Published by SPESFEED cc, P O Box 48, Rivonia, 2128. Tel: (011) 803-2050, Fax: (011) 803-8201
| Inside This Issue |
Welcome to the second newsletter of 1998. It is planned to arrive at what will be a busy time for most of us. The AFMA Forum will be held at Sun City from 6 to 8 May, the SAPA Congress will be held in the Cape from 18 to 20 May, and the inaugural INEX - Animal Science expo will be held at Irene on June 19. I am sure that these will be of interest to most us. I have tried to include a photograph in this edition of the newsletter as an innovation. See what you think.
Courses
The poultry and pig courses went off smoothly, with 22 delegates attending the poultry course and 15 the pig course. The next dairy course is scheduled for the 15, 16 and 17 of September. Should you be interested in attending contact Shaun.
The Internet
All of the items of interest in this issue have to do with poultry health. The first is a summary of the Diseases of Poultry published by Dr Martin Ficken of North Carolina State University. The site address is
http://vetpath1.afip.mil/poultry.ficken.txt. The second and perhaps more useful document is an online publication by Dr Simon Shane, entitled "Handbook on Poultry Diseases". You can find this book on the American Soy Bean Association site in Singapore. http://www.pacweb.net.sg/asa/technical/pdtoc.html.
The final item is an advertisement for a book entitled "Health Free Range Hens" by New Zealander, Neil Christensen.
http://www.peck.co.nz/healthy.htm#.
Feed Intake
In the last newsletter I discussed the importance of feed intake in broilers. In work published in the supplement to British Poultry Science at the end of last year, Weeks and his co-workers from Bristol University reported on the effect of food and feeder colour of young layers and broilers.
Birds were offered pellets coloured with food dye on a free choice basis, alongside normal food as a control. The effect of feeder colour was determined in a similar manner with the feeders being painted different colours. The control was clear. The results appear in the table.
As can be seen there are differences between layers and broilers, although yellow food was favoured by all birds. This is probably to the grains which were selected by free ranging chickens. The results indicate that food colour is a stronger cue than feeder colour and in the case of the layers there were no significant differences between different coloured containers.
Table: Effect on food consumption of broilers and layers aged 5 to 6 w of colouring food or food container (mean consumption as a % of total (After Weeks et al, 1997)
|
Coloured food |
Coloured container |
||||
|
Colour |
Broilers |
Layer |
Broiler |
Layers |
|
|
Red |
21.3ab |
23.2ab |
25.5ac |
17.2 |
|
|
Blue |
16.4c |
22.2ab |
24.7c |
20.5 |
|
|
Green |
17.9bc |
9.3b |
17.7b |
14.3 |
|
|
Yellow |
24.7a |
35.4a |
14.6b |
27.7 |
|
|
Control |
19.8bc |
9.8b |
17.5b |
20.3 |
|
Rick Kleyn
Consultants and consultancy are now a permanent part of the business environment. This is clearly illustrated by the fact that Andersen Consulting is now a larger company than the company that spawned it, Arthur Andersen. There are many reasons why this industry and world wide trend has occurred:
 | Increasing levels of expertise in business and agriculture demand specialist skills. |
| Many companies fail to look after their good staff so they simply move on. |
| Large companies are down sizing and limiting the number of highly paid staff. |
| Consultants are often used as an "insurance policy" by managers. |
| It is often more cost effective to use an experienced contractor than it is to employ inexperienced staff who still need to be trained. |
It is obviously in your best interests to get the most out of any consultant that you employ and there are a number of questions which you need to ask yourself before you take what could be a major step.
Am I a team player? By their very nature consultants specialise in an area. Often a team of experts needs to be assembled. For example a nutritionist, a veterinarian and possibly a financial expert would need you to be their captain.
Am I willing to work with consultants? The effective use of a consultant depends as much on the competence and attitude of the consultant as it does on the client. If you are not open to new ideas and change, or if you are not willing to implement the consultants advice then it may be advisable to delay appointing a consultant.
Do I have clear goals? If you do not at least have a vision for your business it is almost impossible for a consultant to know and understand what has to be accomplished.
Am I expecting a miracle cure? There is no substitute for good management. Finger pointing and playing people off against each other achieves little. Remove individuals who show these tendencies from your team.
