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| ===Risk Factors=== | | ===Risk Factors=== |
| + | Insufficient long fibre in the diet |
| + | Long fibre is essential both for rumen mat formation and |
| + | to stimulate cudding. It is usually defined as fibre longer |
| + | than 2-5 cm. However, if it is longer than 10 cm, it is |
| + | possible for cows to 'sort' the ration and avoid eating the |
| + | fibre. Consequently, long fibre for inclusion in a TMR |
| + | should be chopped to between 2-5 and 10 cm. Provision |
| + | of long fibre in modem diets is problematic as there is an |
| + | increased tendency for silages to be chopped very short |
| + | in the belief that better compaction and fermentation will |
| + | result. Furthermore, there is an inverse relationship |
| + | between fibre content and the 'D-value' (or digestible |
| + | organic matter digestibility [DOMD]) which is correlated |
| + | with the metabolisable energy (ME value). Farmers |
| + | tend to concentrate on making high energy silage at the |
| + | expense of fibre quantity and quality. In the case of |
| + | maize silage, fibre length is often so short that it is best |
| + | to assume that its peNDF content is minimal and additional |
| + | long fibre may be required (eg, 1 to 2 kg of |
| + | chopped hay or straw per cow). |
| + | Inaccurate fodder dry matter estimation |
| + | If the dry matter content of fodder is overestimated, insufficient |
| + | fodder may be provided, thereby leading to SARA. |
| + | Excessive mixing of a TMR diet |
| + | If a diet is overmixed in the TMR mixer wagon, long |
| + | fibre will become less effective. The long fibre (forages) |
| + | should always be placed in the mixer wagon last to |
| + | ensure minimal degradation. |
| + | Excessive feeding of starches and sugars |
| + | Excessive feeding of starches and sugars is a common |
| + | problem, especially soon after calving. Maize silage is |
| + | a rich source of starches and sugars and this property, |
| + | together with its lack of effective fibre, means that it is |
| + | frequently implicated as a factor in the development of |
| + | SARA. A common scenario is for a farmer and his advisors |
| + | to counter poor yields or an excessive loss of body |
| + | condition score during early lactation by feeding additional |
| + | concentrates in order to supply additional energy. |
| + | However, often the problem is one of SARA, and feeding |
| + | additional energy actually makes the situation worse |
| + | - although a temporary increase in milk yield may be |
| + | observed, probably as a result of small intestinal carbohydrate |
| + | digestion. |
| + | Poor dry cow management |
| + | As mentioned earlier, feeding a suitable transition diet is |
| + | essential for rumen papillar development and the acquisition |
| + | of a suitable rumen microflora capable of dealing |
| + | with the lactation diet. |
| + | Feeding post-calving |
| + | While most farmers appreciate the need for a pre-calving |
| + | transition diet, they frequently fail to appreciate the fact |
| + | that the transition period is properly defined as three to |
| + | four weeks pre-calving to three to four weeks post-calving. |
| + | The rumen is not capable of handling high energy |
| + | density diets until this period is complete. Cows should |
| + | be fed a relatively low energy diet during this postcalving |
| + | period. Ideally, the energy density of the diet |
| + | during this time should be no more than 10 per cent |
| + | greater than the transition diet. In practice, this means |
| + | that freshly calved cows should remain on a diet suitable |
| + | for M+25 to M+28 litres during this period. This will |
| + | encourage a maximal dry matter intake and avoid |
| + | SARA. All too often, post-calving cows are fed a diet |
| + | with too high an energy density in the mistaken belief |
| + | that they would otherwise develop negative energy balance. |
| + | Many cows and their lactations are ruined during |
| + | this critical period. |
