ABSTRACT This study aimed to evaluate the lactation curve of female Murrah buffaloes, using mixed nonlinear models (NLM), across three lactation periods (180 d, 210 d, and 240 d). A total of 5334 data on daily milk production (kg) were analyzed. The data were collected every seven days in the interval of one to 250 days of lactation, corresponding to 221 lactations and 145 females, with calvings from 2017 to 2019. The data came from a herd located in the Centro municipality, Tabasco, Mexico. Five NLM were evaluated: Wood (WOD), Wiltmink (WIL), Cobby (COB), Brody (BRO), Sikka (SIK). The best fit model was selected based on the mean prediction error, mean absolute percentage error (MAPE), prediction error variance, coefficient of determination (R2), concordance correlation coefficient (CCC), Akaike (AIC) and Bayesian (BIC) information criteria. A regression analysis was performed between the observed and predicted values. All the NLM had a R2 above 0.91. They tend to underestimate the predictions, without residual autocorrelation. The MAPE showed an average value of 23.5%. The best fit model was WOD, followed by SIK and BRO. For WIL and COB, the mixed model did not improve the fitting. The shortest lactation period showed the best fit, followed by the 210 d and 240 d periods. The relationship between observed:predicted values fluctuated from 0.65 to 1.00, with an average value of 0.94. The use of NLM transcended in the AIC and BIC. The evaluated models showed goodness of fit, with good predictability, but low values in accuracy and precision of prediction.

Abstract Characterizing growth in livestock is important when making management, marketing and genetic improvement decisions. Nonlinear models were tested to identify those with the best fit for growth curves in seven sheep breeds [Blackbelly (n= 19,084); Pelibuey (n= 39,025); Dorper (n= 35,814); Katahdin (n= 74,154); Suffolk (n= 10,267); Hampshire (n= 7,561); and Rambouillet (n= 7,384)]. Using breed registry databases, live weight was assessed from birth to 230 d of age. The SAS program was applied to test six nonlinear models: Brody, Verhulst, von Bertalanffy, Gompertz, Mitscherlich and logistic. The criteria for selecting the best-fit model were the average prediction error; the prediction error variance; the Durbin-Watson statistic; the coefficient of determination; the root-mean-square error; and the Akaike and Bayesian information criteria. For the Hampshire, Pelibuey and Suffolk breeds the best-fit model was the von Bertalanffy, with a sigmoid curve and an inflection point age between 40 and 57 d. For the Katahdin, Blackbelly, Dorper and Rambouillet breeds the best-fit models were the Brody and Mitscherlich models, with a continuous growth curve, no inflection point and constant growth rate. Marked differences were observed in adult weight between breeds, with average values (kg) of 44.6 for Blackbelly, 49.2 for Rambouillet, 52.9 for Pelibuey, 55.6 for Hampshire, 60.2 for Katahdin, 64.7 for Suffolk and 65.2 for Dorper; values tended to be highest in the Brody and Mitscherlich models, and lowest in the logistic and Verhulst models.

Resumen Caracterizar el crecimiento ayuda en la toma de decisiones de manejo, comercialización y mejoramiento genético. El objetivo fue identificar un modelo no lineal (MNL) para describir la curva de crecimiento en borregas de registro a través de siete razas. Se evaluó el peso vivo, desde el nacimiento hasta los 230 d de edad, de las razas Blackbelly (BB; n= 19,084), Pelibuey (PE; n= 39,025), Dorper (DR; n= 35,814), Katahdin (KT; n= 74,154), Suffolk (SF; n= 10,267), Hampshire (HS; n= 7561) y Rambouillet (RB; n= 7,384). Se evaluaron los MNL: Brody (BRO), Verhulst (VER), Von Bertalanffy (VBE), Gompertz (GOM), Mitscherlich (MIT) y Logístico (LOG). Los análisis se realizaron con el software SAS. Los criterios para seleccionar el modelo con mejor ajuste fueron: error de predicción promedio, varianza del error de predicción, estadístico Durbin-Watson, coeficiente de determinación, raíz del cuadrado medio del error, criterios de información Akaike y Bayesiano. Para HS, PE y SF, el mejor modelo fue VBE, con una curva sigmoide y edad al punto de inflexión entre 40 y 57 d. Los modelos BRO y MIT tuvieron el mejor ajuste para KT, BB, DR y RB, con una curva continua, sin punto de inflexión y tasa de crecimiento constante. Para peso adulto se observaron marcadas diferencias, con valores promedio (kg) de 44.6 en BB, 49.2 en RB, 52.9 en PE, 55.6 en HS, 60.2 en KT, 64.7 en SF y 65.2 en DR; con la tendencia de valores mayores para los modelos BRO y MIT, y los menores para LOG y VER.

