The Applicability of Cognitive Mediational and Moderational Models to Explain Children's Depression Inventory Factor Scores in Urban Youth.

This investigation examined whether cognition serves as a direct factor, mediates, or moderates the relationship between stressful life events and Children's Depression Inventory (CDI; Kovacs, 1992) factor scores in urban, ethnic minority youth. Ninety-eight middle school students completed measures of stressful life events, cognition (cognitive triad and locus of control), and depressive symptoms. Results provided support for both mediating and moderating models of depression. Specifically, the cognitive triad mediated the relationship between stressful life events and depressive symptom categories of negative mood, ineffectiveness, and anhedonia, while it interacted with stressful life events to predict negative self-esteem. In addition, locus of control was found to interact with stressful life events to predict anhedonia. Finally, the diathesis-stress model was not supported when predicting the CDI Interpersonal Problems factor score, which taps externalizing behaviors. Implications for school psychology research and practice include the importance of including measures of stressful life events and cognitive styles in assessment of children's social-emotional functioning. In addition, results highlight the need to target children's perceptions for intervention since they appear to play a significant role in psychological reactions to stressors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Estimating teat canal cross-sectional area to determine the effects of teat-end and mouthpiece chamber vacuum on teat congestion

The primary objective of this experiment was to assess the effect of mouthpiece chamber vacuum on teat-end congestion. The secondary objective was to assess the interactive effects of mouthpiece chamber vacuum with teat-end vacuum and pulsation setting on teat-end congestion. The influence of system vacuum, pulsation settings, mouthpiece chamber vacuum, and teat-end vacuum on teat-end congestion were tested in a 2 × 2 factorial design. The low-risk conditions for teat-end congestion (TEL) were 40 kPa system vacuum (Vs) and 400-ms pulsation b-phase. The high-risk conditions for teat-end congestion (TEH) were 49 kPa Vs and 700-ms b-phase. The low-risk condition for teat-barrel congestion (TBL) was created by venting the liner mouthpiece chamber to atmosphere. In the high-risk condition for teat-barrel congestion (TBH) the mouthpiece chamber was connected to short milk tube vacuum. Eight cows (32 quarters) were used in the experiment conducted during 0400 h milkings. All cows received all treatments over the entire experimental period. Teatcups were removed after 150 s for all treatments to standardize the exposure period. Calculated teat canal cross-sectional area (CA) was used to assess congestion of teat tissue. The main effect of the teat-end treatment was a reduction in CA of 9.9% between TEL and TEH conditions, for both levels of teat-barrel congestion risk. The main effect of the teat-barrel treatment was remarkably similar, with a decrease of 9.7% in CA between TBL and TBH conditions for both levels of teat-end congestion risk. No interaction between treatments was detected, hence the main effects are additive. The most aggressive of the 4 treatment combinations (TEH plus TBH) had a CA estimate 20% smaller than for the most gentle treatment combination (TEL plus TBL). The conditions designed to impair circulation in the teat barrel also had a deleterious effect on circulation at the teat end. This experiment highlights the importance of elevated mouthpiece chamber vacuum on teat-end congestion and resultant decreases in CA.     

Response of dairy cattle to transient voltages and magnetic fields

Stray voltages in dairy facilities have been studied since the 1970s. Previous research using steady-state AC and DC voltages has defined cow-contact voltage levels which may cause behavioral and associated production problems. This research was designed to address concerns over possible effects of transient voltages and magnetic fields on dairy cows. Dairy cow response to transient voltages and magnetic fields was measured. The waveforms of the transient voltages applied were: 5 cycles of 60 Hz AC with a total pulse time of 83 ms, 1 cycle of 60 Hz AC with a total pulse time of 16 ms, and 1 cycle of an AC square wave (spiking positive and negative) of 2 ms duration. Alternating magnetic fields were produced by passing 60 Hz AC fundamental frequency with 2nd and 3rd harmonic and random noise components in metal structures around the cows. The maximum magnetic field associated with this current flow was in excess of 4 G. A wide range of sensitivity to transient voltages was observed among cows. Response levels from 24 cows to each transient exposure were normally distributed. No responses to magnetic fields were observed     

