Browsing by Author "Velez, Juan, committee member"

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Open Access
Effects of pre-milking waiting time and selection behavior in cows milked in an automated batch milking system
(Colorado State University. Libraries, 2025) Weng Zheng, Richard, author; Pinedo, Pablo, advisor; Velez, Juan, committee member; Lombard, Jason, committee member
The adoption of automated milking systems (AMS) has transformed the dairy industry by improving efficiency, animal welfare, and milk production. DeLaval's Batch Voluntary Milking System (Batch VMS) provides a structured alternative to traditional AMS for larger dairy herds. Unlike continuous voluntary milking, Batch VMS organizes cows into groups and schedules their milking at set intervals, enhancing herd management while reducing labor demands. As a hybrid approach, it offers a seamless transition from conventional milking methods to automation. Through a literature review and two research studies, this thesis explores how Batch VMS may affect cow health and performance. Chapter 1 contains the literature review. It introduces the changes in the AMS technologies in recent years and compares it to Batch VMS. Secondly, it discusses the effects of pre-milking waiting time on milking performance and cow health in terms of mastitis and lameness. And lastly, it discusses selection behavior in cows, comparing behaviors in conventional and automated milking systems. Chapter 2 explores the effects of pre-milking waiting time (WT) in an automated batch milking system (ABMS). Visit information was collected to calculate pre-milking WT, defined as the time elapsed between the entrance of the cow to the milking barn, as indicated by pedometers attached to each cow that were read by sensors located at the parlor, and the entrance of each individual cow to the robot milking box. WT were categorized into quartiles within each parity group as Q1 ≤ 9 min, Q2 = 10 to 24 min, Q3 = 25 to 46 min and Q4 ≥ 47 mins for primiparous and Q1 ≤ 11 min Q2 = 12 to 30 min, Q3 = 31 to 51 min and Q4 ≥ 52 mins for multiparous. To assess the association between lameness and WT, individual cow WT averages were calculated separately for primiparous and multiparous groups. Lameness was treated as a categorical variable, where 1 indicated a cow diagnosed with lameness and 0 indicated non-lame cow. The results show that the average waiting time for all milking events was 33.6 min (± SD = 28.5), 34.5 ± 28.9 for PP, and 30.7 ± 27.3 for MP. The means for each breed were 25.6 ± 15.2, 42.3 ± 16.8, and 42.3 ± 23.4, for HO, JE, and HJ, respectively. While significant differences in LSM were observed between breeds for most variables, there was little to no significant association between WT and the analyzed outcomes. An increase of 10 minutes in WT was associated with a 23.7% increase in the odds of lameness in multiparous cows (95% CI: 10.2–39.0; p < 0.001). However, no significant association was found in primiparous cows (OR: 1.09, 95% CI: 0.85–1.38, p = 0.462). Chapter 3 discusses selection behavior in an ABMS where cows select between 22 robots each time there are brought to the milking parlor. The objective of this study was to analyze the robotic milking station selection behavior of three breeds including Holstein, Jersey, and Holstein × Jersey crossbred cows in a multibreed dairy farm with a batch milking system with automatic milking units. The study used data from 1,762,461 milking events in 3705 HO (n=1355), JE (1876) and HJ (475) cows from May 2023 to September 2024 in a commercial organic grass-fed dairy in TX. Cows were moved to the milking center twice per day, where they could select their milking visits among 22 robot units (DeLaval, Sweden). For the analysis, robots were also classified by barn location [East (n=11); West] and arm configuration [left (n=11); right]. Milking visit information was collected to determine the frequency of specific robot usage per cow during the study period. Subsequently, the frequencies of selection for the top 1, 3, and 5 robotic milking stations, top barn location, and top arm configuration were calculated for each cow. Preference consistency scores (PCS) were calculated considering the frequency of access to each robotic milking station, barn side, and arm configuration in 30 days periods. Overall, multiparous and HO cows evidenced more consistent behaviors in milking station preference. Dairy cow selection behavior should be considered when analyzing the efficiency of milking procedures.