Am I willing to pay for advice? Few independent consultants come cheap. Remember that you are paying for all additional support services in addition to a salary. In addition, you can’t realistically expect a consultant to earn less than he would in full time employment.
If you believe that your business would benefit from expert input you need to set about selecting a consultant to work for you. Here are some of the areas that you need to consider:
| Does the individual have a comprehensive knowledge of his/her subject area. |
| Are the references that you have received favourable. |
| Does the consultant have integrity |
| Is the consultant properly qualified and registered with the appropriate professional body. He/she will then have to abide by a code of ethics and conduct. |
| Most importantly, do you like the individual and can you work together |
Having chosen a consultant you now need to work with him or her. The first hurdle which needs to be overcome is the old dilemma: "we want to know what everyone else is doing but we are damned if they are going to learn what we are up to." Having resolved this conundrum, we have found that there are a few simple rules which need to be adhered to by both client and consultant if the relationship is to be successful:
| Before going any further make sure that you know how much it is going to cost. There is nothing worse than an unpleasant surprise. |
| Specify the nature and scope of the work. Discuss dates and times and determine what information is required by each party |
| Communication is all important. It is up to both parties to initiate it but the onus probably lies more with the client, as the consultant can’t be expected to know exactly what is going on in any business. |
| Business is not a "one off" activity. Continuity is important. |
| In technical fields there are very few secrets, only many unanswered questions. |
| Both the client and the consultant must know what questions should not be asked. |
| Both parties must be prepared to accept a few home truths. |
If you are happy with the difference that your consultants have made to your business you should enjoy a long and fruitful relationship with your consultant that is rewarding to both parties.
Rick Kleyn
The poultry industry in the United States, and throughout the world, uses millions of tons of high quality feed-grade inorganic phosphates each year. The bioavailability of the phosphorus in these inorganic sources is usually very high for poultry. However, the exact composition of these commercial sources is often confusing. The guaranteed percentage of phosphorus and the range of calcium in these products is known. What is often confusing, however, is the percentage of the actual chemical form of the phosphorus in the product. The question is often asked, "What exactly is DICAL?". Nutritionists use the term, DICAL, in reference to "dicalcium phosphate". Dicalcium phosphate is not just one chemical compound since it contains both monocalcium phosphate and dicalcium phosphate as well as mixtures of both compounds.
A person does not need to be a nutritionist to understand the chemical composition of the various phosphate products available to the feed industry. However, it is necessary to have an appreciation for chemistry in order to understand the basic facts about these products. For instance, the prefixes "mono" and "di" in front of calcium phosphate are often interpreted to mean one and two atoms of calcium in the products monocalcium phosphate (monocal) and dicalcium phosphate (dical), respectively. Such is not the case, even though the prefixes "mono and "di" refer to one and two, respectively.
Monocalcium phosphate really refers to monobasic calcium phosphate and dicalcium phosphate is used to refer to dibasic calcium phosphate.
Through the years, the word "basic" has been eliminated when discussing these ingredients in the feed industry. Likewise, in the classroom a detailed explanation of the chemistry and industrial production of these ingredients is often never presented.
Today, students in animal nutrition classes often only hear the terms, "monocal" and "dical" when reference is made to a source of inorganic phosphorus used in feed formulation. Because of this, misconceptions have developed about the chemistry and number of calcium atoms in these feed ingredients. An explanation of what is meant by the term "basic" when discussing monocal (monobasic calcium phosphate) and dical (dibasic calcium phosphate) assists in the understanding of these ingredients when used as a source of inorganic phosphorus in feed formulation. These two forms of phosphorus are different and poultry performance has been shown to be influenced by which form predominates in the diet. The following briefly explains the industrial processes involved in the production of these feed-grade phosphorus sources which can assist in understanding how the form of phosphorus can exert an influence on performance.
During the manufacturing of feed-grade calcium phosphates, limestone (CaCO3) and phosphoric acid (H3PO4) react together under carefully controlled conditions. When these two ingredients are mixed together, a chemical equilibrium is reached and the final product is a mixture of monobasic calcium phosphate (MCP) and dibasic calcium phosphate (DCP).
The amount of each form (MCP/DCP) present at the end of the chemical reaction depends on the quantities of limestone and phosphoric acid involved in the process. The phosphate manufacturers carefully control the processing conditions so as to optimise the amount of each chemical form desired in the final product that will ultimately be used by the feed industry.
