Higher feeding diets effects on age and liveweight gain at puberty in crossbred Nelore × Hereford heifers

This study was conducted to determine the age and liveweight at puberty of 120 crossbred beef heifers submitted to four diets to achieve predetermined weight gains (kg/day): 0.5 (G500; n?=?32), 0.75 (G750; n?=?32), 1.0 (G1000; n?=?29), and 1.25 (G1250; n?=?27). Animals were classified depending on their level of crossing between Nelore (N) and Hereford (H): 25%N-75%H, 37.5%N-63.5%H, 43.7%N-56.7%H, 50%N-50%H, and 75%N-25%H. Reproductive evaluation was performed at the beginning and at the end of the experimental period by ultrasonography and hormone analysis. The average age and liveweight at puberty were 388.0?±?1.9 days and 331.4?±?1.3 kg, respectively. Animals from the 25%N-75%H group reached puberty earlier than heifers from other genetic groups supplemented with G1250 diet (P?<?0.05). Heifers with higher degree of Nelore (75%N-25%H) fed with G1000 diet showed estrus 42 days prior to mating, but only 57 % reached puberty at mating (P?<?0.05). Heifers with follicles of higher diameter reached puberty (P?<?0.05) earlier. Higher average daily weight gain showed a positive effect on follicular diameter and IGF-I level at puberty (P?<?0.01). Concentrations of GH were lower in heifers fed G1250 compared to G1000 diet (P?<?0.05). There was a significant interaction between nutritional level and insulin levels at puberty (P?<?0.01). We demonstrated the relationship between IGF-I and average daily gain on the onset of puberty in heifers. In conclusion, heifers submitted to the higher feeding level showed a higher follicular diameter and were younger at puberty.     

Morphological and physiological parameters influence the use efficiency of nitrogen and phosphorus by Eucalyptus seedlings

New Forests - Morpho-physiological characteristics in Eucalyptus species can determine N (NUE) and P (PUE) use efficiency and, consequently, the plant's responses to fertilization. The study...     

Growth,water quality and oxidative stress of Nile tilapia Oreochromis niloticus (L.) in biofloc technology system at different pH

The objective of this study was to demonstrate the pH effects on growth, survival, water quality, proximal composition of bioflocs and oxidative stress of Nile tilapia in biofloc technology (BFT) system. Twenty‐five fish (3.68 ± 0.93 g) were distributed in each tank (useful vol. 37.5 L), utilizing treatments with pH 8.3, 7.5 and 6.5 at 60 days. During the experiment, the oxidation of total ammonia was similar among the treatments. However, the NO₂^?‐ N oxidation was slower at pH 6.5 (10.1 ± 1.0 mg/L) compared to pH 7.5 (7.0 ± 0.6 mg/L) and 8.3 (7.1 ± 1.5 mg/L). The final weight was higher for pH 7.5 treatment (44.1 ± 0.9 g) compared to pH 8.3 (37.1 ± 3.9 g), while the pH 6.5 (40.4 ± 4.1 g) was like to the other treatments. Moreover, the survival, daily growth rate and the food conversion rate were not affected by treatments. When evaluating physiological and biochemical parameters, no alterations were detected, therefore, indicating that fish have a good health status. Thus, the present study demonstrates that BFT for a Nile tilapia nursery, utilizing pH 6.5–7.5, promotes the best results in terms of growth, net yield and efficiency.