Optimal management of livestock farming during droughts
Figure 1 clearly shows that rainfall over the last three months was below average in most parts of South Africa. Furthermore, it transpires from Figure 2 that large parts of South Africa were already suffering from varying degrees of drought since September 2006.
The South African Weather Service also predicts low rainfall for the period March to April 2007, with a 40% chance of below average rainfall for the entire country. Hence, it appears as if livestock farmers are heading for a dry winter, with limited supplies of roughage for overwintering their stock. While this is a rather sombre note on which to start this article, it is better to face the unpleasant reality of a looming drought and to prepare for it pro-actively, rather than to be ill prepared. Being pro-active will help to minimise the negative impact of drought on livestock farming.
FIGURE 1 & FIGURE 2
Extensive livestock farming
It is necessary to distinguish between supplementary feeding and drought feeding. With supplementation the aim is to ensure optimal performance by supplementing nutrient deficiencies occuring in the grazing. With 2 supplementation the assumption is that there is ample grazing material available, even though the quality of the material may be rather poor.
Drought feeding, on the other hand, commences when there is limited availability of grazing (roughage), which is only sufficient to supply in about 30% of the nutrient requirements of the livestock. The aim with drought feeding is to keep animals alive, and to maintain such a production level as will optimise the return on investment (in drought feeding strategies).
Because roughage is scarce during droughts, it is usually advisable to identify and sell the worst quality animals. This should be done as early as possible, before any significant drought feeding has commenced, while there is still sufficient grazing available as the basal diet. Animals that deviate sufficiently from breed standards (termed culls) should be marketed first, followed by old animals. The remaining animals in the reproductive herd or flock can then be sub-divided into first- , second- and third flock, in decreasing order of genetic merit. If further selling of animals become necessary, then the third flock animals will be sold first, thereby retaining the best available genetic material for postdrought breeding.
Animals retained on the farm should be kept in production with the least costly strategy, to ensure a consistent income. The best way to manage production is to manipulate the body condition of the animals. On a scale of 1 to 5, where 1 = emaciated (too thin) and 5 = overly fat, dry (non-lactating) animals should maintain a body condition score of 1. As a rule of thumb, animals that enter the drought in a reasonable body condition (score 3) should not be allowed to lose more than 25% of their body weight. For mature ewes weighing 55 kg and mature cows weighing 500 kg, the minimum weights that should be maintained during the drought period are 41 kg and 375 kg respectively. If the animals are allowed to lose more weight, reproductive processes will seize first, followed eventually by feed refusal (in severe cases) and some deaths. If such animals do survive, the cost to get them back into a productive state is prohibitive. In the case of dry animals it is sufficient to supply drought feed only once a week. This strategy should encourage intake of unpalatable grazing (although the latter is scarce). However, the grazing should not be overgrazed (e.g. by supplying supplements that will stimulate aggressive intake of the available material), because overgrazing increases the risk of soil erosion.
Animals that are in a productive state (mating period, last third of pregnancy, and lactating) should be maintained in a body condition score of 2-3 (+/- 48kg for ewes and 435 kg for cows, with mature body weights of respectively 55 kg and 500 kg when in good condition). This does not mean that such animals must be in this condition for 12 months of the year. Use flush feeding from 3 weeks before mating to improve body condition of female animals from score 1 to score 2 (or better). This will stimulate ovulation (duration of the heat cycle is 17 to 21 days, in sheep and cattle respectively), and improve conception (pregnancy rate). In the 3 case of male animals, start improving body condition from 8 weeks before mating, since spermatogenesis (sperm production) takes longer to complete than oogenesis (egg production) in females. Flush feeding should be continued during the mating period (and a couple of weeks thereafter), since the early embryo is highly sensitive to stress conditions and nutritional stress may induce embryo resorbtion. During mating and the first two-thirds of pregnancy female animals should receive drought feed twice a week. The duration of pregnancy is approximately 140 days in sheep and about 270 days in cattle.
During early- and mid-pregnancy (the first third and the second third of pregnancy respectively) the placenta is developing, and animals should normally show moderate weight gain. However, during droughts it should be sufficient just for animals to maintain body weight and condition (at score 2), via drought feed supplied twice a week.
During late pregnancy (the last third of pregnancy, directly before lambing or calving) about 80% of foetus growth takes place. Udder development also takes place during late pregnancy, and nutrition during this period has a direct effect on birth weigh, survival of lambs or calves, and milk yield of the dams (mothers). Furthermore, nutritional status during late pregnancy has a direct bearing on the production of thick, sticky colostrum by ewes. Lambs are unable to suckle this type of colostrum from the teats. It is clearly not sensible to spend money on getting animals pregnant, only to squander potential income by subjecting animals to nutritional stress during late pregnancy.
