Tannins are commonly defined as water-soluble polyphenolic compounds ranging in a molecular weight from 500 to 3000 Daltons. Muller-Harvey (2006) reviewed the effects of different types of tannins on animal nutrition and health. Results indicates that tannins form a highly diverse group of natural products with promising nutritional, veterinary, and environmental effects. Studies feeding a mix of different tannins on lactating dairy cows milk production performance are limited. Recently, two studies at Wisconsin University (USA), feeding a mix of condensed and hydrolysable tannins were carried-out, dietary efficiency of nitrogen (N) utilization was significantly improved in both studies (Aguerre et al., 2015, 2016). The objective of this on-farm research was to evaluate the effect of a commercial mix of condensed and hydrolysable tannins feed additive (Silvafeed® ByPro) to lactating dairy cows milk production performance, milk yield and milk composition.
Material and methods
A high scale dairy farm with two dairy units (about 3000 milking cows each) with similar management and diets was used to evaluate the effect of Silvafeed® ByPro. All lactating cows in one dairy unit received Silvafeed® ByPro, the other unit was Control. Cows were daily supplemented with Silvafeed® ByPro mixed in the total ration at 0.3% of estimated dry matter intake (DMI) per cow. The DMI was weekly estimated by the difference between Total Mixed Ration offered and refusal divided by the total number of cows, and adjusted by ingredients' dry matter (DM) content. Cows were categorized per days in milk (DIM): 0 to 30, 31 to 120, 121 to 365, and over 365 DIM. Variables analyzed were: milk yield/cow, milk fat and protein contents. At time 0, milk yield and composition on all lactating cows between the two dairy units were evaluated (initial). After 4 weeks of mix-tannins supplementation all lactating cows in both dairy units were evaluated to determine the effects of Silvafeed® ByPro (final). The observation units were milking cows. A mixed linear model was used to evaluate treatment effect, which included the following factors and their interactions: supplementation (Control - Supplemented); evaluation time (initial – final), lactation number: (1-6) and days in milk (categorized as 0 to 30, 31 to 120, 121 to 365, and over 365 DIM). Effect of supplementation on each variable was estimated as a contrast between initial and final adjusted means. Contrast = Silvafeed® ByPro (final - initial) - Control (final - initial). Models were adjusted using InfoStat statistical software.
Results and discussion
Because the restrictions of the assay, Silvafeed® ByPro and Control effects may be confounded with dairy units. This drawback of on-farm research was taken in account on the modeling approach. Verifying that all relevant variables at the beginning of the assay, before any treatment was applied, were not different between dairy units. Likewise, the treatments effects were evaluated as the change in mean response between the end and beginning of the assay (final and initial milk tests). Estimated DMI and milk yield per cow were similar in both dairy farms averaging 25.5 kg DMI/cow and more than 36 kg milk/cow per day. Dietary nutrient contents in both dairies were: 17.5%CP (10.7%RDP), 27.5%NDF, 18.5%ADF, 5.5%fat, and 8.6%ash. The main difference between lactating dairy cows’ diet in both dairy units was the dietary supplied in the TMR of a mix of condensed and hydrolysable tannins feed additive Silvafeed® ByPro. Proportion of cows in DIM were: 0-30 DIM 10%; more than 365 DIM 8%; and 31 to 120, and 121 to 365 DIM represented more than 80% of total cows. Milk yield, from 0 to 365 DIM was increased (P<0.01) on cows supplemented with Silvafeed® ByPro (+2.3±0.33 L milk/cow per d) when compared to Control cows with no effect on milk fat and protein contents. Milk yield in early lactation cows (0-30 DIM) was not different between Silvafeed® ByPro and Control. The Standard Errors of the Contrasts (SEC) for fat, protein and lactose milk contents in cows between 0 and 30 DIM were high, more than 2.2 times when compared to lactating cows with more than 30 DIM. Significant responses in Silvafeed® ByPro dairy unit on milk fat and protein content from 31-120 and 121-365 DIM were observed: +0.27±0.065% fat, +0.21±0.032% protein (P<0.01), and +0.17±0.069% fat, +0.11±0.034% protein (P<0.05), respectively. Results are discussed considering the ability of tannins to bind proteins, this process has been referred to as “ruminal escape protein”. Also, the effect of tannins to modulate rumen microbiota changes, improving nutrient utilization efficiency (nitrogen and energy), and the University of Wisconsin studies. Aguerre et al. (2015, 2016) results were very consistent in both studies, increasing true protein content in milk, with a trend to reduce non-protein N in milk, and a significant reduction in N excretion in the manure.
Supplementing a mix of condensed and hydrolysable tannins, to lactating dairy cows in a high scale dairy farm increased lactation performance, and milk fat and protein contents on cows from 30 to 365 DIM. The information contained in this communication is indicative and/or exploratory and should be validated through the execution of an essay adequate to the stated objectives.