BY-Vinay Kumar Mehra1*
1vinay28mehra@yahoo.com
*Animal Biotechnology Centre, ICAR-National Dairy Research Institute, Karnal-13200, Haryana
Farmers prefer female calves of cows or buffalos than male calves as they can produce milk which are more economically beneficial for farmers. According to the 20th livestock census 2019, there are total milch animals (in-milk and dry) in cows and buffaloes are 125.34 Million. Compared to the 2012 census, the milch animals (cow and buffalo) have an increase of 6.0%. Apart from this the demand of milk also increasing day by day and to meet the demand, it is very important to increase the milk production by producing the more female cows and buffalos. For this Sexual selection of desired sex plays important economic role in livestock industries.
There are two types of sperms in bovine i.e X and Y . If X sperm fertilize the bovine egg results in the birth of female calves whereas Y sperms result in male calves and the probability of occurring male or female calf is 50%. Selection of a desired sex calf is not possible with natural breeding because in natural breeding there are 50%- 50 % change of occurring male or female calf, so for this a special technique known as Artificial insemination (AI) is required. By this technique preserved sexed semen is introduced artificially into the reproductive tract of the female and sex of the birth calf is depend on the type of semen (either it has X or Y sperms separately) and separation of X and Y sperms is done by Semen sorting technique and semen is known as Sexed Semen.
How Sexed Semen is produced?
The basic principle for semen sorting based on that defenses between X and Y sperm. The X sperm contains about 3.8% more DNA than the Y sperm in cattle and this difference in DNA content is used to sort the X- from the Y- bearing sperm. There are several methods for semen sexing but flow cytometry based sorting is most efficient method because the purity of sexed semen is more than 90%.
In flow cytometry (Fig.1) an a special DNA-binding dye Hoechst 33342 and electric filed is used which gives the different charge ( + or -) on the surface of sperm and separates the X or Y sperms on the basis of charge and then stored in liquid nitrogen at -196ᵒ C. Finally by using Artificial insemination method desired semen contain either X or Y sperm is transferred into the reproductive tract of the female cow or buffalo.
Fig. 1 Flow diagram of semen shorting by flow cytometry
Benefits of semen sexing:
• Pre-selection of sex can reduce the management
• Calves of desired sex can be produced.
• genetically superior female calf can be produced
• reduce the risk of dystocia
• no risk of introducing diseases
Limitations of sperm sexing:
• More than half of sperm sample are go as waste; only 30% to 40% semen is of desired sex.
• The equipment is highly expensive and special trained persons are require
• Currently there is no company producing sexed semen in India so it is imported from other country and due to this the cost is about 1500-4000 per dose.
Conclusion:
The sexed semen is beneficial for the farmers as they requires only female calves which can reduce the maintaining cost on the male calf and by using this technology superior high milk producing calf can be produced which help in the doubling of farmer income.