The general chemical reaction which occurs between the CaCO3 and the H3PO4 is as
follows:
REACTION I :
CaCO3 + H3PO4 CaHPO4 + 2H2O + CO2
Limestone + Phosphoric Acid yields Dibasic Calcium Phosphate (DCP) + Water + Carbon Dioxide
REACTION II :
CaCO3 + 2H3PO4 Ca(H2PO4-)2 . H2O + CO2
Limestone + Phosphoric Acid yields Monobasic Calcium Phosphate (MCP) + Carbon Dioxide
In reaction I, the end product, CaHPO4=, contains phosphorus in the dibasic (HPO4=) form, while in reaction II, the end product is CaH2PO+ and phosphorus is present in the monobasic (H2PO4-) form.
Note: only one calcium atom is involved in each chemical compound. Although the manufacturers of these products control the production variables, due to reaction kinetics, there is not complete conversion to only one product. Therefore, in the production of MCP there exists some DCP in the mixture. Similarly, in the production of DCP there exists some MCP. The actual composition of the final feed-grade phosphorus source is influenced by processing conditions (ratio of limestone to phosphoric acid, concentration of phosphoric acid, temperature) and the purity of raw materials. The amount of H2PO4 used will always determine the phosphorus content of the feed-grade product as phosphorus is the most closely controlled variable. The calcium content of the product will fluctuate within a range as the ratios of MCP and DCP change, explaining the reason why feed-grade product labels present the phosphorus as a minimum guarantee and the calcium as a range. The forms (MCP or DCP) of phosphorus in feed-grade products are subject to some variability dependent upon the manufacturer's quality control program. For instance, in a product that contains a guaranteed minimum phosphorus concentration of 18.5% it is possible for the product to contain from 20 to 50% of its phosphorus in the monobasic (H2PO4-) form and 80 to 50% of its phosphorus in the dibasic (HPO4=) form.
Also, for a product that is guaranteed to contain 21.0% phosphorus there may be from 60 to 90% of the phosphorus in the H2PO4- form and 40 to 10% in the HPO4= form. Regardless of what form predominates in the final mixture of feed-grade phosphate, MCP + DCP will always equal 100%.
An understanding of the chemistry of the dietary forms of phosphorus will enable a better understanding of how phosphorus reacts and functions in chemical reactions within the body. Of the two forms of phosphorus, monobasic phosphate (H2PO4-) is a strongly acidogenic anion. This is not true for the dibasic form. Being acidogenic means that monobasic phosphate can donate a proton (H+) in reactions within the body of an animal (H2PO4- H+ yields HPO4= + H+) and in so doing is converted into the dibasic form. Not being strongly acidogenic, dibasic phosphate normally acts as a base and is capable of accepting a proton in reactions within the animal (HPO4= + H+ yields H2PO4-). A knowledge of these reactions is essential in understanding acid/base balance (control of pH) in the animal body.
In the animal body, at a normal blood pH of 7.4, these two forms of phosphorus, dibasic and monobasic, normally exist in a ratio of 80:20, respectively. During acidosis (excess H+ which lowers the pH) in the animal body, the dibasic form is important because of its ability to accept a proton and thus be converted into the monobasic form, removing the proton from body fluids and helping to bring the blood pH back up to normal.
Likewise, the monobasic form is beneficial during alkalosis (low H+ which increases the pH) in the
animal body. In this case, the monobasic form donates a proton to body fluids which helps to lower the pH back to normal. Phosphate, in the monobasic and dibasic forms, thus provides one of the important buffer systems in the body which assists in maintaining acid/base balance.
A range of commercial mineral feed phosphorus sources are available. It is possible to measure to P availability in each of the supplements available in terms of it’s relative bio-availability (RBA) with reference to a material such as pure monocalcium phosphate. This is measured by means of a slope ratio technique. Some indicative RBA values of typical feed phosphates are shown in Table 1. When buying these supplements it is important to know what the relative proportions of MCP and DCP are in each product.
