NIVELES ÓPTIMOS BIOLÓGICOS DE LISINA Y TREONINA DIGESTIBLES PARA CERDOS EN CRECIMIENTO

The optimal biological levels (OBL) of digestible lysine and threonine which maximize the productive variables of growing pigs were determined, through two experiments with 100 pigs (75 castrated males and 25 females), distributed in five treatments with five repetitions and two animals per experimental unit. The evaluation consisted in five levels of digestible lysine for four weeks and five levels of digestible threonine for six weeks. To calculate the OBL of each variable, econometric models were built and solved from trends detected through orthogonal contrasts, considered for the regression analysis. The digestible lysine OBL that maximized food consumption and weight gain was 0.74% (P?0.05). The threonine OBLs for food consumption and food conversion were 0.52 and 0.55%, respectively, while for weight gain and final live weight the best response was 0.62% (P?0.05). These results indicate that the lysine and the threonine OLBs depend on the variable that needs to be optimized.Se determinaron los niveles óptimos biológicos (NOB) de lisina y treonina digestibles que maximizan las variables productivas de cerdos en crecimiento, mediante dos experimentos con 100 cerdos (75 machos castrados y 25 hembras), distribuidos en cinco tratamientos con cinco repeticiones y dos animales por unidad experimental. La evaluación consistió en cinco niveles de lisina digestible durante cuatro semanas y cinco niveles de treonina digestible durante seis semanas. Para calcular los NOB de cada variable se construyeron y solucionaron modelos econométricos a partir de tendencias detectadas por medio de contrastes ortogonales, consideradas para el análisis de regresión. El NOB de lisina digestible que maximizó el consumo de alimento y ganancia de peso fue 0.74% (P?0.05). Los NOB de treonina para consumo de alimento y conversión alimenticia fueron 0.52 y 0.55%, respectivamente, mientras que para ganancia de peso y peso vivo final la mejor respuesta fue 0.62% ?0.05). Estos resultados indican que el NOB de lisina y treonina depende de la variable que se quiera optimiza

Evaluation of polyherbal methionine and choline in feedlot rations for lambs

Requirements of lambs for choline and methionine have not been clearly established, but because of their metabolic relationship, the availability of these two nutrients may affect protein synthesis and energy balance. Therefore, a trial was carried out to evaluate the effect on productive performance and blood metabolites of including methionine and choline from polyherbal mixtures in finishing lamb diets. Forty Hampshire x Suffolk lambs weighing 26.9 ± 2.8 kg were used for a 45-day experiment. The treatments were arranged as a 2x2 factorial, in which the factors were dietary supplementation with herbal methionine and choline at two levels (0% and 0.4% of dry matter (DM)). The treatments had no effects on the lambs’ productive variables (daily feed intake, average daily gain, and feed to gain ratio), carcass characteristics and lipid metabolites (P >0.05). The results indicated that the inclusion of polyherbal mixtures containing methionine, choline and their combination at 0.4% of DM in finishing lamb diets showed no benefits in productive response or in blood metabolites related to lipid metabolism. Keywords: amino acid, lipid metabolites, productive performance, ruminally protected, vitami

Reusing intravaginal progesterone releasing devices for oestrous synchoronization in ewes

In this study, the second use of an intravaginal progesterone-releasing device or controlled intravaginal drug release device (CIDR) was evaluated. After a first use of 11 days, the CIDR was again used for either nine or 12 days with 200 or 300 IU equine chorionic gonadotrophin (eCG) being injected on its removal. Sixty-four ewes were randomly distributed to four treatments (n=16/group): CIDR9+eCG200, CIDR9+eCG300, CIDR12+eCG200, and CIDR12+eCG300. The eCG was administered intramuscularly on withdrawal of the device. Thus, the experiment was a completely randomized design with a 2×2 factorial arrangement of treatments. Oestrus presentation did not differ between treatments (P =0.29). However, with the dose of 200 IU of eCG, oestrus presentation tended to increase (P =0.08). The onset and duration of oestrus, percentage of gestation, and return to oestrus did not differ between treatments (P >0.05). Progesterone concentration in serum was greater (P < 0.05) in ewes treated with CIDR12+eCG300. Prolificacy was greatest (1.44) with the CIDR12+eCG300 treatment and was different (P = 0.001) from the treatments CIDR9+eCG200 (1.21) and CIDR9+eCG300 (1.20), but not from the CIDR12+eCG200 treated ewes (1.31). The CIDR12+eCG300 treatement produced the highest percentage of twin births (45.8%) (P =0.001). Leaving the device in place for 12 days increased (P =0.001) the incidence of twin births. Use of the CIDR for a second time synchronized oestrus in ewes successfully with better fertility being obtained when the device was left in place for 12 days, and 300 IU of eCG was injected on its removal. Key words: gonadotropin, progesterone device, synchronizatio