Study of the relationship between the presence of milky cysts, udder imbalances, udder morphological traits and somatic cell counts

Abstract

In France, among the goat breeders on genetic improvement programs, udder scores are recorded annually on primiparous does. New phenotypes include imbalances of the udder (166,929 records since 2016) and milky cysts (100,079 records since 2018). The objectives of this study were to (1) describe the frequency and intensity of these new phenotypes, (2) evaluate their associations with udder conformation traits, (3) determine their impact on milk somatic cell counts (SCC) and dairy production performance. Udder imbalances were defined using a 4-level grid according to the height difference between udder halves. Milky cysts were described as either isolated or numerous. The data were compared with information on mammary conformation (9 traits, each being evaluated on a scale of 1 to 9 with the exception of the length of the teat), SCC (geometric mean calculated over 250 days of lactation) and milk production performance obtained over a reference period of 250 days. In 90.8% (of the cases, udder imbalances were absent or very small, with the most pronounced imbalances (≥10 cm difference between glands) accounting present in only 1.1% of goats. The greatest deficiencies were associated with low udders and poorly attached udders (fore and rear attachments). SCC increased with the degree of imbalance, from 589,000 to 1349,000 cel/ml between no or slight imbalance and an imbalance of ≥10 cm or more. Milky cysts were recorded in 1.9% of the scored udders. Udders with cysts were characterized by poor fore attachments. Likely of traumatic origin, milky cysts were nevertheless associated with increased SCC: 646,000 vs. 912,000 cells/ml for no cysts and numerous cysts, respectively. The hypothesis of a deterioration in milking conditions for the most severe cases remains to be assessed. Finally, impacts on milk production or protein and fat contents reached - 14.1%, - 9.7% and −12.9% respectively for unbalanced udders compared to balanced ones. They were not noticeable for the presence of cysts.