Davi Brito De Araujo
Global Program Manager
Research findings from Selko, the Feed Additive brand of Trouw Nutrition, Nutreco’s animal nutrition division, have shown that the source of trace mineral can help or harm feed palatability. With this insight in mind, scientists have placed a specific focus on the use of trace mineral types in creep feed or pre-weaning diets.
Palatability research in swine and ruminants has demonstrated that mineral source influences feed intake. Research finds that reactive mineral sources, like sulphate-based trace minerals, can change the flavour profile and reduce feed intake, especially when high levels are present in pre- and post-weaning diets. Use of less reactive trace minerals - like hydroxychloride-based trace minerals - can support or even improve intake of feed for young swine and calves. Establishing and supporting strong feed intake early in life can help animals reach their full potential as seen in better adaptation following weaning, along with stronger weight gain earlier and throughout the production process.
TRACE MINERAL DEVELOPMENT
As livestock genetics have improved, animals have started to require higher levels of nutrients than are available in feed ingredients alone. This requirement is prompting the use of supplements including additive trace minerals. Trace mineral types also have seen development advancement since their initial use decades ago. Advances in feed additive technologies have improved mineral bond stability and bioavailability while reducing reactivity (Figure 1). Established in the mid-1990s, hydroxychloride trace minerals provide a more stable covalent bond that is not reactive to liquid at a neutral pH the way that sulphate-based trace minerals are. This insolubility aspect is of interest because weak metal bonds allow trace minerals to dissociate and leave metal ions free to interact with other dietary nutrients and potentially alter feed flavour. Additionally, hydroxy trace minerals have a higher metal concentration – 44-56% - than organic trace minerals and a lower price point.
Figure 1 - Trace mineral type can influence feed palatability, nutrient expression and element function based on how reactive or bound metal ions are.
FEED PALATABILITY FLAVOUR, FEED INTAKE AND FEEDING FREQUENCY
The taste of feed, especially for young animals, can be quite important as taste helps spur or suppress appetite and feed intake. Both ruminants and swine can taste different compounds – pigs have more taste sensors, or taste buds - than humans do, making palatability a priority. While swine can identify a range of flavours including bitter, sweet, sour, fatty or salty only certain flavours encourage pigs to keep eating. Other flavours, like bitter or salty, may prompt animals to slow or stop feed intake increasing the importance placed on feed palatability - especially with young animals learning to eat new feed.
Figure 2 – Several specific flavour compounds play a role in determining how palatable a feed or feed ingredient will be.1
One view of the role taste plays considers the short and long-term control of appetite involved. Short-term control relates to the size of the meal eaten at any one time, while long-term control looks at how often an animal eats or how much time occurs between meals. Feed taste and palatability help dictate how much animals eat, when they eat, how often they consume and how much.
With feed intake, certain flavours including bitter, sour and salty tastes could be related to problems with the material being eaten and often encourage an animal to slow or stop eating specific feeds, which means those flavour profiles should be avoided. (Figure 2)
Figure 3 (1 and 2) – The type of supplemental copper in swine diets tends to have a greater influence on feed palatability than how much is included.
Similarly, some types of trace mineral can alter feed intake by changing flavours and feed palatability. Soluble and reactive trace minerals can start to dissolve in the mouth releasing metal ions and producing bitter or salty flavours and negatively influencing feed intake. Using a more neutral tasting and less reactive trace mineral source may be able to prevent the drop in feed intake from occurring and potentially improve feed intake.
SWINE PALATABILITY RESEARCH COPPER INTAKE INSIGHTS FROM SPAIN AND KANSAS, USA
A series of studies explored the use and palatability of different types of trace mineral in swine feed. Early feeding habits help establish good feed intake during a pig’s lifetime. However, slow early feed intake can lead to digestive problems and low blood copper levels, which can prompt developmental problems.
Figure 4 – Hydroxy copper is more stable and less reactive with other diet ingredients at a neutral pH than copper sulphate.
A set of feeding trials done in at the Universitat Autonoma in Barcelona tracked the dietary preference of young pigs.2 In the first feeding trial, swine were offered two diets, one with 15ppm copper sulphate and one that included either 150 ppm copper sulphate or hydroxychloride copper. In the second, pigs could choose between diets supplemented with 150ppm copper sulphate or 150 ppm hydroxy copper (Figure 3).
Figure 5 – When picking between two copper-supplemented feeds, swine found the feed containing hydroxy copper more palatable.
Feeding trial results indicate that when given the choice between diets with copper sulphate at low (15ppm) or high (150ppm) levels and high levels of hydroxy copper (150ppm) swine are more likely to eat feed with hydroxy copper – especially in the early period of the trial.
Diets in both trials also contained 500 units of phytase and an in vitro assessment of copper source, solubility, and interaction with phytase was conducted. At a neutral pH, similar to what would be found in the mouth, copper sulphate almost completely dissolved while hydroxy copper saw less than 20% solubility. However, at a pH of 2.5, like what would be found in the gut, both copper sulphate and hydroxy copper completely dissolved (Figure 4)
Researchers also tracked phytic phosphorus solubility at a neutral pH (6.5) when copper sulphate or hydroxy copper was present. Copper sulphate reduced solubility of phytic phosphorus, while its levels stayed predominantly consistent when combined with hydroxy copper. This will allow the added phytase to break down more of the phytic phosphorus, as it is only available to the enzyme when it is in solution.