Richard Miles University of Florida
Although only 5 nights long my trip to Turkey in February was non the less very enjoyable. It did help to answer a question I have been asking myself for many years, namely what has happened to all of the "vaaljappie" tractors that used to labour on South African farms. I am now able to confirm that although most of them have died, they are now in tractor heaven, in Turkey. It would seem that every Turkish peasant farmer has a small tractor and an old fashioned "scotch cart" that they use for both farming and commuting. More love is bestowed on these little beasts of burden than on the family dog.
Turkey has an inflation rate of around 100% per annum. I bought 44 000 Turkish Lira for a Rand and as delighted to become a millionaire in an instant. My joy was short lived though. A single bira (beer) costs around TL 250 000 and the box of Turkish delight I bought to bring home for the family set me back TL 1 500 000.
On a more serious note, I spent 3 days presenting parts of the SPESFEED poultry and dairy nutrition courses to about 20 nutritionists from the Turkish feed industry. Having everything that you say translated makes this sort of thing difficult. The meeting was held at a hotel at Kusadasi, which is on the Aegean seaboard of the country and near the ancient city of Ephasis.
Although official figures would indicate that the Turkish feed industry produces about 6.5 million tons per annum, more reliable estimates put this figure at nearer 8.5 million tons. About half of this amount is dairy feed, much of which is sold to small farmers running less than 10 cows. The remainder of the feed produced is poultry feed as there are no pigs in this Muslim country. Despite the fact that Turkish Feed Millers Association has nearly 400 members, most of the feed is manufactured by a few large companies. I met the technical director from the Indonesian company, CP, who have 5 feed mills in Turkey and a large integrated broiler business. The nutritionist from Ralston Purina also attended the meeting and they have a number of mills in Turkey. The biggest single mill in the country produces about 140 000 tons of feed per annum.
During the meeting I was invited to go to the capital, Ankara, to visit Ozhen. Despite the beautiful snow scenes, the seven hour drive to Ankara made me resolve not to moan about the state of South African roads or our taxi drivers again. Ozhen are a family owned business who run both a flour mill and an integrated broiler unique in that the final product is produced by mixed the various grades of flour after milling, as opposed to the normal practice of mixing the wheat prior to milling. This obviously gives rise to some interesting potential savings in terms of least cost formulation of the flour.
The feed mill produces about 120 000 tons of feed per annum in a fully automated van Opstall built feed mill, which is now about 4 years old. It was started as a joint venture company with the Dutch company Hendriks but is now wholly Turkish owned. It was interesting to see that batching was done prior to grinding. In common with South Africa the labour component is very high and on investigation I found that the average wage for a worker is around US$ 150.00 per month. The poultry feeds that they manufacture are very similar to our own, being based largely on maize and imported US Soya.
The Ozhen feed mill in Ankara
I left Turkey with the overall impression that South Africa and Turkey have the more in common than any of the other European countries that I have visited thus far. I returned home at midnight on the Friday night only to grateful to escape the chilly winter temperature of about minus 5 degrees. Even the hotel swimming pool froze over at night.
Rick Kleyn
Animals should be kept within their zone of thermal neutrality. This ensures that the heat production is minimal and the energy available for production is maximal. The lower and upper limits of this zone are called the Lower (LCT) and Upper (UTC) critical temperatures, respectively. Outside the thermo neutral zone, heat production increases and the rate and efficiency of nutrient utilisation is reduced. The LTC of a pig will depend on the heat output of the animal and is influenced by both animal and environmental factors:
ANIMAL FACTORS:
| Body weight: Larger pigs have better insulation and produce more waste heat. Their LCT therefore decreases. |
| Level of feed intake: The higher the level of feeding, the higher the rate of heat production and the lower the critical temperature. |
| Fat reserves: Fat reserves are crucial as insulation in the cold months. A thin sow therefore has lower critical temperature and hence requires more feed energy to maintain her condition. |
The effect of body weight, feed intake and sow condition on critical temperature is shown in Table 1 below:
Table1: Calculated limits of the lower and upper critical temperature (°) for pigs at different levels of feed (Holmes and Close,
|
Feeding level |
|||
|
Body weight (kg) |
Maint. |
2 times Maint. |
3 times Maint. |
|
