Claudio Aguilar | Pontificia Universidad Catolica de Chile (original) (raw)

Papers by Claudio Aguilar

Chilean journal of agricultural research, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized experiment using 36 single male Suffolk Down lambs with an initial age and live weight of 80 d and 25 kg, respectively. The three treatments were: (a) suckling lambs kept with their mothers on annual Mediterranean grassland (GRAZE); (b) weaned stall-fed lambs on a control ration (CONC); and (c) weaned stall-fed lambs on an olive cake-based ration (CAKE). At the end of the 28-d experimental period, lambs were slaughtered, carcass quality evaluated, and samples of subcutaneous fat analyzed for fatty acids. Treatments did not differ in weight gain or carcass weight and quality, but highly significant differences were found in several fatty acid contents. CAKE animals had reduced palmitic acid as well as increased oleic and stearic acid contents. Atherogenic and thrombogenic indices improved with cake feeding. Principal component and discriminant analyses clearly differentiated treatments suggesting they could be applicable for traceability purposes. A laboratory experiment demonstrated that with or without added vitamin E, the dry olive cake did not alter its lipid properties with increased storage time.

Grasslands are complex ecosystems and their processes are affected by soil, meteorological, and m... more Grasslands are complex ecosystems and their processes are affected by soil, meteorological, and management variables. In this context, dynamic simulation models are useful to understand these processes and to design grassland use strategies. The aim of this study was to develop and validate a simulation model of perennial pasture growth based on soil and climate variables. A first approach considered that soil fertility levels were adequate; therefore, soil water availability and phytomass level were the main variables affecting pasture growth. The subroutines considered were water balance, pasture growth, and root biomass dynamics. The hypotheses regarding the functioning of the system were formulated as a group of equations which were solved numerically with a program written in Visual Basic®. Model validation was performed by statistical comparison between simulated DM and DM obtained from experiments conducted in Valdivia (39º47' S., 73º15' W; 9 m a.s.l.). In these experiments we measured DM accumulation on naturalized grassland and ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pastures under frequent defoliation. Soil data, temperature, solar radiation, and rainfall were obtained from a meteorological station located in Valdivia. The coefficient of determination between simulated values and those measured in the experiments were higher in the DM accumulation (R 2 = 98%) simulations. When pasture was subjected to frequent defoliation, the degree of fit of the model was lower (R 2 = 60%); however, the model was able to predict the trend in the data.

Dairy Science & Technology, 2013

The purpose of this study was to characterize the lipid and volatile fractions of three commercia... more The purpose of this study was to characterize the lipid and volatile fractions of three commercially available, farmhouse sheep cheeses from Chile (Chilozabal, Patagonia and Quillahue cheeses) as a preliminary contribution to know, promote, protect and improve their quality. Two cheese samples of each type of cheese were purchased in specialty stores in the capital city: Patagonia, Quillahue, and two different fabrications of Chilozabal cheese (two different stores). Significant differences in the total fatty acid amounts were observed among the cheeses. Quillahue cheese had the highest content of unsaturated and branched-chain fatty acids and the lowest value of the atherogenic index. Chilozabal cheese showed the highest content of CLA and vaccenic acid. The total amount of free fatty acids was highest in one of the Chilozabal cheeses and 85% lower in Quillahue. Short-chain FFA represented 58% of the total FFA in both Chilozabal cheeses, suggesting the use of pregastric lipase-containing lamb rennet paste. In Quillahue and Patagonia cheeses, short-chain FFA were 42% of the total FFA, consistent with the use of commercial rennets without lipase activity. The volatile composition of these cheeses was rather similar to that of other well-known hard and semi-hard sheep cheeses. Volatile acids were the most abundant compounds in all cheeses and significant differences were found in the content of esters, ketones and alcohols among the cheeses. Compositional differences among the Chilean sheep cheeses were essentially due to breed, feed management, and technological factors.

