The effect of antibiotic versus no treatment at dry-off on udder health and milk yield in subsequent lactation: A retrospective analysis of Austrian health recording data from dairy herds

Bovine mastitis is the most commonly diagnosed disease of dairy cows worldwide and causes extensive economic losses to milk producers. Intramammary infection status before dry-off plays a decisive role with respect to udder health and milk yield in the subsequent lactation. The aim of this study was to compare the effect of antibiotic dry cow therapy (DCT) versus no treatment at dry-off on milk yield, somatic cell count (SCC), inflammation of the mammary gland (IMG), and the incidence of clinical mastitis in the subsequent lactation. Dairy herd data from 251 Austrian dairy farms were recorded over an observation period of 12 mo and subsequently analyzed. The data set included 5,018 dairy cows: 2,078 were treated with antibiotics (abDCT group) and 2,940 were not treated (noDCT group) at dry-off. The abDCT group was subdivided, based on the antimicrobial active substances used for drying off, into 4 different groups (penicillins, cloxacillin, cephalosporins, and rifaximin). Based on bacteriological culture results, infections were grouped into those caused by major, minor, and other pathogens. Additionally, the IMG was defined via SCC from milk recording data using a cutoff of 200,000 cells/mL before drying off and after calving. The incidence of clinical mastitis cases within 30 and 90 d in milk was calculated using veterinary diagnosis data. To investigate the effect of different dry cow therapies on the following parameters: milk yield, SCC, and diagnosed clinical mastitis cases, different linear mixed models were constructed. Overall, the abDCT group was determined to have a significantly higher milk yield over 305 d in milk in the subsequent lactation (increase of 6.18%), compared with the noDCT group (increase of 4.29%). Both groups (abDCT and noDCT) demonstrated a decrease in the first SCC after calving compared with the SCC before dry-off, although the treated cows had a significantly higher reduction. Regarding the different antibiotic groups, with exception of the rifaximin treated cows, all antibiotic groups showed a significant difference from not treated cows with respect to SCC. Additionally, we were able to demonstrate that cows with IMG before dry-off had a 2.073 times higher chance of an increased SCC (>200,000 cells/mL) after calving. With respect to the veterinary diagnosis data, neither the IMG before drying off nor the type of DCT had a significant influence on the probability of developing clinical mastitis within 30 or 90 d in milk. Only a small number of treatments was accompanied with a bacteriological examination before drying off. However, the existing data in this study indicates that the intramammary infection status before dry-off in combination with different dry cow treatments influences udder health and milk yield after calving. Nevertheless, further studies with larger data sets of bacteriological examinations are necessary to enable a more in-depth investigation into the effects of different antibiotic substances used for DCT.

Effects of prepartum metabolizable protein supply and management strategy on lactational performance and blood biomarkers in dairy cows during early lactation

Our objective was to investigate the effects of prepartum metabolizable protein (MP) supply and management strategy on milk production and blood biomarkers in early lactation dairy cows. Ninety-six multigravida Holstein cows were used in a randomized complete block design study, blocked by calving date, and then assigned randomly to 1 of 3 treatments within block. Cows on the first treatment were fed a far-off lower MP diet [MP = 83 g/kg of dry matter (DM)] between -55 and -22 d before expected calving and then a close-up lower MP diet (MP = 83 g/kg of DM) until parturition (LPLP). Cows on the second treatment were fed the far-off lower MP diet between -55 to -22 d before expected parturition and then a prepartum higher MP diet (MP = 107 g/kg of DM) until calving (LPHP). Cows on the third treatment had a shortened 43-d dry period and were fed the prepartum higher MP diet from dry-off to parturition (SDHP). After calving, cows received the same fresh diet from d 0 to 14 and the same high diet from d 15 to 84. Data were analyzed separately for wk -6 to -1 and wk 1 to 12, relative to parturition. Dry matter intake from wk -6 to -1 was not different between LPHP and LPLP and increased for SDHP compared with LPLP. In contrast, dry matter intake for wk 1 to 12 postpartum did not change for LPHP versus LPLP or for SDHP versus LPLP. Compared with LPLP cows, LPHP cows had lower energy-corrected milk yield and tended to have decreased milk fat yield during wk 1 to 12 of lactation. Conversely, yields of energy-corrected milk and milk fat and protein were similar for SDHP compared with LPLP. Plasma urea N during wk -3 to -1 increased for LPHP versus LPLP and for SDHP versus LPLP; however, no differences in plasma urea N were observed postpartum. Elevated prepartum MP supply did not modify circulating total fatty acids, β-hydroxybutyrate, total protein, albumin, or aspartate aminotransferase during the prepartum and postpartum periods. Increased MP supply prepartum combined with a shorter dry period (SDHP vs. LPLP) tended to increase whole-blood β-hydroxybutyrate postpartum; however, other blood metabolites were not affected. Taken together, under the conditions of this study, elevated MP supply in close-up diets reduced milk production without affecting blood metabolites in multiparous dairy cows during early lactation. A combination of a shorter dry period and increased prepartum MP supply (i.e., SDHP vs. LPLP) improved prepartum dry matter intake without modifying energy-corrected milk yield and blood biomarkers in early lactation cows.