2 |
31 - 33 |
29 - 32 |
27 - 31 |
|
20 |
26 - 33 |
21 - 31 |
17 - 30 |
|
60 |
24 - 32 |
20 - 30 |
16 - 28 |
|
100 |
23 - 31 |
19 - 29 |
14 - 26 |
|
Pregnant sows |
|||
|
Thin |
20 - 30 |
15 - 27 |
11 - 25 |
|
Fat |
18 - 30 |
13 - 26 |
8 - 24 |
Environmental effects:
| Air movement: An increase in air movement causes an increase in convective heat loss. It is calculated that pigs the LCT is decreased by 1°C at a wind speed of 0.04 m per second (Close 1987). |
| Radiant environment: The difference between air and structure temperature determines the rate at which heat is lost by radiation and convection. A 1 - 2°C change in the temperature of the surroundings is equivalent to a 1°C change in air temperature (Close1987). |
| Bedding and floor type: The nature of the floor determines the extent of conductive heat loss, and as approximately 20% of the animals’ body can be in contact with the floor, there may be considerable heat loss through it. On a cold, uninsulated floor, the conductive heat loss may represent 20 to 25% of the animals’ heat loss. The degree of wetness of the floor will also have a considerable effect upon the animals’ heat loss. If pigs have to lie on a wet floor, conduction to the floor and evaporation from the animals’ surface will increase. Mount (1975) has calculated that a cold, wet floor may have a thermal effect equivalent to a 7 - 10°C decrease in air temperature. |
Table 2: The lower critical temp. of groups of pigs in realtion to differing housing conditions (Adapted from Close, 1997)
|
Body weight (kg) |
|||
|
20 |
60 |
100 |
|
|
Insulated house; straw bedding |
10 |
8 |
2 |
|
Insulated house; no draughts |
14 |
12 |
7 |
|
Insulated house; draughts |
18 |
16 |
13 |
|
Uninsulated house; draughts |
23 |
20 |
17 |
|
Uninsulated house; cold/wet concrete |
29 |
25 |
22 |
(Values appropriate to a feeding level of 3M (M = 440 kj ME/kg 0.75 d)
Economic importance:
If the factors listed above reduce the lower critical temperature of pigs, the heat production rises by between 2 and 4% per 1°C fall in temperature. The following reductions in the LCT and thus increase in feed levels may be seen in pigs housed under different environmental conditions:
Table 3: The effect of different housing conditions on the LCT, energy requirements and feed efficiency of pigs housed at a thermal effect equivalent of 12°C
|
Growing pigs eating 3 times maintenance.
|
LCT of 60 kg pig |
Add. Feed for heat production* (g/day) |
Feed conversion at 60kg (g/g) |
|
Insulated house; straw bedding |
8 |
(-128) |
2.40 |
|
Insulated house; no draughts |
12 |
- |
2.50 |
|
Insulated house; draughts |
16 |
128 |
2.64 |
|
Uninsulated house; draughts |
20 |
256 |
2.78 |
|
Uninsulated house cold/wet concrete |
25 |
384 |
2.93 |
|
Sows fed at maintenance (140kg) |
|||
|
140 kg thin sow, individually housed |
20 |
437** |
|
|
140 kg fat sow, individually housed |
18 |
188** |
|
|
140 kg fat sow; group housed |
17 |
133** |
|
* 32 g increase in feed requirements to maintain growth rate per °C below LCT (Verstegen and Close, 1994)
** 54.6 and 31.4g increase in feed requirements per °C reduction in LCT for fat and thin sows respectively. (Verstegen and Close, 1994)
*** Geuyen et al. (1984) calculated an additional feed requirement of 75 and 40 g/day 1°C drop when sows were kept either individually or in groups.
Practical implication and conclusion:
| Reduced feed efficiency: Table 3 shows that poor environmental conditions reduce the lower critical temperature of pigs. If the growth rate is to remain constant a substantial increase in the feed intake is needed. Under extreme conditions the feed efficiency can b reduced by 20%. |
| Growth loss: In growing pigs an increase in feed intake is not always possible due to limitations in gut fill. If the pig is not able to consume the additional feed, the required energy is simply diverted from growth and burnt up to generate heat. In this instance the growth rate will be reduced. For a 60kg pig the growth reduction is 12g per °C below the pigs LCT (Close and Verstegen, 1994). |
| Thin sows: If the environmental conditions are too cold and if feed intake is limited, mobilisation of body tissue may occur. This limits both maternal body and uterus gain. Repeated and prolonged exposure to these conditions will result in low litter sizes, piglets of low birth weights and a severely emaciated, infertile sow. Such a condition, the "thin sow syndrome" has been reported in practice. |
| Winter feed specifications: The nutrient requirement for heat production is essentially a requirement for energy. Summer feeds are not suited to supply the additional heat during winter for the following reasons: |
 | The nutrient to energy ration is high. This means that expensive protein is overfed. |
| Approximately half of the digestible energy content of surplus protein is lost during the production of urea. Surplus protein reduces the available energy thus to a greater extend and thereby reduces the feed efficiency. |
It is more cost effective if the additional energy is supplied by cereal grains.
