Can i make this shader an alpha cutout

hi guys
i was wondering that can i make this shader’s _MainTex to a alpha cutout
and if yes then how can i do it plz guide me on this
i am realy new to shader writing so i cant figure out how to do it
i ws trying to merge transparent cutout shader and the shader given below but it result in desater
plz help
code given below

Shader "Cg  shader for billboards" {
   Properties {
      _MainTex ("Texture Image", 2D) = "white" {}
   }
   SubShader {
      Pass {   
         CGPROGRAM
 
         #pragma vertex vert  
         #pragma fragment frag 
 
         // User-specified uniforms            
         uniform sampler2D _MainTex;        
 
         struct vertexInput {
            float4 vertex : POSITION;
            float4 tex : TEXCOORD0;
         };
         struct vertexOutput {
            float4 pos : SV_POSITION;
            float4 tex : TEXCOORD0;
         };
 
         vertexOutput vert(vertexInput input) 
         {
            vertexOutput output;
 
            output.pos = mul(UNITY_MATRIX_P, 
              mul(UNITY_MATRIX_MV, float4(0.0, 0.0, 0.0, 1.0))
              - float4(input.vertex.x, input.vertex.z, 0.0, 0.0));
 
            output.tex = input.tex;
 
            return output;
         }
 
         float4 frag(vertexOutput input) : COLOR
         {
            return tex2D(_MainTex, float2(input.tex.xy));   
         }
 
         ENDCG
      }
   }
}

any help wud b much appreciated…
thanks

Try something like this:

Shader "Cg  shader for billboards" {
   Properties {
      _MainTex ("Texture Image", 2D) = "white" {}
      _CutOff("Cut off", float) = 0.1
   }
   SubShader {
      Pass {   
         CGPROGRAM
 
         #pragma vertex vert  
         #pragma fragment frag 
 
         // User-specified uniforms            
         uniform sampler2D _MainTex;        
         uniform float _CutOff;
 
         struct vertexInput {
            float4 vertex : POSITION;
            float4 tex : TEXCOORD0;
         };
         struct vertexOutput {
            float4 pos : SV_POSITION;
            float4 tex : TEXCOORD0;
         };
 
         vertexOutput vert(vertexInput input) 
         {
            vertexOutput output;
 
            output.pos = mul(UNITY_MATRIX_P, 
              mul(UNITY_MATRIX_MV, float4(0.0, 0.0, 0.0, 1.0))
              - float4(input.vertex.x, input.vertex.z, 0.0, 0.0));
 
            output.tex = input.tex;
 
            return output;
         }
 
         float4 frag(vertexOutput input) : COLOR
         {
            
            float4 color = tex2D(_MainTex, float2(input.tex.xy));   
            if(color.a < _CutOff) discard;
            return color;
         }
 
         ENDCG
      }
   }
}