Limiting factors for milk production in dairy cows: perspectives from physiology and nutrition

Milk production in dairy cows increases worldwide since many decades. With rising milk yields, however, potential limiting factors are increasingly discussed. Particularly, the availability of glucose and amino acids is crucial to maintain milk production as well as animal health. Limitations arise from feed sources, the rumen and digestive tract, tissue mobilization, intermediary metabolism and transport, and the uptake of circulating nutrients by the lactating mammary gland. The limiting character can change depending on the stage of lactation. Although physiological boundaries are prevalent throughout the gestation-lactation cycle, limitations are aggravated during the early lactation period when high milk production is accompanied by low feed intake and high mobilization of body reserves. The knowledge about physiological constraints may help to improve animal health and make milk production more sustainably. The scope of this review is to address contemporary factors related to production limits in dairy cows from a physiological perspective. Besides acknowledged physiological constraints, selected environmental and management-related factors affecting animal performance and physiology will be discussed. Potential solutions and strategies to overcome or to alleviate these constraints can only be presented briefly. Instead, they are thought to address existing shortcomings and to identify possibilities for optimization. Despite a scientific-based view on physiological limits, we should keep in mind that only healthy animals could use their genetic capacity and produce high amounts of milk.

The estimation and interpretation of ordered logit models for assessing the factors connected with the productivity of Holstein-Friesian dairy cows in Egypt

The incorporation of novel technologies such as artificial intelligence, data mining, and advanced statistical methodologies have received wide responses from researchers. This study was designed to model the factors impacting the actual milk yield of Holstein-Friesian cows using the proportional odds ordered logit model (OLM). A total of 8300 lactation records were collected for cows calved between 2005 and 2019. The actual milk yield, the outcome variable, was categorized into three levels: low (< 4500 kg), medium (4500-7500 kg), and high (> 7500 kg). The studied predictor variables were age at first calving (AFC), lactation order (LO), days open (DO), lactation period (LP), peak milk yield (PMY), and dry period (DP). The proportionality assumption of odds using the logit link function was verified for the current datasets. The goodness-of-fit measures revealed the suitability of the ordered logit models to datasets structure. Results showed that cows with younger ages at first calving produce two times higher milk quantities. Also, longer days open were associated with higher milk yield. The highest amount of milk yield was denoted by higher lactation periods (> 250 days). The peak yield per kg was significantly related to the actual yield (P < 0.05). Moreover, shorter dry periods showed about 1.5 times higher milk yield. The greatest yield was observed in the 2nd and 4th parities, with an odds ratio (OR) equal to 1.75, on average. In conclusion, OLM can be used for analyzing dairy cows' data, denoting fruitful information as compared to the other classical regression models. In addition, the current study showed the possibility and applicability of OLM in understanding and analyzing livestock datasets suited for planning effective breeding programs.

Metabolic and production parameters of dairy cows with different dry period lengths and parities

To assess the effects of dry period (DP) length on metabolic, reproductive, and productive parameters, second- (SP) and third- (TP) parity cows were assigned to a traditional (9 weeks, T) or short (5 weeks, S) DP, obtaining four subgroups: second-parity cows with traditional (SPT = 8) and short (SPS = 8) DP, third-parity cows with traditional (TPT = 8) and short (TPS = 10) DP. Plasma insulin-like growth factor-I (IGF-I) and non-esterified fatty acid (NEFA) levels were assessed from 5 weeks before to 14 weeks after parturition. IGF-I concentrations were affected by parity (P < 0.05) and by the interaction of time and DP length (P < 0.01). NEFA levels were affected only by time (P < 0.01). S DP cows showed a shorter interval between calving and ovarian cyclicity resumption (P < 0.01) and a higher milk yield (P < 0.01) and fat and protein corrected milk (P < 0.01) compared with T DP cows. Decreased milk protein content was found in the SPS group compared to the SPT (P < 0.05) and the TPS (P < 0.05) group. In conclusion, a short DP length does not affect reproductive performances, except for hastening the resumption of ovarian cyclicity. A short DP appears to increase milk production and is associated with higher IGF-I levels both in the prepartum and the postpartum period.

