Effects of continuous milking during a field trial on productivity, milk protein yield and health in dairy cows

Evaluation of customized dry-period strategies in dairy cows

Shortening or omitting the dry period to improve the energy balance in early lactation have the trade-offs of reduction in milk production and loss of opportunity for dry-cow therapy (DCT; i.e., intramammary antibiotic use at dry-off). Customized dry-period strategies (i.e., deciding upon DCT and dry-period length per cow) could mitigate negative effects of short or no dry periods on milk production and udder health and simultaneously retain benefits from improved energy balance and fertility. In this study, we evaluated 3 decision trees to customize dry-period strategies for individual cows. In the control tree (CT), all cows had a 60-d dry period, with DCT if somatic cell count (SCC) was >150,000 cells/mL before dry-off. In decision tree 1 (T1), parity 1 and parity >1 cows were assigned DCT if SCC was ≥150,000 cells/mL and SCC ≥50,000 cells/mL, respectively; whereas in decision tree 2 (T2), the threshold for DCT was SCC ≥200,000 cells/mL for all animals. In T1 and T2, cows with DCT were assigned a 60-d dry period, whereas cows without DCT were assigned a 30-d or 0-d dry period if their milk production remained >12 kg/d at 67 and 37 d before calving, respectively. Cows were monitored from 8 wk before to 14 wk after calving. Milk production and composition, SCC, body condition score, body weight, and occurrence of treatment for disease (related to calving and start of lactation) were compared between CT (n = 61 cows), T1 (n = 59 cows), and T2 (n = 63 cows). Effects of decision trees (CT, T1, T2) and of dry-period strategies (60-d dry with or without antibiotics, 30-d dry, or 0-d dry) on measured variables were analyzed separately with mixed models, effects on udder-health status with a logistic regression, and occurrence of treatment for diseases with a Pearson chi-squared test. In T1, 36% of cows qualified for 30-d and 2% for 0-d dry periods, whereas in T2 this was 51% and 30% for 30-d and 0-d dry periods, respectively. Compared with CT, cows in T1 and T2 on average produced more milk in the 8 wk before calving (0.2 vs. 3.9 vs. 7.1 kg/d in CT vs. T1 vs. T2), and less in the 14 wk after calving (40.0 vs. 37.0 vs. 35.2 kg/d in CT vs. T1 vs. T2). There was no difference in udder-health status in the transition period among decision trees. In the first 14 wk after calving, recovery of body weight was greater for T2 than CT and T1. Overall, 30-d and 0-d dry periods reduced milk revenues, but this might be financially compensated by improved cow health with customized dry-period strategies.

Review: Dry period length in dairy cows and consequences for metabolism and welfare and customised management strategies

Shortening or omitting the dry period improves the energy balance and metabolic status of dairy cows in early lactation. Metabolic, behaviour and welfare effects throughout lactation, however, are unclear. The current paper reviews long-term metabolic and welfare consequences of short and no dry period, as well as feeding strategies and individual cow characteristics that could support in optimising management of cows with a short or no dry period. The paper will conclude with impacts of short and no dry periods at herd level and in practice. Energy balance after no or a short dry period is more positive during the complete subsequent lactation. After the initial improvement in early lactation, cows after no dry period tend to fatten and may have a too low lactation persistency to be continuously milked until the onset of the subsequent lactation. Reducing dietary energy level for cows with no dry period reduced fattening during the complete lactation but did not improve lactation persistency. Feeding a more lipogenic diet for cows with a short or no dry period did not affect the energy balance or lactation persistency during the complete lactation, although a lipogenic diet resulted in lower plasma insulin and IGF-1 concentration and greater plasma growth hormone concentration, compared with a glucogenic diet. Effects of dry period length on udder health are ambiguous, whereas short and no dry periods improved fertility in most studies. Omission of the dry period changed behaviour of cows both before and after calving, with a longer lying time and greater feed intake after calving, suggesting a better adaptation to a new lactation. Individual cow characteristics like parity, genotype, prepartum body condition score, and milk yield level determined the metabolic response of cows to a short or no dry period. In conclusion, short or no dry periods increase the energy balance in the complete lactation. Feeding strategies can be used to limit fattening of cows with no or short dry period, but the studied feeding strategies did not increase lactation persistency. Improved fertility and behavioural changes around calving suggest a better adaptation to a new lactation in case of no dry period. Customised dry period lengths for individual cows could improve metabolic status of cows at risk of a severe negative energy balance while minimising milk losses.

