L'impacte de la xolla i dels tractaments hormonals (melatonina o cabergolina) durant la lactació en ovelles lleteres
- Autores: Abdelaali El Hadi
- Directores de la Tesis: Gerardo Caja López (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2020
- Idioma: español
- Tribunal Calificador de la Tesis: José Alfonso Abecia Martínez (presid.), Nemesio Fernández Martínez (secret.), Lorenzo Enrique Hernández Castellano (voc.)
- Programa de doctorado: Programa de Doctorado en Producción Animal por la Universidad Autónoma de Barcelona
- Materias:
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- Resumen
Three experiments were carried out in order to evaluate the lactational effects of shearing or treating with hormones (melatonin or cabergoline) in 2 breeds of dairy ewes (Lacaune, LC; Manchega, MN). In Exp. 1, a total of 48 ewes in mid-lactation were used under mild-winter conditions. Ewes were allocated in 8 balanced groups to which the experimental treatments (control unshorn, CO; shorn, SH) were applied. Responses to shearing varied according to breed, the rectal temperature after shearing only decreasing in MN ewes (‒0.36ºC). Feed intake increased 5% in the LC-SH, when compared to LC-CO, but did not vary in MN ewes. Milk yield of LC-SH ewes was 10% greater than LC-CO, but no differences were detected in MN ewes. No effects in milk composition, nor on milk fatty acid profile, were observed in either breed, but LC-SH yielded 9% more milk protein than LC-CO ewes. Moreover, no effects were detected in on plasmatic glucose, NEFA, cortisol and insulin, as well as in body reserves of either breed.
In Exp. 2, a total of 72 dairy ewes in early-lactation under autumn conditions were penned indoors in 12 balanced groups. Treatments were: Control (CO), that did not receive any treatment, and Melatonin (MEL), that received 1 implant (18 mg/ewe) s.c. in the ear base. No MEL effects were detected on feed intake, milk yield and milk composition in either breed. MEL values in plasma showed a significant increase in the MEL-treated ewes of both breeds, but PRL in plasma only decreased in the MN ewes. No MEL effects were detected in plasmatic IGF-I and body reserves values of either breed throughout the experiment.
In Exp. 3, a total of 30 ewes in late-lactation and managed as a single flock under spring conditions, were used. Ewes were allocated in 3 groups to which the treatment were assigned. Treatments consisted of a single i.m. injection of cabergoline, a dopamine antagonist, at different doses per ewe: low (L, 0.56 mg), high (H, 1.12 mg) and control (CO, 1 mL saline). No local reaction in the injection site was detected but milk yield fell rapidly after treatment in both breeds (MN vs. LC, ‒54% vs. ‒27%) and milk fat and protein contents increased similarly in both breeds and at both cabergoline doses (23%, on average), when compared to CO ewes. PRL decreased dramatically in the cabergoline treated ewes, when compared to CO ewes. Nevertheless, on d 14 of treatment, PRL values rebounded transitorily, being 58% greater in the cabergoline treated than in CO ewes. Udder volume was similar for the cabergoline treated ewes, but both values were lower than those of CO ewes as a result of mammary involution.
In conclusion, shearing dairy ewes during lactation under mild-winter conditions, is a suitable management option that may increase feed intake and milk production, without deleterious effects on milk composition. The use of exogenous MEL implants in early-lactation and under autumn conditions has no effects on the lactational performances of dairy sheep in early lactation. Finally, cabergoline injection may be a useful tool to facilitate the decrease of milk production by inhibiting PRL secretion of dairy ewes at dry-off.
