Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218
Performing Department
DAIRY SCIENCE
Non Technical Summary
Current teatcup removal strategies applied to both conventional and automatic milking installations have been derived from studies in the 1990's performed in conventional parlors. AMS installations have the ability to determine milk flow at the quarter level and can detach during milking also at the quarter level. The economic return on an AMS installation is partly driven by the number of cows milked per hour. Given that the capital cost of a single AMS unit is high, any strategies that improve the number of cows that can be milked through a single unit without compromising milk yield can be highly useful in facilitating the use of this technology. Additionally, the allowable milking frequency applied to cows in an AMS installation is derived from milking frequency studies conducted in conventional farms and parlors. Further work is required to clarify the optimal milking frequency settings for AMS parlors.The experimental design for this proposal affords the opportunity to further explore the physiological mechanisms responsible for reduced milk yield where cisternal milk left behind at the end of milking is increased resulting in an undermilked cow and the potential interaction with milking frequency. Previous experimental work conducted in this area has only focused on reducing milking interval and not via increased cisternal milk.The quarter milker device proposed for this research will mimic the role of an AMS installation so that research findings can then be applied to commercial AMS devices. Furthermore, milk harvesting strategies resulting in higher residual milk yields applied in conventional parlors could be derived from this research.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The overall objective of this research is to understand the influence of residual milk/udder fill, milking frequency and their potential interactions on milk yield and teat health. The outcomes of this research will be improved understanding of the physiological mechanisms controlling milk yield which will result in new strategies for managing milking.Specific Aim 1. Determine the effect of udder fill on milking time and milk yield.Specific Aim 2. Determine the main and interactive effects of udder fill and milking frequency on milking time, and milk yield.Specific Aim 3. Determine the underlying physiological and cellular mechanisms that account for milk yield suppression in response to changes in milking frequency and degree of udder evacuation.Specific Aim 4. Determine changes in teat end hyperkeratosis, teat barrel congestion, teat end congestion, and teat canal keratin levels, associated with different milking management strategies.
Project Methods
This project is a continuation of Hatch project 1006518-Experiment 1: Twelve healthy, multiparous cows will be enrolled in this experiment, which will be conducted at the UW Dairy Cattle Center. Assignment of the treatment and control half-udders shall be on an alternating basis as cows are enrolled. This will result in an N=12 treatment (20% of residual milk left behind) and N=12 control (0% residual milk left behind) half-udders. Any quarter treatments for mastitis shall remove the cow and all quarters from the study as will treatments for systemic illness. The take-off/residual milk settings for the treatment quarters shall be set based on previous individual milk yield information (specific aim 1). Cows will be enrolled on day 5 in milk after calving and will remain on study until day 47 in milk (resulting in a 42 d experiment) and milked 2x daily for the duration of the experiment. Hence, it will take about one month to enroll the required cows based on typical monthly calving records for the UW herd. The take-off settings/residual milk for each treatment half-udder shall then be adjusted on a weekly basis to take into account changes in overall milk production as days in milk increases. It is anticipated that the treatment half-udder will result in a 10% decrease in daily milk yield relative to the control half throughout the 42-day experimental period for each enrolled cow. Throughout the trial period enrolled cows shall be milked with a quarter milking device and half-udder milk yield will be recorded.Experiment 2: Individual cow enrollment into Experiment 2 will be as described for Experiment 1 (day 5 in milk through day 47 in milk, for a total of 42 days) although the number of cows enrolled will be higher than for Experiment 1. Experiment 2 will commence after the completion of Experiment 1. The protocol devised in Experiment 1 for residual milk settings will determine residual milk settings for treatment half udders. Again, throughout the trial period enrolled cows shall be milked with a quarter milking device. Healthy, multiparous cows (balanced for parity) will be enrolled and assigned randomly to a 2X milking group or a 3X milking group with equal numbers recruited into each group. Treatment and control half udders shall be