234- Lactation 1

Lactation 1

• One of the distinguishing features of mammals is that they possess mammary glands
• Lactation is critical for neonatal survival and reproductive success
• It is manipulated in animal husbandry and management

The National Dairy Herd

• The Holstein is the predominant breed (>90%)
• The Average yield is 7,800kg in 305 days
• Target yield is 10,000-12,000 kg
• The Average Milk composition is 4% fat and 3.2 % protein
• One of the targets at this current time is to increae protein

Intensive Dairying

• In post-war years when food was scarce farmers were encouraged to produce as much as possible
• Yield has been increased progressively through

-Improved Genetics such as AI

-Improved Nutrition

-Improved technology (Biotechnology)

• Historically emphasis was given to increase fat content
• Latterly this has changed to decreased fat and increased protein
• Yield has proven to be more plastic than composition

Overproduction and Quotas

• Overproduction has led to introduction of Milk Quotas in the mid 1980s
• The expansion of the EU exacerbates this problem
• Nevertheless, most farmers still aim for increased yield by;

-Maximising peak yield

-Minimising calving interval

• Quotas planned to be abolished in 2015

Dairy Cow Yield Curve

• Milk yield increaes during Calving for the first 60 days
• Milk yield peaks at 60 days 
• As milk yield starts to decline thats when cows start to mate again
• Milk yield continues to decline until 'Dry Off' at 300 days after calving until re-calvin at 360 days 

Conventional Lactation: 3 risk periods 

Extended Lactation: 2 risk periods therefore Less milk/cow/year

Persistent Lactation: 3x day milking, Lower peak? Genetics?

Problems associated with Lactation

• Decreased fertility
• Compromised immune function
• Increased lameness, mastitis
• 'Metabolic Stress'
• Problems are concentrated in early lactation

Product Composition

• Major components of all milks is protein, fat and lactose (carbohydrate)
• Bovine: 4% fat , 3.2% protein, 4.5% lactose
• Human: low protein, high lactose
• Rodent: High Fat and Protein
• Aquatic Mammals: Very high fat, little lactose

Protein

• Major proteins are the Caseins (>80%) found in curd
• Whey proteins include;

-B lactoglobulin

-a lactalbumin

-Immunoglobulins; remember colostrum (and mastitis)

• Casein types include a-s1, B, k, a-s2 and Y
• Protein A2 beta Casein-Wiseman marketing for "lactose intolerance"
• Processing properties and yield of cheese dependent on casein types and amount

Casein Variation

• Composition and yield of Casein varies through lactation
• As the Lactation weeks progress, Casein concentration generally increase g/l (peaks at 23)
• As the Lactation weeks progress, Milk yield graually decreases kg/d/gland (peaks at 2.25)
• As Lactation progresses, Y casein % increases gradually (peaks at 23%) whereas a casein gradually decreases (lowest at 12%).

Fat

• Vital for Neonatal nutrition and survival
• Health-conscious consumers avoid dairy fats
• Semi-skimmed milks have become increasingly popular, however so has cream!
• Conjugated Linoleic Acid- and omega-3 enriched milks are available;

-by dietary manipulation of animal (M&S)

-by post-processing supplementation

Variation in composition

• Holstein (3.9% Fat, 3.2 % Protein)
• Jersey (5.4% Fat, 3.9 % Protein)
• As well as across breeds Variation also occurs;

-Across lactation

-Across milking

-With season

-According to nutrition

Colostrum

• Pre-partum milk secretion that…