NEW DELHI (Reuters) - Stopping Rohingya refugees from crossing India s porous eastern border with Bangladesh is straining the resources of guards battling to halt a flow of smuggled cattle in the opposite direction, security officials say. More than half a million Muslim Rohingya, a stateless ethnic minority, have fled Myanmar for Bangladesh since violence erupted on Aug. 25, but it is not clear how many then sought to travel on to India. Last month India ordered its border guards to use  rude and crude  methods, such as  chilli and stun grenades , to block their entry. But that directive clashes with another task India s Hindu nationalist government has set its border guards - to keep cows, seen by many Hindus as sacred, from being smuggled into Bangladesh for slaughter, in a trade worth $600 million a year.   It s hard to stop cows and human beings at the same time,  a senior official of India s Border Security Force (BSF), which has about 30,000 troops patrolling the frontier with Bangladesh, said in New Delhi, the capital.  The collective duty to seize cattle and push Rohingyas is having a negative impact on the morale of our troops,  added the official, who declined to be identified because he was not authorized to speak to the media.   We have conveyed this message to the top government officials.   He was one of four senior officials who told Reuters that Prime Minister Narendra Modi s government must decide which task  should get priority. An official of the Indian home ministry told Reuters the  authorities were working to tackle the concerns of the border guards, who have been successful in blocking entry of the Rohingya. India wants to deport about 40,000 Rohingya refugees who arrived in previous years, calling them a threat to national security, despite an outcry from rights groups. Since the violence in Myanmar, there has been a sudden rise in the number of cattle coming from India, said traders in Bangladesh, which considers the border trade legal.   There are fewer obstacles to getting cattle from India right now,  said Rabiul Alam, secretary of the Bangladesh Meat Traders  Association, which has about 1,000 members. In July, India s top court suspended a government ban on the trade of cattle for slaughter, giving a boost to its meat and leather industries, worth more than $16 billion in annual sales, and run mostly by members of the Muslim minority. The slaughter of cows was already banned in most parts of India, but Hindu hardliners and cow vigilante groups have been increasingly asserting themselves since Modi s government came to power in 2014. Stopping the cattle smugglers is not easy. At least 400 border guards have been injured and six killed in such operations since 2015, BSF figures show.  The guards often have to wade through fields and ponds, wielding bamboo sticks and ropes to deter smugglers and round up the cattle.    Injuries to guards is almost a routine affair now,  said R. P. Singh, a BSF official in West Bengal state, which shares a 2,216-km (1,375-mile) border with Bangladesh. 