Ref Code: CAT21

Category

Teaching - not applicable

Research - 4

Objective

1. Feeding trials assess the nutritive value of feeds and determine the feed requirements for particular beef production targets. Digestibility and balance experiments determine the digestibility of forages or mixed diets using single lines or breed types of cattle, and/or the balance between the ingested and excreted dietary minerals or diet components.
2. Grazing trials determine the production of different lines or breed types of cattle, or the assessment of pasture types or management strategies in terms of cattle output.

Alternatives to animal use

Animal performance, carcase quality, and perhaps meat quality, are influenced by intake and nutritive value of the diet. These effects can be modified by various animal factors such as genotype, disease status, etc, and can only be evaluated reliably in feeding experiments.

Details of procedure

1. Feeding trials may be conducted on pasture, in feedlot style yards or in an animal house. The two most common types of feeding experiments are:

   (i) Those where only intake and digestion are studied.
   (ii) Production experiments where intake, live weight gain, carcase and meat quality, and feed efficiency are determined.

Digestion may be also studied in these experiments.

The design of feedlot-style yards should comply with the Australian Model Code of Practice for the Welfare of Animals: Cattle, particularly the section applying to cattle welfare in feedlots.

Cattle can be group-housed or held in individual pens in animal houses for periods up to 150 days. The animal house should be cleaned regularly, every 2-3 days, and should be well ventilated. Pens should be sufficiently large enough to allow the class of cattle being used to turn around.

Tethering of cattle (see SOP CAT34) may be necessary for periods of up to 2-3 weeks for digestibility/balance studies. Unless otherwise justified, animals should be removed from pens and allowed to exercise in cattle yards for at least 20 minutes each day. This could coincide with routine weighing or other husbandry procedures.

Measurement of the digestibility of feedstuffs depends on the careful weighing of the feed offered to an animal and the total collection of the faeces voided. Sub-samples are kept in a forced-air drying oven to express intake-excretion on a common dry matter basis. Steers are the preferred sex since faeces and urine excretions can be readily separated. There are two preferred procedures, a metabolism crate (or pens which can be adjusted to reduce steer movement), or total faeces collection harness attached to the animal to collect faeces whilst it is fed in pens or yards.

For digestibility determined on feedstuffs fed to cattle in crates, the crate should be 2000mm x 800mm floor area for a 400kg steer, or 2200mm x 900mm floor area for steers up to 500kg. Steers above 500kg are unsuitable for crates and ought not be used. In pens, the harness gear should allow normal movement and the pens should be a minimum of 1500mm x 2200mm floor area for steers up to 400kg and 1700mm x 2400mm for steers up to 550kg. Steers above 550 kg should not be used. Digestibility studies should be done over a minimum of seven days, with at least three steers per diet, with the daily intake restricted to ensure intake of the offering is complete.

Metabolism crates are more suited to balance studies than are pens in which the animals must be tethered and restricted. Similar conditions apply as for digestibility estimates but, in addition, urine must be collected. Catheters are necessary for females, so their use should be avoided unless the ‘balance’ estimate applies to an aspect of female reproductive physiology.

2. Grazing trials. The grazing area must be surveyed to establish soil and pasture variation. With the assistance of a biometrician, the minimum number of animals required and the appropriate experimental design is determined to achieve the set objectives. When the design results in a number of small paddocks containing few animals, care should be taken to ensure sufficient water and shade are available to satisfy accepted welfare standards. Daily checking of animals is mandatory.

Mustering (SOP CAT25), drenching (SOP CAT16), fat assessment (SOP CAT35), calf marking (SOP CAT4), mating and weighing (SOP CAT23) are the main features of grazing studies, but pasture assessment should also be carried out. When the DM availability is <2000kg/ha or the adult animal is losing weight, consideration of supplementary feeding is necessary unless this conflicts with clearly defined objectives on performance, which would need to be outlined separately in an AEC protocol. When cattle require dosing with Controlled Release Devices which release ‘markers’, and faeces (SOP CAT7) and blood (SOP CAT6) samples are collected, these actions should be described separately.

Drugs, chemicals, or biological agents

Nil apart from drenches etc used for normal husbandry.

If collecting urine, preservatives (acids or heavy-metal salts) must be applied.

Impact of procedure on the wellbeing of animal(s)

Minimal in experiments where production feeding is being studied. In experiments where diet quality is low or where feed intake is restricted, some weight loss may occur. Excessive loss of weight or body condition should be avoided.

Reuse and repeated use

Feeding experiments with cattle may continue for up to 250 days. This is consistent with industry practice (eg the long-fed Japanese market). Cattle are never re-used in production experiments, and are rarely used more than once in intake and digestion studies. In changeover designs where digestibility is determined at a restricted level of intake, each animal may receive three or four diets. The period of restriction on each diet should not normally exceed two weeks, and animals should be fed to appetite during the intervening periods.

Steers should not be kept in metabolism crates beyond 10 days. Feet should be examined daily whilst in crates to ensure no discomfort. Steers may be reused after a break of at least 3 weeks from crate confinement, provided they have been exercised regularly during their confinement.

Steers should not be confined in pens restricted by total faeces collection harness for more than 14 days.

Cows used in grazing experiments should be examined annually from their seventh year to assess their fitness to continue. Cows over 11 years old should be culled from experiments undertaken in hot, harsh environments.

Care of animal(s) during/after procedure

Normal husbandry practices.

All animals confined in pens should be observed on a daily basis with a night check also being made on cattle confined to metabolism crates.

Daily supervision of animals in studies based on small paddocks is required, but in large studies where cattle have access to creeks and plentiful shade, observation may be reduced to twice a week except during mating and calving, when daily or twice daily observation is necessary.

Pain relief measures

Not required

Qualifications, experience or training necessary to perform this procedure

Training in ruminant nutrition and experience with cattle husbandry and animal house routines if appropriate. Should have experience with experimental design.