| Improving the environment: Under cold conditions where the animal may be below its LCT, actions such as structural improvements to the buildings, the provision of supplementary heating or insulation |
(bedding), or increasing the animal’s feed allocation may be taken to improve the environment. The decision will depend upon the cost of fuel energy relative to that of feed energy, and hence the prevailing economic circumstances.
| Benefits of animal productivity vs. Cost of environmental improvement: Housing can reduce the "thermal stress" of animals in both cold and hot conditions and improve their performance. It also allows better control of both the quantity and quality of feed, a reduction in the energy expenditure and improvement in animal comfort and welfare. However the costs of construction, maintenance and labour must be set against any improvement in performance. It is likely that the high cost and quality of the end-product, the improved use of feed and resources, the improvement in fertility and fecundity and the increase in survivability will far outweigh these structural costs. |
Walter Scharlach
Winsgewendheid van Varkboerdery
Die winsgewendheid van 5 produksie eenhede oor ‘n 12 maand periode is hieronder getabuleer. Die eenhede veerteenwoordig die volgende in terme van biologiese resultate: ‘n swak eenheid, ‘n goeie eenheid, ‘n groeiende eenheid en 2 gemiddelde eenhede.
Winsgewendheid van 5 produksie eenhede 1 September 1996 tot 31 Augustus 1997 (Rand per sog per jaar).
|
Debiet |
Krediet |
|
|
1. Inkomste* (R/sog/jaar) |
7696 |
|
Brandstof Veerarts/Medisyne Vervoer Voerkoste |
4728 77 296 65 4290 |
|
Elektrisiteit Herstel Onderhoud Skaafsels Bruik materiaal |
507 112 168 150 32 45 |
|
|
Bruto marge [1-(2+3)] |
2461 |
|
Diverse Onderhoud Voertuie Permanente Lone Permanente Rantsoene Brandstof Professionele dienste Salarisse Versekeringe en lisensies Waardevermindering |
1101 68 3 531 38 5 28 230 78 120 |
|
|
5. Totale Produksie koste (2,3 & 4) |
6336 |
|
|
6. Netto wins per sog** |
1360 |
* Die inkomste sluit jongsog aankope in.
** Rente en aansuiwerings is nie in aanmerking geneem nie.
Dr. Pieter Grimbeek
Predicting the DM intake (DMI) of a lactating cow is probably the most difficult and frustrating part of dairy nutrition. Emmans published an article recently in which he concluded that even the best prediction of DMI would still have a 12% variation. That means that if a DMI of 20 kg is predicted, it could vary between 17.6 kg and 22.4 kg! High DMI is, however, also the driving force behind profitable dairy farming. The focus of dairy cow nutrition and management is thus promoting intense feeding behaviour. This requires an understanding of the factors that will affect DMI. These factors are numerous, but can be broadly divided into; gut fill, nutrient requirement and cow comfort. The purpose of this article is to focus on cow comfort, specifically the grouping of cows, and its effect on DMI.
Why group cow?
The most important reason for grouping cows is to meet their changing nutrient requirements over the whole lactation as accurately as possible. All other reasons or criteria are secondary to this one. Grouping should therefore lead to more efficient and profitable milk production. Early lactation and high producing cows receive a diet high in protein and energy to ensure they reach their potential peaks while late lactation and low producing cows receive a cheaper diet (higher roughage). Other advantages of grouping include; better management (heat detection), more uniform milking time i.e. less time waiting, more time eating, better management of body condition score and better reproduction.
