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Drylands are generally defined in climatic terms as lands with limited rainfall. Drylands are characterized by low (100-600 mm annually), erratic and highly inconsistent rainfall levels. The main characteristic of dryness is the negative balance between annual rainfall and evapotranspiration rates.
Rainfall is scarce, unreliable and concentrated during a short rainy season, with the remaining period tending to be relatively dry. High temperatures during the rainy season cause much of the rainfall to be lost in evaporation, and the usual intensity of storms ensures that much of the rainfall runs off in floods. Water is not only meagre in absolute terms, but also scarce for natural and human uses.
As defined by FAO, drylands are zones falling between 1-74 and 75-119 growing days, representing arid and semi-arid lands, respectively. the growing period, which is defined as the period when both water and temperature permit crop growth
FAO Classification of Drylands (Length of growing period in days/year) 1-74 75-119 120-180 Arid Semi-arid Dry sub-humid
Semi arid = Semiringkai Curah hujan rendah dan eratik (sekitar 700 mm dengan variasi 20 -50%), suhu tinggi, radiasi matahari tinggi, evapotranspirasi tinggi, kesuburan tanah bermasalah, tipe vegetasi savanah Hasil panen pertanian tidak stabil (irregular), namun produk rumput memuaskan (Goodin & Northington, 1985).
Mayoritas penduduk di lahan-lahan Arid dan semi-arid bergantung pada Pertanian dan pastoral: Tipe iklim ini memiliki tantangan berupa: Pola curah hujan yang tidak menentu; Hujan turun lebat dan hilang sebagai run-off; Evapotranspirasi tinggi; Gulma (weeds) tumbuh lebih cepat daripada tanaman pangan, berkompetesi untuk mendapatkan kelembaban (air); Kandungan bahan organik rendah, kecuali beberapa saat setelah panen atau penebaran pupuk kandang; dan Respon yang sangat bervariasi terhadap pemupukan.
Dari semua faktor yang mempengaruhi produksi ternak, Iklim dan lokasi paling signifikan. Karakter2 klimatologi seperti Suhu ambien dan pola curah hujan mempengaruhi ketersediaan sumberdaya pastura dan pangan sepanjang tahun, jenis wabah penyakit dan parasit hewan.
Dalam literatur, terdapat banyak tipe klasifikasi iklim Klasifikasi paling umum adalah Klasifikasi Köppen classification that roughly divides world climates under the following categories: Tropical (Group A), Dry (Group B), Temperate (Group C), Continental (Group D), Polar (Group E), and Alpine (Group H).
Jenis iklim ini mempengaruhi produktivitas ternak: Distribusi hujan yang tidak merata selama musim basah dan kering (tropical), Periode kering yang panjang selama beberapa tahun (Dry), Musing winter dingin yang ekstrim dan panjang (Temperate), Summers yang panas dan panjang (Continental), atau Winter dengan curahan salju yang signifikan (Alpine).
Hewan ternak yang sudah terseleksi oleh kondisi iklimnya telah mengembangkan strategi dalam menghadapi variabilitas iklim Melalui pengaturan suhu tubuh (homeostasis) baik pada suhu lingkungan tinggi ataupun rendah melalui sejumlah respon fisiologis; Atau dengan adaptasi terhadap kekurangan nutrisi musiman, terutama melalui Seasonal Weight Loss (SWL) melalui adaptasi prilaku dan fisiologis atau dengan kemampuan mengatasi parasit dan penyakit2 endemik.
Iklim Tropis (Group A) dibagi ke dalam 3 subgrup Tropical rainforest, Monsoon and Tropical wet and dry, or Savannah. Ketiga subkelompok tsb dicirikan oleh musim kering dan hujan dengan durasi yang bervariasi bergantung kepada lokasi geografis
Cuaca dan iklim dan berpengaruh terhadap produksi ternak dan produksi agronomik. Informasi cuaca dan iklim penting untuk menjaga atau meningkatkan tampilan produksi ternak seperti survival, pertumbuhan, reproduksi, produksi susu dan daging. Intervensi manajemen diperlukan tidak saja untuk memperbaiki potensial genetik ternak/hewan tetapi juga membantu mengatasi kendala-kendal produksi yang ditimbulkan oleh faktor iklim, lingkungan fisik, dan ancaman kesehatan di suatu wilayah. Kebijakan-kebijakan On-farm biasanya meliputi desain dan manajemen fasilitas produksi, sedangkan pada tataran yang lebih luas membutuhkan kebijakan secara nasional maupun regional.