ABSTRACT The objective was to evaluate the effect of three levels of cull pinto beans (CPB; Phaseolus vulgaris) on ruminal fermentation, kinetics, and nutrient digestibility in hair lambs. Six cannulated lambs averaging 56.6±3.8 kg were used and were randomly assigned to one of three treatments. Treatments were: 0.0 kg kg−1 of CPB in the supplement (control); 0.25 kg kg−1 of CPB in the supplement (CB25); and 0.40 kg kg−1 of CPB in the supplement (CB40). Dry matter intake, ruminal pH, NH3, and volatile fatty acid (VFA) concentration, methane production, Kp (passage rate), MRT (mean retention time), and digestibility of dry matter, crude protein, and neutral detergent fiber were evaluated. Data were analyzed in a Latin square design, repeated in line, by MIXED procedure of SAS. Estimates used for Kp and MRT were obtained by a non-linear regression model (PROC NLIN). Dry matter intake was reduced by supplementation of CPB. No differences were found in ruminal pH or ruminal NH3. During the trial, differences were found for ruminal VFA concentration (mM), which were greater for the CB25 group. The propionate:acetate ratio was greater for the CB40 treatment. Methane production (mM/m) differed among treatments, but it was the greatest for the CB40 group. Passage rate (kg kg−1/h) and MRT (h) were similar among treatments and the digestibility (kg kg−1) of dry matter, crude protein, and neutral detergent fiber was not different among treatments. The inclusion of 0.25 kg kg−1 of CPB in the diet of hair lambs allows for appropriate nutrient digestion without affecting Kp and MRT and increases the molar proportion of the ability of VFA to maintain acetate:propionate ratio without increasing methane production.

ABSTRACT The objective was to evaluate the effect of cull pinto beans (CPB) (Phaseolus vulgaris) on performance of feedlot lambs. Seventy-two crossbred hair-breed lambs (Dorper × Pelibuey and Kathadin × Pelibuey) were used (75±6 days old and 18.7±3.89 kg of initial body weight). Animals were fed twice daily. Diets consisted of 20% alfalfa hay and 80% concentrate based on ground sorghum grain and were formulated to contain 17.9% crude protein and 2.60 Mcal/kg metabolizable energy. Treatments were (dry matter basis): no CPB (0%), 10% CPB, and 20% CPB. Lambs were blocked by body weight and treatments and arranged in a 2 × 3 arrangement of treatments. Body weights were recorded initially and subsequently at 14-day intervals for a total 70 number of days. Dry matter intake was recorded daily. Apparent dry matter digestibility was predicted using insoluble acid detergent fiber. Data were analyzed as a randomized complete block design. Final body weight and average daily gain decreased linearly with increasing CPB level and were greater for males than females. A level × gender interaction was observed for dry matter and crude protein digestibility. Data for hot carcass weight and cold carcass weight decreased linearly as CPB level increased and were greater for males. Carcass yield, longissimus muscle area, and dressing percentage were greater for males. Dressing percentage quadratically increased as CPB level increased. Cull pinto beans are a suitable ingredient for feedlot hair-breed lambs, but the inclusion of more than 10% of CPB level decreases animal performance.