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.

No 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 (R 2 ), 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 R 2 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.

-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, NH 3 , 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 NH 3 . 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.

The objective of this study was to evaluate the effect of a mixture of direct-fed microbials (DFM), yeast, and digestive enzymes on animal performance in feedlot cattle, as well as digestibility when finishing feedlot cattle. Thirty crossbreed (Charolais × Beefmaster) steers averaging 15 months old and 321.83±3.73 kg of initial body weight were used. Animals were randomly assigned to one of two treatment groups: control (basal diet) and a mixture of DFM, yeast, and digestive enzymes (basal diet + 30 g of the mixture). Each group contained fifteen experimental units. Animals were fed individually twice a day, and dry matter intake (DMI) was recorded daily. Body weights were recorded initially and subsequently at 28-day intervals for a total of 140 days to evaluate average daily gain (ADG). The gain:feed ratio (G:F) was also calculated per period. Dry matter digestibility, crude protein (CPD), and neutral detergent fiber (NDFD) were evaluated in the finishing phase. Ten steers per treatment were randomly selected for digestibility evaluations. Insoluble acid detergent fiber was used to calculate apparent digestibility. A completely randomized design with measurements repeated over time was used to evaluate animal performance, and a completely randomized design was used to evaluate apparent digestibility. No effect of treatment was observed for DMI. At the end of the trial, differences for ADG were found between treatments, with higher values in control than the treatment group. However, no effect for G:F was found. Dry matter digestibility, CPD, and NDFD were similar between treatments. The addition of the mixture of DFM, yeast, and digestive enzymes as a feed supplement in the diet of feedlot cattle does not improve animal performance and nutrient digestibility.

The objective of this study was to evaluate the effect of three levels of cull pinto beans (CPB) on animal performance, energy balance, and digestibility of hair ewes during pregnancy-lactation. One hundred and sixty-eight Pelibuey ewes were used (105 multiparous and 63 primiparous). Seven ewes of each type were randomly assigned to each of the 24 pens. Then, the twenty-four pens were randomly assigned to one of three treatments. Treatments were assigned on DM basis at: 0 g kg-1 of CPB in the supplement; 250 g kg-1 of CPB in the supplement; and 500 g kg-1 of CPB in the supplement. Data was analyzed by using the PROC MIXED of SAS. Lamb birth and weaning weight were also evaluated with the GLM procedure of SAS. All variables were analyzed as a completely randomized design. No differences among treatments were observed for body weight, body condition score, non-esterified fatty acids, and body weaning weight. During late pregnancy, dry matter intake was different among treatments, but it was similar during lactation. Body birth weight was different among treatments and showed a quadratic effect. At day 30 of lactation, a treatment effect was found for digestibility of dry matter (DM). At the end of lactation, digestibility of crude protein was different among treatments. In day 60 of lactation, differences among treatments were found for digestibility of neutral detergent fiber. Due to equal ewe performance among treatments of CPB and its low cost, its use is recommended in hair ewe feeding for these productive stages: 500 g kg-1 DM of the supplement during pregnancy and 400 g kg-1 DM during lactation.

Staphylococci are important mastitic-pathogens of humans and livestock. Chlorate is reported to be a potent inhibitor against staphylococci but adaptation by the microbes can occur. Presently, we cultured multi-drug resistant Staphylococcus aureus strain ATCC 12600 anaerobically at 39oC in nitrate-supplemented (5 mM) Tryptic Soy broth. The broth was treated without (control) or alone with 5 mM sodium chlorate (ClO3) or 9 mM of either 2-nitro-1-propanol (NPOH), ethyl nitroacetate (ENA) or ethyl 2-nitropropionate (E2NPA) or with combinations of CLO3 and respective nitrocompound. Control and treated cultures were incubated in triplicate and growth was measured via absorbance (600 nm) at during 9 h. An analysis of variance revealed an inhibitory effect of treatments (P < 0.05; SEM = 0.078) on mean specific growth rates of S. aureus, with rates during logarithmic growth being most rapid in controls and cultures treated with ENA or EN2PA (1.45, 1.23 and 1.21 h-1, respectively) and more than 92% slower in NPOH and NPOH+CLO3-treated cultures (0.09 and 0.03 h-1, respectively). Growth rates of cultures treated solely with CLO3 (0.66 h-1) were more than 50% slower than controls and were decreased further in cultures treated with combinations of CLO3 plus E2NPA or ENA (0.39 and 0.45 h-1). After 9 h of growth, maximum optical densities (maxOD) were highest for controls and cultures treated with ENA or EN2PA (0.52, 0.52 and 0.50 maxOD, respectively), intermediate in cultures treated with CLO3 alone (0.21 maxOD) and lower yet in cultures treated with CLO3 plus ENA, E2NPA or NPOH (0.15, 0.11 and 0.02 maxOD, respectively). The maxOD for cultures treated with NPOH alone was 0.02 and did not differ from cultures treated with the combination of CLO3+NPOH. Results demonstrate marked synergistic and prolonging effects of combing ENA and E2NPA with CLO3 but no additional effect of the potent anti-staphylococcal activity of NPOH.

We tested the effects of Galena or Chinook hops treatment (6% wt/wt) of simulated composts (13 d) of wood chip litter (WCL) alone or mixed 3:1 with ground Bluestem hay (BSH). Results revealed that net losses of urea and ammonia in the WCL litter composted without BSH (n = 3/treatment) were unaffected by hops treatment (P = 0.37 and 0.13, respectively), averaging 0.32 ± 0.7 and 0.03 ± 1.5 µmol/g, respectively). The loss of uric acid was 60% less (P = 0.04) in the Galena hops-treated WCL compost than in the negative control compost (13.9 ± 3.8 vs 24.4 ± 5.6 µmol/g, respectively) and intermediate in the Chinook-treated compost (16.0 ± 2.7 µmol/g). Nitrogen losses during compost of WCL: BSH (n = 2/treatment) were unaffected by hops treatment (P = 0.77, 0.73 and 0.14 for uric acid, urea and ammonia, respectively), averaging 12.21 ± 3.1, 0.64 ± 0.6 and 1.07 ± 0.1 µmol/g, respectively, respectively). Assessment of potential carry over effects of residual hops in the composts during in vitro rumen fermentation (0.2 g of treated and control compost, in triplicate, mixed with 10 mL freshly collected rumen fluid) for 24 h at 39oC under 100% CO2 revealed no effects of hops treatment on H2 accumulations in incubations with WCL or WCL: BSH composts (P = 0.22 and 0.17, respectively), averaging 0.23 ± 0.1 and 0.17 ± 0.1 µmol/mL fluid, respectively. Accumulations of CH4 in rumen incubations of WCL composts were unaffected by hops treatment (P = 0.24), averaging 15.07 ± 2.0 µmol/mL, but were increased (P = 0.0002) in incubations of WCL: BSH composts, averaging 14.1 ± 0.4 and 13. 8 ± 0.6 µmol/mL in Galena- and Chinook-treated compost compared with 11.2 ± 0.4 µmol/mL in control incubations. Results indicate hops treatment may lessen uric acid degradation composting poultry litter without inhibiting rumen fermentation.