Under tropical conditions, seasonal variations may also influence the sperm characteristics of Bos indicus. The objective was to evaluate the motility of thawed sperm of bulls from the Peruvian tropics throughout the year. Over 24 months, 129 ejaculates were evaluated based on semen quality and subjected to slow horizontal freezing in 0.5 mL straws. After thawing, the individual, seasonal period, and season effect on motility and kinetic parameters were analyzed using a Sperm Class Analyzer^® (Microptic S.L.U., Barcelona, Spain). There was an individual effect on volume, motility, fresh concentration, and kinetic parameters when thawed. In the dry period, higher straight-line velocity (VSL) (p < 0.05) and beat cross frequency (BCF) were found than in the rainy period (p < 0.01). In summer and autumn, there was greater total motility, fast, circular routes, curvilinear velocity, average path velocity, VSL, amplitude of lateral displacement of the head, and BCF (p < 0.01). Greater volume and motility were found in winter and spring, but in summer and autumn, greater speed and vigor of movement were obtained in thawed sperm. The variation in annual climate patterns influences the seminal quality of bulls, and its effect needs to be assessed to propose adaptation strategies to climate change in tropical areas.

The performance of estrus synchronization protocols may be influenced by stressful environmental conditions, even in tropically adapted cattle. This study evaluated the efficacy of two synchronization protocols for fixed-time artificial insemination (FTAI) in crossbred Gyr dairy cows and their relationship with heat stress under Peruvian tropical conditions. Multiparous lactating cows under semi-intensive systems were synchronized and divided into two groups: the conventional protocol (PC9) and the prolonged proestrus protocol (J-Synch6). Estrus manifestation, pregnancy rate, and their association with the temperature–humidity index (THI) were analyzed across seven phases of the FTAI program (73 days). In PC9 cows, no significant effect of the number of hours in each heat stress category according to THI was found. Conversely, in J-Synch6 cows, more hours in Category 0 (THI < 72) during Phases 1 to 4 (follicular emergence to preovulatory follicle) had a positive effect on the estrus manifestation, whereas in Phase 3 (follicular growth), higher exposure to Category 3 (THI ≥ 83) had a negative effect on estrus manifestation. Both protocols demonstrated similar estrus and pregnancy rates, although heat stress affected estrus rates in J-Synch6, but not pregnancy. The choice of protocol should account for heat stress risks during specific periods of the year to maximize success.

Tropical livestock production relies on the availability of adapted forages capable of sustaining productivity under limiting soil conditions. This study evaluated the performance of three Urochloa hybrids grown in low-fertility soils of a seasonally dry tropical forest in the Peruvian Amazon. The experiment was conducted at the Estación Experimental Agraria El Porvenir–INIA under a randomized complete block design with three replications and five consecutive harvests at 60-day intervals. Soil characteristics and Growth, yield, productive, and quality parameters were evaluated. Rotational harvesting improved soil properties, including organic matter and nutrient availability. During the initial harvests Cobra showed better growth and yield performance; however, Mavuno and Mulato II surpassed it at later stages, especially in fresh and dry matter yield. In the fourth and fifth harvests, Mavuno achieved the highest production (32.10 and 32.94 t ha ⁻¹ of fresh matter, and 7.65 and 7.18 t ha ⁻¹ of dry matter), followed by Mulato II (28.82 and 29.15 t ha ⁻¹ of fresh matter, and 6.73 and 6.70 t ha ⁻¹ of dry matter), both significantly better than Cobra (20.51 and 21.51 t ha ⁻¹ of fresh matter, and 5.00 and 5.16 t ha ⁻¹ of dry matter). Annual carrying capacity was highest for Mavuno (3.72 TLU ha ⁻¹ ⸱year ⁻¹ ), followed by Mulato II (3.41 TLU ha ⁻¹ ⸱year ⁻¹ ) and Cobra (2.97 TLU ha ⁻¹ ⸱year ⁻¹ ). The protein contents of Mavuno (9.61 g⸱kg ⁻¹ ) and Mulato II (9.54 g⸱kg ⁻¹ ) were significantly higher than that of Cobra (6.33 g⸱kg ⁻¹ ). Mavuno and Mulato II hybrids have proven to be promising forage alternatives for sustainable livestock systems in seasonally dry tropical conditions.