Body Condition Score and Milk Production on Conception Rate of Cows under a Small-Scale Dairy System

SIMPLE SUMMARY: Small-scale dairy farms are important because they generate jobs in rural areas and improve food security, income, and livelihood worldwide. On the other hand, high fertility is strongly associated with the profitability of dairy farms. Therefore, improving reproductive performance would increase milk production and farmers’ incomes. In the present study, we focus on the effect of body condition score (BCS) of Holstein cows at calving and when they are bred for the first time (after calving) on a key reproductive performance indicator: conception rate to first service. Additionally, we studied the association between BCS at calving and milk production, assuming that cows had a moderate genetic potential for milk production. Our results highlight the importance of BCS on the future reproductive performance and productivity of cows in a small-scale dairy system. These results are useful to implement management strategies in order to increase conception rate to first service and milk production in this type of dairy farm. ABSTRACT: Management and production characteristics impact conception rate to first service (CR1S) in small-scale dairy farms, but the impact of body condition score (BCS) and milk production levels on cows’ fertility is unknown. Our objective is to determine the effect of BCS and milk production on CR1S in small-scale dairy farms of western Mexico. Logistic regression models are used to determine the effect of BCS (at calving and first service), 60-d and 305-d milk production, protein and fat production, lactation number, and days at first service on CR1S. BCS at calving does not affect CR1S in cows with three or more lactations (39.5%; p > 0.1). However, first-lactation cows with BCS < 3.0 at calving and second lactation cows with BCS ≤ 2.5 at calving have higher CR1S (63.2 and 67.9%, respectively; p < 0.1). This result is perhaps due to reduced milk production, which leads to lower metabolic stress. BCS ≤ 2.5 at calving is associated (p < 0.05) with a reduced milk yield, explaining partially the observed higher CR1S in these groups. Cows with BCS ≤ 2.5 at first service in the higher quartile of 60-d milk production (≥ 28kg/day) show lower CR1S (23.9 and 51.1%, respectively; p < 0.01). In conclusion, BCS at calving and at first service, 60-d milk production, and lactation number are factors associated with CR1S.