Browsing by Subject "Milchproduktion"

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Genetic relationships among resilience, fertility, and milk yield in dairy cattle performing in sub-Saharan Africa
(2025) Oloo, Richard Dooso; Chagunda, Mizeck G. G.
Despite the relevance of dairy production in the fight against food insecurity in sub-Saharan Africa (SSA), the negative effects of climate change and general changes in the production environment pose tremendous challenges to its profitability. Genetic improvement of resilience, the capacity of animals to be either minimally affected by an environmental disturbance or rapidly recover from a disturbance in their environment, is deemed as a part of the solution to low dairy productivity and poor cattle adaptability in SSA. However, to breed for resilience, reliable and practical methods for quantifying and analyzing resilience in SSA need to be described and undertaken. This thesis explored the measurement of resilience using different indicators and examined the relationships of resilience with fertility and milk production in dairy cows performing in SSA. Chapter two of this thesis reviewed potential solutions to enhance the sustainability and productivity of the dairy sector in SSA with an emphasis on breeding for resilience. It described the dairy production in SSA, and environmental challenges cattle have to weather in this region. The chapter further discussed different forms of resilience (general resilience and specialized resilience), indicators for measuring resilience, and provided insights into the data that can be utilized to quantify resilience in SSA’s dairy production systems. It is concluded that improving resilience of dairy animals in SSA would contribute to poverty alleviation, animal welfare improvement, and better preparedness in lieu of climate change in this region. In chapter three, the potential of quantifying general resilience using indicators based on deviations in milk yield was examined. Three indicators of general resilience were defined: variance (LnVar), lag-1 autocorrelation (rauto), and skewness (Skew) of deviations in milk yield based on actual and standardized deviations of observed milk yield from predicted milk yield. The heritability estimates of all resilience indicators except Skew were significant and ranged from 0.05 to 0.19. Weak to moderate genetic correlations were observed among indicators of general resilience, suggesting that these indicators captured different aspects of resilience. LnVar indicators indicated that resilient cows are genetically associated with better longevity. The use of actual deviations and standardized deviations to define indicators yielded identical traits except in LnVar. Standardization of deviations or correcting for the milk production potential of animals ensures that the resultant LnVar indicator does not inaccurately categorize low-producing animals as inherently resilient. The study concluded that LnVar holds a significant potential as a robust resilience indicator for dairy animals performing in SSA. The fourth chapter investigated the response of milk production at varying heat loads as an indication of heat tolerance, which is a specialized resilience. Random regression models, including reaction norm functions, were fitted to derive two resilience indicators: the slope of the reaction norm (Slope), and its absolute value (Absolute), reflecting changes in milk yield in response to varying heat load. Heritability estimates for these indicators ranged from 0.06 to 0.33 and were mostly significantly different from zero. The correlation analysis between these indicators and average milk yield revealed that high- producing cows are more vulnerable to heat stress and have less stable milk production under heat-stress conditions. The study demonstrated the possibility of using the slope of the reaction norm and its absolute value to measure the specialized resilience of dairy cattle to heat stress conditions in SSA. Chapter 5 examined the genetic parameters and relationships among resilience, fertility, and milk production traits. The heritability estimates of age at first calving (AFC), calving interval (CI), and test-day milk yield (MY) were 0.17, 0.06, and 0.35 respectively, and were all significantly different from zero. AFC was negatively correlated with both CI and MY, showing that animals that attain sexual maturity earlier exhibit longer calving intervals and higher milk production. A positive correlation between CI and MY showed that high-yielding cows faced challenges in maintaining shorter calving intervals. There was a generally positive correlation between resilience and fertility, implying that resilient animals might have better fertility. All indicators, except the variance of actual deviation corrected for milk production and variance of standardized deviations, revealed an antagonistic relationship between resilience and milk production. This thesis showed the potential for quantifying and breeding for resilience in dairy cattle performing in SSA. Cows with more than 50% Zebu genes and those performing in semi-arid environments had higher resilience, higher AFC, shorter CI, and lower MY. This suggests that zebu genes confer resilience advantage to animals and exposure of animals to various disturbances in semi-arid environments improved their resilience capacity. Different directions of relationship observed among the traits studied imply that developing a multi-trait selection index that combines all these traits could strike the right balance among resilience, fertility, and milk production. The implications of these findings are valuable in improving the productivity of dairy cattle through selective breeding for resilience to environmental stressors, particularly in low-income countries situated in tropical regions.