Small Ruminant Research, 2009

The objective of three experiments was to determine the influence of high condensed tannin (CT) g... more The objective of three experiments was to determine the influence of high condensed tannin (CT) grain sorghum on gastrointestinal parasite fecal egg counts (FEC). Sixteen naturally infected Boer crossbred mixed-sex goats were used. Animals that were supplemented with grain daily were removed from pasture and placed in individual pens and fed treatment diets for 21 or 14 days (Experiment 3). Goats were allowed ad libitum access to water and diets containing high or low CT cracked grain sorghum. On day 0 and every 7 days thereafter, PCV, FEC and FAMACHA ® eyelid color scores (EYE; Experiment 1 only) were recorded. For Experiment 1, percentage of animals dewormed, PCV and EYE were not influenced by treatment and averaged 13.6 ± 4.5% per treatment period, 23.4 ± 0.8% and 3.2 ± 0.12, respectively, for all animals. The FEC increased after day 0 for control but not high tannin grain sorghum fed goats (treatment by day interaction, P < 0.02). As expected, EYE and PCV were negatively related (r = −0.45; P < 0.0005). For Experiment 2, there was no influence of diet on PCV or FEC, but there was an effect of day on FEC (P < 0.002) in which all goats had higher FEC on day 0 (1956 ± 219 eggs/g) than any other sampling day. For Experiment 3, there was no effect of feeding high CT grain sorghum on FEC (2992 ± 591 eggs/g) or PCV (25.1 ± 0.5%). In these studies, high CT grain sorghum did not consistently influence FEC and did not impact PCV or number of animals requiring chemical anthelmintic treatment.

Olive oil extraction yields a residual cake rich in oil that can be used in animal diets as a sou... more Olive oil extraction yields a residual cake rich in oil that can be used in animal diets as a source of monounsaturated fat. Milk and cheese from sheep are high in saturated fatty acids (FA) thus, it was hypothesized that supplementing olive cake to lactating ewes would result in naturally enhanced milk and cheese with healthier FA profiles for human consumption. Nine lactating ewes were randomly assigned to a replicated (n = 3) 3 × 3 Latin square design. Diets were supplemented with 0, 10 or 25% of dry olive cake. Except for total solids, dry matter intake, milk yield and milk composition were not affected by dietary treatments. Oleic acid, n-6/n-3 ratio and monounsaturated FA gradually increased (P < 0.05), while saturated FA and atherogenicity index decreased (P < 0.05) in milk and cheese as inclusion of olive cake was increased in dietary treatments. Overall, FA profile of milk and cheese from sheep can be naturally improved by supplementation of olive cake.

Animal Production Science, 2009

Búsqueda Avanzada. ...

Chilean journal of …, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized ...

Small Ruminant Research, 2006

A simulation model was developed and validated to analyze the bioeconomic performance of alternat... more A simulation model was developed and validated to analyze the bioeconomic performance of alternative technologies applied to lamb production systems in the Mediterranean-type rangelands of Central Chile. The model includes consideration of climatic events that affect pasture growth, the nutritive value of the forage on offer, and animal performance as affected by energy and protein intake of directly grazed native pastures and supplements.

Ciencia e investigación agraria, 2014

E. Vargas-Bello-Pérez, R. R. Vera, C. Aguilar, R. Lira, I. Peña, and F.A. Tello. 2014. Feeding ex... more E. Vargas-Bello-Pérez, R. R. Vera, C. Aguilar, R. Lira, I. Peña, and F.A. Tello. 2014. Feeding extruded linseed to dairy ewes under extensive grazing conditions. Cien. Inv. Agr. 41(1): 115-122. The aim of this trial was to evaluate the effect of dietary supplementation of extruded linseed on the milk and cheese fatty acid (FA) profiles of ewes under extensive grazing conditions. Over 26 days, a group of nine lactating ewes (Latxa × Milchschaf × Corriedale) in mid-lactation were managed under grazing conditions and given supplements during each manual milking (0830 and 1800 h) of 50% corn and 50% oats (500 g ewe -1 milking -1 ; control, TC) for the first 6 days. From day 7 to 20, the supplement was 25% corn, 25% oats and 50% extruded linseed (500 g ewe -1 milking -1 ) (extruded linseed; TEL). From day 21 to 26, the ewes were fed TC. The saturated FA content in milk was reduced (3.6%), and the monounsaturated, polyunsaturated and n-3 FA (7, 10 and 25%, respectively) were increased when the ewes were supplemented with extruded linseed. A correlation between rumenic acid with vaccenic acid (R 2 =0.68) was found in the milk fat from ewes fed TEL. In cheese obtained from TEL, the contents of n-3 and polyunsaturated FA were increased (21 and 7%, respectively). In conclusion, a supplement of extruded linseed in ewes under grazing conditions could be an alternative lipid source to produce cheese with additional nutritional value. However, the effect of extruded linseed supplementation in ewes under the same conditions with longer experimental periods and a more suitable statistical design must be investigated.