Effects of feeding rumen-protected linseed fat to postpartum dairy cows on plasma n-3 polyunsaturated fatty acid concentrations and metabolic and reproductive parameters

High-yielding dairy cows experience a negative energy balance and inflammatory status during the transition period. Fat supplementation increases diet energy density, and plasma n-3 polyunsaturated fatty acids (PUFA) have been proposed to improve immune function. This study tested the hypothesis that dietary supplementation with a rumen-protected and n-3 PUFA-enriched fat could ameliorate both the energetic deficit and immune status of postpartum high-yielding dairy cows, improving overall health and reproductive efficiency. At 11 d in milk (DIM), cows were randomly allocated to groups (1) n-3 PUFA (n = 29), supplemented with encapsulated linseed oil supplying additional up to 64 g/d (mean 25 ± 4 g/d) of α-linolenic acid (ALA), or (2) control (n = 31), supplemented with hydrogenated palm oil without ALA content. Fat supplements of the n-3 PUFA and control groups were available through an automated, off-parlor feeding system, and intake depended on the cow's feeding behavior. Plasma ALA concentrations were higher in n-3 PUFA than control cows, following a linear relation with supplement ingestion, resulting in a lower n-6/n-3 ratio in plasma. Metabolic parameters (body condition score and glucose and β-hydroxybutyric acid blood concentrations) were unaffected, but milk yield improved with increased intake of fat supplements. Plasma total adiponectin concentrations were negatively correlated with ingestion of n-3 PUFA-enriched fat supplement, following a linear relation with intake. Conception rate to first AI increased with higher intake of both fats, but a decrease of calving-to-conception interval occurred only in n-3 PUFA cows. Postpartum ovarian activity and endometrial inflammatory status at 45 DIM were unaffected. In conclusion, this study evinced a positive linear relation between rumen-protected linseed fat intake and plasma n-3 PUFA concentrations, which modulated adiponectin expression and improved reproductive parameters.

Effects of dry period length on milk yield and content and metabolic status of high-producing dairy cows under heat stress

The objective of the present study was to investigate the effects of shortening dry period (DP) on milk yield, milk composition, and blood parameters in cows under heat stress. For this purpose, three DP groups were considered (30, 45, and 60 days), and 14 heat-stressed high-producing dairy cows (7 primiparous and 7 multiparous) were assigned to each DP group. The results showed that shortening the DP (from 60 to 30 days) decreased a 305-day milk yield in subsequent lactation. The difference in milk yield between 30- and 60-day DP groups was significant in the second 100 days of lactation. Accounting for additional milk yield before calving completely compensate for the loss of milk production resulting from shortening the DP. Milk protein, lactose, and solids non-fat percentages were significantly lower for cows with a 60-day DP compared to cows with a 45- or 30-day DP. Serum BHBA and urea concentrations were significantly higher, and serum glucose concentration was significantly lower for cows with a 60-day DP compared to cows with a 30-day DP. In conclusion, results showed that shortening the DP improved the metabolic status of heat-stressed transition dairy cows without decreasing total milk yield.

Effect of some non-genetic factors on the productivity and profitability of Holstein Friesian dairy cows

Background and Aim:

Milk yield (MY) is one of the main factors that affect the economic profitability of dairy farms. Thus, increasing the MY per animal and decreasing the feed cost can lead to economic gains, so the objective of this study was to evaluate the effect of dry period length (DPL), days open (DO), and days in milk (DIM) on the productivity and profitability of dairy cow farms.

Materials and Methods:

Data used in this study were taken from 3095 lactation records of Friesian dairy cows of private and governmental sectors. The data were classified into 4 DPL categories: DPL₁ <45 days; DPL₂ 45-60 days; DPL₃ 61-75 days, and DPL₄ >75 days, 3 DO categories: DO₁ ≤90 days; DO₂ 91-110 days and DO₃ >111 days, and 8 DIM categories: DIM₁ 180-210 days; DIM₂ 211-240 days; DIM₃ 241-270 days; DIM₄ 271-300 days; DIM₅ 301-330 days; DIM₆ 331-360 days; DIM₇ 361-447 days; and DIM₈ >447 days.