Pengetahuan akan bagaimana Stresor lingkungan (Temperatur ambien, Kelembaban, Radiasi panas, kecepatan udara) yang secara langsung dapat mempengaruhi tampilan produksi ternak, kesehatan dan kesejahteraan ternak sangat penting! Konsekuensi tidak langsung dari pengaruh iklim terhadap kualitas dan ketersediaan pakan, juga harus dapat diidentifikasi.
Components of energy use has been studied and identified. Figure 12.2 makes it clear that thermal energy exchanges between the animal and its ambient environment interact with the residual dietary energy available for productive purposes.
Fisiologis hewan berfungsi secara efisien ketika berada dalam thermoneutral zone Bila berada di atas atau di bawah zone kritis tsb, hewan stres dan berpengaruh terhadap proses produksi. Temperatur kritis tsb tidak menjadi patokan tetap bagi setiap species atau tipe hewan, tetapi dapat berubah sesuai umur dan kondisi fisiologis hewan.
Seleksi alamiah maupun buatan pada lingkungan yang ekstrim dapat memperbaiki daya adaptasi terhadap kondisi tsb Terjadi melalui perubahan sifat-sifat fisologis dan morfologis yang adaptif, kadang melalui beberapa generasi. Misalnya, sapi Holstein di zone tropical dan subtropical memiliki perbedaan dalam hal karakteristik bulunya (hair-coat) dibandingkan sapi di daerah temperate.
Respon spesifik individu hewan dipengaruhi banyak faktor (internal dan eksternal): Growth; reproduction; feed intake and conversion; mortality; and milk, egg and wool production telah lama digunakan sebagai parameter performans hewan dalam respon terhadap faktor-faktor lingkungan.
Parameter termoregulator (seperti, ritme suhu tubuh) merupakan signal terhadap gangguan aktivitas feeding selama musim panas Parameter tingkah-laku (Behavioural measures) Posture, orientation, shelter-seeking, huddling or dispersion) Juga berhubungan dengan respon termoregulator hewan terhadap lingkungannya.
In estimating those consequences, it is important to consider the resilience of animals, within limits, to maintain normal functions through adaptive and compensatory capabilities (Hahn, 1982) Care must be taken in comparing different types of animals with respect to their performance in a given environment. For example, tropical and European breeds of livestock can hardly be compared one to another for their growth rate or their reproductive performance in a tropical environment.
Livestock native to these countries have been subject to natural selection in their environments and high economic performance of animals is not a choice for nature – it is a human choice, because many of its aspects can unfairly influence the animals’ fitness. As for nature, females must give a milk yield that corresponds exactly to the quantity needed by their young: a yield in excess of this quantity can adversely affect the physiological balance.
Thus, the low producing ability of native livestock is not a sign of inferiority, but of a perfect adaptation to their specific environment. On the other hand, the high productive performance of the European breeds of livestock is only the consequence of hundreds of years under artificial selection for a given purpose
Animals living in deserts and extremely dry environments must have an efficient protection against the loss of water vapour and the intense solar radiation; those living in cold regions must be protected against the loss of body heat; those in tropical regions must be able to dissipate heat excess through the skin and from the respiratory surfaces, and at the same time they must avoid incoming thermal energy from the environment.
Such protective properties depend on the morphological characteristics of the skin (colour, thickness, sweat glands, and so on) and of the hair coat (especially the thickness of the coat, number of hairs per unit area, diameter of the hairs, length of the hairs and angle of the hairs to the skin surface), which allow the animal to exchange heat with the environment through the four transfer modes noted in Table 12.1.
In certain kinds of animals such as pigs and water buffaloes, which do not present hair coat (their skin is scarcely covered by bristles) or sweating, heat exchange occurs mainly by convection, although the animals can eventually moisten their body surface with water or mud in order to increase heat loss by evaporation.
The role of pigmentation and other skin and hair ‑ coat characteristics in heat transfer by radiation in animals has been extensively studied In particular, skin pigmentation is of utmost importance to protect deep tissues against excess exposure to solar short-wave radiation in tropical zones. In general, it is accepted that dark-coated animals acquire greater heat loads from solar radiation than do the light-coloured ones consequently, light coats have been considered the most desirable ones for livestock in tropical areas
Windbreaks Grazing animals or animals giving birth will seek shelter from strong winds, especially during cold weather. Structures or trees can markedly reduce wind speed and can be beneficial to the survival of exposed animals (especially newborns). Windbreaks have an importance far beyond these benefits, however, especially in tropical and subtropical regions. Shades Shades and other minimal measures should be thought of as a form of insurance for protecting farm animals in hot climates. In a tropical region, the solar irradiance is high even during the winter, when its value is often the double (1 000 W –2 or more) that observed in a location at 40° latitude (500 W –2 or less). The most effective shades are trees, as they provide protection from sunlight, combined with beneficial cooling as moisture evaporates from the leaves.
