XXXX yield and mammary growth effects due to increased milking frequency during early lactation.

@entity665 @entity291 @entity16033 @entity6155
Increased milking frequency (IMF) at the beginning of lactation has been shown to increase @entity6155 yield not only during IMF but also after its cessation. The objectives of this experiment evaluated the effects of increased milking frequency initiated during early lactation on mammary growth and effects on @entity6155 yield (MY). Thirty-one @entity291 were divided into treatment groups: 1) 2X: @entity291 milked twice daily (2X) beginning at parturition (d 1), 2) IMF1: @entity291 milked four times daily (4X) from d 1 to 21 postpartum (PP) and 3) IMF4: @entity291 milked 2X d 1 to 3 and 4X d 4 to 21 PP. The 4X @entity291 were milked immediately before 2X @entity291 and again approximately 3 h later, at the end of the normal milking routine. All @entity291 were milked 2X from d 21 to 305 postpartum. @entity6155 yields were 34.5, 37.8 and 37.6 kg/d during wk 1 to 44 for 2X, IMF1 and IMF4, respectively. Mammary biopsies from four @entity291 per treatment were obtained on d 7 and 14 PP to evaluate mammary cell proliferation. @entity665 incorporation tended to increase on d 7 in IMF1 @entity291 , and arithmetic means of the percentage of cells expressing Ki-67 proliferation antigen were consistent with a proliferative response to IMF though not significant. Blood was sampled three times per wk during the first 2 wk and then once per wk during wk 3, 4, 5, 6, 8, and 10. Plasma @entity16033 ( @entity16033 ) averaged 20.1 ng/ml in IMF @entity291 vs. 24.2 in 2X but was not accompanied by a change in bST. Prolactin was also not affected by treatment. Neither @entity6155 yield nor potential effects on mammary cell proliferation were correlated with systemic @entity16033 . Implementing an IMF routine increases MY during treatment and elicits a carryover effect on the remainder of lactation. @entity6155 yield responses after an IMF routine may be the result of increased mammary cell proliferation.