Sampling strategies for total bacterial count of unpasteurized bulk milk

The purpose of this study was to assess bulk tank milk sampling strategies for estimating total bacterial count (TBC). Nine large dairies in Wisconsin that produced and shipped at least 1 milk load per day were selected for this study. Total bacteria count was performed for each milk load produced during a 13-mo period. The milk shipment frequency was once (n=3), twice (n=4), or 3 times daily (n=2 farms). A threshold of 8,000 cfu/mL was used to define increased TBC. The proportion of increased TBC (TBCref) during the study period was defined as the reference probability of an increased TBC for each farm. The number of milk loads that would need to be tested to estimate TBCref precisely (TBCref ± 0.05) in selected time periods (month, quarter, 6 mo, or a year) was calculated assuming independence among TBC measurements. Sampling simulations (systematic or simple random sampling) were used to assess the validity of the independence assumption and compare different sampling schedules (every second, every third, or every seventh milk load) used for estimating TBCref in a 13-mo or 30-d TBC series. The number of milk loads tested to estimate TBCref depended on the time period of interest. For farms with daily milk shipments, at least 94% of all milk loads produced would need to be tested to estimate TBCref during a 30-d period. In contrast, when the period of interest was a year, reductions of up to 88% in the number of milk loads tested could be achieved. As the probability of an increased TBC departed from 0.50 toward 1 or 0, fewer samples were needed to estimate TBCref. A sampling schedule based on TBC performed on every second milk load resulted in 100% of 5,000 random samples (taken from the 13-mo TBC series) within the range of TBCref ± 0.05, indicating that sampling half of the milk loads would precisely estimate TBCref. Results of this study suggest that dairy consultants and processors can adjust the frequency of testing of milk loads depending on the goal of the milk quality monitoring program.     

Short communication: Increasing the teatcup removal settings of the last milking quarter did not reduce box time in a pasture-based automatic milking system

This research followed our previous experimental and simulation work on the effect of different teatcup removal settings based on the rolling average milk flowrate and on milking duration at the quarter and udder levels. The aims of this experiment were to (1) quantify the differences in quarter milking duration in a pasture-based automatic milking system and (2) test the effect of increasing the milk flowrate at which teatcups are removed on the last milking quarter on udder milking duration, box time, milk production rate, and somatic cell count (SCC). Milking duration is an important component of efficiency and profitability in conventional and automatic milking systems. Additionally, quarters within an udder have significantly different milk yields and milking durations. This study used data from April to May 2018 of a pasture-based automatic milking system to evaluate quarter milking duration differences between quarters of an udder. Subsequently, we experimentally evaluated the use of 2 percentage-based teatcup removal settings applied to the last milking quarter (i.e., the last quarter with a teatcup still attached) on milking duration, box time, milk production rate, and SCC. The teatcup removal settings were at 30 or 50% of the last quarter's rolling average milk flowrate, while the other quarters remained at the 30% level. The selection of the quarter that would receive the more aggressive teatcup removal setting was determined by identifying the last quarter with a teatcup attached in every milking. Sixty-nine cows were divided into 2 groups that each received 1 of the 2 treatments for a 1-wk period and then switched to the other treatment for a second week. For the months of April and May 2018, quarter milking duration was significantly different between the quarter with the longest and the second longest milking duration within an udder. The quarter with the longest milking duration was milked on average 49 s longer than the quarter with second longest milking duration. However, in 36% of the milkings, the quarter with the longest milking duration was different from that of the previous milking. In the experimental part of this study, we saw no differences in milking duration, box time, milk production rate, or SCC between the 30 and 50% teatcup removal setting applied to the last milking quarter. Further research on using a variation of this percentage-based setting to target the quarter with the average longest milking duration or using an absolute milk flowrate switch-point or a maximum milking duration setting on the last quarter for reducing cow milking duration and box time is warranted.     

