Our objective was to describe cow and quarter-level factors associated with drying-off, and to evaluate their impacts on new intramammary infections (IMI) during the dry period. Data from 300 cows in five research herds were collected starting 2 weeks prior to scheduled drying-off. Variables of interest included daily milk production, teat-end integrity, formation of the teat-canal keratin plug, and quarter-milk bacteriological culture results. Overall, 11% of quarters developed new IMI in the dry period; this varied by herd, parity and time of the study. Most new IMI were caused by environmental streptococci and coliform organisms (34 and 30%, respectively). Quarters that had a cracked teat-end had higher odds of developing new infections than those without cracks (15 and 10%, respectively). Quarters that formed a keratin plug early in the dry period had a lower odds than those that did not close (10 and 14%, respectively). After 6 dry weeks, 23% of quarters were still open. The hazard of quarters closing if milk production on the day prior to drying-off was >21 kg 1.8-times less.
"The formation of a teat-canal keratin plug prevents the penetration of bacteria and is therefore an important protective factor for the mammary gland (Cousins et al., 1980; Capuco et al., 1992). Lower milk production at drying-off is associated with rapid closure of the teat canal (Dingwell et al., 2004; Odensten et al., 2007a). "
[Show abstract][Hide abstract] ABSTRACT: A cow's risk of acquiring a new intramammary infection during the dry period increases with milk production at drying-off. A method commonly used to reduce milk production is a drastic reduction in feed supply in the days that precede drying-off. Milk production can also be reduced by inhibiting the lactogenic signal driven by prolactin (PRL). This study aimed to compare the effects of these 2 drying-off procedures on milk production, metabolism, and susceptibility to intramammary infection in cows. A total of 21 Holstein cows in late lactation were assigned to 1 of 3 treatments based on milk yield, somatic cell count, and parity. The cows were fed a lactation diet until drying-off (control), only dry hay during the last 5 d before drying-off (DH), or the same diet as the control cows but with twice-daily i.m. injections of 4 mg of quinagolide, a specific inhibitor of PRL release, from 5 d before drying-off until 13 d after (QN). On d 1 to 7 after the last milking, the cows were challenged by daily teat dipping in a solution containing Streptococcus agalactiae at 5 × 107 cfu/mL. Quinagolide induced a decrease in PRL concentration in blood on all the injection days. Blood PRL was also depressed in the hay-fed cows before drying-off. Both the QN and DH treatments induced a decrease in milk production, which at drying-off averaged 12.0, 10.0, and 21.7 kg/d for the QN, DH, and control cows, respectively. The DH treatment decreased blood concentration of glucose and increased blood concentrations of β-hydroxybutyrate and nonesterified fatty acids before drying-off. Somatic cell count at drying-off was greater in the milk of the QN cows than in that of the control cows but after drying-off was greater in the mammary secretions of the control cows than in those of the QN cows. The number of S. agalactiae colonies found in mammary secretions on d 8 and 14 after the last milking was lower for the QN cows than for the control cows. The percentage of S. agalactiae-infected quarters was also lower in the QN cows than in the control cows and on d 14 averaged 17.2, 33.7, and 57.5% in the QN, DH, and control cows, respectively. No differences between the DH and control groups were observed for either bacterial count or infection rate. In conclusion, this experiment shows that PRL-release inhibition could be an alternative for reducing milk production and improving resistance to intramammary infection at drying-off.
"Older cows had a higher risk of new infection during the dry period and of CM at calving supporting the findings by other researchers [10,14,16]. Age-related anatomical changes of the teat with negative effects on local resistance (e.g. increase in diameter of the teat canal, diminished function of the teat canal sphincter) and reduced general resistance with increasing age are possible reasons for this increased risk of infection [10,14,16]. Considering the cure rate during the dry period, it was surprising that older cows had a lower risk of having no bacterial cure (BC) than younger cows. "
[Show abstract][Hide abstract] ABSTRACT: Factors affecting bacteriological cure rates (BCR) and new intramammary infections (IMI) during the dry period as well as clinical mastitis (CM) during early lactation were investigated in 414 German Holstein dairy cows receiving dry cow therapy. Cows were treated with either benethamine benzylpenicillin (300,000 IU), penethamate hydriodide (100,000 IU), and framycetin sulphate (100 mg, n = 136), or cefquinome (150 mg, n = 135), or benzathine cloxacillin (1,280 mg, n = 143). Overall BCR, IMI, and CM at parturition were 86.4%, 20.7%, and 4.3%, respectively. The three antibiotic treatments differed only in BCR, with cloxacillin yielding better results than the others. Udder quarters from cows with > 4 lactations had a higher risk of IMI and CM at calving. Chronic changes in udder tissues were linked to a lower BCR and were associated with a higher risk of CM during early lactation. The risk of CM at calving was higher in udder quarters with unspecific or subclinical mastitis before drying off. In conclusion, with antibiotic dry cow therapy, age and health status of the udder appear to be major determinants of IMI and CM during the dry period and early lactation, while BCR was associated with the antibiotic type and udder tissue status.
"where Cmp, Cp, Ccm ij , Cai, and RPO i indicate, respectively, the costs of lower milk production (€/kg), calf price (€), cost of calving management (€), cost of AI (€), and retention pay-off (€). The Ccm ij is calculated by adjusting a basic Ccm (input) for the estimated dry-off milk yield of cow i at VWP j , representing the increased risk of mastitis in the next lactation following a higher milk yield at drying off (Dingwell et al., 2004), with 10% incidence rate of pp clinical mastitis. The RPO i is based on a function of parity and LV of cow i and is defined as the difference in expected future net revenue between a culled cow and its replacing heifer, including the cost of buying and raising this replacing heifer as well as the returns of selling the culled cow. "
[Show abstract][Hide abstract] ABSTRACT: The voluntary waiting period (VWP) is defined as the time between parturition and the time at which the cow is first eligible for insemination. Determining the optimal VWP from field data is difficult and unlikely to happen. Therefore, a Monte-Carlo dynamic-stochastic simulation model was created to calculate the economic effects of different VWP. The model is dynamic and uses time steps of 1 wk to simulate the reproductive cycle (ovulation, estrous detection, and conception), the occurrence of postpartum disorders, and the lactation curve. Inputs of the model were chosen to reflect the situation of Dutch dairy cows. In the model, we initially created a cow of a randomly selected breed, parity, month of calving, calf status of last calving, and expected 305-d milk yield. The randomly varied variables were based upon relevant distributions and adjusted for cow statuses. The lactation curve was modeled by Wood's function. The economic input values in the analysis included: cost of milk production (€0.07 to €0.20 per kg), calf price (€35 to €150 per calf), AI cost (€7 to €24 per AI), calving management cost (€137 to €167 per calving), and culling cost, expressed as the retention pay-off (€118 to €1,117). A partial budget approach was used to calculate the economic effect of varying the VWP from 7 to 15 wk postpartum, using a VWP of 6 wk as reference. Per iteration, the VWP with either the lowest economic loss or the maximum profit was determined as the optimal VWP. The optimal VWP of most cows (90%) was less than 10 wk. On average, every VWP longer than 6 wk gave economic losses. Longer VWP were in particular optimal for the first parity of breeds other than Holstein-Friesian, cows calving in winter with low milk production, high milk persistency, delayed peak milk yield time, a delayed time of first ovulation, or occurrence of a postpartum disorder, and while costs of milk production are low and costs for AI are high.
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