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"Experientia docet" - Experience is the best teacher

Prof Jannes van Ryssen                    Students busy with the quiz

I am certain that all delegates who have attended the last three SASAS Congresses agree the student quiz session has been one of the most exciting, intriguing and talking points.

We thank Prof Jannes Van Ryssen for agreeing to ‘blog’ on the questions that were posed at the recent SASAS Congress that was held in Stellenbosch.  Let’s re-visit the memorable time we had in Stellenbosch by going through the questions, answers and explanations/background information given below (NB. We welcome comments on these blogs. We also invite members to submit blogs for the website).


1. Which foodstuff contains, on a per kilogram dry matter basis, the highest vitamin A concentration?

                a.             Carrot

                b.             Pumpkin

c.             Grade A3 lamb’s meat

                d.             Yellow maize meal

Plants do not contain any vitamin A, but only precursors of vitamin A, the carotenes such as β-carotene that can be converted to vitamin A in the body.

Some carotenes have antioxidant properties in the body and can be classified as such as a nutrient.  

2. Which animal species or breed cannot convert β-carotene in their bodies into vitamin A?

                a.             Jersey cow

                            b.             Cats  

                c.             Rabbits

                d.             Dalmatian dogs

Cats, as true carnivores, must receive vitamin A through their diets, i.e. usually through animal tissues.

Jersey cows have a lower ability to convert carotene to vitamin A than the Holstein, and their milk fat is consequently more yellow than that of Holsteins.

3. The giraffe is a:

                             a.             Ruminant

                b.             Hindgut fermenter

                c.             Omnivore

                d.             Ratite

The giraffe has the typical four-chamber stomach arrangement of the ruminant.  The question is, does a giraffe ruminate?

The process of regurgitating fibrous feed from the rumen into the mouth for chewing is stimulated by the scratching effect of the mat of fibrous material floating on top of the fluid in the rumen. In the case of the giraffe which is a browser, highly digestible plant leaves containing little fibrous material are consumed. Mat formation and thus regurgitation and rumination do not readily occur in the giraffe.

It would be interesting to hear if giraffe has been observed chewing the cud.

It is often observed that giraffes chew bones. However, this is probably owing to pica, “abnormal appetite”, a symptom of phosphorus deficiency.

4. Coprophagy is the term used for:

                a.             Crop feeding in birds

                b.             Feather pecking in poultry

                c.             Animal with a craving for copper

                              d.             Animals eating their own faeces

5. Coprophagy (eating their own faeces) does not occur in which species?

                              a.             Goat

                b.             Elephant 

                c.             Rabbit

                d.             Horse

Coprophagy occurs in monogastric species and especially hindgut fermenters, but not in ruminants.

In rabbits coprophagy (called caecotrophy because of the ingestion of “special” faeces) is their primary way of ingesting vitamins.

Foals practise this, with preference to the faeces of their dams. This is also observed in young elephants. It has been recorded that mature horses on a protein deficient diet ingest horse faeces.

6. Which beef production system has the lowest methane emission per kg of dry feed consumed?

              a.             Grazing on cultivated pasture

              b.             On a feedlot diet                 

c.             Veld grazing fed with supplements (licks)

d.             Veld grazing fed without inorganic supplements (organic)

Methane production by ruminants is affected by the type of feed and the amount of feed consumed. The duration of the finishing period, i.e. to reach a specific slaughter weight contributes substantially to the amount of methane produced.

Any animal science student who has completed the basic animal nutrition course should be able to calculate the approximate methane production of weaner calves on a feedlot diet (approximately 130 days) versus their full brothers that are finished on grazing (200 plus days depending on the quality of the grass).

7. Judith Capper calculated in her article in SAJAS (volume 43, no 3) that if all USA inhabitants don’t eat any meat on Mondays in a Meat-free Monday campaign, it will reduce the USA national Green-house gas production by:

                a.             18%

                b.             8%

               c.             1%

                            d.             0.3% 

The article by Capper in the S. Afr. J. Anim. Sci. (2013, volume 43 published on this SASAS website) points out the ridiculous claim by meat-free Monday campaigners that they save the world.

8. In general, which laying hen production system has the highest mortality rate among the hens over a production cycle?

                a.             Hens in a battery system

                b.             Hens on a deep-litter system within a shed

                c.             Hens in enriched cages

                             d.             Free-ranging hens

Although mortality rates differ in different studies, the mortality rate in free-ranging hens is consistently and substantially higher than in the other production systems, e.g. a rate of 8% to 10% among free range hens compared to 2% to 4% in hens in cages has been quoted, i.e. at least two to three times higher.

This points to an interesting contradiction in claims by free-range egg producers, viz, that free ranging is a very humane production system compared to the other systems. Are free-ranging hens with a mortality rate three times higher than in other systems “more happy” than hens in the other production systems with much lower mortalities?

This does not even address the dubious claims that free-range eggs are more healthy than egg from other production systems.

9. Under optimal conditions the modern laying hen lays an egg:

                a.             Every day at the same time

                             b.             Every day an hour later than the previous day, and then skips a day

                c.             Anytime of the day, whenever the urge develops to lay.

                d.             Usually when the lights come on / sun lightens up the chicken house.

10. On average, approximately how many eggs does a modern highly productive laying hen in a battery, lay over a production cycle of a year?

                a.             One egg every day = 366

                              b.             ± 300

                c.             ± 230

                d.             An egg every second day = 180

An animal will produce optimally if it is not under stress.

