Background Diets with increasing levels of energy were fed for 42 days to 200, 1-day old male broiler chickens to evaluate growth performance, carcass characteristics and chemical composition of meat. The study was performed in the subtropical area of northeastern Mexico. Treatments diets (T) for starter and finisher phases had apparent metabolizable energy (AME; kcal/kg) of: 2960 and 3040 (T1); 3000 and 3080 (T2); 3040 and 3120 (T3); 3080 and 3160 (T4), respectively. Within each of the growing phases the four treatment diets were formulated to contain similar levels of crude protein, amino acids, and other nutrients. In a completely randomized design, birds were allocated to the four treatments with five replicates (floor pens) of 10 birds each. The trial was divided in two phases (starter and finisher) of 21 days each (42 days total).ResultsWeight gain was not influenced by energy level; however, feed conversion efficiency was improved in the diets with 3040 and 3120 kcal/kg AME (T3; P < 0.05). There was no influence of treatment on total carcass weight or carcass cuts (P > 0.05). Meat from breast muscle had similar crude protein percentages among treatments; ether extract was higher in T1 than T4 (P < 0.05). The percentages of water, ether extract, ash and crude protein in thigh meat were not significantly different (P > 0.05) among treatments. ConclusionsFor this study carried out in a dry tropical area, the moderate increase in dietary energy concentration (diet with 3040 and 3120 kcal/kg AME, T3) enhanced feed conversion efficiency of broiler chickens.

Vegetable oils (VO) and animal fats are conventional lipid sources used in feed formulations. Frying fats (FF) and calcium soaps of palm oil (CaSPO) are low-cost lipid sources. This study evaluated the productive performance of broiler chickens fed diets with CaSPO in substitution for VO or FF. Two hundred, 1-day old male broiler chickens were allocated in a randomized design with factorial arrangement ( 22). Diets included 2 lipid sources (FF and VO) and 2 CaSPO levels (0 and 50%). The study had two phases (starter and finisher) of 21 days each. For the starter phase there was no effect (p>0.05) of dietary treatments on the chickens' productive performance. For the finisher phase birds fed diets with FF had higher feed intake and feed conversion ratio (main effect; p<0.01) than those fed diets with VO. Over the 42-day feeding period animals fed FF had higher feed conversion ratio (main effect; p=0.02) and tended (p=0.08) to show higher feed intake than those fed diets with VO. The CaSPO substitution for VO or FF had no effect (p>0.05) on the productive performance of broiler chickens. There was no influence of treatment on carcass yield. The drumsticks plus thighs were higher (main effect; p<0.01) in birds receiving VO than in those receiving FF. The interaction (fat source*CaSPO) was not significant (p>0.05). These results may indicate that VO is superior to FF and CaSPO may substitute for VO or FF without affecting productive performance of broiler chickens. Lipid source showed small influence on carcass characteristics.

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Introduction: The cow-calf system consists of the production of calves, which will then be fattened for meat production. The state of Tabasco a high percentage of farmers are engaged in this activity, however, most of the technology transfers are focused on the dual purpose system, which has not allowed to make significant improvements in the productive variables of the cow-calf system. The objective of this study was to characterize the cow-calf system and identify the factors that affect the production of calf in the State of Tabasco.                     Method: Therefore, 342 farmers were interviewed through a structured survey to get information about the farmer date, social characteristics, infrastructure, herd structures, management practices and productive. To identify the types of farmers, a cluster analysis was performed by the Ward method and Euclidean square distance, and to identify the variables that explain the production of calves, a linear regression analysis.Results: The cluster analysis identified three types of farmers (small, medium, and large). 63.40% of the farmers were classified as small (<of 14 cows in production), 29.0% as medium (between 15 and 34 cows in production) and 7.60% as large producers (between 35 and 80 cows in production). In the three types of farmers the number of cows in production, index of adoption of technology and quantity of concentrated feed explain the production of calf.Discussion or Conclusion: The characterization of the cow-calf system of tropical regions is important because more than half of the livestock in these regions use this system of production. In addition, knowing the factors that determine the production of calf can help generate strategies for the support of this type of farmers and improve the productive variables of the system.

Plant extracts have been used over time in traditional medicine, mainly for their antimicrobial activity as well as for their medicinal effects. Plant-derived products contain secondary metabolites that prevent pathogenic microbial growth similar to conventional medicines. These secondary metabolites can enhance animal health and production in a more natural or organic manner and may contribute to the reduction in the use of pharmacological drugs in animal feed, which is of great concern for emerging microbial resistance. Plant secondary metabolites can be cost effective, while improving the production efficiency of ruminants, non-ruminants, and aquatic food animals. Among the plant-derived products is the Yucca schidigera extract (YSE), containing steroidal saponins as their main active component. YSE has multiple biological effects, including inhibition of some pathogenic bacteria, protozoa, and nematodes. YSE is used to control odor and ammonia and consistently enhance poultry production by enhancing intestinal health and function. In pigs, results are as yet inconclusive. In ruminants, YSE works against protozoa, has selective action against bacteria, and reduces the archaea populations; all these effects are reflected in the reduction in emissions of polluting gases, mainly methane, although the effects are not observed in all feeding conditions. These effects of YSE are discussed in this review. YSE has potential as a natural feed additive for sustainable animal production while contributing to the mitigation of contaminant gas emissions.