Cienc. Inv. Agr

La rentabilidad de la producción ovina tradicional entre productores pequeños y medianos es muy b... more La rentabilidad de la producción ovina tradicional entre productores pequeños y medianos es muy baja, razón por la cual es deseable buscar alternativas con mayor valor agregado y diferenciación. Una alternativa de interés es la producción de leche ovina para la ...

Animal Production Science, 2013

Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual M... more Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual Mediterranean pasture (GRAZE), weaned followed by a concentrate plus hay diet (CONC), or weaned and fed a concentrate with 33% dry olive oil cake plus hay (CAKE). Grazing lambs averaged a liveweight gain of 334 g/day during the 28-day experimental period, which was higher (P < 0.05) than that of CONC and CAKE (283 and 276 g/day, respectively); however, there were no differences in empty body or dressed carcasses weights due to dietary treatment. The feed conversion of the olive seed cake supplement (kg supplement/kg gain) was lower (P < 0.01) than that of the maize-based supplement. Despite some significant differences between carcasses traits, all were small and of little commercial consequence. Simulation modelling of whole-system performance suggested that early weaning of lambs followed by concentrate feeding would reduce the finishing period, marginally increase the liveweight of ewes and would have little effect on pasture availability. It was further concluded that olive oil cake can be a large proportion of concentrate diets without negatively affecting carcass quality.

Ciencia e investigación agraria, 2009

R.R. Vera, C. Aguilar, and R. Lira. 2009. Differentiation of sheep milk and cheese based on their... more R.R. Vera, C. Aguilar, and R. Lira. 2009. Differentiation of sheep milk and cheese based on their quality and composition. Cienc. Inv. Agr. 36(3):307-328. Traditional sheep production for meat and wool for meat and wool among small and medium-sized Chilean farmers has low profi tability. Therefore, there is interest in producing value-added, differentiated products. One alternative is the production of sheep milk and cheese. This article analyzes and discusses existing alternatives for modifying milk and cheese compositions with the aim of differentiating these products. Also, analytical techniques that allow the chemical characterization of milk and cheese are briefl y mentioned. The main international thrusts are focused on the modifi cation of the content and composition of milk fatty acids and on the identifi cation of volatile compounds, terpenes, polyphenols and other analytes that allow differentiation of cheese types on the basis of aroma, taste and fl avor and that would help in ensuring traceability.

Chilean journal of agricultural research, 2009

A mathematical model was developed to analyze beef production systems in Southern Chile. The stud... more A mathematical model was developed to analyze beef production systems in Southern Chile. The study considered the identification of the main components of systems under different beef steer management strategies, using pasture with or without supplementation and back grounding cattle on pasture followed by a winter period of confined feeding with pasture silage and concentrates. Validation of model outputs using 200 kg LW Hereford steers against real experimental data showed no significant differences (P ≥ 0.01) between simulated and observed final weights. In order to analyze the interaction between the stocking rate (SR) and supplementation, three SR of 2, 2.5 and 3 steers ha -1 with and without pasture silage supplementation at the rate of 5 kg DMd -1 steer -1 for the length of the entire period were simulated. Means were compared by the least significant difference (LSD, P ≤ 0.05). Significant differences were found in terms of final weights, which decreased with increasing SR regardless of the supplementation level, although silage supplementation tended to reduce differences between SR. A second set of simulation runs was carried out to simulate on-farm finishing of the steers through a final phase of confined feeding based on a ration of silage and concentrates. Final weights differed between SR and systems and results showed that the optimum corresponded to 2.5 steers ha -1 , since at this SR the largest income corresponded to the smallest mean cost. It is concluded that a stocking rate of 2.5 steers ha -1 is feasible if winter supplementation is available, independently of a finishing period in feedlot.