Open Access
Impact of low-level tannin supplementation on enteric methane emissions, estimated nitrogen excretion, oxidative stress, and animal performance in organic dairy heifers
(Colorado State University. Libraries, 2023) Schilling, Ashley, author; Stackhouse-Lawson, Kim, advisor; Place, Sara, committee member; Pinedo, Pablo, committee member; Velez, Juan, committee member; Moore-Foster, Rhyannon, committee member
Heightened attention and concern regarding the role of anthropogenic greenhouse gas (GHG) emissions in climate change has challenged every industry to reduce their environmental impact. In cattle production systems, the importance of feeding the growing human population while minimizing environmental impacts has been given significant attention throughout the 21st century (Steinfeld et al. 2006; Golub et al., 2012; Eisler et al. 2014). In 2020, the United States dairy industry was responsible for approximately 1.4% of total anthropogenic GHG emissions (EPA, 2021). The GHGs with the largest global warming potential (GWP) equivalents in dairy cattle production systems are nitrous oxide (N2O) and methane (CH4) (Rotz et al., 2021). The use of tannins as a feed additive in cattle production systems has been explored as a GHG mitigation strategy given their potential to reduce enteric CH4 and reactive-nitrogen (N) emissions, while also benefiting animal health. Tannins are secondary components of plants comprised of phenolic compounds of diverse molecular weights and of variable complexity (Place et al., 2011). They are classified into two major classes: 1) hydrolysable and 2) condensed tannins and exhibit variable affects depending on their class, concentration/purity, dose, type, and other factors such as animal species, animal physiological state, and diet composition (Makkar 2003; Aboagye and Beauchemin, 2019). When fed to ruminants, such as dairy cattle (Bos taurus), tannins act as rumen modifiers by altering protein and carbohydrate degradation in the rumen. Moreover, tannins have demonstrated anti-microbial, anti-parasitic, antioxidant, anti-inflammatory, and anti-viral effects in animals and the ability to serve as a bloat control mechanism (Mangan, 1988; Jones et al., 1971, Min et al., 2005). Since tannins target rumen microbial populations that assist in fiber degradation, unintended consequences can include reductions in feed intake, digestibility, and rate of BW gain when tannins are supplemented at concentrations greater than 55 g condensed tannins/kg dry matter (DM) (Min et al., 2003). Therefore, the objective of this study was to determine the impact of low-level tannin (< 0.30 g/kg DMI) supplementation on enteric CH4 emissions, estimated N excretion, oxidative stress, and performance in organic Holstein heifers. Heifers (n=20) were supplemented with Silvafeed® ByPro, a Schinopsis lorentzii condensed tannin product, at increasing levels as recommended by the manufacturer: 0% (CON), 0.075% (LOW), 0.15% (MED), and 0.30% (HIG) of dry matter intake (DMI). Based on animal success to a 28 d acclimation period, 20 certified organic Holstein heifers (BW = 219 ± 17 kg) were randomly assigned into one of the four treatment groups and stratified based on initial body weight (i.e., a completely randomized design). A 7 d pretrial gas analysis was performed prior to study initiation to account for individual animal emission differences. Daily, heifers were supplemented with one kg of sweet feed and tannin in accordance with the assigned treatment in individual feeding stanchions for 45 d and fed a basal total mixed ration (TMR) diet through four SmartFeed Pro intake measurement bunk systems (C-Lock Inc., Rapid City, SD) which allowed for measurement of individual animal feed intake. Additionally, CH4 and carbon dioxide (CO2) production was measured using one GreenFeed automated head chamber system (AHCS, C-Lock Inc., Rapid City, SD) for the entirety of the study. Statistical analysis was conducted in R© (R Core Team, 2021, v. 4.1.2). Data were analyzed as a completely randomized design with animal (n=20) as the experimental unit, using the Type III ANOVA procedure. Post-hoc pairwise comparisons for dependent variables by treatment were performed using the least squared means procedure with the Tukey HSD adjustment applied. Daily CH4 production ranged from 136.5 to 140.1 g CH4/hd/d between treatments. No significant difference was observed between treatments for daily CH4 production (P=0.95), CO2 production (P=0.95), CH4 as a percent of gross energy (GE) intake (Ym; P=0.87), CH4 yield (MY; g CH4/kg DMI; P=0.80), and CH4 emission intensity (EI; g CH4/kg of BW gain; P=0.70). Similarly, a treatment effect was not observed for DMI (kg/d; P=0.92), average daily gain (ADG; kg BW gain/d; P=0.53), or feed efficiency (G:F; kg of BW gain/kg of DMI; P=0.42). Nitrogen intake ranged from 195 to 214 g/d among treatments (P=0.93). No significant difference was observed among treatments for fecal output (P=0.98), fecal N (FN; P=0.98), fecal neutral detergent fiber (NDF; P=0.33), or fecal acid detergent fiber (ADF; P=0.30). Estimated urine nitrogen (UN) (P=0.77), FN:UN (P=0.93), and N excretion (P=0.86) did not differ among treatments when estimated using methodologies described by Kohn (2005) (Table 5). Similarly, estimated UN (P=0.66), FN:UN (P=0.94), and N excretion (P=0.72) did not differ among treatments when estimated using methodologies described by Reed (2015). Moreover, no significant difference was observed among treatments for serum parameters, blood urea nitrogen (BUN; P=0.99) or creatinine (P=0.20), the common oxidative stress biomarker malondialdehyde (MDA; P=0.63), or antioxidant enzyme biomarkers superoxide dismutase (SOD; P=0.26) and reduced glutathione (GSH; P=0.19). Ultimately, the results of this study would not indicate that low-level tannin supplementation alters CH4 emissions, estimated N excretion, oxidative stress, or animal performance in organic dairy heifers.