Results:

The average net profit (NP) was significantly different (p<0.05) among different categories of DPL, DO, and DIM in both production sectors, where high estimates of NP were calculated for DPL₃ (30667.3 EGP), and it was the lowest for DPL₁ (19690.6 EGP). DO₂ had the highest NP (30754.1 EGP), while DO₃ had the lowest NP (24875.5 EGP). DIM₃ had the highest NP (29569.3 EGP), while DIM₈ had the lowest NP (19528.4 EGP).

Conclusion:

Finally, we can conclude that DPL 61-75 days, DO 91-110 days, and DIM 241-270 days had the highest level of total MY, total return, and NP. Private dairy cow farms achieve a higher level of NP than governmental ones under subtropical Egyptian conditions.

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.

Piecewise modeling of the associations between dry period length and milk, fat, and protein yield changes in the subsequent lactation

Our objective was to develop predictive models of 305-d mature-equivalent milk, fat, and protein yields in the subsequent lactation as continuous functions of the number of days dry (DD) in the current lactation. In this retrospective cohort study with field data, we obtained DHIA milk recording lactation records with the last DD in 2014 or 2015. Cows included had DD from 21 to 100 d. After editing, 1,030,141 records from cows in 7,044 herds remained. Three parity groups of adjacent (current, subsequent) lactations were constructed. We conducted all analyses by parity group and yield component. We first applied control models to pre-adjust the yields in the subsequent lactation for potentially confounding effects. Control models included the covariates mature-equivalent yield, days open, somatic cell score at 180 d pregnant, daily yield at 180 d pregnant, and a herd-season random effect, all observed in the current lactation. Days dry was not included. Second, we modeled residuals from control models with smooth piecewise regression models consisting of a simple linear, quadratic, and another simple linear equation depending on DD. Yield deviations were calculated as differences from predicted mature-equivalent yield at 50 DD. For validation, predictions of yield deviations from piecewise models by DD were compared with predictions from local regression for the DHIA field records and yield deviations reported in 38 experimental and field studies found in the literature. Control models reduced the average root mean squared prediction error by approximately 21%. Yield deviations were increasingly more negative for DD shorter than 50 d, indicating lower yields in the subsequent lactation. For short DD, the decrease in 305-d mature-equivalent milk yield ranged from 43 to 53 kg per DD. For mature-equivalent fat and protein yields, decreases were between 1.28 and 1.71 kg per DD, and 1.06 and 1.50 kg per DD, respectively. Yield deviations often were marginally positive and increasing for DD >50, so that the highest yield in the subsequent lactation was predicted for 100 DD. For long DD, the 305-d mature-equivalent milk yield increased at most 4.18 kg per DD. Patterns in deviations for fat and protein yield were similar to those for milk yield deviations. Predictions from piecewise models and local regressions were very similar, which supports the chosen functional form of the piecewise models. Yield deviations from field studies in the literature typically were decreasing when DD were longer, likely because of insufficient control for confounding effects. In conclusion, piecewise models of mature-equivalent milk, fat, and protein yield deviations as continuous functions of DD fit the observed data well and may be useful for decision support on the optimal dry period length for individual cows.

Do biological and management reasons for a short or long dry period induce the same effects on dairy cattle productivity?

