fiona Reynolds told delegates at this year’s British Society of Animal Science annual conference.
ZnO is frequently added to nursery piglet diets at pharmacological levels to combat scouring and to improve performance of weaned piglets. “It is anecdotally recognised in the pig industry that piglets do not like the taste of zinc although increased feed intake is frequently reported,” added Miss Reynolds.
The study involved 60 piglets which were weaned at 7.8kg and 27.8 days of age into eight mixed sex groups of seven or eight piglets per pen. Groups were balanced for litter origin, weaning weight and sex, and housed in fully slatted weaner pens. Piglet feeding behaviour was constantly recorded by a multi-spaced feed intake recording system.
Each pen of pigs was offered ad-lib access to two different foods, each in two troughs per pen. Feeding time – in minutes – was recorded for each individual at each trough. Foods (16.2MJ DE, 1.6g lysine/kg) differed only in the level of ZnO supplementation – unsupplemented or supplemented at a rate of 3.1g/kg.
The unsupplemented feed contained a basal level of zinc (100ppm). Piglets were weighed at weaning and at day seven and 13 thereafter. The experiment ran for 13 days. Piglets were then categorised by weaning weight into three categories: small, less than 7.0 kg); medium, more than 7.1kg but less than 8.0kg; and large, more than 8.1 kg.
“And we saw that, on a pen basis, groups of piglets showed significant preference for the unsupplemented food in both week one and two post weaning,” said Miss Reynolds. “Average piglet gain was low, at 0.039kg and 0.272kg per day in week one and two respectively.
“When feeding behaviour data were examined on an individual basis, the effect of weaning weight and gender on proportion of time spent eating each food did not influence diet choice.”
Miss Reynolds said that ZnO has proven positive effects on piglet health and performance post weaning, although the newly weaned piglet would have no prior experience of such.
“The proportion of time spent eating the supplemented food was not influenced by weaning weight or gender. And, ironically, diet selection by piglets on this experiment is associated with poor performance and incidence of scour, highlighting the importance of ZnO on the health and performance of the weaned animal,” she added.
Reducing protein to a low level in pig diets in the later stages of growth reduced nitrogen intake – a major factor in nitrogen losses to the environment – with relatively few deleterious effects on performance except that fat thickness was increased, particularly in the leaner breed.
“This suggests that energetic efficiency was increased on the low protein strategy,” said Bristol University’s Jeff Wood, presenting the findings of a trial – to compared three ‘nutritional strategies’ providing different protein and energy levels as pigs of two breeds grew from 40 to 120kg live weight – to delegates at this year’s British Society of Animal Science annual conference.
“Dietary protein is the main source of nitrous oxide and nitrates – harmful pollutants that are produced in pig units. So reducing the level of protein in the diet may be environmentally friendly. But will this compromise performance?” he asked.
The study involved 192 entire male pigs – half 75% Large White and half 75% Duroc. They were reared on one of three ‘nutritional strategies’ from 40 to 120kg live weight at Harper Adams University College.
The dietary ingredients were the same in all strategies and ‘state of the art’ and ‘low protein’ diets were balanced with amino acids so the ratios with lysine were the same as in the ‘baseline’ diet. The pigs were fed ad lib from hoppers and reared in groups of eight pigs per breed and strategy.
At approximately 120kg live weight, the pigs were transported to the University of Bristol abattoir where they were slaughtered and samples were removed for analysis. For individual pigs slaughter weight, carcass weight, P2 fat thickness, and daily live weight gain were statistically analysed. Intakes and food conversion ratios were also analysed for each pen.
“Of the data recorded on individual pigs, only P2 fat thickness was significantly different between factors, being greater in Duroc than Large White pigs fed the low- protein, baseline and state-of-the-art diets,” said Professor Wood.
“The small numbers of observations for data recorded on a pen basis was partly responsible for the lack of significant effects for intake parameters. When breeds were pooled, there were no significant effects of nutritional strategy on these parameters except for nitrogen intake per kilogram of weight gain, which was lowest for pigs fed the low-protein diet,” he added.