Bio-sekuriteit op die melkplaas 

Deur Anton Gresse AFGRI Veevoere 

In die veebedryf word boere elke dag uitgedaag deur verskeie patogene, byvoorbeeld die bek-en-klou-seer epidemie wat ‘n ontnugtering vir baie is. Boere het die finansiële effek ongelukkig gevoel met die verbod op veilings en uitvoere. Ek glo dit is dus duidelik dat dit nodig is om respek te toon vir die skadelike mikrobes wat in ons omgewing voorkom. 

Hoe versprei ‘n patogeen 

Om bio-sekuriteit op ‘n melkplaas effektief te bestuur is dit belangrik om te verstaan hoe ‘n patogeen vanaf ‘n dier wat besmet is na ‘n gesonde dier oorgedra word. Daar is 5 primêre verspreidingsroetes vir patogene, naamlik: 

1. Die lugweg, mikrobes word oorgedra in vogdruppels van ‘n nies of hoes. 

1. Oraal, die dier vreet voer wat besmet is of kou/lek besmette voorwerpe. 

1. Vel, wonde wat oop is word besmet. 

1. Reproduksie, gedurende dekking of infeksie van die fetus in utero. 

1. Bloed, die dier word gebyt deur ‘n insek wat die patogeen versprei of ‘n besmette voorwerp soos ‘n naald of neustang wat die vel breek.  

Sommige patogene versprei deur slegs een roete terwyl ander ‘n kombinasie van die bogenoemde roetes kan gebruik. Die tabel hier onder wys van die algemene siektes en die roete van verspreiding. Dit illustreer hoe maklik ‘n siekte tussen diere en tussen kuddes oorgedra kan word indien die nodige bestuurspraktyke nie in plek is nie.  

Algemene siektes by melkbeeste (aangepas uit Jordan et al., 2016) 

Bekamp ‘n patogeen só 

Die mees doeltreffende meganisme vir die voorkoming van siektes is om kudde immuniteit op te bou en te onderhou. Dit begin met die passiewe immuniteit wat aan die kalf oorgedra word in die biesmelk kort na geboorte. Immuniteit word verder onderhou deur ‘n volledige inentingsprogram wat stiptelik gevolg moet word. Die dier se immuunstelsel bou ‘n “geheue” as dit blootgestel word aan die biologiese produk in ‘n entstof. Dit bewerkstellig ‘n vinnig en doelgerigte reaksie teen die patogeen/siekte sodra die dier met dit besmet word, wat die simptome en die negatiewe effek op produksie minimaal hou. Diere moet gehalte voeding ontvang wat die nodige energie, aminosure, vitamiene, makro en spoorminerale voorsien vir die immuunreaksie teen ‘n patogeen.  

Dit is van kardinale belang om siek diere so gou moontlik te identifiseer, asook die patogeen/siekte wat die simptome veroorsaak. Dié diere moet dan in kwarantyn geplaas word tot hulle herstel. Karkasse van diere wat vrek moet ook op ‘n veilige manier verwyder en vernietig word. Beweging vanaf die siek kamp (en karkasse) moet gereguleer word om te keer dat patogene deur die omgewing versprei. Alhoewel dit stremming op bestuur plaas, sal dit goed wees om ontsmetting-stasies op die been te sit, veral by die kalwers. 

Streng maatreëls rakende besoekers, voertuie en aangekoopte diere wat van buite af kom moet op die plaas toegepas word. Daar moet ‘n vaste roete wees vir die vragmotor wat voer aflaai of melk kom haal asook konsultante, veeartse en selfs familie wat kom kuier. Onnodige beweging op die plaas moet vermy word. Aangekoopte diere moet in kwarantyn gehou word vir minstens 14 dae en indien hulle gesond bly kan hulle by die res van die kudde aansluit. Dit is belangrik om ‘n volledige inentingsverslag van aangekoopte diere te ontvang. Só kan jy verseker dat nuwe diere effektief in skakel by die plaas se gesondheidsprogram.  