Sites The selection of a site for housing or another intensive production system is fundamental to minimizing the effects of local weather. Climatic factors vary with height above the ground at a specific location and with varying terrain in a general location. Observations of the microclimates in a general location will reveal much variation in thermal conditions resulting from terrain features, differential exposure, wetlands, rivers, type and height of vegetation, human activities and other factors. Proper selection of a site to emphasize factors for enhanced heat dissipation (minimal radiation, air temperature and humidity, maximal air velocity) will have long-term protection benefits.
Partially or totally enclosed shelters Enclosed shelters are not recommended for tropical climates because of the decreased natural air velocity and sanitation. In temperate regions, partially enclosed shelters can reduce the thermal radiation received by animals during hot weather.
Genetic improvement for adaptation Acclimation and adaptation are different processes. Animals are considered acclimated to a given ambient temperature when body temperature returns to pre-stress Adaptation, on the other hand, requires modifications of the genetic structure and is a process involving populations, not individuals. Intriguing, however, is the fact that in poultry, the exposure of chicks to high environmental temperatures during embryonic development results in permanent changes in responses to heat stress in adults
Environmental modification Many forms of environmental modification are available. In hot weather, water can serve as an effective cooling agent for farm animals, especially for species that maintain homeothermy primarily by regulating heat production (such as swine). Direct wetting of animals is often used as an emergency measure and can be a very effective protective device.
For cold weather, the benefits of environmental modification beyond shelters or windbreaks to minimize the effects of weather extremes are less clear. Neonates of all species are vulnerable, and require some protection for survival. Growing and mature animals can survive relatively severe cold if they are adequately fed and disease problems are absent (Figure 12.6). Production efficiency can be markedly reduced, however (National Research Council, 1981). Controlled ventilation systems in enclosed housing can use minimal sensible heat to buffer extremes of cold for improved efficiency, while added artificial heat is essential for survival or economically beneficial.
Forage and pasture the frequent onset of droughts causes considerable losses of animals due to scarcity of fodder, it is vitally important to supplement pasture amelioration with fodder trees and shrubs in order to minimize such losses (WMO, 2004 a). These trees and shrubs will not only supply food for animals, but also serve as a shelter from the solar radiation and create a microclimate more favourable for regrowth of grass spoiled by the dry conditions
In recent years the increasing use of intensive livestock production systems has become a source of solid, liquid and airborne emissions that can be both a nuisance and environmentally harmful. The most important greenhouse gases are methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). In spite of the low amount of CH4 in the atmosphere relative to that of CO2, its importance as a pollutant is considered to be 21 times greater than that of CO2, while that of N2O is 310 times greater (Hartung, 2003).
(a) Replacement of roughage in the cattle diet with concentrates; (b) Development of low-emission production system facilities, including filters, scrubbers, covered manure pits and shallow manure application. (c) Reduction in the concentration of animals in intensive production units to the extent possible, by using more pens and pastures;
(d) Use of feed additives to reduce CH4 emissions (research results have shown that some additives can have this effect). Lower amounts of nitrogen in manure and urine can reduce N2O emissions. (e) Increase in feed digestibility and feed conversion efficiency (CH4).
A comprehensive review of the management strategies for mitigation of greenhouse gas emissions can be found in WMO (2004 b). As for carbon dioxide, it is generally considered the principal greenhouse gas, but it is produced mainly from the combustion of fossil fuels and cannot be sufficiently absorbed by growing biomass, a problem of increasing importance because of expanding deforestation. The contribution of livestock farming to the current amounts of CO2 in the atmosphere is very low.
Some studies have been carried out on this subject, however. Kibler and Brody (1954) measured the respiratory CO2 of Holstein cows exposed to 20°C (153 L/h/cow), 27°C (151 L/h/cow) and 35°C (139 L/h/cow). For cows of the same breed, Yousef and Johnson (1967) found average amounts of 174.6 L/h/cow and 136.2 L/h/cow, for ambient temperatures of 18°C and 35°C, respectively. Those figures show that CO2 emission is reduced as the animals are exposed to a rising temperature.
Cows of the same breed were measured by Loureiro et al. (2005) in a tropical environment (20°C–33°C), with lower results (128.2 and 131.9 L/h for milk yields of 20 kg/day, respectively. The observed skin CO2 elimination was 0.17 L/h/m2 on average. Those are very low figures, confirming that CO2 plays no role in the livestock production sector.