11. The foot section of a cow is called:

                a.             Hoof

                b.             Paw

                              c.             Claw

                d.             Talon

The Yanks seem to use the word, hoof, but horses have hoofs.

12. The keratinized epidermal part of claws and horns of cattle is sometimes ground and sold as a feedstuff, “hoof & horn meal”. It should:

                a.             Be high in calcium and phosphorus

                b.             Contain plenty of highly digestible protein

                              c.             Have the same aphrodisiac potential as rhinoceros horn

                d.             Be a good source of biotin

“Hoof & horn” meal has no nutritional value. It consists of the same component as rhino horn, i.e. mainly keratin, with an aphrodisiac potential of zero, as in rhino horn.

A “hoof & horn” meal sample analysed at the UP Nutrilab contained 72% crude protein, 2.4% Ca and 2.0% P. However, the protein in keratin would be largely indigestible because of strong disulphide bonding of the amino acids. Poultry feathers, also consisting of keratin, have to be hydrolysed under high pressure and temperature to hydrolyse the chemical bonds, and to produce an animal feed, “hydrolyzed poultry feather meal”.   

13. The underlying reason why sheep defecate pellets and cattle pies is:

a.             Sheep are adapted to arid climatic conditions, cattle not

b.             Relative to body size, cattle drink much more water than sheep

              c.             In proportion to body size, cattle have a much shorter colon (large intestine) than sheep 

                            d.             Sheep can eat much more selectively than cattle

Jarman-Bell Principle: While the relative sizes of organs decreases with increasing body weights, gut capacity remains a constant fraction of body weight. A consequence is that a larger reticulo-rumen of grazers leads to an obligatory size reduction in other organs, for instance the colon descendens. For very large grazers, a "regular" faecal water absorption as in other ruminant species is no longer possible. In cattle, less water is absorbed, resulting in wetter faeces than the drier pellet in sheep.

(Clauss et al., 2003. The maximum attainable body size of herbivorous mammals. Oecologia 136, 14-27).

14. What was the name of the first cloned animal in Africa?

  1. Thuli
  2.             Futhi
  3. Thabi
  4. Dolly

The first cloned animal on the African continent, a Holstein heifer, was born at Brits in the North West Province on the 19th of April 2003. No semen or bull was involved in the birth of the calf. It has been derived from a single cell taken by biopsy from the ear of a donor cow, inserted into an empty cow-egg and later implanted into a recipient cow. The heifer has been named “Futhi”, meaning “replica or repeat” in Zulu. The donor cow was a former South African milk-production record-holder with her yield peaking at 78 litres a day. (Google)



15. What is the function of the proline-rich protein in the saliva of some herbivores?

         In browsers the protein binds (de-activates) tannin in leaves. This is one of the main reasons why some herbivore species (browsers) can take in tree leaves that is normally high in tannin, and grazers (cattle, sheep) consume only grasses free of tannin.

         (See also article by Mlambo et al., 2015. S. Afr. J. Anim. Sci. 45, 441-451 on SASAS website).

16. Which South African sheep breed prefers to browse rather than to graze if conditions permit it? The Damara sheep breed: an exception because sheep are generally considered as grazers.  

17. What is die upper permissible water content in maize grain when a farmer delivers it to a maize silo?                     

          ≤14% water.  At a moisture content of above 14%, microbial growth in stored maize kernels becomes a serious problem, not only because of any toxic effects, but also because of the generation of heat and the risk of spontaneous combustion.   Grain silos are monitored on a continuous basis for any increase in temperature which would prompt the immediate removal and drying of the maize. 

18. What is “in ovo” nutrition?

           Supplementing an egg during incubation with a nutrient, using a syringe and a small hole in the eggshell. (Two articles on this topic have been published in the South African Journal of Animal Science, volume 42 (2012), pages 131 and 210).

19. Explain why excreta of birds consist of a white fraction and a dark fraction.

           The white is the urine (containing uric acid), the dark the faeces.

20. In poultry nutrition, diets are formulated on an “as fed” basis. What is the assumed overall dry matter content of the feed ingredients?

           90% DM, (10% water) in pig and poultry diets, when “dry” feed ingredients are used to compile the ration.

            In ruminant nutrition, diets are formulated on a dry matter (100% DM) basis because the moisture content of the ingredients in ruminant diets can vary substantially.

21. In pig nutrition, why is a measurement of ileal amino acid digestibility more reliable/useful than faecal amino acid digestibility?

           After the ileum, protein is further digested in the large intestine through microbial fermentation, but the pig cannot benefit from this because the amino acids cannot be absorbed from the large intestine.

22. What is hermaphroditism in fish?

Fish that possess both genders, and can decide which gender to “switch on”.

23. On a dry, fat-free basis, what is the ratio of protein to ash in the mammalian carcass?

          80% protein : 20% ash  i.e. 4 : 1 ratio (except in “double-muscled” animals).

           A correction: It refers to the animal body without the digestive tract content. “Gross body composition of mature animals in a good state of nutrition is very similar when expressed on a dry, fat-free basis.”

24. What is the relationship between concentration of fat and water in the body of animals?

          The fat to water percentages in the body are inversely related, viz. the fatter the animal the lower the percentage water in the body.

These concepts in questions 23 and 24 form the basic, underlying principles of some of the techniques to estimate body composition in live animals, including humans: Water content is measured, and through formulae obtained for the specific situation, fat content and from there, muscle (protein) and bone (ash) content at a specific body weight are estimated.


Professor Jannes van Ryssen


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