Article Similarities and Differences
The three articles reviewed give different approaches to optimal udder preparation practices before and after milking to obtain high-quality milk. The papers involve primary studies investigating teat disinfection practices that affect iodine levels in milk. In all three studies, the variable measured in milk iodine content following pre- and post-milking teat preparation and dietary iodine consumption. Two of the articles involve two independent variables – dietary iodine and teat disinfection (Castro, Berthiaume, Robichaud, & Lacasse, 2012; Śliwiński, Brzóska, Węglarzy, Szybiński, & Kłopotek, 2015).
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In contrast, in Galton, Petersson, Merrill, Bandler, and Shuster’s (1984) study, the only independent variable considered is under preparation. The three articles make a similar finding, which is that iodine spraying, 1% iodophor treats, and iodine-rich salt licks raise iodine levels in milk. Further, pre-dipping of teats in iodine-based disinfectants (1% iodophor) followed by drying with a paper towel was found to decrease iodine levels in milk.
The articles differ regarding study aims, design, sample size, and procedures Castro et al. (2012) sought to assess how iodine intake and teat-disinfection practices (dipping) affect iodine levels in milk. In contrast, Galton et al. (1984) compared different teat preparation methods – water hose, soaked towel, and iodophor treat dip – concerning their effects on the microbial count and iodine concentration in milk. Śliwiński et al. (2015) investigated the levels of iodine in cow’s milk and blood after iodine intake and teat disinfection.
Castro et al. (2012) use a 3 × 3 factorial design for experiment 1 (n=63) and experimental design (4 treatments) in experiment 2 (n=32) and a total sample size of 95 lactating cows. Galton et al. (1984) employed a generalized randomized block design with a sample of 276 cows assigned to six experiments. In their part, Śliwiński et al. (2015) used a three-group experimental design involving experiment 1 (n=60) and experiment 2 (n=28). Unlike in the other two studies, Galton et al. (1984) measured bacterial counts (Staphylococcus spp.) after each teat disinfection method. Further, they also investigated sediment in milk after disinfection. Of the three articles, only Śliwiński et al.’s (2015) study investigates plasma iodine content after teat disinfection.
The first study (Castro et al., 2012) performed two experiments to determine the influence of dietary iodine and teat-dipping on the concentration of iodine in cows’ milk. In the first experiment, the study randomly assigned 63 cows in their mid-lactating periods to 3 by 3 factorial design. The main effects were dietary iodine at 0.3, 0.6, and 0.9 mg/kg while the minor effects are teat-dipping post-managements with chlorhexidine, 1% iodine dip, and 1% iodine spray. In the second experiment, the study randomly assigned 32 cows in their mid-lactating periods to four treatment groups, namely, no pre-dip, 0.5% iodine pre-dip with a complete cleaning, 1% iodine pre-dip with complete cleaning, and 0.5% iodine pre-dip with incomplete cleaning.
In the second article, Galton et al. (1984) undertook series of experiments to determine the effects of different methods of udder preparations on the population of bacteria, amount of sediments, and concentration of iodine. In the first experiment, 39 cows were randomly assigned to 13 groups formed from the combination of udder preparation methods relating to the use of water, wet towel, and sanitizer with or without drying.
The second experiment added pre- and post-milking disinfectant dip to selected groups in experiment one. The third experiment assigned seven cows to udder preparations that involve the use of sanitizer, disinfectant, and forest ripe. To determine sediments, 39 cows were assigned to 13 groups with different combinations of udder preparations in the fourth experiment. In the fifth experiment, the study determined the effect of post-milking iodine teat-dip among 70 cows assigned to four groups, namely, no treatment, pre-milking teat-dip, pre- and post-milking teat-dip, and pre-milking teat-dip without drying.
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In the last experiment to determine the effect of post-milking teat-dip on iodine residue, the study assigned 76 cows to four groups of no treatment, 0.5% iodine pre- and post-milking teat-dip, 1% iodine post-milking teat-dip, and 1% iodine pre- and post-milking teat-dip.
The third article performed two experiments to determine the influence of teat dipping and iodized salts on the concentration of iodine in blood plasma and milk (Sliwinki et al., 2015). In the first experiment, the study assigned 66 cows in their mid-lactating periods to three groups under the dietary intake of zero iodine, 150 mg/kg, and 300 mg/kg. In the second experiment, the experiment assigned 28 cows to two groups, the control group under the chorine teat dip and the experimental group under iodine solution.