| + | The objective during the post-calving period is to |
| + | maximise dry matter intake rather than keep up with the |
| + | daily energy requirements of the cow. |
| + | Sorting of long fibre |
| + | If the fibre in a TMR is longer than 10 cm, cows are likely |
| + | to sort the food and only consume small particles and |
| + | short fibres, leaving the long fibre alone (Lammers and |
| + | others 1996). Cows which sort food in this manner will |
| + | be at risk of developing SARA. If feed barrier space is |
| + | restricted, dominant cows may sort the food and thus |
| + | develop SARA. Subordinate animals, such as heifers and |
| + | lame animals, will then consume the sorted diet and |
| + | so obtain a diet of lower energy but greater fibre content |
| + | than is intended. The net result is that both groups are |
| + | at risk of negative energy balance, although for different |
| + | reasons. Ensuring that fibre length in a TMR is adequate |
| + | to prevent SARA, but not too long such that sorting |
| + | occurs, is problematic. Many mixer wagons will not cut f0o1age to an appropri ate leng-Ith (25 to 10() cm1) and thet e |
| + | is eur-r-elItIx no suitaSlic for-age choppei- on the UK miarket, |
| + | althouLgh sonic. but 1ot 1all, stli\ax clioppers Wxill Cut to a |
| + | suLitahble length. OneoCptioll is to nSe a stationiarx foIagce |
| + | hair-\cstel fromil xxhich blades cani he reni-oved it' reqUoired |
| + | to enlsui e the conICCt Chop leingth. Hoxxcxeri, the nise ot' |
| + | suLICh miachineiv inI this 1manIler is not xxithout risk to the |
| + | oper-atoi- a1njid appr-oprialtc safectV guLardl-CIs illust be eni1ployed. |
| + | Slug feeding of concentrates in the |
| + | milking parlour |
| + | It' giealtei- th.an 3 to 4 kg-, of co-ceniiti ates arc fed at a timlie. |
| + | I-Lillmen IpH is likelx to tall anid i-emiiain loxW fol- mnLIchI of |
| + | the time. The pi-ohlemi is comI)pounided if cox\x7 aIre receCixinc |
| + | a TMR at the Itcd bhai-i iei- that is hiTh inI en-erx |
| + | coni-pari-ed to gri-ass silalc. It mIulst he remicemicber-ed that |
| + | suIbstitution effects xvill also he oCCurlrine so that, the |
| + | miore cake is fed, the less foraoc xxill be coIlsumLIed. In |
| + | the conitext ol' 1K ag1i cuIltuIre, tIlC aIthor- considers this |
| + | pr-actice of hxhl-id TMR feedii-Ig to bc a miajoi factoIr iII |
| + | thIe dex elopmenlet o(fSARA. |
| + | Food deprivation and irregular feeding |
| + | InI oidel- to naiilalisc dr- illattei intake, a TMR should be |
| + | axllablc at all times. It is gen1erall recomimiiciided that |
| + | 5 to 11) pei cenit of the ationi should be left ox er each daxl |
| + | anid remiosved befoi-c t'frcshi food is ot't'ered. It is comImIIIonto |
| + | ftind situation-s xxheci ther-c is 0o f'ood in frouit of the |
| + | coW s. su(estinSt it ian out )A thin the last fcxx flurs. |
| + | AlteiratxVcly f(oodI ilay he Pliscilt, but unlax ailable to |
| + | the cox s since it Ilas not benCI puLshed uip to tile barl--icr SO |
| + | that thex cani eat it. Peliods ot' food deprixvatioil mia disrLipt |
| + | the riLiIeillniicrobial pOpu-lation. aIld tencd to caulse |
| + | coxs to oxvercat xvhleu food is cintioduced. Both of thesc |
| + | factol S ilneealse the i-isk of SARA dcx eloping. Most |
| + | tfaric- s tccd a TMIR oil-ce daIilvx, elerallx, iil the illoiilillg |
| + | t im.av be adxaitagLeouLs to feedl the TMR ii the |
| + | afterilooni, tllerbhy CilsuIr-lgtl tilat fooCd is il tfr(lilt of the |
| + | cox S aIt iiglit (XxV1lCl tilexC arC ilMatteilded). DuLingt the |
| + | dax!' food cain casily bhc psiledC uIP to tile barrier as tai-ll |
| + | staff arec ceilerallN, illiattendalnlce. |
| + | Poor cow comfort |
| + | Pooi covx coilltort xxi -Csuilt in lcss tinle beint spceit |
| + | 1uillila.1til-L xxith ani associated r-eduLctioll in saliaa produLIctionI |
| + | anIdi runlinaiial hbfl't'clrilng |
| + | Miscellaneous factors |
| + | Lailileiless. pooi tfeedl hbianci-s. aildtc so olil. ill.a all play a |
| + | Phart il tlic dcx\cloPi-ille-it of'SARA. |
| | | |
| ==Signalment== | | ==Signalment== |