Ter afsluiting 

Voorkoming is baie goedkoper as behandeling wanneer dit kom by veesiektes. Indien daar onsekerheid is oor ‘n effektiewe bio-sekuriteitprogram op jou melkplaas, nader jou veearts of klop aan by jou buurman om só ‘n program te bespreek. Ons melkboere moet daagliks verskeie uitdagings oorkom en ek vertrou dat dieregesondheid (en mensgesondheid) net nog een sal wees wat suksesvol bestuur word. 

By SP Els, AFGRI Animal Feeds

Sound nutrition and management practices during the transition period will have a positive financial impact on dairy businesses.

Most farmers have specific, quantifiable goals regarding milk production, milk solids, feed and labour costs, and profitability in terms of profit per hectare or per cow. However, it seems that the opposite is true for reproduction and cow comfort.

Low dry matter intake (DMI), with subsequent negative energy balance (NEB) and metabolic disorders, as well as management and environmental factors occurring during the transition period, are responsible for reproductive failure and profit loss, and not high milk production as is commonly believed.

Pre- and postpartum feeding

 The transition period generally extends from three weeks before calving until three weeks after calving. During this phase, the cow undergoes dramatic physiological, immunological, metabolic and nutritional changes.

Formulating diets with a negative dietary cation-anion difference (DCAD) in the prepartum period in a bid to reduce subclinical and clinical hypocalcaemia and its associated diseases, is but one aspect of the nutritional strategy aimed at supporting metabolic adaption during the transition period.

Demand for amino acids, glucose and fatty acids at day 250 of gestation, increases approximately fivefold at day four postpartum for some of these nutrients. Furthermore, changes in the demand and supply of these nutrients, minerals and trace minerals postpartum directly impact immune function.

The question remains whether the feeding strategy is amended pre- and postpartum to help the liver function optimally and adapt the rumen, which is going through morphological, functional and microbiota changes, to achieve the   following:

• Higher DMI.
• Shortened duration of NEB.
• Higher glucose concentrations.
• Increased levels of circulating IGF-1.
• Lower non-esterified fatty acid (NEFA) concentrations.

Higher levels of NEFA in the blood is associated with lower reproduction and reduced oocyte quality and may lower the survival rate of the embryo after fertilisation. If the cow produced a calf from an inferior embryo, the gene expression of the calf may be negatively impacted, a process known as epigenetics. Epigenetics is a change in the genes’ core functionality and is impacted by something other than DNA; in this case, ‘poor’ nutrition pre- and postpartum.

Carbohydrates, amino acids, minerals 

Further nutritional strategies to consider are to feed a mix of carbohydrates and to finetune the amount of carbohydrates based on the dry, fresh and/or early lactation diets, as well as the total fermentable carbohydrates fed. The digestibility of starch as well as neutral detergent fibre (NDF) must also be measured.

The fibre in diets affects intake and rumen function. The amount of physically effective NDF (peNDF) needed in the fresh diet depends on intake, total starch and rumen degradable starch, forage digestibility and particle size. In addition, supplementing amino acids (the building blocks of enzymes and hormones), which is important in several biological functions during the transition period, has been shown to:

• Reduce oxidative stress.
• Increase DMI.
• Affect embryonic gene expression.
• Improve immune-metabolic status.

One should be aware of contradictory statements regarding ‘fats’ in transition diets and that only specific fatty acids may have positive effects, for instance decreasing the NEFAs in the liver. Special attention must be given to improving trace mineral availability that will positively impact immune function, and ultimately reproductive performance.

Improving feeding behaviour

Feeding behaviour associated with calving, stocking density, grouping and pen movement, may have a negative impact on rumen health. Key factors to remember when wanting to improve feeding behaviour in fresh cows, are:

• Reduction of heat stress.
• Maximising opportunities for cows to eat during the day.
• Keeping fresh cows separate.
• Avoiding overcrowding in fresh cow pens with a stocking density below or at 85%.

Remember, all dairy cows may experience low DMI, NEB and metabolic disorders to some extent. How these factors are minimised during the transition period through nutrition and sound management, as well as how environmental factors are managed, will positively affect profits.

