Localized mammary gland changes in milk composition and venous blood metabolite concentrations result from sterile subclinical mastitis.

Subclinical mastitis reduces milk yield and elicits undesirable changes in milk composition, but the mechanisms resulting in reduced milk production in affected mammary glands are incompletely understood. This study investigated the effects of sterile inflammation on mammary gland metabolism by assessing changes in milk and venous blood composition. Mid-lactation primiparous Holstein cows (n = 4) had udder halves randomly allocated to treatments; quarters of 1 udder half were infused with 2 billion cfu of formalin-fixed Staphylococcus aureus (FX-STAPH) and quarters of the opposite udder half were infused with saline (SAL).

Effects of oyster glycogen intramammary challenge on primiparous cow milk somatic cell counts, milk yields, and milk composition.

Mastitis is a common and costly disease in the dairy industry that reduces milk production in affected mammary glands. The local mechanisms that result in reduced milk production of affected mammary glands are incompletely understood; elucidation of these mechanisms is dependent on the use of hypothesis testing studies, but few experimental models exist. The objective of this study was to develop a mastitis challenge model, using a split udder design, to reduce milk yields by approximately 15% in udder halves challenged with oyster glycogen, a known inducer of leukocyte recruitment, relative to udder halves treated with saline.

Cellular proliferation and apoptosis in Staphylococcus aureus-infected heifer mammary glands experiencing rapid mammary gland growth.

Intramammary infections in nonlactating mammary glands are common and can occur during periods of rapid mammary epithelial cell (MEC) accumulation, which may ultimately reduce total MEC numbers. Reduced MEC numbers, resulting from impaired MEC proliferation and increased cellular apoptosis, are expected to reduce future milk yields. The objective of this study was to measure the degree of cellular proliferation and apoptosis in the epithelial and stromal compartment of uninfected and Staphylococcus aureus-infected mammary glands hormonally induced to grow rapidly.

Effects of different vitamin A supplies on performance and the risk of ketosis in transition cows.

This experiment investigated the effects of feeding low and high supplies of vitamin A (VA) during the transition period on plasma metabolites, prevalence of ketosis, and early milk production. In a randomized complete block design, 42 prefresh Holstein cows and 21 heifers were blocked by parity and calving date and assigned to 1 of 3 dietary treatments (n = 21 per treatment unless noted): CON, a transition diet with supplemental VA (75,000 IU/d) to meet the requirement; LVA, a transition diet with no supplemental VA; or HVA, a transition diet receiving supplemental VA (187,500 IU/d) 2.5 times greater than the requirement.

Histological tissue structure alterations resulting from Staphylococcus aureus intramammary infection in heifer mammary glands hormonally induced to rapidly grow and develop.

Intramammary infections (IMI) are common in nonlactating dairy cattle and are expected to impair mammary growth and development and reduce future milk production. The objective of this study was to histologically evaluate how IMI alter tissue structure in growing and developing heifer mammary glands. A total of 18 nonpregnant, nonlactating heifers between 11 and 14 mo of age were used in the present study.