Nutritional, ecological, and economic evaluation of dairy farming systems and feeding strategies in semi-arid environments
Arid and semi-arid regions have limited arable land and water resources. As a result, production of grain and forage is often insufficient to fulfil the requirements of lactating animals. The absence of grassland has led to the dominance of grains based diets imported from overseas. This has an ecological impact due to the emissions of greenhouse gases (GHGs) from land change activities. In addition, the prices of these grains are increasing. Therefore, the objectives of this thesis were to evaluate the nutritional and ecological aspects of the dairy farming systems and feeding strategies dominant under semi-arid environmental conditions in Jordan, and to evaluate how dairy production systems will respond to future changes in feed items and feed prices. The framework of the ecological, nutritional and economic assessment of dairy farming system consisted of several steps: 1) data on dairy development and its drivers in three countries in the Middle East were collected and analysed, 2) the nutritional and ecological analysis is based on nine dairy farms of different farm size and management schemes. Feed, milk and fecal samples as well as data on estimated dry matter intake (eDMI), animal performance, herd structure were collected and analysed, 3) feed samples (traditional feed collected from farms and food industry by-products collected from food manufactories (n=69)), fecal samples (n=108) and milk samples (n=78) were collected from the farms and analysed for their chemical composition. All feed and food by-product samples were analysed for their metabolisable energy (ME) contents and organic matter digestibility (mOMD) in vitro according to Hohenheim-Feed-Test. Furthermore, fecal nitrogen concentration was determined to estimate in vivo organic matter digestibility (eOMD). Based on the farmer’s estimate of DMI and the analysed composition of the feed ingredients, ME and nutrient intakes were compared to recommended standard values for adequate supply of ME, utilizable crude protein (uCP), rumen undegradable crude protein (RUCP), phosphorus (P), and calcium (Ca). 4) greenhouse gas emissions (GHGs) were calculated using the Technology Impact Policy Impact Calculation model (TIPI-CAL) complemented with a partial Life Cycle Assessment model for estimating GHG emissions of milk production at the farm gate, the results are converted to CO2 equivalents (CO2 eq.). The model takes into account CH4, N2O, and CO2 gases emitted directly and indirectly. 5) to investigate what could be the ecological and economic consequence of using alternative feed resources, four feeding scenarios (AD: Actual diet, feeding diets that are typically used by dairy farmers; ID: Improved diet based on actual feedstuffs used on the farm; AB: Diet including few available by-products; DL: Diet with no limitation for feeds availability). The scenarios were developed and evaluated for their nutritional, economic and ecological impacts using different optimization and calculation models. All scenarios fulfilled the animal’s nutrients and energy requirement. Results of the nutritional and ecological evaluation revealed that average daily energy corrected milk yield (ECM) was 19 kg/d and ranged between 11 and 27 kg. Diet evaluation showed that the mean of ME intake of all farms was 184 MJ/d with range between 115 and 225 MJ/d in low and high yielding cows, respectively. Intake of RUCP was lower than the requirements, which ranged between 19 and 137 g/d in six farms. On the other hand, it was higher (32 and 93 g/d) in two farms, and matched the requirements in one farm. P intake was higher than the requirements in all farms (mean oversupply= 19g/d) and ranged between 3 and 30 g/d. Milk nitrogen efficiency (milk N/intake N) varied between 19% in low producing animals and 28% in high producing animals, with mean of 24% in all farms. Total (CO2 eq.) emission ranged between 0.90 and 1.80 kg CO2 eq./ kg ECM milk. Where the enteric and manure CH4 gas comprised (52%) the highest proportion of CO2 eq. emissions. Followed by the indirect emissions of N2O and CO2 gases which comprised 28% from total CO2 eq. emissions. Emissions per cow were significantly driven by the level of milk production (r2=0.93) and by the level of eDMI (r2=0.88), while the total emissions were not influenced by diet composition. A different of 16 kg ECM/d in milk yield, 85 g/d in milk nitrogen and mitigation of 900 g CO2 eq./kg in ECM milk observed between low and high yielding animals. The status-quo analysis of three typical farm types showed that cost of milk production is 21% lower in the small scale farm type compared to large scale farm type. Model application of alternative feeding scenarios revealed that the cost of milk production in the large scale farm can be reduced by 6 US-$/ 100 kg ECM when applying the DL scenario compared to the actual scenario. Similarly, when applying the DL scenario (high inclusion of food by-products in the diet), GHGs emissions (in CO2 eq.) were reduced by 15% and was driven by lower concentrate feeding of 70% in the diet compared to the actual feeding scenario. Overall, a total mitigation of CO2 eq. emission between 70 and 290 g/kg ECM produced is achievable. Alternative feeding management scenarios need to be considered for future developments of dairy farming systems. These include the development of low input concentrate feeding systems which insure profitability and reduce ecological impacts of farming systems.
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