assigned to each cow irrespective of milking frequency. The study design is a 2x2 factorial design (specific aim 2). Cows will be enrolled on day 5 in milk through day 47 in milk (a total of 42 days on experiment). Twenty-two multiparous cows (balanced for parity) will be enrolled on the study, and randomly assigned to 2x daily milking (N=11) or 3x daily milking (N=11). Additionally, half-udders on each cow will be assigned to a 20% increase in residual milk (treatment; N=22) or will be completely evacuated of milk (control; N=22). Half-udder milk yield will be recorded daily as described in experiment 1.Experiment 3: The purpose of this experiment is to examine the physiological processes underlying increasing residual milk, as well as the interaction between increasing residual milk and milking frequency. To this end in experiment 1, quarter milk samples will be taken weekly at the first milking of the specified days and will be analyzed for overall milk composition (fat, lactose, protein; AgSource) and somatic cell count (Milk Quality Laboratory). Additionally, we will measure milk sodium and potassium content (by Atomic Absorption) to assess alveolar cellpermeability in response to alterations associated with undermilking (14). An increase in sodium/potassium ratio in the milk isan indicator of mammary epithelial cell permeability (14). Blood samples (coccygeal vein) will be taken weekly immediately aftermilk sampling. Blood samples will be assessed for growth hormone (radioimmunoassay) and prolactin (radioimmunoassay) inorder to assess the endocrine status of the cow at the time of milking to ensure that animals are responding to treatmentsimplemented similarly.In order to determine the effects of residual milk and the interactions with milking frequency, we will collect samples duringexperiment 2. On days 0, 7, 14, 21, 28, 35 and 42 after enrollment, blood samples will be collected from the coccygeal veinand milk samples will be collected from each half-udder during the first milking of the specified day. Blood samples will beanalyzed for prolactin (RIA), growth hormone (RIA) and serotonin (ELISA). Milk samples will be analyzed for overall milkcomposition (fat, lactose, protein; AgSource), somatic cell count (Milk Quality Laboratory) as well as sodium and potassiumcontent (Atomic Absorption) to assess alveolar cell permeability in response to alterations associated with undermilking (14).Six cows from each of the 2X and 3X groups will biopsied (half-udder) on day 0 and day 42, resulting in a N=6 per treatmentdescribed in Figure 1. Mammary tissue for histological staining will be placed in 4% paraformaldehyle for 24 hr at 4°C and thenmoved to 70% ethanol until taken to pathology at RARC. Paraffin embedded tissues will be sectioned and stained withhematolxylin and eosin to assess alveolar structure, integrity, size and number in response to undermilking. Mammary tissuewill also be frozen immediately in liquid nitrogen for the purpose of mRNA extraction (TriReagent) and converted to cDNA usingiScript (Bio-Rad). cDNA samples will be sent to the UW Biotechnology center for Microarray Analysis, and data analysis will beconducted at the UW Biotechnology center. Genes that result in significant changes from the microarray analysis will then beanalyzed using real-time quantitative PCR (BioRad CFX 96) for confirmation of results. Mammary tissue will also be analyzedfor total serotonin content (Beckman Coulter; ELISA). Additionally quarter milk samples will be taken weekly at the first milkingof the specified days (days 0, 7, 14, 21, 28, 35 and 42) and will be analyzed for overall milk composition (fat, lactose, protein;AgSource) and somatic cell count (Milk Quality Laboratory). Additionally, we will measure milk sodium and potassium content(by Atomic Absorption) to assess alveolar cell permeability in response to alterations associated with undermilking (14). Anincrease in sodium/potassium ratio in the milk is an indicator of mammary epithelial cell permeability (14). Blood samples(coccygeal vein) will be taken weekly immediately after milk sampling. Blood samples will be assessed for growth hormone(radioimmunoassay) and prolactin (radioimmunoassay) in order to assess the endocrine status of the cow at the time of milkingto ensure that animals are responding to treatments implemented similarly.Experiment 4: The purpose of this experiment is to examine the effects of different milking strategies on teat health. To this end during experiment 1 and experiment 2, on days 0, 7, 14, 21, 28, 35 and 42, cows will undergo teat assessment (on all 4 teats) to determine teat hyperkeratosis, color and barrel scores according to the system as described by Neijenhuis et al (22). In addition to this scoring, teat canal keratin will be harvested utilizing the system described by Bright et al (21) to estimate keratin turnover and production in treatment and control quarter teat ends. These observations will then be analyzed to determine how treatment conditions might affect teat tissue stress during the milking process.