Similarly, a feeding trial conducted in 2016 tracked feed intake and swine preference when provided diets containing 160ppm copper and 110ppm zinc from either a sulphate or hydroxychloride source for a 34-day period.3 Pigs consumed more of the feed with hydroxy-based trace mineral throughout the length of the trial but were especially likely to consume the feed from days 0-14.
Figure 6 – Mineral supplements used outdoors are in danger of being damaged or degraded by weather events if the type of mineral does not have strong bonding abilities.
A study conducted at Kansas State University looked at preference in older pigs and tracked diet selection by grower-finisher animals.4 in the trial, 150 pigs were provided one of three diets – a control with no additional copper, and two experimental diets with 150ppm copper from either a sulphate or hydroxychloride source. Pigs were provided options between either the control and copper sulphate, the control and hydroxy copper, or copper sulphate and hydroxy copper. Results of the palatability trial found that swine preferred the diet with no added copper, but when choosing between the control and a supplemented feed more were willing to eat the feed containing hydroxy copper. However, when pigs picked between the two supplemented feeds the diet containing hydroxy copper was almost twice as popular. (Figure 5)
Improving the palatability of feeds, especially for young swine is important for the animal’s long-term development and performance. A study done in 2017 tracked feed intake during early life and found that improved feed intake pre-weaning spurred better daily gain through the post-weaning period.5 By day 42, animals that started with higher feed intake and receiving feed with hydroxy copper weighed an additional 1.6 kg.
Figure 7 – Sulphate-based trace minerals decrease the intake of creep feed in calves.
Improving feed palatability before weaning helps establish better feed intake, higher daily gain, and improved performance for pigs throughout production. Any boost to feed intake before weaning supports post-weaning growth and can provide significant reduction in total days to market.
RUMINANT RESEARCH REVIEW
Palatability also plays a role in feed and mineral intake for ruminants especially when minerals are provided in an ad libitum form and supplement intake needs to be managed.
An initial step in guiding the use of freely provided mineral supplements is reducing waste of the mineral. A study done at the University of Florida examined the amount of trace mineral that can be destroyed by weather conditions based on the type of minerals being provided to an outdoor herd.6 The study looked at hydroxychloride minerals, organic trace minerals and sulphate-based trace minerals and compared how mineral blends survived a series of 2-, 4- or 6-inch rainfall events. The trial found that when blended minerals or a complete mineral premix interacted with a rain event both sulphate and organic trace minerals saw larger reductions in the metals provided compared to the losses seen by hydroxy-based trace minerals (Figure 6).
Figure 8 – Hydroxy-based trace mineral use creates a diet preferred by calves and calves with better mineral intake weather the stress of weaning better allowing for improved post-weaning weight gain.
Providing a mineral less prone to interacting with weather means more is in place to be used by livestock.
In a palatability study at the University of Florida examining trace mineral inclusion in creep feed for limit-fed calves, researchers found that removing sulphate-based minerals from the feed improved feed intake.7 There was about an 8-fold difference as supplement intake increased from 20g to 160g during the 14-week trial (Figure 7)
A two-year study, also at the University of Florida, explored the use of creep feeds combined with no mineral, or a blend of copper, zinc, and manganese from either a sulphate or hydroxy-based mineral source.8 Creep feeds were provided starting 84 days before weaning. The researchers found that calves ate the largest amount of the hydroxy-fortified creep feed -0.109kg/day or 8.73kg for the period – followed by intake of the control feed. However, intake of the sulphate-fortified diet was significantly lower, with the hydroxy feed seeing about a 26% increase in consumption.
Similarly, feeds with hydroxy-based trace minerals out-performed those with either sulphate or organic trace minerals in a 14-day examination of mineral concentrate intake. Additional research also demonstrated that calves with better mineral intake have a faster post-weaning recovery (Figure 8a).8
Additionally, preweaning intake for both beef and dairy calves has been linked to improved post-weaning performance. In dairy heifers, strong post-weaning performance helps dictate age at first calving, which also influences lactation performance meaning that mineral use can have a long-term influence throughout the cow’s lifetime. In cattle intake and body weight at weaning plays a role in weight gain and feedlot performance.
As feed contains flavours that animals avoid, feed intake may decrease in the presence of such flavours. These tastes can include bitter, sour, and salty flavours, similar to flavours released by highly soluble trace minerals. As such, sulphate-based mineral inclusion produces an adverse response for several species when the additives are present in feed, while use of less reactive trace minerals such as IntelliBond hydroxychloride minerals can support or increase feed intake.
In reviewing the findings, researchers concluded that calves and pigs prefer to consume more stable trace mineral sources such as IntelliBond over sulphate or also over organic trace minerals across a variety of supplementation stages and strategies. Increased preferential intake and palatability as a result of stable, non-reactive trace mineral source supplementation can help lead to greater performance results including higher feed intake, daily gain and also body weight at and after weaning. Research shows that higher weaning weights also result in higher lifetime performance in swine and ruminant species.
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1- Adapted from Roura and Navarro 2018; Fothergill and Furness 2018
2- Villagomez-Estrada, S., et al. 2020. Dietary Preference of Newly Weaned Pigs and Nutrient Interactions According to Copper Levels and Sources with Different Solubility Characteristics. Animals.
3- Internal Trouw Nutrition research.
4- Coble et al., 2014 MWASAS Abstract
5- Drayton Animal Health Ltd, UK, 2017
6- Wiebusch et al., 2015. J. Anim. Sci. 93(Suppl. s3):824
7- Moriel & Arthington. 2013. J. Anim. Sci. 91:1371-1380
8- Caramalac et al. 2017. J. Animal Sci. 95:1739-1750