| Multiple experiments were conducted to evaluate sheep as a potential model to evaluate effects of a human antidepressant, fluoxetine (FLX), on lactation and neonatal growth. We hypothesized that FLX would depress lactation and limit neonatal growth. Experiment one was a lactation study with treatments of 0 or 40 mg FLX given approximately 21 d prepartum. Experiment two was treatments of 0 or 80 mg FLX 21 d prepartum and continued 21 d after lambing. We observed that milk yields over the first 5 or 9 days of lactation were similar (P > 0.10) between control and FLX-treated ewes in year 1 and 2, respectively. Lamb birth weight and ADG was unchanged ( P > 0.10) in both years. In the second year, lambs were followed throughout development and blood samples were collected. The resulting serum samples were evaluated for IGF-I, triiodothyronine (T3), and prolactin (PRL). Lambs exposed to FLX had lower (P < 0.05) concentrations of IGF-I, T3, and PRL compared to controls. Ewe lambs from the second year were kept for subsequent evaluation and age at puberty and pregnancy rates were determined. Ewe lambs produced by control and FLX-exposed ewes were similar (P > 0.10) in age at puberty and pregnancy rates. We also attempted to end lactation at weaning with 0, 40, or 80 mg FLX (year 1) or 0, 80, or 160 mg (year 2). We observed in year 1 that milk yield was similar (P > 0.10) between control and FLX-treated ewes, however in year 2, as dosage of FLX increased, milk yield was declined equivocally, (linear; P < 0.05). We observed a quadratic effect of treatment (P < 0.05) in year 1, as the 80 mg FLX dose resulted in the greatest serum lactose concentration. In year 2, serum lactose concentrations were similar (P > 0.10) across treatments. We concluded that using an oral dose of FLX is not a viable option and additional research should be conducted to determine a more direct method to apply FLX for use in livestock applications. |
