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Explained: What is sexed semen and how does the technology work?

The Indian Express explains the technology behind sexed semen pioneered by the United States, how and when it entered Punjab and if it can help in solving the stray cattle problem:

Written by Divya Goyal | Ludhiana | Updated: December 17, 2019 11:14:13 am
Explained: What is sexed semen and how does the technology work Union Minister for animal husbandry, dairying and fisheries Giriraj Singh said that the plan is to provide dairy farmers with ‘sexed semen’ for cattle for as cheap as Rs 100 per straw by 2020.

During the recently held 14th Progressive Dairy Farmers Association (PDFA) International Dairy and Agri Expo 2019 at Jagraon, Union Minister for animal husbandry, dairying and fisheries Giriraj Singh had said that the plan is to provide dairy farmers with ‘sexed semen’ for cattle for as cheap as Rs 100 per straw by 2020. The Indian Express explains the technology behind sexed semen pioneered by the United States, how and when it entered Punjab and if it can help in solving the stray cattle problem:

What is sexed semen, and what is the technology behind it?

Sexed semen is specially processed semen of bulls from which ‘Y’ chromosomes in sperm cells — which lead to the birth of a male calf — are either removed through a ‘sorting’ process or killed. Semen which has only ‘X’ chromosomes can ensure that a female calf is born.

Dr Prakash Singh Brar, dean, College of Veterinary Sciences, Guru Angad Dev Veterinary and Animal Sciences University (GADVASU), said, “The reproduction system of cattle is similar to humans. Cows carry XX chromosomes while bull semen carries both X and Y. If the egg fertilises with an ‘X’ chromosome, a female calf is born and if with ‘Y’, a male is born. There are two techniques to produce sexed semen: One is the ‘sorting process’ in which ‘X’ and ‘Y’ chromosomes are separated. ‘X’ are retained and ‘Y’ discarded. The other is in which ‘Y’ chromosomes are altogether killed. Both technologies are pioneered by the United States-based companies and use an instrument called ‘Flow Cytometer’. Cows are impregnated using sexed semen through the artificial insemination process with consumption of one straw per cow.

Why is this method being used?

Considered a financial burden, male calves are either killed or abandoned on the roads by farmers as they do not give milk. This had led to an increasing number of cattle roaming the streets, which has caused fatal road accidents as well. Cows are also abandoned when they stop giving milk. “If a commercial farmer owns a hundred cows and even fifty of them give birth to male calves, he cannot afford to raise them. They become a burden,” said an expert.

Who pioneered the ‘semen sorting’ technology and its large scale application on cattle?

George E. Seidel, a reproductive physiologist at Colorado State University (CSU) in the US is credited for his pioneering research in the ‘sorting process’. According to one of his interviews, some “original research had taken place in the 1980s at the Lawrence Livermore National Laboratory in California and their studies of sperm led to discoveries regarding differences between sperm cells carrying ‘X’ or ‘Y’ chromosomes”. However, for cattle, it was in the late 1990s that Seidel and his team at CSU developed a process for creating sex-sorted cattle semen for freezing and use in artificial insemination and also got patent rights. Through the CSU Research Foundation, they formed a company, XY Inc., which was later sold to Sexing Technologies (ST), based in Texas.

“The sperms are pumped through a Flow Cytometer (cell sorter) in tubing past a detector that measures the brightness of individual sperm exposed to laser light. That information is processed by the computer and used to sort sperm, one at a time, at a rate of about 25,000 sperm/second,” reads Seidel’s research paper titled ‘Sex-selected semen’.

“Currently, ST has rights over semen sorting technology and it installs the entire set-up after taking the royalty amount,” said Dr Inderjeet Singh, director, animal husbandry, Punjab and additional CEO, Punjab Livestock Development Board.

“After ST, another US-based company ABS Global (formerly American Breeding Services) came up with a cutting edge technique that kills ‘Y’ chromosome,” he added.

Does sexed semen have a 100 per cent success rate?

“No, the guarantee of a female calf being born is never 100 per cent. It can be up to 90 per cent. In 10 per cent cases, a male calf might be born despite using sexed semen because even after sorting/killing, some Y chromosomes may pass,” said Dr Brar.

