Free gossypol supplementation frequency and reproductive toxicity in young bulls.

The aim of the present study was to analyze seminal quality of young bulls subjected to different frequencies of gossypol supplementation. Forty-eight Nellore bulls, with 19 months of age and weighing 357.8 ±â€¯7.2 kg, were used in this study. Animals were fed with 10.5 kg of standard supplement containing free-gossypol from whole cottonseed (WCS) at the following frequency: 3x/week (G3x), 5x/week (G5x) or 7x/week (G7x - Control). Additionally, a negative control was provided, and the treated animals received only mineral supplement (MM) ad libtum. The experiment lasted for 84 days and semen was collected at the beginning and at the end for analysis and cryopreservation. Fresh semen was used for initial analysis and plasma membrane integrity and sperm morphology were also determined. General motility using computer assisted sperm analysis (CASA), plasma and acrosomal membranes integrity, mitochondrial activity, and induced oxidative stress were assessed in post-thawed semen. The study design was completely randomized. Parametric data were analyzed by ANOVA and non-parametric data by the Wilcoxon test, using the statistical program SAS. Level of significance was set at 5%. Supplementation with WCS, regardless the frequency, increased total (P = .009) and head (P = .005) defects in comparison to animals receiving only forage and mineral supplement. Infrequent supplementation, particularly 5 times in the week (G5X), increased head (P = .026) and midpiece (P = .014) abnormalities. Sperm motility in fresh semen was lower in animals that received daily supplementation than those supplemented on alternate days (P = .021). Additionally, animals supplemented daily showed lower percentage of spermatozoa with intact acrosome compared to those supplemented on alternate days (P = .005). Thus, regardless the frequency of supplementation, free-gossypol supplementation affects sperm quality. Although the amount of free gossypol supplied weekly was the same among treatments, daily supplementation compromised sperm kinetics, differently from infrequent supplementation that led to sperm defects developed during spermatogenesis.

Suitable strategy to improve nitrogen utilization and reduce the environmental impact of Nellore bulls supplemented on tropical pasture.

Expansion of the biodiesel industry has increased the crude glycerin (CG) supply. Crude glycerin has the potential of replacing corn in ruminant diets because the glycerol can be converted to glucose in the liver of ruminants, providing energy for cellular metabolism. The objective was to evaluate the effects of CG with urea, soybean meal, cottonseed meal, and corn gluten feed, respectively, on intake, digestibility, microbial protein yield, and efficiency of N utilization. Five Nellore bulls (initial BW of 448 kg [SD 14]) grazing tropical pasture were used in a 5 × 5 Latin square design. The supplements were control (no supplementation; only free-choice mineral mixture ad libitum), CG with urea (CG-Urea), CG with soybean meal, CG with cottonseed meal, and CG with corn gluten. Crude glycerin was used in all supplements to replace corn (15% of DM supplement). There were differences between CG-Urea and other supplements with regard to intake of DM (% of BW and total; < 0.01), OM ( < 0.01), CP ( < 0.01), and TDN ( < 0.01). The digestibility of CP was greater ( = 0.04) for animals supplemented with CG-Urea than for those fed other supplements. Animals supplemented with CG-Urea showed greater N intake ( < 0.01) and N ammonia ( = 0.04) than those supplemented with other treatments. Nitrogen retained (g/d) was not affected by protein source but was greater for cattle fed a protein supplement compared with cattle fed the control supplement ( < 0.01). Supplementing the animals with protein sources increased ( = 0.02) the daily production of rumen microbial nitrogen (g/d) compared with the control group. Microbial protein (g/d) was lesser for the control than for protein sources ( = 0.02). However, when expressed relative to TDN ( = 0.35) and CP ( = 0.82), there were no differences across treatments. Crude protein intake per digestible OM intake (g CP/kg digestible OM intake) was greater for animals fed protein sources compared with animals fed control supplements ( < 0.01). Based on nutrients intake and microbial protein yield, CG-Urea supplement has a greater feeding value compared with other protein sources. Crude glycerin, when used to replace corn in 15% of DM supplement, may be effective to improved N utilization and microbial protein yield in rumen of Nellore bulls grazing cv. Marandu.