Rethink Feeding in Tough Times

 

Published: Stock and Land.  20th July, 1995

Dr Theresa Craig, a ruminant nutrition specialist from the United States, is in Australia to look at the way we feed our stock.
In this article, Dr Craig explains some research results of work in the U.S. on alternative feeding systems for lambs – something she says is very topical given that after the very dry season, pasture may not be the best source of feed.  Editor, “Stock and Land”

The current rains have helped eliminate stress associated with the drought.  However, feed supply is still limited, and what is available is very costly. 
This has caused producers to rethink their feeding systems to try to economise on feed and the associated cost.  There are options available other than grazing pasture.

With the extended drought, pasture may have not been able to support animals to their desired growth potential.  However, a constant supply of lamb meat is required even though supply is seasonal.  Differing feeding regimes allow for a more consistent, year-round supply of lamb to the market.  Presently there is a shift to a heavier and leaner lamb.  Consumers want lean, tender meat.

Lamb exports to the U.S. for 1994 totalled 9,157 tonnes.  Projected export is about the same, or possibly slightly lower, this year.  It is therefore to a lamb-producer’s benefit that a marketing strategy encourages American consumption of lamb.

There is also another marketing program for the Victorian lamb industry known as “Elite Lamb”.  This aims to provide a consistent supply of lambs with carcass weights of 22kg or more and a fat score of two to three.  Larger, leaner lambs are what abattoirs require to meet consumer expectation both here and abroad.

The production of leaner lamb allows for animals to be turned off younger, thereby allowing an increased stocking capacity.  The greatest percent of fat deposition in the animal is put on later in the growth phase.  Therefore, a younger animal is leaner by nature.  A heavier, leaner lamb requires less total feed than a heavy fat lamb.

Good quality pasture is hard to beat from a cost per gain perspective.  Yet, to fulfill demands of a year-round supply, lambs require more than just pasture.  A split system of pasture feeding followed by a feedlot period may be a viable option under certain climatic and economic conditions.  This will allow out-of-season production of finished lambs and premium prices paid.  For example, current market prices are 280c/kg dressed weight for 16-18kg carcasses compared with approximately 130-140c/kg for August through September lambs in 1994.  This option will also decrease the total number of days on feed – an important factor with interest rates on borrowed money of about 11.5 percent.

Another option is to lotfeed lambs from weaning to slaughter.  Producers would find it advisable to forward contract finished lambs to an abattoir or retailer.  This would ensure a guaranteed income to the producer, allowing managerial decisions to be based on economic returns.

Self-feed systems allow for reduced labour costs, while increasing the scale of the operation.  Pellets, a ground mix, lucerne pellets and grain, or a high concentrate ration can all be used in a self-feeder system.  This allows for maximum feed consumption, resulting in an increase in daily gain and improved feed efficiency.

Feedlot rations can be silage based or a mixture of hay and grain.  The advantage of this system is an increase in control over feed intake, allowing the rate of gain to be regulated.  Days on feed are also decreased.  Feeding lambs on crop residues prior to entry into the feedlot will help reduce overall costs of gain.  However feed conversion will not be as efficient for late-weaned animals (see table). 

Feed Conversion Ratios (kg of feed to kg of gain)

Pre-weaned lambs 0.9 - 1.1 : 0.5
Early weaned lambs 1.1 - 4.0 : 0.5
Late weaned lambs 2.7 - 3.6 : 0.5

 

Abnormal climatic conditions, such as drought, may indicate the need for supplementary feeding or lotfeeding lambs.  Optional finishing systems have been studied.  One such study, conducted in the United States, evaluated three such systems.  These were: grazed Lucerne; lofted with 100% concentrate diet; or 42-day grazed ryegrass followed by lotfeeding on a concentrate diet. 
Average daily gain was found to be highest for direct lotfeeding.  This was thought to be due to the difference in energy intake.

Lambs on Lucerne gained 211 grams a day.  Those undergoing lotfeeding gained 316g/day and lambs grazing ryegrass followed by lotfeeding gained 180g/day.  In all three feeding systems, lambs were fed to an equal slaughter weight of 48kg live.  An increase in days on feed was needed to compensate for the difference in daily gain.  Lambs grazing Lucerne were fed for 96 days while direct feedlot lambs finished in 63 days.  The lambs grazing ryegrass followed by lotfeeding required 113 days to meet the target weight.

Further analysis showed the lucerne-fed lambs were found to have lower dressing percentages compared with lambs on the other two feeding systems.  Also it was found that the amount of lean (muscle mass as opposed to fat) in the lamb carcass was not affected by various feeding systems.  However, fat deposition was reduced 20 percent in Lucerne-finished lambs compared with those finished on concentrate.

Similar carcass composition was seen in lambs placed directly into the feedlot and lambs that grazed ryegrass then lofted.  Meat cuts indicated no difference in weight or composition in such cuts as the lamb leg or shoulder.  However, the Lucerne-fed lambs had a lower loin weight compared with the other two feeding systems.  Rack weight was heaviest for concentrate-fed lambs followed by the split-feeding system.

This research indicated how average daily gain could be increased by lotfeeding or using a split-feeding system.  It also revealed that diets within the feedlot must be made to optimize production but limit fat deposition.  With grain hard to obtain, the option of restricted feeding of lambs may at times be appropriate.

Another study fed lambs at 100, 85 and 70 percent of voluntary intake.  The diets were formulated to have equal daily intake of protein, vitamins and minerals, regardless of intake level.  The energy level of the diet met 100, 85 and 70 percent of required needs.  In order to monitor how diet restrictions affected carcass composition, all lambs were slaughtered at the same target weight.

Restricted feeding resulted in a linear decrease in average daily gain.  As the level of food intake was reduced, average daily gain also decreased.  This decrease in average daily gain was found to be due to a decrease in the fat deposition rate.  Restriction of feed intake resulted in an increase in the quantity of lean tissue of the carcass and a decrease in fat for an equal carcass weight.  Days on feed were also increased when lambs were fed restricted diets.  Feed efficiency was not affected by the level of feed intake.

The carcass cuts from this trial revealed that, with a decrease in feed intake, total loin weight was also decreased.  However, within the loin, the percentage of lean increased and the fat decreased.  Rack and shoulder weight were not affected by a decrease in feed intake

The trial indicated that the decrease in feed intake, which reflected a decrease in energy intake, was still sufficient to meet lean-tissue deposition needs of the lamb.  Therefore, in times of feed restriction, a lean carcass can be obtained on less than adequate energy levels.  However, it must be remembered that this was with increased days on feed in a controlled, restricted situation.  By no means should animals be starved.  This type of restricted feeding should only be considered in stress periods, as it is still most advantageous to maximize gain over the shortest time period possible, while producing a leaner, heavier carcass.

Restricted feeding is not the only alternative; however it may be considered an option during times of limited pasture and grain availability.  If intake is restricted, the nutrient content of the diet must be redefined to a higher level to meet the animal’s needs for protein, vitamins and minerals.

Lambs need to consume feed to meet the energy needs of the body.  This is known as the maintenance level.  Additional energy is used to build bone, tissue and lean.  Once the needs for maintenance, bone and lean tissue are met, energy will be used to put on fat.

In a restricted feeding situation, the energy level is limited to that needed for maintenance and protein deposition only.  The feeding system of choice must consider the animal’s health and welfare, performance and economic return.

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