The pregnancy rate with sexed semen also reduces as sperm count goes down after sorting or killing. “While one straw of conventional semen contains 10-20 million sperms, the count is down to 2-4 million only in sexed semen straws (0.25 ml each). So, while conventional semen will impregnate 60-70 animals out of 100, the rate is 45 to 50 with sexed semen,” said Dr Narinder Singh, assistant animal physiologist, GADVASU.

How did sexed semen enter Punjab for farmers? When did the government start procuring and giving it on subsidy?

It was in 2008 that the Progressive Dairy Farmers Association (PDFA), the largest association in Punjab with more than 7,000 registered commercial dairy farm owners, had first imported sexed semen from the US. They have been doing it every year since then. Daljit Singh Sadarpura, president, PDFA, said, “We first imported 25,000 sexed semen straws in 2008 from the US. The success rate is better on heifers than adult cows. Since then we are regularly importing it from the US and this year we gave it for Rs 1,500 to 1,700 per straw including transportation cost. Currently, very few rich farmers use it,” he said.

In December 2011, the Punjab government imported 5,000 straws followed by 6,280 straws in 2014 and 25,000 straws in 2016- all from the US. “Till August last year we were giving straws to farmers on 50 per cent subsidy, so a straw costing Rs 1,200 ($16-17 each) was being given for Rs 600. However, later the subsidy was reduced and it was being given for Rs 1,000. Now we have again proposed more than 75% subsidy and it might be given for Rs 300 only. We have floated tenders to procure sexed semen this year too,” says Dr Inderjeet Singh.

How costly is sexed semen compared to conventional ones?

High quality conventional semen straws are available for just around Rs 20-40 per straw only whereas sexed semen costs at least Rs 1,200 per straw without subsidy. “It is a costly affair till manufacturing does not start in Punjab itself and currently it is at least 60 times costlier than conventional semen,” said Dr Narinder Singh.

Can sexed semen be used for indigenous cattle and buffaloes?

Dr Prakash Singh Brar from GADVASU said, “In the 1960s, we bred our indigenous cows with foreign breeds to increase milk production but now government’s focus is on promoting pure indigenous breeds. Cross-breeding can be done but it is not highly recommended. Sexed semen units are currently more focused on foreign breeds like Holstein Friesians (HF) and cross-bred bulls and sexed semen is mostly used on HF or cross-bred cows only. It can be produced for indigenous cow breeds like Sahiwal, Gir and also buffaloes like Murrah but in Punjab, majority farmers own foreign cross-bred cattle and problem of abandoning or killing male calf lies with cross-bred not indigenous cattle.”

How can sexed semen solve the stray cattle problem in Punjab?

According to the latest Livestock Census 2019 data, there are 25.32 lakh cattle in Punjab of which only 4.26 lakh are indigenous breeds.

“It is mostly foreign or cross-bred like HF and Jersey bulls and non-lactating cows which are abandoned by farmers on roads. If a male calf is born, it is also abandoned or killed. Farmers rarely abandon indigenous breeds. If sexed semen is used widely for cross-bred, stray cattle problem might be solved to some extent,” says Dr Brar. Over one lakh stray cattle is on roads in Punjab approximately.

If only female calves will be born, can it lead to semen shortage?

No, say experts. “We need a controlled male population with high quality genetic potential and they are being bred at semen stations. Semen is frozen and supplied to farmers. Controlled male population is enough to meet semen demand,” said Dr Brar.

“Sexed semen assures 90 per cent female births not 100 per cent. Also, it won’t be possible to cover entire cow population with sexed semen so male births will be there anyway,” says Dr Inderjeet Singh.

Is Giriraj Singh’s statement to provide farmers with sexed semen Rs 100 per straw viable?

Experts are clueless on the calculation used by the minister here. “Even if manufacturing starts in Punjab, initial project installation will cost crores. According to our initial estimates, we might have to pay royalty of $13 per straw (Rs 900 approx) to the operating company. Providing it to farmers for just Rs 100 seems too far-fetched as of now even if 50 per cent subsidy is given,” said an official.

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