High Concentrate Diets For Dairy Bulls

Finishing bulls on high concentrate diets is a high cost system with a large input of concentrate feeds. This article outlines the system required to ensure maximum performance, whilst remaining profitable, says Siobhán Kavanagh, Teagasc Specialist Service.
calendar icon 24 January 2011
clock icon 11 minute read

Introduction

Finishing bulls on high concentrate diets is a high cost system with a large input of concentrate feeds. For the system to be profitable concentrates must be cheap and calves must be relatively cheap and of high growth potential. This system requires careful diet formulation and excellent feeding management to ensure maximum performance and minimum risk of digestive upsets. This paper will outline target intake levels as well as guidelines on diet formulation and appropriate feeding management.

Target Weight Gain

Table 1 outlines guidelines for liveweight gain (LWG) on different classes of inishing animal. At best, this is a guideline to target gains as actual LWG will be dictated by a number of factors including the previous history of the animal, weight for age, diet type, feeding management, husbandry etc.

The scope for compensatory growth depends on the previous nutritional history of the animal. Lifetime performance to the start of the finishing period will have a major bearing on animal performance over the finishing period. The lighter an animal’s weight for age, the greater the animal’s potential for compensation. Differences in compensatory growth potential can result in big variations in response to concentrates. Animals with little compensatory growth tend to have poorer performance and efficiency.

Table 1. Suggested target weight gains for finishing bulls offered diets with different concentrate proportions

  50:50*
LWG kg / day
90 : 10
LWG kg/day
Friesian 1.1 1.2-1.3
Continental Cross 1.2 1.5
*Assumed silage quality of 72 DMD plus 4-5 kg meals for steers and heifers, for bulls it is assumed that silage is constituting 35 per cent of the total DM content with the remainder as concentrates.

Duration of the finishing period

Unlike steers, where performance starts to decline after 80-90 days on ad-libitum meals, young bulls have been successfully fed for up to 270 days, but rate of gain declines significantly over time. The duration of the meal feeding period will be dictated by the start weight, carcass weight required, level of fatness and other factors such as lameness, particularly for bulls on slats. It will also depend on where an animal is on the growth curve. Animals with a lot of growth potential might be expected to continue thriving for longer than an animal with high lifetime performance to that point. As a rule of thumb a maximum feeding period of 170-180 days is preferable. Starting weight for high concentrate feeding of dairy bulls will be dictated by target slaughter weight but assuming a liveweight gain of 1.25 kg / day, animals should be within 220 kg of slaughter, when high concentrate feeding begins. High ratesof gain over short periods of time are very efficient, all else being equal.

Dry Matter Intake

Achieving high dry matter intake is essential for good performance. Table 2 outlines the level of intake achieved by dairy bulls in research studies at Teagasc, Grange. Young calves at 12 weeks (Batch 1) on an ad libitum concentrate diets achieved an intake of 2.8 per cent of body weight but this declined significantly over the next 140 days. The overall intake from 110 kg to 442 kg body weight (Batch 2) was 2.2 per cent of body weight. On average, heavier animals might be expected to achieve 2.0-2.1 per cent of body weight on an ad libitum feeding system. Experience would suggest that dairy bulls will achieve intakes of 2.1-2.2 per cent of BW for a high concentrate feeding period of 170-180 days but this will decline over time to 1.8-1.9 per cent of BW, with slaughter weights of 500 -600kg.

Table 2. Example dry matter intakes on high concentrate feeding systems of dairy bulls over time to 1.8-1.9 % of BW, with slaughter weights of 500 -600kg.

Batch Initial weight
Kg
Final Weight
Kg
Intake
kg DM
Intake as %
of BW
1 110 289 5.59 2.8%
2 110 442 6.07 2.2%
3 320 448 8.06 2.1%
4 300 550 9.35 2.2%

Feed Efficiency

The feed conversion efficiency achieved on high concentrate diets with dairy bulls across six experiments is presented in Table 3. The average feed conversion efficiency was 5 kg DM feed per kg liveweight gain for animals with an initial weight of 98 – 230 kg and a final weight of 448-454 kg. Similar studies have recorded feed efficiency of 9.0 kg DMI per kg carcass gain for similar animals.