Bacterial isolates exhibiting multidrug resistance, hemolytic activity, and high 16S rRNA gene similarity with well-known pathogens found in camel milk samples of Riyadh region

Customary consumption of unpasteurized milk by the population in the central Najed region of Saudi Arabia may pose a health risk. Therefore, 80 camel milk samples were collected aseptically from seven different stations of Riyadh region. The biochemical and microbiological properties of these milk samples were determined. Nutrient agar and brain heart infusion agar were used to determine mesophilic aerobic counts (MACs). The MAC in each mL of milk varied from 60 to 16 × 10⁴  CFU/mL on nutrient agar. Based on the colony morphology, 176 colonies were collected from different samples, and these isolates were de-replicated into 80 unique isolates using rep-PCR analysis. Surprisingly, the 16S rRNA sequence analysis of these strains revealed that more than one-third of the collected milk samples contained strains that share maximum sequence similarities with well-known pathogens, such as Brucella, Bacillus anthracis, Listeria monocytogenes, and MRSA. Furthermore, many strains exhibit 16S rRNA gene similarity with opportunistic pathogens such as Citrobacter freundii and Kytococcus schroeteri. Many strains exhibit β-hemolytic activity and resistant to six different antibiotics. Our study suggested that consumption of raw camel milk from this region constitutes a great health risk.

Effects of dry period length on production, cash flows and greenhouse gas emissions of the dairy herd: A dynamic stochastic simulation model

Shortening or omitting the dry period of dairy cows improves metabolic health in early lactation and reduces management transitions for dairy cows. The success of implementation of these strategies depends on their impact on milk yield and farm profitability. Insight in these impacts is valuable for informed decision-making by farmers. The aim of this study was to investigate how shortening or omitting the dry period of dairy cows affects production and cash flows at the herd level, and greenhouse gas emissions per unit of milk, using a dynamic stochastic simulation model. The effects of dry period length on milk yield and calving interval assumed in this model were derived from actual performance of commercial dairy cows over multiple lactations. The model simulated lactations, and calving and culling events of individual cows for herds of 100 cows. Herds were simulated for 5 years with a dry period of 56 (conventional), 28 or 0 days (n = 50 herds each). Partial cash flows were computed from revenues from sold milk, calves, and culled cows, and costs from feed and rearing youngstock. Greenhouse gas emissions were computed using a life cycle approach. A dry period of 28 days reduced milk production of the herd by 3.0% in years 2 through 5, compared with a dry period of 56 days. A dry period of 0 days reduced milk production by 3.5% in years 3 through 5, after a dip in milk production of 6.9% in year 2. On average, dry periods of 28 and 0 days reduced partial cash flows by €1,249 and €1,632 per herd per year, and increased greenhouse gas emissions by 0.7% and 0.5%, respectively. Considering the potential for enhancing cow welfare, these negative impacts of shortening or omitting the dry period seem justifiable, and they might even be offset by improved health.

The effects of dry period length and dietary energy source on natural antibody titers and mammary health in dairy cows

In earlier studies, natural antibodies (NAb) were related not only to the energy balance (EB) of dairy cows, but also to somatic cell count (SCC) and clinical mastitis (CM). The first objective of our study was to evaluate the effects of dry period length and dietary energy source on titers of NAb binding keyhole limpet hemocyanin (KLH) and lipopolysaccharide (LPS) in plasma and milk, SCC and CM occurrence in dairy cows in two subsequent lactations. Our second objective was to study the relationship between NAb levels and mammary health. Holstein-Friesian dairy cows (N=167) were randomly assigned to three dry period lengths (0, 30 or 60-d) and two early lactation rations (glucogenic or lipogenic). Treatments were repeated during two subsequent lactations (years 1 and 2). In year 2, 19 cows which were planned to have 0-d dry period dried off naturally and were assigned to an additional group 0→30-d dry period. In year 1, cows with a 0-d dry period had a higher SCC, a higher titer of immunoglobulin G (IgG) binding LPS in plasma, and higher titers of IgG and IgM binding KLH and LPS in milk compared with cows with a 30-d or 60-d dry period. In year 2, cows with a 60-d dry period had a lower SCC than cows with a 30-d and 0→30-d dry periods. In year 2, dry period length did not affect NAb titers in plasma or milk. The CM occurrence was 17 percent in year 1 of the experiment and 25 percent in year 2, and did not differ according to dry period lengths or rations. For both years, an increasing titer of IgG binding LPS in plasma was associated with decreased odds of a high SCC and decreased odds of CM occurrence. Also up to three weeks before the CM occurrence, an increasing titer of IgM binding KLH and LPS in plasma was associated with a decreased odds of CM occurrence. In conclusion, omitting the dry period increased SCC, NAb titers in milk and IgG binding LPS in plasma compared with a short (30-d) or conventional (60-d) dry period. The effects on NAb titers, however, were only present in the first year after omitting the dry period and disappeared after repeated omitting the dry period. Moreover, an increasing titer of IgG binding LPS in plasma was associated with decreased odds of high SCC and CM occurrence.