During lactation the nutrient requirements of females are as high as it will ever be during the total production cycle. Females suckling lambs or calves should therefor have access to sufficient feed, to ensure optimal milk production. Logically, the ability of lambs or calves to grow is directly linked to the milk yield of their dams. Ewes reach peak milk yield approximately 3 weeks after lambing, whereas beef cows reach peak milk yield about 6 weeks after calving. Strive to increase peak milk yield by good nutrition after lambing or calving, thus ensuring good early growth in the offspring, which improves the chances of early weaning. During late pregnancy and early lactation drought feed should be supplied three times a week.
Young animals have an appreciably better feed conversion ratio (kg feed needed to produce 1 kg of body weight gain) than older animals. Shortly after birth the young animals need about 1 kg milk to gain 1 kg body weight, whilst old animals may need 10 kg of feed (or more) for 1 kg gain. Therefor it stands to reason to wean young animals at an early age, accompanied by good nutrition which they are able to use efficiently. The (less efficient) dams can then be put back on a cheaper maintenance feed earlier than usual, and body condition can be downmanaged to a minimum of score 1, until such time that flush feeding must start for the next mating period.
Lambs can be successfully weaned at the age of 8 weeks, with a minimum body weight of 15 kg. Although it is possible to wean lambs at lower body weights, it will increase the risk of mortality substantially. Calves can be weaned under farm conditions at about 5 months of age.
It is cheaper to start with supplementary feeding earlier rather than later, and then to switch to drought feeding as soon as the available roughage becomes seriously limiting. Do not delay supplementation beyond the point where animals that were in a moderately good condition (score 2 – 3) had lost 10% of their body weight.
Drought is an unpleasant experience under the best of circumstances. To minimise loses, farmers should use the guidelines given above, thus getting rid of less productive animals while retaining the best genetic material available for the future.
Broom (1995) published a list of 11 points as guidelines for dairy farmers facing a drought. These guiding principles are listed below:
Broom’s suggestions are as valid today as they were 22 years ago. It is clear that the farmer should call upon other expertise to help plan his drought strategy, for example experts in irrigation, animal nutrition, and financial matters. Timely action is required to negotiate the best positions. These days it is also possible for farmers to use market instruments like hedging as part of their drought management strategy, something that was not possible in 1995.
In an intensive farming system, such as a dairy, it is not really possible to use stock reduction to mitigate the negative effects of a drought. Should there be a few unwanted animals on the farm, they should be sold first. However, the focus should rather be placed on alternatives for the most limiting resources, probably feeds like silage and hay, and irrigation water (as a consequence of which pasture-based systems will likely have less grass available for grazing).
In most cases, silages are produced on-farm, and during droughts yields are usually lower, whilst the silage that is produced will likely be of a lower quality (nutritive value). The availability of hay (grass, lucerne) is a limiting factor during droughts, and since demand tends to suddenly outstrip supply, price hikes occur (which may be rather drastic).
Hence, a dairy farmer should take stock of all farm-produced feeds, to compare it with the feed that will be needed to maintain a given production level. The shortfalls should be made good with the most cost-effective alternatives. The strategy may be to feed a bought-in total mixed ration (TMR) or semi-complete ration to the most productive animals (fresh cows; highest yielding cow group). The (limiting) farm-produced feed and bought-in concentrates can then be fed to the rest of the lactating cows, dry cows, heifers, and calves. Another strategy may be to consider non-conventional alternative feeds to fill gaps in the fodder flow. A good example of this will be products that are used to stretch the silage supply (silage extenders) or to stretch the supply of pasture grass and/or hay.
Quality of farm-produced feeds and alternative roughages will have a significant influence on the expected milk yield of cows. With the help of biological models (like AMTS.cattle and Cornell Penn Miner (CPM)) the effects of quality variations in feeds (for example lucerne hay or grass hay) on biological performance can be simulated with reasonable accuracy. In so doing, more realistic decisions can be made about the value of different feed sources or commercial offers. The cheapest feed is not necessarily the most cost-effective choice. We can assist farmers in this regard.
Meadow Feeds have available several products that dairy farmers can consider using during drought situations. To name a few examples: Silage Cubes (V18771, Act 36 of 1947; as a silage extender), Herbivore Sweetfeed Pellets (V19426, Act 36 of 1947; a lower-cost alternative for growing out calves after weaning), and a wide range of TMR’s and semi-complete feeds (in situation where locally available roughages are limiting).
Please contact Stephen Slippers or Joubert Nolte for more information about products and services that you may need during the drought. Our telephone number is 011-991 6000.
Broom, D., 1995. Surviving the drought. Kwazulu-Natal Dairy 9.1.1995. In: T.J. Dugmore (Ed.). Dairying in KwaZulu-Natal. KZN Department of Agriculture, Pietermaritzburg. Page 265.
South African Weather Service, 2007. http://www.weathersa.co.za
Date published: 2007-12-10
& Joubert Nolte