ICAR AICE-JRF/SRF Applied Animal Nutrition I: Ruminants: practice questions

Question 1 · medium

Butyrate produced by fermentation of calf starter is important for the young ruminant mainly because it:

1. closes the oesophageal groove reflex when milk is fed
2. stimulates growth and development of the rumen papillae
3. provides the main substrate for lactose synthesis later
4. inhibits methanogenic archaea and so spares rumen energy

Question 2 · medium

Why is cobalt deficiency in grazing ruminants expressed clinically as a vitamin B12 deficiency?

1. Cobalt is the dietary vitamin precursor that the liver converts into B12 for later storage
2. Rumen microbes need cobalt to make vitamin B12, cofactor in propionate metabolism
3. Cobalt is needed by the abomasum to secrete intrinsic factor for absorbing dietary B12
4. Cobalt blocks copper uptake, and the copper shortage then lowers the B12 stored in liver

Question 3 · medium

Which fatty acid intermediate of incomplete rumen biohydrogenation is accepted as a direct inhibitor of milk fat synthesis in the udder?

1. cis-9, trans-11 conjugated linoleic acid
2. vaccenic acid (trans-11 octadecenoic acid)
3. stearic acid (octadecanoic acid)
4. trans-10, cis-12 conjugated linoleic acid

Question 4 · hard

Goats in a new region develop alopecia, goitre and poor growth on a diet rich in Leucaena leaves, whereas goats in another region on the same diet stay healthy. The best explanation is that the healthy goats:

1. carry rumen bacteria that degrade DHP, the goitrogenic mimosine metabolite
2. have been given iodine so the mimosine is chelated and excreted harmlessly
3. lack the rumen enzymes that would convert the leaf tannins into toxins
4. eat the leaves only in the dry season when the mimosine content is zero

Question 5 · hard

Using NEL (Mcal/kg) = 0.0929 × fat% + 0.0547 × protein% + 0.0395 × lactose%, what is the energy content of milk with 4.0 percent fat, 3.3 percent protein and 4.8 percent lactose?

1. 0.74 Mcal/kg
2. 0.37 Mcal/kg
3. 1.12 Mcal/kg
4. 0.55 Mcal/kg

Question 6 · hard

In modern metabolisable protein (MP) systems, MP is defined as:

1. crude protein in the diet minus the protein lost as nitrogen in the faeces
2. true protein absorbed in the intestine: microbial protein plus digestible RUP
3. rumen-degradable protein plus non-protein nitrogen supplied in the ration
4. crude protein in the diet multiplied by its biological value in growth trials

Question 7 · hard

A sensitivity (ranging) analysis on a least-cost ration shows that groundnut cake stays in the solution only while its price is between 30 and 46 units per kg. If its price rises to 50 units, the program will most likely:

1. keep the same amount of cake and cut the energy minimum to make up the cost
2. replace some or all of it with another protein source and raise the ration cost
3. keep the cake in the ration at the same level, since its CP content is fixed
4. remove every other protein feed so that the cake share can rise to fill the gap

Question 8 · hard

Mature cows in a herd weigh 650 kg. A heifer born at 40 kg is to reach 55 percent of mature weight by 15 months (456 days). What average daily gain is needed?

1. 0.78 kg/day
2. 1.50 kg/day
3. 21.17 kg/day
4. 0.70 kg/day

Question 9 · medium

Lucerne and berseem are harder to ensile than maize because they have:

1. high sugar content and very low buffering capacity
2. high lignin content that blocks the lactic bacteria
3. low water-soluble sugar and high buffering capacity
4. low crude protein and too much starch in the leaves

Question 10 · hard

Dark brown silage with a tobacco-like smell has been heat-damaged. Which laboratory measure best quantifies the loss of protein availability?

1. Water-soluble carbohydrate content
2. Acid detergent insoluble nitrogen (ADIN)
3. Neutral detergent soluble ash
4. Silage pH measured on fresh sample (by electrode)