Smallholder milk production in the Punjab of Pakistan and the evaluation of potential interventions
(2007) Teufel, Nils; Gall, Christian
The potential offered by milk production and marketing to increase rural income has long been recognised. Yet, milk production by smallholder households, the great majority of the 4.1 million households with dairy animals in the Punjab of Pakistan, has remained practically unchanged. In order to facilitate improved decisions on the allocation of limited development resources, this study analyses smallholder milk production, determines the effects of a variety of technical improvements and evaluates these by their household effects. For this, a linear programming model simulates household decisions based on identified objectives, recorded resources and technical characteristics. Multiple objectives are considered through compromise programming. Ten improvement scenarios are formulated. These include the introduction of new feeds (maize grain, commercial concentrates, molasses and hybrid sorghum), improved reproductive performance (reduced age at first calving and reduced inter-calving period), improved veterinary health (reduced mortality of calves and of adult females) and the introduction of genetically improved animals, through selective breeding (buffalo and cattle) or crossbreeding (cattle). Model data were collected during a cross-sectional survey of 322 randomly selected households and a 13-month longitudinal survey of 64 specifically selected smallholders in the central region of the irrigated Punjab of Pakistan. Cluster analysis identifies seven household classes in the cross-sectional sample. The three largest are considered in the model, characterised as "smallholders with marginal land resources" (class 1), "smallholders with subsistence orientated milk production" (class 2) and "smallholders with market orientated milk production" (class 3). The classification is applied to the longitudinal survey sample by discriminant analysis, identifying 9, 23, and 31 households in classes 1 to 3, respectively. Herd sizes are similar in household classes 1 and 2, with 2.1 and 2.3 adult female buffaloes respectively, while 3.6 are kept in class 3. Only 0.5 adult female cattle are kept in all classes. Land availability is similar for classes 2 and 3 (2.4 ha), but only 1.0 ha in class 1. Cropping patterns are dominated by wheat and rice. Berseem (Egyptian clover) and sorghum plus maize are important fodder crops. The nutrient supply calculated from feeding records corresponds well to estimated livestock nutrient requirements. Nevertheless, feed shortage periods in spring and early winter demand attention. Feed energy constrains livestock nutrition throughout the year in all classes. In addition to maximising family income, households also aim at maintaining their welfare against negative shocks. Also, opportunity costs of family labour are difficult to determine. Thus, maximising farm income and livestock assets (for insurance) as well as minimising loan requirements and family labour use are defined as model objectives in this order of importance. Food requirements are formulated as constraints. The activity levels produced by the base household model correspond well to longitudinal survey data. However, milk marketing is not only determined by the milk price but also by the reliability of marketing systems. Therefore, the milk price within the model is reduced to simulate recorded milk marketing levels. The price reduction is interpreted as the ?perceived? risk associated with milk marketing at village level. Model results of the ten improvement scenarios show positive effects for most interventions. Cheap high-energy feeds ("molasses", "hybrid sorghum") provide the greatest benefits for all classes. Increasing annual milk output ("inter-calving period", "selective breeding") is mainly effective in households selling substantial amounts of milk. Reducing replacement requirements ("adult mortality", "age at first calving") does not considerably improve the attractiveness of milk production. High-value concentrates (?maize grain?, ?commercial concentrates?) are unattractive as long as alternatives (e.g. wheat grain) are self-produced at current opportunity costs of land and labour. Finally, reducing calf mortality has practically no effect and crossbred cattle are only attractive under good marketing conditions with effective institutions. Including only income as objective indicates rising incomes when herd sizes are reduced in favour of cash crops. In a third model version, the effects of higher "perceived" milk prices simulate reactions to improved milk marketing. Despite considerable improvements in the adjusted base model, low-cost feeds still manage to produce considerable benefits. The study shows that introducing targeted interventions, such as providing cheap high-energy feeds, to smallholder milk production and improving market access are effective approaches for decreasing rural poverty.
The effects of rumen nitrogen balance on nutrient digestion, protein metabolism, and performance of dairy cows as influenced by diet composition
(2021) Kand, Deepashree Dilip; Dickhöfer, Uta
Feeding excess dietary crude protein (CP) beyond the requirements of dairy cattle and microbes in the rumen increases production costs for farmers, excretion of nitrogen (N) to the environment, and has negative effects on the cows’ health and reproductive performance. Researchers have been interested in exploring the effects that diets with negative rumen nitrogen balance (RNB) may have on the dairy cattle and their rumen function. Results so far have been inconsistent may be due to the performance level of the animal with high-yielding dairy cows being more sensitive than low performing ones. Moreover, it may be supposed that variable responses to negative RNB in different studies may at least partly be related to varying ingredient composition and the type of main carbohydrate or N sources in the animals’ diets. The overall objective of the thesis was to generate a comprehensive understanding on the effects of interactions between the RNB levels and carbohydrate and N sources in cattle diets on rumen fermentation, the efficiency of microbial CP synthesis, and on N use efficiency in vitro and in vivo. The results of the present thesis indicate that the effects of negative RNB levels may vary with dietary composition in dairy cows. Therefore, outlining a single minimum RNB balance threshold for dairy cattle diets may not be appropriate when optimizing N utilization in dairy cows, because several animal and dietary factors modify the requirements of rumen microbes.