Factors associated with coliform count in unpasteurized bulk milk

The objective of this study was to identify factors associated with bulk milk coliform count (CC). Dairy farms (n = 10) were visited once weekly on sequential weekdays over a period of 10 wk. During each visit, in-line drip samplers were used to collect 1 milk sample from 2 points of the milk line (between the receiver jar and milk filters, and after the plate cooler). During the same period that in-line milk samples were collected, university personnel observed milking performance and hygiene and collected liner (n = 40) and teat skin swabs (n = 40). Coliform counts were determined for milk samples and swabs using Petrifilm CC plates (3M, St. Paul, MN). A mixed model was used to assess the association between in-line milk CC (ILCC) and several potential predictor variables. The mean duration of each visit was 73 min and the time between start of milking and beginning of milk sampling was 154 min. The mean number of cows milked during each visit was 236. For all milk samples (n = 181), geometric mean ILCC was 37 cfu/mL. In-line milk CC varied by farm, ranging from 5 to 1,198 cfu/mL. Rate of fall-offs, rate of cluster washes, outdoor and indoor temperature, indoor humidity, sampling duration, and parity group were unconditionally associated with ILCC but did not enter the final multivariate model. In-line milk CC was 4 times greater (115 cfu/mL) when milking machine wash failures occurred compared with ILCC after normal washes (26 cfu/mL). Pre-filter and post-cooler ILCC were not different when milk samples were collected at the beginning (<33% of herd milked) or at mid-milking (33 to 66% of the herd milked), whereas pre-filter ILCC was less than post-cooler for samples collected at the end of milking (>67% of the herd milked). Geometric mean ILCC (cfu/mL) increased 6.3% for every 10% increase in in-line milk SCC (cells/mL). Geometric mean ILCC increased 2.3% for every 10% increase in liner CC (cfu/mL). Results of this study provide novel information about farm factors associated with CC, as estimated in milk before storage in tankers or bulk tanks, and highlight the importance of proper and consistent milking machine washes in minimizing bulk milk coliform contamination. The nature of the associations between liner CC, rate of cluster washes, rate of milking units fall-offs, and ILCC indicates that managing and monitoring such events has the potential for improving bacteriological quality of farm bulk milk.     

Association of milking interval and milk production rate in an automatic milking system

The primary aim of this research was to describe the association between milking interval (MI) and milk production rate (MPR) at the quarter level in a large commercial farm using an automatic milking system. A secondary aim was to determine whether a 2-h decrease in MI would increase MPR at the cow level in midlactation multiparous cows. Six months of data from 1,280 cows were used to assess the association between MI (h) and quarter MPR (kg/h). Increasing MI was associated with decreased MPR for early, mid, and late lactation, both primiparous and multiparous cows, and all 4 quarter positions and across time. The decrease in MPR is approximately 2%/h of increasing MI for multiparous cows and 1.5%/h for primiparous cows. Regardless of quarter, multiparous cows had a greater MPR than primiparous cows, and rear quarters had greater MPR than front quarters. An experiment to test the causal relationship between changing MI and cow-level MPR was conducted using 26 animal pairs matched on MI, days in milk, and milk yield. During the 21-d treatment period, the average MI of treatment cows was decreased by 2.4 h compared with control cows. In both the 21-d treatment and 42-d posttreatment periods, no significant difference was found in cow-level MPR between the treatment and control groups. Despite the negative association between increasing MI and MPR being consistent across all assessed days in milk windows and all quarters, results from this experiment suggest that intervention to decrease MI might require an MI change greater than 2 h or be applied in early lactation to significantly increase MPR.     

Effect of incomplete milking on milk production rate and composition with 2 daily milkings

The primary aim of this study was to assess the effects of incomplete milking on milk secretion and milk composition at the quarter level. Twelve cows were enrolled beginning at 5 d in milk and remained on study through 47 d in milk. Half of each contralateral udder was incompletely milked (treatment), detaching the teat cup early to leave approximately 30% of the total milk yield behind. This target milk remaining in the gland was based on weekly calibration milking measurements of quarter total milk yield. Control quarters were milked completely until milk flow had decreased to 0 kg/min based on visual assessment. Harvested milk yield was measured twice daily at each milking, and milk components (fat, protein, lactose, solids nonfat, milk urea nitrogen) and somatic cell count, were measured twice weekly at the quarter level. The experimental unit in this design was the half-udder, and a mixed-model approach was used to assess the main and interactive effects of experiment week and treatment on milk production rate, milk remaining in the gland, and milk composition. The effect of treatment on milk production rate was significant, with the average control half-udder producing 0.97 kg/h and the treatment half-udder 0.73 kg/h. The effect of week on milk production rate and the interaction of week × treatment were also significant. The effect of treatment on milk remaining in the gland was significant, illustrating that an increase in milk remaining in the cisternal compartment had been achieved. We detected a significant decrease in milk lactose percentage in treatment half-udders, and a significant increase in somatic cell count (log₁₀). The increase was relatively small, from a geometric mean of 26,300 cells/mL in control quarters to 48,300 cells/mL in treatment quarters. The decrease in milk production rate in treatment half-udders supports current knowledge about how mammary epithelial cell secretion, proliferation, and apoptosis are modulated by autocrine-paracrine factors.