Table 3. Examples of feed conversion efficiency on high concentrate feeding systems of dairy cowsTable 3. Examples of feed conversion efficiency on high concentrate feeding systems of dairy cows

Exp. No. Initial weight
Kg
Final Weight
Kg
Live Weight
gain (kg/day)
Total dry matter intake
kg/day
Feed Conversion
Efficiency (kg DMI kg live weight gain)
1 99 448 1.25 5.8 4.7
2 98 416 1.18 5.5 4.7
3 125 442 1.27 6.9 5.4
4 114 447 1.25 6.5 5.2
5 110 448 1.22 6.3 5.2
6 233 454 1.24 5.9 4.8

Considerable work has been done at Teagasc Grange comparing dairy bulls slaughtered at different slaughter weights. Animals were fed high concentrate diets for six months (179 days) or nine months (272 days). Daily gain over the first six months was 1.4 kg / day. This fell to 1.2 kg / day for the period from six months to nine months. Slaughter weight was 550 kg after six months and 670 kg after nine months. Total concentrate consumption was 1.76 t for six months and 3.0 t for nine months. Feed conversion efficiency was 7.2 and 8.1 kg DMI / kg LWG for the bulls slaughtered at six and nine months, respectively.Considerable work has been done at Teagasc Grange comparing dairy bulls slaughtered at different slaughter weights. Animals were fed high concentrate diets for 6 months (179 days) or 9 months (272 days). Daily gain over the first 6 months was 1.4 kg / day. This fell to 1.2 kg / day for the period from 6 months to 9 months. Slaughter weight was 550 kg after 6 months and 670 kg after 9 months. Total concentrate consumption was 1.76 t for 6 months and 3.0 t for 9 months. Feed conversion efficiency was 7.2 and 8.1 kg DMI / kg LWG for the bulls slaughtered at 6 and 9 months, respectively.

Diet Specification

Energy, protein, fibre and minerals are the primary components of the diet that need to be balanced correctly.

Energy

High energy feeds should be fed for maximum weight gains. Dietary energy density will depend on concentrate cost, the response in carcass gain from increasing / decreasing energy density and the corresponding value of carcass gain. The minimum energy density in the concentrate mix should be 0.95 UFV / kg as fed or 1.09 UFV / kg DM. Grange studies, with young bulls slaughtered at 12 months, showed that when a low energy concentrate feed was used, compared to a high energy feed, carcass weights were up to 28DM. Grange studies, with young bulls slaughtered at 12 months, showed that when a low energy concentrate feed was used, compared to a high energy feed, carcass weights were up to 28 kg lighter on the low energy feed.

The selection of feed ingredients for this system is critical. The primary energy sources are based on starch or digestible fibre. Cereals such as barley, wheat and maize grain are based on starch, while citrus pulp, beet pulp and soya hulls are based on digestible fibre. A mixture of these energy sources is preferable to stimulate intake and reduce the risk of digestive upsets such as acidosis. See sample concentrate mixes below (Table 4).

Table 4. Sample concentrate mixes

Mix UFV CP% PDI
40% barley : 35% distillers grains : 25% citrus pulp + minerals 0.98 14.7 99
40% barley : 25% citrus pulp : 20% maize grain : 15% soyabean meal + minerals 0.96 14.4 100
30% maize distillers : 30% citrus pulp : 36% barley : 4% molasses + minerals 0.94 13.3 90
25% barley : 25% distillers grains : 25% citrus pulp : 25% maize meal +minerals 0.99 12.8 88

The mix being used at Johnstown Castle and the nutritional value (on a fresh weight basis) is presented below.

80% barley Energy 0.96 UFV
14% soyabean meal Crude protein 14.7%
3.5% molasses PDI 100 g
2.5% minerals Starch 41%

One source of energy e.g. cereal may be used in the high concentrate system, provided it is correctly balanced for protein, minerals and long fibre. It is imperative that feeding management is excellent. This system is inherently more difficult to manage and there is a greater risk of digestive upsets.

Protein

During the growing phase bulls need adequate protein to build a frame and to ensure that they do not remain small and fat. Finishing animals will have a lower requirement for protein because their frame is already established and high levels of protein are not required to lay down lean & fat tissue. Protein may be more critical with Holstein dairy animals that tend to continue to grow rather than lay down tissue. The crude protein content of the concentrate will depend on the composition of the diet, for example where sugar beet, fodder beet or other low protein feeds are being offered a higher crude protein in the concentrate will be necessary.

