Torres Astacio, Daianna N.

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    Efecto de la disponibilidad de pasto en diferentes épocas del año sobre el perfil de la leche producida por el ganado lechero en Puerto Rico
    (2024-07-09) Torres Astacio, Daianna N.; Ruiz López, Teodoro M.; College of Agricultural Sciences; Fernández Van Cleve, John A.; Santana Nieves, Carmen S.; Department of Animal Science; Bonet Olivencia, Samuel A.
    In winter (January to March) and summer (July to September), the effect of forage availability on production and composition in terms of fat, protein, and lactose in milk was evaluated. To this end, a study was carried out on two dairy farms, Lajas (rotational grazing) and San Sebastián (intensive rotational grazing). On each farm, forage was sampled in winter (March) and summer (September); and concentrate (supplemented to rotational grazing), only once. Samples were analyzed for chemical composition and a yield estimate was obtained using the disk method (Santillan et al., 1979). The Lajas concentrate was higher in NDF and ADF; and that of San Sebastián had more protein and energy. In winter, CP, TDN, NEL, Ca, and K were lower in the forage from Lajas than in that from San Sebastián. In summer, CP, ADF, NEL, TDN, Ca, and P were lower in the forage from San Sebastián than in that from Lajas. On both farms, daily DM yield was higher in summer; and, it was greater in San Sebastián than in Lajas, in both periods. However, the availability of DM per cow per cycle and per cow per day was greater in Lajas, in both seasons; and, on both farms, in summer. The climate, the quality of the forage and concentrate, as well as the yield by farm and season, influenced the milk production and its quality. Dairy protein was lower in summer than in winter on both farms. Milk production and lactose were lower in San Sebastián than in Lajas; while, the opposite case occurred for the fat and protein variables. There were interactions between farm and season on fat, protein, and lactose (P < 0.05). Fat percentage was lower in summer on the San Sebastián farm; and lower in winter, on the Lajas farm (P < 0.0002). Protein was higher in winter on both farms (P < 0.0333). Lactose increased, as fat and protein decreased (P < 0.0001). A change in climate and season will not necessarily result in significant differences in milk, fat, and lactose production.