fs.fed.us

In Chilean mediterranean ecosystems, rainfall and biomass production is correlated. Biomass produ... more In Chilean mediterranean ecosystems, rainfall and biomass production is correlated. Biomass productivity in the north is between 300 and 1200 kg/ha in the fall-winter period; in the south, maximum productivity is about 5000 kg/ha in the spring through fall months. Major restrictions for animal use are water, slope, soil nutrients, toxic plants, and weeds. Management has drastically changed with land tenure circumstances. Natural pastures provide more than 80 percent of grazing, but most research is in cultivated pastures. The few research projects in natural pastures have produced a very important impact.

Chilean journal of agricultural research, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized experiment using 36 single male Suffolk Down lambs with an initial age and live weight of 80 d and 25 kg, respectively. The three treatments were: (a) suckling lambs kept with their mothers on annual Mediterranean grassland (GRAZE); (b) weaned stall-fed lambs on a control ration (CONC); and (c) weaned stall-fed lambs on an olive cake-based ration (CAKE). At the end of the 28-d experimental period, lambs were slaughtered, carcass quality evaluated, and samples of subcutaneous fat analyzed for fatty acids. Treatments did not differ in weight gain or carcass weight and quality, but highly significant differences were found in several fatty acid contents. CAKE animals had reduced palmitic acid as well as increased oleic and stearic acid contents. Atherogenic and thrombogenic indices improved with cake feeding. Principal component and discriminant analyses clearly differentiated treatments suggesting they could be applicable for traceability purposes. A laboratory experiment demonstrated that with or without added vitamin E, the dry olive cake did not alter its lipid properties with increased storage time.

Chilean journal of agricultural research, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized experiment using 36 single male Suffolk Down lambs with an initial age and live weight of 80 d and 25 kg, respectively. The three treatments were: (a) suckling lambs kept with their mothers on annual Mediterranean grassland (GRAZE); (b) weaned stall-fed lambs on a control ration (CONC); and (c) weaned stall-fed lambs on an olive cake-based ration (CAKE). At the end of the 28-d experimental period, lambs were slaughtered, carcass quality evaluated, and samples of subcutaneous fat analyzed for fatty acids. Treatments did not differ in weight gain or carcass weight and quality, but highly significant differences were found in several fatty acid contents. CAKE animals had reduced palmitic acid as well as increased oleic and stearic acid contents. Atherogenic and thrombogenic indices improved with cake feeding. Principal component and discriminant analyses clearly differentiated treatments suggesting they could be applicable for traceability purposes. A laboratory experiment demonstrated that with or without added vitamin E, the dry olive cake did not alter its lipid properties with increased storage time.

Grasslands are complex ecosystems and their processes are affected by soil, meteorological, and m... more Grasslands are complex ecosystems and their processes are affected by soil, meteorological, and management variables. In this context, dynamic simulation models are useful to understand these processes and to design grassland use strategies. The aim of this study was to develop and validate a simulation model of perennial pasture growth based on soil and climate variables. A first approach considered that soil fertility levels were adequate; therefore, soil water availability and phytomass level were the main variables affecting pasture growth. The subroutines considered were water balance, pasture growth, and root biomass dynamics. The hypotheses regarding the functioning of the system were formulated as a group of equations which were solved numerically with a program written in Visual Basic®. Model validation was performed by statistical comparison between simulated DM and DM obtained from experiments conducted in Valdivia (39º47' S., 73º15' W; 9 m a.s.l.). In these experiments we measured DM accumulation on naturalized grassland and ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) pastures under frequent defoliation. Soil data, temperature, solar radiation, and rainfall were obtained from a meteorological station located in Valdivia. The coefficient of determination between simulated values and those measured in the experiments were higher in the DM accumulation (R 2 = 98%) simulations. When pasture was subjected to frequent defoliation, the degree of fit of the model was lower (R 2 = 60%); however, the model was able to predict the trend in the data.

