Effects of melatonin implants on the rate of pseudopregnancy in high-yielding dairy goats

This study aimed to evaluate the effects of melatonin implants (MIs) on the rate of pseudopregnancy (PPG) in Saanen and Saanen X Alpine goats. During a 12-month period (2023/2024), all does with PPG (n = 49) were considered from five farms, with a 7.1 % (49/688) prevalence of PPG. Twenty percent of the non-PPG goats (79 pregnant and 62 non-pregnant does) were randomly selected. Mating occurred after previous MIs (n = 52), P4-based protocol (positive control; P4-P; n = 63), or natural estrus without previous treatment (NE, negative control; n = 75). The reproductive status was determined by uterine transabdominal ultrasonography, between Day 30 and Day 40 after removal of the bucks from the breeding groups. Multivariable logistic regression analysis showed that the estrus induction protocols and parity influenced the rate of PPG (P < 0.001). The MI group had approximately 15 times (Odds ratio = 0.07; P < 0.001) and 40 times (OR = 0.03; P < 0.001) lower likelihoods of developing PPG than the NE and P4-P groups, respectively. The P4-P group was twice as likely (OR = 2.6; P = 0.01) to have PPG than the NE group. Primiparous does (n = 37) were twice as likely (OR = 2.3; P = 0.05) to have PPG than multiparous does (n = 153). However, Pearson's correlation analysis showed a significant association (P < 0.01) between P4-P and primiparous does, and between MI and multiparous does. This association can partially justify the highest incidence of PPG in primiparous does. Our results show that MIs are advantageous in preventing PPG. Specific reproductive management strategies are required, particularly for primiparous does.