SP Els, AFGRI Animal Feeds

When the grazing platform changes from ryegrass to kikuyu and/or the neutral detergent fibre (NDF) increases and the protein content decreases – historically the first nutrient nutritionist would increase is the crude protein (CP) concentration in the dairy meal. Making decisions based on CP concentrations as well as energy expressed as mega joules metabolizable energy per kg feed (MJME/kg) are based on old ideologies.

Formulating rations on CP, soluble protein (SP), rumen degraded protein (RDP), rumen undegraded protein (RUP) and non-protein nitrogen (NPN) which is the amount of nitrogen (N) analysed times 6.25 to give the CP value. This calculation assumes that all proteins in animals and plants have a 16% N content, which is not accurate. Furthermore, the CP value of a feed does not give any indication what the nutritional value of a protein source is, making it invaluable to use as a nutrient. Instead the profile of the amino acids (A/A) of the specific protein source and digestibility will determine the nutritional value. What is further important is that the total NPN and total or individual A/A available in the rumen and lower intestine are met for specific production targets. Frequently advise is given to increase the concentrations of CP in the diet before the profile of the A/A or limiting A/As has been looked at or are known. The profile of the A/A or limiting A/As cannot be overlooked or brushed aside when given advise to increase the concentrations of CP in the diet.

Lowering the CP of the cow’s diet offers an opportunity to improve the profitability as well as nitrogen utilization. Some dairy nutrition software has a dynamic rumen model wherein the passage rate of feeds determines the outflow of nutrients from the rumen. This passage rate of feeds is largely determined by feed intake but also adjusted by ration forage content and particle size. Nutrients that are not constant will vary according to feed consumption and ration ingredient such nutrients are metabolizable protein (MP), metabolizable energy (ME), amino acid content of MP, and rumen available protein (peptides and ammonia). Thus, linear programming can no longer be used and dynamic digestion models – nonlinear programming is required.

While the ryegrass pasture quality deteriorate and/or kikuyu comes in play consultants will more likely increase the CP content of the dairy meal, without considering that although CP of the pasture decreased, the higher lignin and NDF content and consequently lower NDF digestibility negatively impact dry matter intake (DMI). Generally, cows grazing on 24-hour rye or kikuyu pasture RDP is oversupplied in contrast with the energy especially fermentable carbohydrates which are deficient. On pasture farms energy is still the first limiting nutrient whereas rumen ammonia exceeds 200% of requirements and even on low quality pastures the rumen ammonia requirements are still above 150% – feeding a 10% CP meal. It is important to feed the correct energy and protein “package” instead of CP and ME content.

Non-protein nitrogen (NPN) consumed or ammonia derived from the degradation of true protein in the rumen is either used by rumen microbes – the amount used will be determined by the number of and how rapidly they are growing, in other words it will depend on the amount of energy available to the microbes. The rest of the ammonia is either recycled to the rumen via saliva or will be excreted in the urine or as milk urea nitrogen (MUN). The ammonia derived from NPN and from degraded true protein and not used by the microbes will not be of any value. The amount of A/A that is not supplied by the microbes needs to be supplied from bypass feed sources that is digestible in the lower intestine. Research showed from Figure 1 that diets with different CP percentage in lactating cows had no effect on milk nitrogen output – which is milk protein and should not be confused with MUN. Furthermore, as the CP percentage increased in the diets the oversupply of N was excreted as manure (faecal & urine).

Urea is then produced in the liver from the excess ammonia and this process uses energy, energy which could instead be used for other requirements. Dairy cows are particularly efficient in recycling urea when fed low-protein diets. It has been proven by some feed systems in the UK that the efficiency of using protein for milk protein synthesis is better for diets which are deficient or marginal in protein than those which are adequate.

When looking from a nutritional point of view, the standpoint would be not to apply CP any longer, but still CP are being used by nutritionist and/or consultants probably due to fear of the unknown. Ipharraguerre and Clark, 2005 found a significant curvilinear relationship between milk yield and the concentration of CP of the diet on 112 research trials. As indicated in figure 2 diets on the same CP concentration varied in 20kg milk yield per day. Which means that if there is a decline in milk production it’s less expected to be from a CP concentration and more probably a decrease in DMI and/or diet digestibility.

by Tian Keet, Technical Advisor, AFGRI Animal Feeds.