Dairy Science & Technology, 2013

The purpose of this study was to characterize the lipid and volatile fractions of three commercia... more The purpose of this study was to characterize the lipid and volatile fractions of three commercially available, farmhouse sheep cheeses from Chile (Chilozabal, Patagonia and Quillahue cheeses) as a preliminary contribution to know, promote, protect and improve their quality. Two cheese samples of each type of cheese were purchased in specialty stores in the capital city: Patagonia, Quillahue, and two different fabrications of Chilozabal cheese (two different stores). Significant differences in the total fatty acid amounts were observed among the cheeses. Quillahue cheese had the highest content of unsaturated and branched-chain fatty acids and the lowest value of the atherogenic index. Chilozabal cheese showed the highest content of CLA and vaccenic acid. The total amount of free fatty acids was highest in one of the Chilozabal cheeses and 85% lower in Quillahue. Short-chain FFA represented 58% of the total FFA in both Chilozabal cheeses, suggesting the use of pregastric lipase-containing lamb rennet paste. In Quillahue and Patagonia cheeses, short-chain FFA were 42% of the total FFA, consistent with the use of commercial rennets without lipase activity. The volatile composition of these cheeses was rather similar to that of other well-known hard and semi-hard sheep cheeses. Volatile acids were the most abundant compounds in all cheeses and significant differences were found in the content of esters, ketones and alcohols among the cheeses. Compositional differences among the Chilean sheep cheeses were essentially due to breed, feed management, and technological factors.

Small Ruminant Research, 2009

The objective of three experiments was to determine the influence of high condensed tannin (CT) g... more The objective of three experiments was to determine the influence of high condensed tannin (CT) grain sorghum on gastrointestinal parasite fecal egg counts (FEC). Sixteen naturally infected Boer crossbred mixed-sex goats were used. Animals that were supplemented with grain daily were removed from pasture and placed in individual pens and fed treatment diets for 21 or 14 days (Experiment 3). Goats were allowed ad libitum access to water and diets containing high or low CT cracked grain sorghum. On day 0 and every 7 days thereafter, PCV, FEC and FAMACHA ® eyelid color scores (EYE; Experiment 1 only) were recorded. For Experiment 1, percentage of animals dewormed, PCV and EYE were not influenced by treatment and averaged 13.6 ± 4.5% per treatment period, 23.4 ± 0.8% and 3.2 ± 0.12, respectively, for all animals. The FEC increased after day 0 for control but not high tannin grain sorghum fed goats (treatment by day interaction, P < 0.02). As expected, EYE and PCV were negatively related (r = −0.45; P < 0.0005). For Experiment 2, there was no influence of diet on PCV or FEC, but there was an effect of day on FEC (P < 0.002) in which all goats had higher FEC on day 0 (1956 ± 219 eggs/g) than any other sampling day. For Experiment 3, there was no effect of feeding high CT grain sorghum on FEC (2992 ± 591 eggs/g) or PCV (25.1 ± 0.5%). In these studies, high CT grain sorghum did not consistently influence FEC and did not impact PCV or number of animals requiring chemical anthelmintic treatment.

Olive oil extraction yields a residual cake rich in oil that can be used in animal diets as a sou... more Olive oil extraction yields a residual cake rich in oil that can be used in animal diets as a source of monounsaturated fat. Milk and cheese from sheep are high in saturated fatty acids (FA) thus, it was hypothesized that supplementing olive cake to lactating ewes would result in naturally enhanced milk and cheese with healthier FA profiles for human consumption. Nine lactating ewes were randomly assigned to a replicated (n = 3) 3 × 3 Latin square design. Diets were supplemented with 0, 10 or 25% of dry olive cake. Except for total solids, dry matter intake, milk yield and milk composition were not affected by dietary treatments. Oleic acid, n-6/n-3 ratio and monounsaturated FA gradually increased (P < 0.05), while saturated FA and atherogenicity index decreased (P < 0.05) in milk and cheese as inclusion of olive cake was increased in dietary treatments. Overall, FA profile of milk and cheese from sheep can be naturally improved by supplementation of olive cake.