Open Access
Individual quarter dry-off procedure in dairy cows
(Colorado State University. Libraries, 2025) Ibarguren, Clara, author; Pinedo, Pablo, advisor; Velez, Juan, committee member; Lombard, Jason, committee member
Mastitis, defined as inflammation of the mammary gland, has a major impact on the dairy industry, affecting profitability and animal welfare due to reduced milk production, increased antibiotic use, and pain and discomfort in the affected animals. This health disorder concerns researchers, producers, and consumers worldwide. The "individual quarter dry-off" procedure, which consists of stopping milking the affected quarter is an alternative to the use of antibiotic treatment in unresponsive cases. Understanding the relationship between the multiple factors involved in the disease and this procedure is crucial. Through an extensive review of mastitis and a descriptive statistical analysis of this dry-off practice, this thesis focuses on understanding the dynamics of this procedure within a lactating dairy herd. Chapter 1 includes a literature review on mastitis, and the possible management practices conducted by the dairy industry to mitigate the problem. Due to the limited information available on individual quarter dry-off, the information provided in this chapter consists of a discussion of the anatomy of the mammary gland, physiology, pathology of mastitis disease, and management practices. Once general knowledge of the root of the problem is established, technical implications regarding the individual dry-off procedure are explained in the following chapter. The objective of chapter 2 is to describe the dynamics of individual quarter dry-offs in certified organic dairies. The data were collected from PCDart (©DRMS) spanning from 2018 to 2023 from four organic dairies in CO, USA. The dataset included 2,881 cows with at least one dried quarter (QDO), of which 769 cows (26%) had a second dried quarter (QDO2). The variables considered in this study were quarter location, parity, days in milk (DIM), season, and survival after the first quarter dry-off (QDO). The statistical analysis was completed in SAS (SAS Institute Inc.), employing chi-square goodness of fit, logistic regression, and ANOVA. The results showed that QDO was more prevalent in front quarters among both primiparous (PP) and multiparous (MP) cows, with higher frequencies observed during winter across both parity categories. The mean ± SE of days in milk at QDO was smaller for primiparous cows compared to multiparous cows, and it took approximately one year to have a second dried quarter to occur. Parity category had no effect on the likelihood of QDO2, and the number of days to culling after QDO were not significantly different between parities, averaging around 365 days. Additionally, cows with QDO had lower actual and projected 305 milk yield compared to healthy cows (597 kg [PP] and 436 kg [MP] less for actual 305 milk production; 628 kg [PP] and 495 kg [MP] less for projected 305 milk production). Overall, milk yield was consistently lower in cows with QDO compared to their herdmates. These findings provide valuable insights into the dynamics of quarter dry-off, contributing novel information to support the control of mastitis in certified organic dairies. Chapter 3 explores the dynamics of milk yield following the individual dry-off of quarters (QDO) in dairy cows. The study focused on cows that had one quarter dried off due to a chronic mastitis event and had milking records available for 30 days post-procedure. Data were collected from 144 cows on an automatic milking system (AMS) dairy farm in Colorado, of which 79% (n=144) were multiparous and 21% (n=30) primiparous. Information was sourced from DelPro and DairyComp on-farm software, and linear mixed models with repeated measures and estimated marginal means (emmeans) were generated using RStudio. Although the sample size of primiparous cows was limited, results showed a slight decrease in milk production following QDO. Conversely, multiparous cows displayed increased production in the opposite quarters, with an overall milk yield rising over the 30-day period after the dry-off. Total milk production following QDO was higher in cows ≤120 days in milk (DIM) compared to those with >120 DIM. Additionally, cows experienced greater milk yields when the dry-off procedure was performed on rear quarters versus front quarters. Of the variables analyzed, the number of days in milk after the procedure showed the most statistically significant relationship with milk production, while presence of other diseases did not exhibit a significant effect. These findings offer valuable insights into milk yield dynamics and implications for management strategies in dairy herds.