Spring is an exciting time in the dairy industry especially for the farmer milking off pasture-based systems. This is your time for more profitable milking due to generally lower input costs and expected higher milk production. Spring however, seem to past far quicker than what we want, thus you need to get the most out of it while it lasts. To achieve this, you need to complement your pasture to get maximum milk production out of it and sustain that level of production for as long as possible. With issues related to our current economy, high costs of land and increasing production costs, pasture-based systems will require higher per animal production.

What does your pasture supply?

Crude Protein (CP) of pastures grazed in Spring typically range from 23 – 30 percent. This mainly consists of highly degradable protein which gets broken down in the rumen to ammonia.  The recommended dairy CP requirements for a lactating dairy cow range from 15 percent. With the high CP content of Spring pasture, you will easily exceed the CP requirements with a typical ration consisting of 70% pasture. Furthermore, the ammonia produced through pasture protein degradation in the rumen, will far outweigh that what can be used by the rumen microbes.

Neutral detergent fibre (NDF), primarily obtained from roughages, is extremely important in all ruminant diets.  Dairy cows, as in all ruminants, require enough fibre for optimal rumen function and to stimulate rumination. Through rumination cows mechanically break down fibre further and produce saliva which buffers the rumen. Fibre also forms a rumen mat and slows down the rate of passage which facilitate rumen microbes to break down fibre more efficiently. Neutral Detergent Fibre (NDF) typically range from 40 – 50 percent in pasture, thus can easily meet the dietary requirements of 28 – 35 percent NDF for lactating dairy cows. However, newly planted Spring ryegrass may have levels below 40 percent NDF at the first grazing.

What does your pasture need?

Energy is the first limiting nutrient for high producing cows grazing high quality pastures as the only feed (Kolver and Muller, 1998). Cows on pasture-based systems are often expected to walk great distances to paddocks to graze. Furthermore, dry matter intake (DMI) are significantly less for cows on pasture compared to cows on total mixed rations (TMR). Thus, losing a lot of energy through higher activity but also not getting enough energy in, due to lower DMI. Our African climate with higher temperatures adds to the issue. Cows willingly eat less in times of heat stress in an attempt to reduce metabolic heat. In addition, cows under heat stress have a higher energy cost to maintain body temperature.

It is essential to supply a good, well-balanced premix consisting of minerals and vitamins to meet the requirements of high producing cows. Soil profiles in and between farms vary significantly in mineral composition, hence the importance of a premix to supply the shortfalls. Certain vitamins (A, D and E) are recommended to be supplemented to cows housed in confinement. Cows on pasture, on the other hand, don’t need supplementary vitamin D as it is synthesized in the presence of sunlight.

Young Spring pasture, in difference to more mature pasture, have lower NDF. This causes a quicker rate of passage and sub-optimal rumen mat formation. By supplying a small amount of good quality hay or maize silage (1 – 2 kg DM) will stabilise rumen conditions and slow down the rate of passage.

Benefits of complementing your pasture with the right concentrate

Higher milk production can be expected with supplementing concentrate. Supplementary concentrate will supply the energy that falls short on pasture-based systems and allows cows to reach their genetic potential. It is important to supply highly available energy. Rumen microbes need energy to grow. With enough available energy, rumen microbes will grow and function more efficiently. Fresh in milk cows are in a negative energy balance, concentrate feeding can help them get out of that negative energy balance far quicker. Furthermore, cows will hold body condition better or recover body condition sooner.

Rumen ammonia will reduce with concentrate feeding. The rumen microbes now have the needed energy to utilise this free-flowing ammonia and convert it into microbial protein. Excess rumen ammonia is converted to urea in the liver which is an energy costly process. In utilizing rumen ammonia more efficiently, the cow conserve energy. Studies have shown that supplementing concentrate to cows on pasture, increase milk protein (Petch et al., 1997; Sayers, 1999; Reis and Combs, 2000).

To summarise

Milking off pasture-based systems are most profitable when pastures are utilised to the fullest. In this, you only need to supply where pasture falls short and not replace what it already supplies. Hence complimenting your pasture. By doing so you will meet all the requirements of a high producing dairy cow, milk those cows to their genetic potential and sustain milk production for longer.