A recent survey of the top producing herds in the U.S revealed that 67% of producers used a total mixed ration (TMR) and that they averaged 2.9 groups of cows that were fed 2.7 times daily. Research has shown that shifting a herd from one group to two groups increased fat corrected milk (FCM) 1-3%. Moving to three groups increased FCM by a further 2% while shifting to four groups only increased it by a further 0-1%. The conclusion is that three milking groups are optimal. Many producers will also have an additional group for first-calf heifers and two dry cow groups (far-off and steam-up).
The effect of group on DMI
Cow comfort has a crucial effect on DMI and moving cows from one group to another is a primary part of the cows environment. Cows have a definite social order within the groups. Social dominance correlates strongly with age, body size and seniority in the herd. This social dominance is determined when individuals initiate and win encounter. Most of these encounters take place at the feed bunk and the most competitive periods coincide with periods of intense feeding i.e. the return of cows from the parlour, when fresh feed is offered and when feed is pushed up. Along with the social changes, the cows moving into the new group also have to adapt to a new diet.
The social and nutritional stress that a cow encounters when moved to a new group is the major disadvantage of grouping. These stresses inevitably lead to a drop in DMI and a drop in milk production. If not managed properly this drop in milk production will cancel any improvement in production efficiency. The average decrease in production is probably about 1-2 litres of milk/day for the first 4-7 days. However, cows appear to adapt to regrouping over time and this drop in milk production becomes less. There are, however, some important steps that can be taken to make the regrouping process effective. Grouping should not only minimise negative social interactions, but proper grouping strategy will also decrease within-group variation and increase across-group variation.
Group size, density and feed availability
Traditionally, cows have been managed in relatively small groups (30 to 60-100 cows). Improvements in milking and feeding systems have allowed group sizes to increase to 200 or more. The question that arises is what effect does group size have on DMI. Research in this area is limited but at this stage it appears that actual group size is of little consequence. Rather, a number of daily management decisions such as overcrowding with insufficient feed bunk space plays a more important role. The availability of sufficient, fresh feed at the right times is crucial. The availability of fresh feed is in turn a function of how often fresh feed is put out and feed bunk space. Traditionally the "rule of thumb" has been that 60-70 cm/cow of feed bunk space is required. Table 1 summarises the relationship between bunk space and DMI.
Table 1: Bunk space and DMI
|
Bunk space |
Effect on DMI |
|
<20 cm |
Reduced eating time and DMI |
|
20-5- CM |
Increased competition, variable effect on DMI |
|
>50-60 CM |
No measurable effect on DMI |
Feed trials with large, high producing (34 litres/day) herds have shown that reducing bunk space to 35-40 cm/cow did not reduce DMI or production BUT this was only because fresh feed was available 24 hours a day allowing cows to have several small meals throughout the day. Besides simply providing inadequate amounts of feed daily, other common, but less obvious causes of feed restriction include long time spent in holding area at the parlour; long time in an exercise lot without access to feed and water; unstable, highly fermented silage; poor ventilation; slippery floors; inadequate or poorly maintained free-stalls and rough mangers. In terms of group size relative to parlour capacity, a good "rule of thumb" is cows should spend no longer than 45 minutes to an hour waiting to be milked. This usually means that in for herringbone and parallel parlours the group size should be four times the parlour size. In terms of "living space" the most common recommendation is 3.5-5 square meters/cow. The alley between the feeding line and the first row of free stalls should be approximately 4m wide.
Moving cows between groups
There are certain measures that can be taken to reduce the fall in production when cows are moved. From a social interaction point of view moving larger numbers of cows into a new group is less disruptive than moving a few or just one. Also, permitting some sort of contract before grouping will also help. An example of this would be having the steam-up group adjacent to the fresh cow group. Overall, research has shown that the social effects of moving cows are transitory. Most observations indicate that the social impacts of regrouping last less than seven days.
Ration changes, particularly the density, are often the primary cause of a drop in milk production. The change in nutrient density of TMRs among groups should be limited to less than 15%. The range of milk production among cows within a group should be approximately 10 litres. Also, cows moved to a lower density diet after they have reached their peak milk production (6-8 weeks) but before they have reached peak DMI (10-12 weeks) will adapt their DMI more effectively than cows that are moved after peak DMI is reached.
Conclusion
Intense feeding behaviour is crucial if efficient milk production is to be achieved. Grouping of cows has a definite effect on DMI but good feed bunk and housing management a well as careful planning of the regrouping makes grouping of cows a viable practice.
Shaun Storer
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