Effects of teat end score on milk yield and quality in Holstein-Friesian cows

Introduction - Hyperkeratosis develops in the teat end (TE) because of degeneration of the keratin layer. The functional errors and higher vacuum of the milking machine, increased milk yield, prolongation of milking, dirtiness of the animals and insufficient bedding are the reasons of the formation of hyperkeratosis on the TE. The lesions at the teats are risk for mastitis and there is a positive correlation between somatic cell count (SCC) and TE hyperkeratosis. Aim - The aim of this study was to determine hyperkeratosis level on the TE of Holstein-Friesian (HF) cows by using a scoring system and also the effect of TE score on the quality of milk. In addition, the effects of SCC on milk yield, fat content (FC, %) and non-fat dry matter content (NFDMC, %) and the loss of milk yield due to SCC were determined. Materials and methods - A HF herd in Aydin, Turkey, was visited monthly for nine months to score the TE for hyperkeratosis level, and to take milk samples for the determination of FC, NFDMC, and SCC. The level of hyperkeratosis on the TE were scored from 1 to 4. Correlation coefficients among the traits were also determined. Results and Discussion - The means of TE score, Log10SCC, morning (MMY) and evening (EMY) milk yield, FC and NFDMC were 2.45 +/- 0.069, 5.66 +/- 0.045, 10.88 +/- 0.289 kg, 10.88 +/- 0.283 kg, 3.96 +/- 0.070% and 10.38 +/- 0.043%, respectively. Among the parities, the lowest mean (2.02 +/- 0.102) for TE score was determined in the first lactating cows, and the cows that calved in the summer (2.37 +/- 0.090) had lower TE score than those that calved in winter (3.04 +/- 0.109) (P <0.05). Log10SCC averages were higher in cows with higher TE score and higher parities (4th and 5th+). Log10SCC means of the cows whose TE score are 4 (6.26 +/- 0.094) and 3 (5.86 +/- 0.093) are higher than those with 1 (5.48 +/- 0.118) and 2 (5.51 +/- 0.078) scores (P <0.05). High SCC in milk resulted in 1.73 kg (14.32%) decrease in MMY (P<0.05) and 3.24 kg (13.41%) in daily milk yield. Correlation coefficient between TE score and Log10SCC was positive and moderate (r=0.41). Conclusion - In conclusion, the TE hyperkeratosis caused by insufficient maintenance-management and barn and milking management conditions on the farm, leads to a significant increase in SCC and decrease in FC (24.4%). A significant milk yield loss were also determined in the daily milk yield due to high SCC. Scoring the TE of dairy cows gives an idea about the operating conditions on the dairy cattle farm and significant losses in milk yield and milk constituents could be prevented by decreasing SCC through improving TE score.