Table 5. Dietary protein requirements for bulls

Category Crude protein % / kg diet DM
Bulls (growing) 14 - 16
Bulls (finishing) 12 - 13

Roughage Source

Roughage is required for the satisfactory functioning of the digestive system. At least 10 per cent of the DM intake must be a source of long roughage but this should not exceed 15 per cent. This may be silage, straw or hay. Anecdotal evidence would suggest that straw / hay is the preferred option. If feeding hay it is important to ensure intake is not excessive as this will affect performance, but otherwise it is a safe feed. Roughage may be fed separate or mixed with the concentrate. If feeding separately, it is important to ensure animals have adequate access to the roughage and it is regularly freshened up.

Minerals

Cattle need minerals to maintain good health. This is particularly important on a high concentrate feeding system where issues such as hoof health may be compromised if animals are on a high concentrate diet for long periods of time. It is important that a standard beef ration is not used for ad libitum feeding as the mineral specification will be in excess of requirements and may lead to poor performance and the risk of toxicity and severe diarrhea.

Grain Processing

Ground cereals should not be used in high concentrate feeding systems. Pelleted rations are generally manufactured with ground cereals – check with the manufacturer.

Water

Water intake will be high on this system. Animals on ad libitum concentrate have a high rate of metabolism and dissipate a lot of sweat. Fresh water must be available at all times. It is recommended that water troughs be inspected daily and cleaned at least 2-3 times a week or immediately if water is fouled. Animals must never be left without water on this system. Inadequate water intake will depress feed intake and consequently performance.

Feeding Management

Feeding management is critical. There are a few basic rules that must be adhered to:

Introducing the concentrate

An introductory period of approximatnely 3 weeks is necessary to allow animals adapt to a concentrate based diet. Start off on 3 kg concentrates and every 4 days add 1.5 kg concentrates. Animals should have full access to silage / roughage while being built up to high concentrate diets. A suggested program for introducing cattle to a concentrate based diet is presented in Table 6.

Table 6. Routine for introducing ad-libitum concentrate

  kg concentrate/ day Roughage available Feeding routine
Day 1 3 Ad lib Feed once / day
Day 5 4.5 Ad lib Feed twice / day
Day 9 6.0 Ad lib Feed three times / day
Day 13 7.5 Ad lib Feed three times / day
Day 17 9.0 Ad lib Feed three times / day
Day 21 10.5 Ad lib Feed three times / day
Day 24 Ad-libitum 10% of DM intake Feed ad lib

By gradually introducing cattle to a high concentrate diet, the risk of acidosis or feed sickness is reduced. At any sign of excessive scouring or digestive upset, decrease the concentrate level to the previous step for a few days. Animals should be watched closely and regularly during the introductory period. A culling policy should be put in place whereby problem animals are removed. These animals will most likely not perform throughout the finishing period, incur large costs and therefore result in reduced returns.

Frequency of feeding

Subsequent to the introductory period once daily feeding should be satisfactory after the introductory period, if troughs are large enough. It is not safe to ever go below 5 per cent remaining in the trough. Do not have cattle waiting on empty troughs for the next feed.

Feed trough management

Good feed trough management is essential in preventing digestive upsets. It is essential to recognize that even slight digestive upsets will affect growth rates and therefore your profitability long before an animal is recognisably sick. Bird / vermin infestation can be a problem where animals are being fed high levels of concentrates. Methods to overcome this include the use of shorter troughs or preferably hoppers.

Housing

Providing less than recommended space will cause stress in animals, depress feed intake and consequently reduced animal performance. In general, slatted pens are not ideal for high concentrate feeding for long periods of time. Straw bedding or out-wintering pads are preferable options.

It is critical that the housing is thoroughly checked out before housing animals. The principles of good ventilation must be followed. These include adequate pitch of the roof (15o), as well as adequate inlets and outlets and space sheeting on the roof. The importance of air movement cannot be over- emphasised.

Animals on high concentrate feeding systems dissipate a lot of sweat to keep themselves cool. Signs of animals sweating excessively translates into lack of air movement in the house. This is energy wasted that could otherwise be used for liveweight gain. Feed intake and performance will suffer severely /unless this is dealt with.

January 2011

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