Article

Factors associated with milk urea concentrations in Ontario dairy cows.

Department of Clinical and Population Sciences, University of Minnesota, St. Paul 55108, USA.
Journal of Dairy Science (Impact Factor: 2.55). 02/2001; 84(1):107-14. DOI: 10.3168/jds.S0022-0302(01)74458-X
Source: PubMed

ABSTRACT All DHI test-day data, including milk urea concentrations measured by infrared test method, were collected from 60 commercial Ontario Holstein dairy herds for a 13-mo period between December 1, 1995, and December 31, 1996. The objectives of this study were to describe the relationships between milk urea concentrations and seasonal factors, sampling factors, cow factors, and test-day production of milk, milk fat, protein, and SCC. Milk urea was associated with month and season; concentrations were the highest from July to September. Milk urea was generally lower in first-lactation cows. Milk urea was lowest during the first 60 d of lactation, higher between 60 and 150 d in milk, and lower after approximately 150 d in milk. In herds on an alternating a.m./p.m. test schedule, milk urea was generally lower in a.m. than p.m. tests. There was a positive nonlinear association between milk urea and milk yield, fat-corrected milk, and energy-corrected milk. There was a negative nonlinear association between milk urea and both milk fat and total protein percentages. While there was a negative nonlinear association between cow-level milk urea and linear score, the study found no association between herd average milk urea and herd average linear score. The associations described in this study using Dairy Herd Improvement test-day samples from commercial dairy herds and using an infrared test to measure milk urea are generally consistent with results from studies that used individual animals housed under research conditions and chemical methods to measure milk urea. Because milk urea varies by season, month, parity group, stage of lactation, and sample type, studies should control for these variables. Because of the apparent effect of a.m. and p.m. sampling on urea concentration, producers on an alternating a.m./p.m. test schedule should test routinely to establish a herd pattern for urea and submit the same sampling time consistently or both.

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    • "The transformed-SCC was not different with respect to MUN (P>0.05). This is contrary to reports by Godden et al. (2001), Hojman et al. (2004), and Rajala-Schultz and Saville (2003), who found a highly significant negative relationship between MUN and SCC. On the contrary, Pedraza et al. (2006) reported that MUN concentration increased significantly with increasing SCC values. "
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    ABSTRACT: The objective of this study was to evaluate lactose and milk urea nitrogen (MUN) in milk from Holstein cows and their relationship with days in milk (DIM), milk yield, milk fat, milk protein, and somatic cell count (SCC). A total of 1,034 records corresponding to morning and afternoon milkings of 148 Holstein cows were used. Records were taken from 16 herds located in the Northern and Eastern dairy regions of Antioquia (Colombia). The curves were fitted using a generalized additive mixed model with smoothed estimates to find the best smoothing intensity factors involved in MUN and lactose concentration. Regarding MUN, the contemporary group effect was highly significant, but the parity effect was not significant. The DIM, lactose and milk fat smoothed covariates were highly significant, while milk yield and fat and SCC showed no statistical difference. Regarding lactose content, the contemporary group effect was highly significant, while the parity effect was not significant. Days in milk, MUN, milk fat, milk protein, and afternoon-milking SCC smoothed covariates were highly significant, while milk yield and morning-milking SCC were not significant. Lactose and milk urea nitrogen concentrations are affected by various factors throughout lactation, mainly by days in milk.
    Revista Brasileira de Zootecnia 09/2014; 43(9):479-484. DOI:10.1590/S1516-35982014000900004
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    • "In accordance with other studies ( Godden et al . , 2001 ; Arunvipas et al . , 2003 ; Nyman et al . , 2009 ) , we found a negative association with milk urea concen - tration and SCC . To our knowledge , the association between bovine milk urea concentration and LDH , NAGase , or AP activities in milk is scarcely described ."
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    ABSTRACT: The objective of this study was to investigate if and how cow factors and intramammary infection (IMI) are associated with 4 different udder-health indicators in dairy cows as a first step in investigating whether the diagnostic performance of these indicators can be improved. The investigated indicators were somatic cell count (SCC), lactate dehydrogenase (LDH), N-acetyl-β-d-glucosaminidase (NAGase), and alkaline phosphatase (AP) measured in milk. In this cross-sectional study, approximately 1,000 cows from 25 dairy herds were sampled for bacteriology (quarter milk samples) during 3 consecutive days: the day before test milking, at the day of test milking, and at the day after test milking. The whole-udder test milking sample was analyzed for milk composition, SCC, LDH, NAGase, and AP. Cow data (parity, breed, milk yield, percentage of milk fat and protein, milk urea concentration, and days in milk from the sampled test milking) were collected from the Swedish milk-recording scheme. Of the sampled cows 485 were considered IMI negative and were used in multivariable mixed-effect linear regression models to investigate associations between cow factors and the udder-health indicators. A second modeling including all cows, both IMI negative and IMI positive (256 cows), was also performed. The results showed that all udder-health indicators were affected by cow factors but that different cow factors were associated with different indicators. Intramammary-infection status was significantly associated with all udder-health indicators except AP. Parity and milk urea concentration were the only cow factors associated with all indicators in all models. The significant cow factors explained 23% of the variation in SCC and >30% of the variation in LDH, NAGase, and AP in IMI-negative cows, showing that LDH, NAGase, and AP are more affected than SCC by cow factors. The IMI status explained 23% of the variation in SCC in the model with all cows but only 7% of the variation in LDH and 2% of the variation in NAGase, indicating that SCC has the best potential as a diagnostic tool in finding cows with IMI. However, further studies are needed to investigate whether the diagnostic properties of these udder-health indicators will improve with adjustment according to their associations with different cow factors when used as a diagnostic tool for finding cows with IMI.
    Journal of Dairy Science 07/2014; 97(9). DOI:10.3168/jds.2013-7885
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    • "Possible reasons for this variation include differing grazing habits or differences in the rate of urea excretion by the kidneys (Schoeman 1989). Other known sources of variation in BUN concentration are dietary protein and energy levels, hydration status at time of sampling, time of sample collection , age of the animal, dry matter intake and the particular method of analysis (Godden et al. 2001; Kauffman and St- Pierre 2001; Rajala-Schultz and Saville 2003; Hossein-Zadeh and Ardalan 2011). Mitchell et al. (2005) demonstrated that variation in MUN is genetically determined and has a heritability of 0.15. "
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    ABSTRACT: This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n = 369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or palpation was performed 4-8 weeks after a 3-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP, respectively. After stratifying for herd and adjusting for age, heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P = 0.011). In the herd with the highest estimated nitrogen intake (n = 143), heifers with relatively higher BUN were less likely to become pregnant (P = 0.013) and if they did, it was only later during the breeding season (P = 0.017), after adjusting for body mass. These associations were not present in the herd (n = 106) with the lowest estimated nitrogen intake (P > 0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.
    Tropical Animal Health and Production 05/2014; 46(6). DOI:10.1007/s11250-014-0608-3
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