Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Milk synthesis Milk 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 seconds Milking 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/minute Milking Expansion Phase Massage Phase Milk 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 oxytocin Involution • 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 performance Decreasing 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 tissue Bovine 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 MY Milking 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 milk Photoperiod--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 required Photoperiod – Dry Period • Cows on 8 h vs 16 h during dry period produced ~ 7 lb/d more milk during early part of subsequent lactation Cow health issues – transition period • Milk fever (parturient paresis) • Ketosis • Retained placenta Displaced Abomasum Normal Left DA Right Mastitis • Infectious disease • Inflammation of secretory tissue Classification • Clinical – Shorter duration – Causes visible changes in udder and milk – Acute cases – become systemic infections • Subclinical – Longer duration – Majority of mastitis cases – May be chronic Detection of mastitis • Appearance of milk • Somatic Cell Count – Leukocytes & epithelial (secretory) cells • leukocytes • secretory cells • California Mastitis Test (CMT) – detects DNA in milk • Bacteriologic testing