Context Heat stress is one of the most important challenges facing the poultry industry, affecting the performance, antioxidant status, and immune response of broiler chickens.Aims This study evaluated whether dietary chromium propionate (CrPr) and alpha-lipoic acid (ALA) improve broiler performance, antioxidant status, and immune responses under both normal and heat-stress conditions.Methods Heat stress was imposed from Day 24 to Day 42 at 35 +/- 2 degrees C. In total, 576 as-hatched Ross 308 chicks were assigned to a 3 & times; 2 & times; 2 factorial design, combining three doses of CrPr (0, 750, and 1500 mu g/kg) with two doses of ALA (0 and 300 mg/kg).Results Under normal temperatures, the highest average weight gain and the lowest feed conversion ratio were observed in birds receiving 750 mu g/kg CrPr with 300 mg/kg ALA (P <= 0.05). The lowest abdominal fat was observed in heat-stressed broilers given 1500 mu g/kg CrPr plus 300 mg/kg ALA (P <= 0.05). Heat stress reduced blood antioxidant enzyme concentrations compared with normal temperatures (P <= 0.05). ALA at 300 mg/kg lowered triglycerides, cholesterol, and glucose under heat stress (P <= 0.05). Triglycerides and superoxide dismutase were highest under normal temperatures with 1500 mu g/kg CrPr plus 300 mg/kg ALA (P <= 0.05). For heat-stressed groups, the combination of 750 mu g/kg CrPr and 300 mg/kg ALA produced the highest glutathione peroxidase activity (P <= 0.05), and antibody titers against sheep red blood cells at Day 28 were highest with 300 mg/kg ALA under heat stress (P <= 0.05).Conclusions Simultaneous 750 mu g/kg CrPr and 300 mg/kg ALA improved broiler feed conversion, antioxidant status, and lipids.Implications Implementing this targeted CrPr-ALA supplementation could be a practical, feed-based approach for poultry industries aiming to maintain productivity and health during summer or high-heat management conditions, although further work may be warranted to confirm dose scalability, cost-effectiveness, and consistency across different breeds, farm environments, and stress durations.
Context The balance of dietary calcium (Ca) and phosphorus (P) plays a crucial role in laying hen performance and egg quality, yet optimal concentrations for these minerals are not well-defined, particularly across different ages.Aims This study aimed to evaluate the effects of dietary Ca and P concentrations, along with hen age, on egg performance and quality in Lohmann Brown hens.Methods In total, 432 Lohmann Brown hens, aged 30-42 weeks, were distributed in a completely randomized design with a central composite rotatable design (2(2) + central and axial points), resulting in nine treatments with eight replicates and six birds per experimental unit. The data were analyzed via ANOVA, regression models, and the Tukey-Kramer test (alpha = 0.05).Key results Increasing dietary Ca concentrations reduced feed intake and improved the feed conversion ratio (FCR), while enhancing eggshell quality. Specific gravity and eggshell weight showed a quadratic response to dietary P, with optimal values of 0.43% and 0.36% respectively. Age negatively affected egg production and egg mass, but increased yolk percentage and eggshell thickness. The optimal yolk percentage was achieved with either low Ca and high P or high Ca and low P, whereas the maximum albumen percentage was reached with 4.1% Ca or 0.34% P.Conclusions This study has highlighted the importance of optimizing dietary Ca and P concentrations according to the hens' laying phase to enhance both productivity and egg quality.Implications The findings have provided valuable insights for formulating diets that support the health and efficiency of laying hens, leading to improved egg production and quality in commercial poultry systems.
