I.	Dry Period and Subsequent Productions

	1.	Dry Period

		A.	Non-lactating (dry) period prior to 
			an impending parturition
		B.	Optimizes Milk Production in the 
			subsequent lactation
		C.	Needs to be at least 45-50 days
			a.	Less than 40 days results in lower 
				milk yield the next lactation
				i.	450-680 kg less milk
				ii.	62-75% reduction if no dry period 
					at all (Twin Study)
		D.	Long dry period also show a reduction 
			in subsequent lactation
			a.	Over 70-80 days
		D.	Changes occur in the mammary gland during the dry 
			period which influences proliferation 
			and function in the subsequent lactation

	2.	Methods

		A.	Withdrawl of grain and reduction of water supply 
			several days before initiation
			a.	Drastically reduces milk production
		B.	Milking is halted 45-60 days before expected date 
			of parturition
			a.	Intramammary pressure increases
			b.	Milk products accumulate in gland
			c.	Further milk production is inhibited
		C.	Infusion with antibiotics is a good practice 
			at drying
			a.	Prevent early involution infections
		D.	Re-milking
			a.	If udder becomes congested
			b.	Can cause problems
				i.	Stimulates further milk synthesis
				ii.	Removes leukocytes 
					to prevent infection
			c.	Usually not needed when milk production 
				is below 40 lb/day at time of drying-off

	3.	 Other Species

		A.	Goats may not need a dry period
			a.	Usually still a common practice
		B.	Most species aren't pregnant and lactating 
			at the same time
			a.	Also have a non-lactating period 
				after weaning

II.	Mammary Physiology during the Dry Period

	1.	Three Phases
		A.	Active Involution
		B.	Steady-State Involution
		C.	Redevelopment and Colostrogenesis

	2.	Active Involution
		A.	Begins with cessation of periodic milk removal
			a.	Weaning or Milking
			a.	Probably complete by 21 to 30 days (cows)
		B.	Transition phase
			a.	Lactating to not lactating state
		C.	Changes in the mammary secretion volume
			a.	Milk volume increases for 2-4 days
			b.	Declines rapidly over the next week
			c.	Continues to decrease for ~30 days
		D.	Changes in milk-specific components
			a.	Milk-specific components decline
			b.	Caseins, a-LA, and b-LG, and milk fat
				i.	Decline slowly during first 2-3 wks
				ii.	Never completely disappear
			c.	Lactose concentrations decline rapidly
				i.	Follow Fluid changes
		E.	Changes in proteins of serum origin
			a.	Immunoglobulins and serum albumin increase 
				in concentration during the 1st week
			b.	Immunoglobulins
				i.	IgG1, IgG2, IgA, IgM
			c.	Serum Albumin
				i.	Increase due to breakdown 
					of tight junctions
				ii.	Not as high as acute inflammation
		F.	Lactoferrin
			a.	Concentrations increase markedly 
				during active involution
			b.	Bacteriostatic
			c.	May limit oxidative degeneration 
				of cellular components
		G.	Cells
			a.	Increase in leukocyte concentrations
			b.	PMN (Polymorphonuclear neutrophils)
				i.	Phagocytic lymphocytes
				ii.	Predominate 1st 3-7 days
			c.	Macrophages
				I.	Phagocytes
				ii.	Predominate after day 7 post-drying
				iii.	Remove large quantities of fat 
					and cellular debris
				iv.	Also remove dead PMNs
				v.	Also predominant in colostrum
			d.	Lymphocytes
				I.	Always present
				ii.	Increase in proportion to macrophages
				iii.	May predominate during mid-dry period
				iv.	Function in mammary gland unknown
		H.	Apoptosis
			a.	Alveolar-lobular tissues reduced 
				during involution by programmed cell death 
				or apoptosis
			b.	Steps of apoptosis
				i.      Chromatin Condensation
                        	ii.      DNA Fragmentation
                       		iii.      Cytoplasmic baling (cell shrinkage)
                        	iv.      Macrophage digestion
			c.	Needed so new alveolar cells can 
				be regenerated for lactogenesis

	3.	Steady-State Involution

		A.	Teats have become sealed
		B.	Small fluid volume in the gland
		C.	High concentration of leukocytes
		D.	Little milk fat, casein, or debris
		E.	Lactoferrin is very high
		F.	Immunoglobulin concentrations are elevated
		G.	Some apoptosis continues
		
	4.	Redevelopment and Colostrogenesis

		A.	Transition from nonlactating to lactating state
		B.	Concentrations of major milk components increase 
			~2 wk prepartum
			a.	Increase markedly ~3-5 days prepartum
		C.	Leukocytes and Lactoferrin decrease
		D.	Immunoglobulins (antibodies) increase as colostrum 
			is being formed
		E.	Cell Division and Differentiation
		F.	Lactogenesis

III.	Dry Period and Mastitis

	1.	The early dry period is the time of highest incidence 
		of new intramammary infection (new IMI)
	2.	Mid-dry period is the time of lowest incidence of new IMI.
	3.	Contributing Factors during Active Involution
		A.	Milk is no longer periodically removed
			a.	Milk is an excellent growth medium 
				for bacteria
		B.	Teat Leakage
			a.	Bacteria can enter
		C.	Teat-end disinfection is stopped
		D.	Leukocytes busy ingesting milk fat, casein, 
			and debris
		E.	Lactoferrin still low
		F.	Antibodies (Igs) are still low
		G.	Intramammary dry-cow antibiotic therapy very helpful
			a.	After last milking
			b. 	Controls mastitis, except coliforms
	3.	Low incidence during Steady state involution
		A.	Teats sealed
		B.	Small milk volume
		C.	Composition less conducive to bacterial growth
		D.	High concentration of leukocytes
			a.	Little debris, so they are more effective
		E.	Lactoferrin high
		F.	Immunoglobulins high
	4.	Incidence increases during redevelopment phase
		A.	Fluid accumulation
		B.	Teat Leakage
		C.	Low Leukocytes
			a.	Confronted with milk components again
		D.	Lactoferrin low