If there are other areas nearby, what about allotting these areas specifically for the cattle outside the preserve? Or what about building a low cattle fence around the preserve to keep cattle out but allowing tigers to come and go? 

I don't know what resources are available, and these are ideas you may have already thought of, but maybe it could be a starting point. 

If they are all feral cattle then provision of sending them to Vulture safe feeding zone could be an option to start with.

Can you impose or set up a small fee for grazing (it is a symbolic fee per head per day). You will generate income which you will use toward improving protected area and control pressure through ecological carrying capacity

Demarcation of feeding zone is a justified approach

I think you can apply two approaches: First, Promotional approach for qualitative livestock keeping. It includes a number of approaches from awareness/outreach to subsidy to qualitative livestock breed. Second, effective law enforcement approach in close coordination with district level security agencies, local communities and political parties.  

The starting of an educational/informational program involving citizens adjacent Shuklaphanta Wildlife Reserve (SWR) to show benefits of undisturbed habitat for wildlife and water quality?  Showing local citizens and government officials the destructive affects of the cattle populations on public land resources of SWR might provide you with the least conflicting alternative because local people will be more in tune with the cultural sensitivities of the region.  Also, maybe there is a possibility of inexpensively and effectively fencing -(cattle proofing)- portions of the SWR, while allowing tigers and other wildlife access over or under fence. 

Maybe there are some breeding colonies of vultures nearby?  The presence of vulture colonies have been influential in causing concerned conservationists to create "humane" cattle farms that help discontinue use of "vulture killing drug"  diclofenac and replacing this drug with meloxicam to create "vulture safe zones" that provide a simulated "jatayu restaurant".  "These "humane" farms buy old cattle at the end of their working lives that are otherwise destined to be sold to cattle traders (for use as meat) or else abandoned by their owners in forest land or outside villages. In Nepal, old cattle can be purchased for around US $2 and many animals are given to the project, as it saves local people from otherwise feeding or abandoning an animal that is otherwise a burden".

Exploring newer techniques in sterilizing bull calves and bull adults could help work toward prevention of recycling or increasing damage from cattle grazing. The newer techniques of bull sterilization can be performed by one person and with bull in standing position. Comparing the newer sterilization techniques of bulls with older castration methods of bulls shows that newer techniques of sterilization are more simple and have lower incidence of complications for bulls.

Thanks for the opportunity to learn from your question!

http://www.biologicaldiversity.org/programs/public_lands/grazing/index.html

http://www.save-vultures.org/save_solution_vulturesafezones.html

http://jatayurestaurant.com/

Article The Sterilization of the Bull: A Review of the Literature

Through some field knowledge working in Nepal, It is utmost first you have some knowledge on how to incorporate community. It was really ghost matter to establish community forestry in Nepal at initial stage but now community forestry in Nepal is one of the successful practice. What in essence need to know is internalization of community towards conservation and securing livelihood. Overgrazing means cattle rearing, in more is higher number of cattle rearing. It is necessary to uplift livelihood by alternative means of economy generation securing life which in turn reduces cattle number ultimately minimizing grazing intensity. However for this it is necessary to have communities consensus since conservation are for people and without participation of people conservation could proceeded but it will limp. I better suggest to hear community's participation and their livelihood alternatives.

you can reduce the  grazing pressure by the divided the grazed area in to several areas and apply the alternation of grazing between these areas to give the chance for the grazed area to be restored again and with these you can keep the vegetation permanent with out lost .  

Have cattle-proof fences been considered? And sterilisation? Not cheap either way, indeed

If the community are not involved you will not succeed. There should be a governance by local community. Your role or any government authority is only to facilitate. Fencing may work in Australia and USA where land tenure is straight  forward. In this case I would go for social fencing agreed and implemented by community. The only side down this process takes time.

Thanks to all for your suggestions!

@ Kristen & Hein, cattle proof fence for whole reserve seems near to impossible for now but we are trying to allocate certain area in buffer zone to keep unclaimed cattle.

@ Santosh & Jonathan! We are trying to construct a big enclosure (~50 ha) to keep unclaimed cattle and develop it as vulture restaurant.