Context The use of an automated head chamber system (AHCS) for determining methane (CH4) emissions in ruminants has increased in recent years; however, assessments of emissions in grazing systems remain limited, constrained by a lack of knowledge regarding the minimum number of AHCS visits needed for gas flux measurements. Additionally, appropriate CH4 determination allows the evaluation of existing models for predicting CH4 emissions from grazing cattle. Aims This study aimed to determine the minimum number of AHCS visits to determine gas flux and to evaluate the sensitivity of retrieved equations for estimating enteric CH4 emissions in yearling steers under grazing conditions. Methods Individual gas flux from a total of 141 yearling cross-bred steers (398 +/- 53 kg of body weight [BW]) that visited the AHCS at least 100 times under grazing was included in the analysis. Gas flux variables for each steer were estimated by increasing 5-visit intervals until the full 100-visit dataset was utilized. Residual variance, Pearson, and Spearman correlations were calculated to determine the minimum number of AHCS visits. Then, 31 retrieved equations to estimate CH4 production were evaluated according to the individual CH4 emission from 154 yearling steers (394 +/- 54 kg BW), using root mean square prediction error (RMSPE) and concordance correlation coefficient (CCC) analysis. Key results Steers required at least 55 visits to AHCS to represent gas flux emissions, resulting in Spearman and Pearson correlation coefficients greater than 0.95. In addition, four equations for predicting CH4 emissions had excellent agreement (i.e. RMSPE was between 15.6 and 19.0 g/d and CCC was between 0.83 and 0.86) with individual CH4 production, using the 55-visit average of CH4 production. Conclusions In the evaluated grazing environments, yearling steers required at least 55 visits to represent the gas flux, using the AHCS. In this analysis, four equations had excellent agreement between predicted and observed CH4 emissions in the evaluated yearling steers under grazing conditions. Implications This study defined the required number of visits to properly determine enteric CH4 emissions using the AHCS and identified four models that allow enteric CH4 emission estimation from yearling steers under grazing conditions.
Context Smallholder cattle fattening in Ethiopia is important for rural livelihoods, but remains constrained by feed scarcity, weak markets, and limited support services. Aims This study assessed cattle fattening practices, marketing systems, and associated constraints in Geressie and Mirab Abaya districts of southern Ethiopia. Methods A cross-sectional survey of 174 households was conducted using a structured questionnaire. Data were analysed using descriptive statistics, chi-squared tests, Student's t-tests, and index ranking. Results Most farmers fattened young bulls and relied almost exclusively on local cattle breeds. Natural pasture, crop residues, and improved forages were the main feed resources. Cattle were mainly sourced from local markets or household herds, and selection was based on body condition and frame size. Marketing was highly seasonal, with most sales being concentrated around major holidays, particularly Meskel. Brokers dominated market transactions and information flow, limiting farmers' bargaining power. Feed shortage and high feed cost were the most important production constraints, whereas market seasonality, broker dependence, and low prices were the key marketing challenges. Average profit per animal was about 10,000 ETB, with returns being higher in lowland areas. Conclusions Cattle fattening in the study area is constrained by inadequate feed resources, seasonal marketing, and strong intermediary dominance in cattle trade. Implications Improving feed supply, strengthening extension services, and enhancing direct market access are critical to improving productivity and profitability of smallholder cattle fattening systems.
Context Reducing neonatal lamb mortality remains a major challenge globally, and early survival is strongly influenced by the ewe’s ability to provide adequate colostrum and milk. Udder and teat traits have been shown to affect lamb growth and survival; however, their genetic parameters are not well defined in Australian Merinos, particularly regarding how these traits change within a lactation and over the ewe’s lifetime. Aims This study aimed to estimate preliminary genetic parameters for four visually scored traits, udder depth, udder cleft, teat size and teat placement, recorded at lambing and weaning within a single lactation, as well as across age classes. Methods A total of 1257 ewes were scored at both lambing and weaning, and longitudinal records were collected from 2 to 6 years of age to assess the stability of the traits across lactations. Key results Heritability estimates were low to moderate (0.11 ± 0.04 to 0.42 ± 0.09) both within lactation and across age stages, indicating these traits have potential to be improved through selection. Genetic correlations between records taken at lambing and weaning were moderate to high (0.59–0.95), suggesting that most traits are consistently expressed throughout the lactation. Similarly, high genetic correlations (≥0.90) across age classes indicate that udder and teat traits are genetically stable across the ewe’s productive life, perhaps except for teat size, which showed lower correlations between early and later life measurements (0.70). Conclusions Together, these findings imply that a single recording at either lambing or weaning may be sufficient to capture an animal’s genetic merit for udder depth and teat placement. However, repeatability across age stages was low to moderate (0.21–0.29), suggesting that multiple assessments over successive lactations may still improve the accuracy of selection, particularly for teat size, which showed greater variability in genetic expression with age. Implications The estimates within this study provide sound foundational knowledge for how genetic variation in udder and teat traits changes over time in Merino sheep, which have been selected for wool and meat production rather than milking ability.
