維生素是健康和生產(chǎn)的重要營養(yǎng)

Vitamin nutrition is understood very well and has been the subject ofcomprehensive research over many years. This has yielded valuable tools toensure that domestic animals in human care are given the best opportunity torealise their genetic potential in terms of health, growth and feed efficiency.Not only do vitamins contribute significantly to production economy and animalwelfare but they also play a major role in reducing the carbon footprint fromanimal farming and food production.

Vitamins are normally added to the overall feed programme via the premixcomponent of the diet and typically this might be 25kg inclusion into a tonneof finished compound feed. Where the calculated inclusion of a specific vitaminmight be 5-50g per tonne of finished feed, the precision of the mix dispersionand general feed manufacture must be carefully managed by the vitamin andpremix manufacturer, the compound feed manufacturer and the home mixing farmer.

Vitamins – or as they were known at one time ‘vital amines’ – have a range ofactivities in animal feed programmes from the low end where deficiency symptomsare evident (and these are well documented) all the way through to the middlerange where there are curvilinear relationships with animal performance. Thenthere is the top end to very high levels of input, where effect is focused onspecial applications like boosting immune response or meat quality traits.

In formulating complete feed programmes, this middle band is where the industryoperates. Figure 1 (see attached pdf) gives a schematic illustration of thelevels of general vitamin inputs towards the expectation of post-weaning pigletgrowth. Extremities of input should be avoided but it is also an economicnecessity to strike the correct optimum position for maximum profitability.

Vitamins – definitions& functions
Firstly some basic notions on vitamin functions. Vitamins are active substancesessential for the life and well-being of the animal and this applies topiglets, growing/finishing pigs, sows and also boars. Vitamins arecharacterised by two basic properties:
1. Daily requirements for each vitamin are very small – usually measured in mgor μg.
2. Vitamins are organic compounds and hence differ in this respect from tracemineral nutrients.

Vitamins express catalytic functions: they can facilitate both synthesisand degradation of other nutrients – and therefore play a major role in thecontrol of general metabolism. They are always required for optimum health andnormal physiological functions such as growth, body development andreproduction. Most vitamins cannot be synthesised by the animals and they mustbe obtained from the feed.

In Table 1 (seeattached pdf) a general description ofthe major vitamins that are required in animal nutrition is given plus a basicfunction for each. It can be seen that many of these compounds impact ongeneral growth, feed efficiency and health status - in other words they have aprofound influence on the overall performance and profitability of the animal.

Deficiency symptoms inpigs
Vitamin deficiency symptoms are still seen on pig farms on a regular basis.Symptoms could be severe necrosis due to biotin deficiency, navel bleeding dueto a vitamin C deficient sow and splayed hind legs due to pantothenic aciddeficiency.

The reasons why vitamin deficiencies arise are many and varied but not leastdue to an inadequate feed intake (for management reasons) which is inextricablylinked to inadequate vitamin intake. The presence of vitamin antagonists isalso a cause. Mixing errors and poor formulation are a major problem. Poordigestion and hence absorption due to chronic or acute diseases are also majorcauses.

Vitamin requirements
Specific vitamin requirements vary widely and are influenced by the fact thatmany vitamins have positive or negative interactions amongst them. Vitamins cantherefore never be considered in isolation but better as a whole programme. Fatsoluble vitamins, for example, must be fed in correct ratios as they allcompete for intestinal absorption. Water soluble vitamins are also regulatorsof the intermediary metabolism of protein, fats and carbohydrates (energy) anda lack of any one can increase the need for the others.

Figure 2 (see attached pdf) presents a schematic to show the complexity of vitamin interactions andthe consequence of this is the difficulty in arriving at specific requirementsfor individual vitamins in the feed. It can be seen from this representationthat almost all of the vitamins listed in Table 1 have an interactive functionin both energy metabolism via Krebs Cycle and also in protein deposition andlean tissue growth via the control of the amino acid pool.

Impact
Vitamin applications are used at relatively small inclusions into finishedfeeds but the impact of this component on the finished feed has majorconsequences for growth, feed efficiency and reproductive processes. Somevitamins also have significant effects on carcass the quality. The actualvalues applied in commercial nutrition are also very much a ‘movable feast’ in thatgenetic improvement constantly changes the game and further research gives newinsights. DSM estimate that due to constant genetic change in growing pigsthere is likely to be a 1% change every year in overall vitamin requirements.

With constant selection and improvement of feed conversion ratios, feed intakeitself tends to be reduced over time. Thus, there is a need to revise theactual in-feed concentrations of vitamins to maintain the daily consumption peranimal. In addition, there is also an effect of modern animal productionmethodology at optimum stocking densities and in large populations underintensive conditions. This can induce chronic stress reactions in livestock,subsequently affecting vitamin requirements and in-feed concentrations.

The take home message for producers and farm managers is that they should beaware of these issues and relationships and understand the effects on their ownanimals and farm units. DSM Nutritional Products have developed the OptimumVitamin Nutrition concept, aimed at providing commercial nutritionists andnutritional advisers to home mixers with effective tools and guidelines forhigh precision formulation. The next two articles in this series will discussspecific vitamin values for pigs as well as the formulation of working diets.