@ Mounir, That is a great idea but grazing is not allowed legally in core areas of Wildlife Reserve.

@ Maheshwar sir, That's true. But scenario is different in SWR, its not just the issue of law enforcement. When we talk with locals they say, we also don't want to keep these cattle but how to remove them? nobody buys. Some families make their cattle feral which ultimately goes in Reserve, others graze their cattle in reserve.

@ Mohan & Mounir, Very true! We are in regular consultation with communities.

@ Fernando, That's a valid point. About 17 % of tiger diet comes from cattle& buffalo (paper attached).

Form a cooperative society of local community including people who owns land. Reserve the plot for grazing. Those who are members of the society, may use the grazing plot with prior booking in advance and minimal fees. You can create multiple grazing plot with time difference so that you would have a plot for grazing at any given time. 

National Tree Growers Cooperative Federations Ltd, Anand, Gujarat, India has done this successfully. 

I'm not sure if this is feasible but supplemental feeding (hay or other) of domestic ungulates is an option that is sometimes used in the US where there are wolves (similarly, water is sometimes provided to allow livestock to temporarily persist in an area where they otherwise could not in order to get them farther away from, for example, a denning wolf pack).  These can both very labor intensive and very costly but can help to solve immediate problems.   Long term solutions sometimes require changing land use patterns and that is very difficult if there is not social / community support. 

Hi, I sent the link to an article that you can serve as a guide to what you need

Regards

http://www.sciencedirect.com/science/article/pii/S1462901115300976 

I think some parallels that you could look into are those cases where the population of wild animals has become too large for a protected area, but animal-rights activists and cultural standards prevent standard culling methods. There are many examples in Africa, and I think in Europe and North America. in every case, authorities had to either (a) let the population increase unchecked; (b) cull, even though public sentiment was against the operation or (c) come up with creative solutions. The most obvious one that I can think of is the case of elephants in the Kruger National Park, but there are many others, including deer in a park in Canada, bison in Yellowstone, etc.

Some options include (a) translocation; (b) revised management strategies which allow for varying population densities in different parts of the protected area (but how to implement those densities is another problem) and (c) sterilization, as several commenters have suggested.

For translocation and sterilization, either standard game capture methods, or the methods used by Argentinian and Australian ranchers when rounding up feral cattle would suffice. For sterilisation, I think the old-fashioned methods of castration will probably be cheapest and quickest, but if that is unacceptable for cultural reasons then the chemical methods should be investigated. Just bear in mind that you need to reduce the male population ratio to below about 1 bull to 25 cows, probably much less (1 bull to 25 cows is the standard ratio used by commercial ranchers, but I don't know what an appropriate ratio would be for feral cattle).

I suggest that you build a population model of your cattle population, then investigate various scenarios - for example, how many animals to translocate, or sterilise, or cull, to significantly reduce the grazing pressure, and how long before the population recovers? Can you reduce the population to a density where natural predation by tigers keeps it low? Is there an influx of additional feral animals from outside the park?

Parallel to the population model, I suggest that you also construct ecosystem models of the park, to try and predict the likely impact on the vegetation of the various population densities. The ecosystem models don't need to be detailed, quantitative GIS-type models; they can be simple, descriptive, qualitative models based on local experience, the literature and expert opinion. I suggest you use something like the state-and-transition model approach to construct possible ecosystem scenarios for different ecosystems in the park (riverine areas, floodplains, forest, etc). I also suggest you look into the "thresholds of potential concern" approach developed in Kruger National Park, where ecosystem thresholds of acceptable change are defined.

For the population model, I would suggest either picking a suitable equivalent wild ungulate where the population dynamics are well known (such as buffalo), or using population models from communal cattle herds. In Africa, we have a fair amount of information on growth rates, mortality rates etc of communal cattle herds.

If you want more information on any of the above, I'll send you some papers and data. Most of it is relevant to Africa, Australia or the Americas - unfortunately I have very little knowledge of Asia.

Dividing the zone in to alternate grazing sub-zone