Milk synthesisSlide 2Milk ejectionMilking EquipmentPowerPoint PresentationMilk ejection IIInvolutionDecreasing milk productionBovine SomatotropinMilking 4x or 6xPhotoperiod--LactationPhotoperiod – Dry PeriodCow health issues – transition periodDisplaced AbomasumMastitisClassificationDetection of mastitisMilk synthesisMilk synthesis•Proteins – major groups are caseins and whey proteins•Lactose – unique to mammary gland•Fat – droplets enveloped by membrane–Ruminants – fatty acids synthesized from volatile fatty acids (acetate)Milk ejection•Milk “letdown”•Neuroendocrine reflex•Milk not removed solely by suckling action–Passive removal possible from gland cistern•Controlled by myoepithelial cells–Oxytocin stored in posterior pituitary gland•Action within 30 – 60 secondsMilking Equipment•Pulsation system alternately…–Introduces atmospheric air into hoses and teat cup chamber–Removes air from system–Pulsation rate = # of cycles of alternating negative and atmospheric pressure; ~ 50 cycles/minuteMilkingExpansion Phase Massage PhaseMilk ejection II•New milk synthesis inhibited after ~ 18 h of milk non-removal•Complementary or residual milk (10- 20% of total)•Inhibition–Stress, emotional upset•Administration of exogenous oxytocinInvolution•45 – 60 d in dairy cows•“Regression” & “remodeling” in the mammary gland–Decreased metabolic activity–Altered size, shape, # of alveoli•Length of dry period influences subsequent lactational performanceDecreasing milk production•Lack of milk removal–Pressure builds up in gland–FIL: chemical signal in milk to cells?–After 16-18 h, milk synthesis decreases–Important to avoid in early lactation•Mastitis leading to development of scar tissueBovine Somatotropin•Increase milk yield ~ 10 lb per cow•Increases nutrient utilization by the mammary gland•Milk yield–increases gradually during rbST supplementation, up to max ~ d 6–Administration after peak milk yield •Increased costs: labor, rbST, DMI–Increase in DMI lags behind MYMilking 4x or 6x•Milking frequency: ~ 8 lb per cow–Early in lactation: increased peak and persistency–Milk fresh cows first and last at each milking for first 21 d–Increased labor, use of milking equipment, feed costs -- 0.5 lb DM for 1 lb milkPhotoperiod--Lactation•16 to 18 h light per day increases MY 5 to 15%–Low investment, size neutral•Barns are traditionally dimly lit•Estimate # of fixtures needed to increase lighting•Cleaning requiredPhotoperiod – Dry Period•Cows on 8 h vs 16 h during dry period produced ~ 7 lb/d more milk during early part of subsequent lactationCow health issues – transition period•Milk fever (parturient paresis)•Ketosis•Retained placentaDisplaced AbomasumNormal DALeftLeftRightRightMastitis•Infectious disease•Inflammation of secretory tissueClassification•Clinical–Shorter duration–Causes visible changes in udder and milk–Acute cases – become systemic infections•Subclinical–Longer duration–Majority of mastitis cases–May be chronicDetection of mastitis•Appearance of milk•Somatic Cell Count–Leukocytes & epithelial (secretory) cells•leukocytes•secretory cells•California Mastitis Test (CMT) – detects DNA in milk•Bacteriologic