A comparison of the methods shows that they are not similar regarding the number of sampled cows, experimental period, dietary intake, and methods of udder preparations. Castro et al. (2012) sampled 63 cows, performed the experiment in about 15 days, fed cows with 0.3, 0.6, and 0.9 mg/kg of iodine, and prepared udder with pre-dip iodine. Galton et al. (1984) sampled a variable number of cows ranging from 60 to 7, undertook the experiment in about 23 days, did not feed cows with iodine, and used 13 combinations of udder preparation methods.
Sliwinki et al. (2015) sampled 60 and 28 cows, performed the experiment in 90 days, fed cows with 0, 150, and 300 mg/kg of iodine, and washed udder with iodine and chlorine solutions. To address the issue of dissimilarity in methodology, future study should consider an adequate sample of cows, extended experiment period, standard dietary intake of iodine, and conventional methods of udder preparation.
Results and Research Question Comparison
The analysis and comparison of results from the three papers show that they do support their respective research questions. The results of Castro et al. (2013) support the research question for they indicate that iodine concentration in milk increased with diet as 0.9 mg/kg resulted in 341 µg/kg of iodine in milk. Moreover, the use of iodine teat dip and inappropriate udder preparation practices increased iodine concentration in milk from 164 to 252 µg/kg level.
The results of Galton et al. (1984) also do support the research question because they illustrate that pre- and post-milking teat dipping with a 1% iodine solution significantly increases the concentration of iodine solution by up to 84.2 µg/100ml (p<0.01). In their results, Sliwinki et al. (2015) supported their research question by stating that dietary intake does not influence plasma levels of iodine significantly, but teat dipping did increase the concentration of iodine in milk from by about 15 µg/L from 44 to 59.3 µg/L.
A comparison of results demonstrates that both dietary intakes of iodine and teat dipping increase the concentration of iodine in milk significantly. In this view, the results suggest a reduction of dietary intake of iodine and the adoption of appropriate teat dipping practices to reduce the residue of iodine, and consequently the concentration of iodine in milk.
Impacts of the Articles
The three articles’ findings that teat disinfection – through either teat dips or sprays – and dietary iodine affect milk iodine levels will impact pre- and post-milking teat disinfection practices. Castro et al.’s (2012) finding that milk iodine levels rise with increasing amounts of dietary iodine has implications for the production of cattle feeds and licks. Nutritional iodine should be within the recommended limits (<1mg/kg DM) for high-quality milk. Further, post-milking teat disinfection with iodine is only useful when it involves teat dips. The finding that iodine-based sprays increase milk iodine content implies that these sanitizers should be avoided during spraying.
Galton et al.’s (1984) article will impact udder cleaning and post- and pre-milking disinfectant practices aimed at reducing sediment and iodine levels in milk. Teat cleaning using water or pre-milking disinfectant dips (1% iodophor) and drying for <10s can help minimize iodine levels in milk and environmental bacteria causing udder infection or mastitis. Therefore, pre- and post-milking disinfectant teat dips should be followed by drying.
Besides, reduced sediment in dairy products can be achieved through adequate teat cleaning (Galton et al., 1984). Śliwiński et al.’s (2015) article have implications for iodine-based disinfectant use by farmers and cattle feed content. Increasing iodine levels in salt licks by 150-300mg I/kg results in “65 to 85 μg I/1000 mL” in the milk (Śliwiński et al., 2015, p. 249). This concomitant increase implies that the recommended iodine levels in milk can be attained by reducing iodine content in cattle feeds. Pre-milking teat dips should be iodine-free, as iodine-based sanitizers raise milk iodine levels by up to 35% (Śliwiński et al., 2015).
The overall conclusion made based on the results of the articles reviewed is that post-milking teat disinfection through dips results in elevated milk iodine levels. Similarly, giving cows iodine-based diets results in a concomitant increase of iodine in milk. Therefore, effective techniques in reducing iodine residues include post-milking teat treatment based on iodine-free disinfectants, reducing nutritional iodine levels, and teat drying after pre-milking dips.
Castro, S., Berthiaume, R., Robichaud, A., & Lacasse, P. (2012). Effects of iodine intake and teat-dipping practices on milk iodine concentrations in dairy cows. Journal of Dairy Science, 95(1), pp. 213-220. Web.
Galton, D., Petersson, L., Merrill, W., Bandler, D., & Shuster, D. (1984). Effects of premilking udder preparation on bacteria population, sediment, and iodine residue in milk. Journal of Dairy Science, 67(11), pp. 2580-2589. Web.
Sliwinki, B., Brzoska, F., Weglarzy, K., Klopotek, E. (2015). The effects of iodized salt licks and teat-dipping on the iodine content of cow’s milk and blood plasma. Endokrynologia Polska, 66(3), pp. 244-250. Web.