influences on milk composition

influences on milk composition

1. inherited variation

   • solid-not-fat = quality marker
     • amount of fat can dictate price
       • historically = higher fat higher price
       • sheep notoriously high fat! (7% average)
   • friesian vs Guernsey
     • F higher yield low fat + SNF
       • average = FAT 3.7g/100g milk
     • G low yield high Fat/SNF
       • average =FAT 4.6g/100g milk

2. Cow nutrition

   • changing animals diet can impact milk
     • eg. oil inclusion study
       • feed high oleic rapeseed oil (w. low unsaturated fat proportions)
         • 600g/day
         • milk contains 30% more oleic
   • microbes digest starch/cellulose
     • due to ruminent stomach
       • 4 compartments
         • rumen basically large fermentation vat
           • enzymes/bacteria degrade diet
             • cellulose-digesting produce acetic acid
               • fat synthesis
                 • gives milk fat content
             • starch-digesting produces propionic acid
               • glucose and some amino acid synthesised
   • substrate influence
     • winter vs summer diet
       • winter = hay/cereal + oilseed concentrate
         • higher cellulose
       • summer = grass
         • more must be eaten to meet energy requirements
         • low cellulose / high h20
       • summer milk is lower fat
         • produces less acetic acid due to less cellulose
         • but also high in carotene / vitamin A
           • both Friesian / Guernsey increase by 50%
             • G = 24mg -> 50mg
             • F = 12mg -> 24mg
       • b vit level remains constant
         • produced by bacteria in rumen

3. environmental temperature

   • mechanism unsure
     • could be fat mobilisation
       • to maintain homeostasis
       • fat increase @ temp >22.23 / <1

4. age

   • older = less fat + decreased lactation
     • often removed from herd

5. lactation stage

   • palurition (post-calving)
     • produce COLOSTRUM
       • secretion have different composition
         • colour change
         • decrease lactose
         • increase mineral salts
         • increase proteins
           • serum proteins
             • immunoglobulins
           • casein

6. disease

   • eg. mastitis
     • decrease fat/snf/lactose/casein
     • increase serum proteins = immunoglobulins
     • increase in chloride
       • previously was used as quality indicator

7. time of milking

   • when being milking fat/snf increase