Animal Production Science, 2009

Búsqueda Avanzada. ...

Chilean journal of …, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized ...

Small Ruminant Research, 2006

A simulation model was developed and validated to analyze the bioeconomic performance of alternat... more A simulation model was developed and validated to analyze the bioeconomic performance of alternative technologies applied to lamb production systems in the Mediterranean-type rangelands of Central Chile. The model includes consideration of climatic events that affect pasture growth, the nutritive value of the forage on offer, and animal performance as affected by energy and protein intake of directly grazed native pastures and supplements.

Ciencia e investigación agraria, 2014

E. Vargas-Bello-Pérez, R. R. Vera, C. Aguilar, R. Lira, I. Peña, and F.A. Tello. 2014. Feeding ex... more E. Vargas-Bello-Pérez, R. R. Vera, C. Aguilar, R. Lira, I. Peña, and F.A. Tello. 2014. Feeding extruded linseed to dairy ewes under extensive grazing conditions. Cien. Inv. Agr. 41(1): 115-122. The aim of this trial was to evaluate the effect of dietary supplementation of extruded linseed on the milk and cheese fatty acid (FA) profiles of ewes under extensive grazing conditions. Over 26 days, a group of nine lactating ewes (Latxa × Milchschaf × Corriedale) in mid-lactation were managed under grazing conditions and given supplements during each manual milking (0830 and 1800 h) of 50% corn and 50% oats (500 g ewe -1 milking -1 ; control, TC) for the first 6 days. From day 7 to 20, the supplement was 25% corn, 25% oats and 50% extruded linseed (500 g ewe -1 milking -1 ) (extruded linseed; TEL). From day 21 to 26, the ewes were fed TC. The saturated FA content in milk was reduced (3.6%), and the monounsaturated, polyunsaturated and n-3 FA (7, 10 and 25%, respectively) were increased when the ewes were supplemented with extruded linseed. A correlation between rumenic acid with vaccenic acid (R 2 =0.68) was found in the milk fat from ewes fed TEL. In cheese obtained from TEL, the contents of n-3 and polyunsaturated FA were increased (21 and 7%, respectively). In conclusion, a supplement of extruded linseed in ewes under grazing conditions could be an alternative lipid source to produce cheese with additional nutritional value. However, the effect of extruded linseed supplementation in ewes under the same conditions with longer experimental periods and a more suitable statistical design must be investigated.

Cienc. Inv. Agr

La rentabilidad de la producción ovina tradicional entre productores pequeños y medianos es muy b... more La rentabilidad de la producción ovina tradicional entre productores pequeños y medianos es muy baja, razón por la cual es deseable buscar alternativas con mayor valor agregado y diferenciación. Una alternativa de interés es la producción de leche ovina para la ...

Animal Production Science, 2013

Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual M... more Three lamb feeding strategies were compared, including finishing of suckling lambs on an annual Mediterranean pasture (GRAZE), weaned followed by a concentrate plus hay diet (CONC), or weaned and fed a concentrate with 33% dry olive oil cake plus hay (CAKE). Grazing lambs averaged a liveweight gain of 334 g/day during the 28-day experimental period, which was higher (P < 0.05) than that of CONC and CAKE (283 and 276 g/day, respectively); however, there were no differences in empty body or dressed carcasses weights due to dietary treatment. The feed conversion of the olive seed cake supplement (kg supplement/kg gain) was lower (P < 0.01) than that of the maize-based supplement. Despite some significant differences between carcasses traits, all were small and of little commercial consequence. Simulation modelling of whole-system performance suggested that early weaning of lambs followed by concentrate feeding would reduce the finishing period, marginally increase the liveweight of ewes and would have little effect on pasture availability. It was further concluded that olive oil cake can be a large proportion of concentrate diets without negatively affecting carcass quality.