The dry period is a well-established factor that determines lactation success. A retrospective observational study used 32,182 lactations from 16 farms to determine whether management versus biological reasons for deviations from the targeted 60-d dry period have the same associations with subsequent lactation performance. Herd inclusion criteria were Holstein cows, herd size ≥900 cows, breeding by artificial insemination, and (minimally) bimonthly milk testing. Dry period length (DPL) and gestation length (GL) were each categorized as short [>1 standard deviation (SD) below mean within herd; means 45 d DPL, 269 d GL] or long (>1 SD above mean within herd; means 73 d DPL, 284 d GL) and combined to generate the following 7 study groups: short DPL, short GL (S_DS_G, n = 2,123); short DPL, average GL (S_DA_G, n = 1,418); average DPL, short GL (A_DS_G, n = 1,759); average DPL, average GL (A_DA_G, n = 19,265); average DPL, long GL (A_DL_G, n = 3,325); long DPL, average GL (L_DA_G, n = 2,573); and long DPL, long GL (L_DL_G, n = 1,719). Responses evaluated included milk and component yields at first test and over the whole lactation, days to first service, first service conception risk, days open, and herd retention through 60 and 365 d postpartum. Continuous data were analyzed by mixed models and time to event data by Cox proportional hazard models, both accounting for clustering at the herd level. First test and whole-lactation milk and component yields were lowest for S_DS_G. Within cows that experienced calving difficulty, rates of receiving first service were 13 and 20% less for S_DS_G and A_DS_G compared with A_DA_G. Hazard of leaving the herd by 60 d in milk (DIM) was 34% greater for A_DS_G than A_DA_G. Similar effects between S_DS_G and A_DS_G but not S_DA_G indicated that short GL was a greater contributor to poor performance than DPL itself. Overall production was similar between A_DA_G and S_DA_G; however, somatic cell linear score at first test was greater for S_DA_G, and milk yield at first test was lesser for S_DA_G cows with greater milk at last test before dry-off. Although short DPL might be a successful strategy for some herds or cows, cows with high milk yield at dry-off should not be subjected to a short dry period. Long DPL or GL did not influence early-lactation or whole-lactation milk yield. Cows with a long DPL due to early dry-off (L_DA_G) likely experienced issues related to excessive lipid mobilization, as milk fat concentration and fat:protein ratio at first test were greater and hazard of leaving the herd was 30 and 24% greater compared with A_DA_G by 60 and 365 DIM, respectively. We conclude that deviations in DPL length caused by biology (short GL) were associated with greater effects than management causes of short DPL, whereas management reasons for long DPL were associated with more negative outcomes than long GL.

Phenotypic and genetic effects of pregnancy on milk production traits in Holstein-Friesian cattle

Pregnancy is a prerequisite for the initiation of lactation and for maintaining the milk production cycle. Pregnancy affects milk production and therefore should be accounted for in the genetic evaluation. Furthermore, there might be genetic differences in pregnancy effects on milk composition. The objective of this study was to estimate phenotypic and genetic effects of pregnancy on milk production traits. For this purpose, test-day records and conception dates of 1,359 first-parity Holstein-Friesian cows were analyzed. Significant effects of pregnancy on all milk production traits were detected except somatic cell score (e.g., the cumulative effects of pregnancy on milk yield were -247 kg). The pregnancy effects on milk yield, lactose yield, protein yield, fat yield, and fat content were small during early gestation (<150 d) and substantially increased in late gestation. The effects of pregnancy on milk protein yield were relatively stronger than those on fat yield. The effects of pregnancy on milk production traits differed for DGAT1 genotypes. Milk yield, lactose yield, protein yield, and fat yield of DGAT1 AA cows were more affected by pregnancy than that of DGAT1 KK cows (e.g., the cumulative effects of pregnancy on milk yield were negligible for DGAT1 KK cows and were -443 kg for DGAT1 AA cows). These results suggest that DGAT1 KK cows may be more suitable for shortening or omitting the dry period than DGAT1 AA cows.

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.

Dynamic forecasting of individual cow milk yield in automatic milking systems

Accurate forecasting of dairy cow milk yield is useful to dairy farmers, both in relation to financial planning and for detection of deviating yield patterns, which can be an indicator of mastitis and other diseases. In this study we developed a dynamic linear model (DLM) designed to forecast milk yields of individual cows per milking, as they are milked in milking robots. The DLM implements a Wood's function to account for the expected total daily milk yield. It further implements a second-degree polynomial function to account for the effect of the time intervals between milkings on the proportion of the expected total daily milk yield. By combining these 2 functions in a dynamic framework, the DLM was able to continuously forecast the amount of milk to be produced in a given milking. Data from 169,774 milkings on 5 different farms in 2 different countries were used in this study. A separate farm-specific implementation of the DLM was made for each of the 5 farms. To determine which factors would influence the forecast accuracy, the standardized forecast errors of the DLM were described with a linear mixed effects model (lme). This lme included lactation stage (early, middle, or late), somatic cell count (SCC) level (nonelevated or elevated), and whether or not the proper farm-specific version of the DLM was used. The standardized forecast errors of the DLM were only affected by SCC level and interactions between SCC level and lactation stage. Therefore, we concluded that the implementation of Wood's function combined with a second-degree polynomial is useful for dynamic modeling of milk yield in milking robots, and that this model has potential to be used as part of a mastitis detection system.

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.