Ciencia e investigación agraria, 2009

R.R. Vera, C. Aguilar, and R. Lira. 2009. Differentiation of sheep milk and cheese based on their... more R.R. Vera, C. Aguilar, and R. Lira. 2009. Differentiation of sheep milk and cheese based on their quality and composition. Cienc. Inv. Agr. 36(3):307-328. Traditional sheep production for meat and wool for meat and wool among small and medium-sized Chilean farmers has low profi tability. Therefore, there is interest in producing value-added, differentiated products. One alternative is the production of sheep milk and cheese. This article analyzes and discusses existing alternatives for modifying milk and cheese compositions with the aim of differentiating these products. Also, analytical techniques that allow the chemical characterization of milk and cheese are briefl y mentioned. The main international thrusts are focused on the modifi cation of the content and composition of milk fatty acids and on the identifi cation of volatile compounds, terpenes, polyphenols and other analytes that allow differentiation of cheese types on the basis of aroma, taste and fl avor and that would help in ensuring traceability.

Chilean journal of agricultural research, 2009

A mathematical model was developed to analyze beef production systems in Southern Chile. The stud... more A mathematical model was developed to analyze beef production systems in Southern Chile. The study considered the identification of the main components of systems under different beef steer management strategies, using pasture with or without supplementation and back grounding cattle on pasture followed by a winter period of confined feeding with pasture silage and concentrates. Validation of model outputs using 200 kg LW Hereford steers against real experimental data showed no significant differences (P ≥ 0.01) between simulated and observed final weights. In order to analyze the interaction between the stocking rate (SR) and supplementation, three SR of 2, 2.5 and 3 steers ha -1 with and without pasture silage supplementation at the rate of 5 kg DMd -1 steer -1 for the length of the entire period were simulated. Means were compared by the least significant difference (LSD, P ≤ 0.05). Significant differences were found in terms of final weights, which decreased with increasing SR regardless of the supplementation level, although silage supplementation tended to reduce differences between SR. A second set of simulation runs was carried out to simulate on-farm finishing of the steers through a final phase of confined feeding based on a ration of silage and concentrates. Final weights differed between SR and systems and results showed that the optimum corresponded to 2.5 steers ha -1 , since at this SR the largest income corresponded to the smallest mean cost. It is concluded that a stocking rate of 2.5 steers ha -1 is feasible if winter supplementation is available, independently of a finishing period in feedlot.

fs.fed.us

In Chilean mediterranean ecosystems, rainfall and biomass production is correlated. Biomass produ... more In Chilean mediterranean ecosystems, rainfall and biomass production is correlated. Biomass productivity in the north is between 300 and 1200 kg/ha in the fall-winter period; in the south, maximum productivity is about 5000 kg/ha in the spring through fall months. Major restrictions for animal use are water, slope, soil nutrients, toxic plants, and weeds. Management has drastically changed with land tenure circumstances. Natural pastures provide more than 80 percent of grazing, but most research is in cultivated pastures. The few research projects in natural pastures have produced a very important impact.

Chilean journal of agricultural research, 2009

The purpose of this experiment was to determine the extent to which lamb carcass quality and fat ... more The purpose of this experiment was to determine the extent to which lamb carcass quality and fat composition could be altered by applying a dry olive cake-based ration instead of a conventional ration or pasture feeding. Three treatments were compared in a completely randomized experiment using 36 single male Suffolk Down lambs with an initial age and live weight of 80 d and 25 kg, respectively. The three treatments were: (a) suckling lambs kept with their mothers on annual Mediterranean grassland (GRAZE); (b) weaned stall-fed lambs on a control ration (CONC); and (c) weaned stall-fed lambs on an olive cake-based ration (CAKE). At the end of the 28-d experimental period, lambs were slaughtered, carcass quality evaluated, and samples of subcutaneous fat analyzed for fatty acids. Treatments did not differ in weight gain or carcass weight and quality, but highly significant differences were found in several fatty acid contents. CAKE animals had reduced palmitic acid as well as increased oleic and stearic acid contents. Atherogenic and thrombogenic indices improved with cake feeding. Principal component and discriminant analyses clearly differentiated treatments suggesting they could be applicable for traceability purposes. A laboratory experiment demonstrated that with or without added vitamin E, the dry olive cake did not alter its lipid properties with increased storage time.