Effect of canola oil supplementation level on total tract digestion, ruminal fermentation, and methane emissions of cows grazing Urochloa sp. supplemented with a fixed amount of concentrate.

Four rumen-cannulated cows (Bos taurus × Bos indicus, 657 ± 92 kg body weight, BW) in a rotational grazing (Urochloa sp.) system were assigned to different canola oil (CO) inclusion levels, 0.0, 0.40, 0.80, and 1.2 g/kg according to shrunk body weight (SBW, BW adjusted for gastrointestinal filling) in a 4 × 4 Latin Square design to evaluate CO on the CH4 emissions and dietary energy intake. CH4 emissions were estimated using an infrared analyzer methodology (Sniffer method). Grass intake and fecal production were estimated using Cr2O3 as an external marker. CO supplementation increased (linear effect, P ≤ 0.05) total dry matter and gross energy intake with a linear increase (P = 0.09) in neutral detergent fiber (NDF) intake. While digestible energy (Mcal/kg) linearly increased with increasing CO supplementation level (linear effect, P < 0.05), total tract digestion of organic matter, NDF, and CP was comparable (P > 0.05) between levels. Maximal CO supplementation (1.2 g/kg SBW) significantly decreased total ruminal protozoa population, acetate:propionate ratio, and enteric methane production (g/kg DMI) by 9, 5.3, and 17.5%, respectively. This study showed that, for cows grazing tropical forages, CO can be supplemented up to 1.2 g/kg SBW (5.8% of the total diet) without negatively affecting intake and nutrient digestion while reducing ruminal fermentation efficiency and enteric methane emission (≤ 17.5%).

Use of a nonlinear model to estimate milk losses due to subclinical mastitis in Holstein-Zebu cows.

The objective of this observational study was to estimate milk loss from subclinical mastitis (SCM) using a nonlinear one-phase exponential decay function fitted to the relationship between the sum of the California mastitis test scores of productive quarters (x1, 0 to 16) and daily milk production per cow (y, kg/day). The function was y = (a - b)e-c1*x1 + b, where a is the predicted y when x is zero, b is the y when x1 tends to infinity, and c1 is a rate constant. The fitted function was y = (10.02 - 5.76)e-0.06137*x1 + 5.76, with an adjusted coefficient of determination (R2adj) of 0.0692, a standard deviation of the residual (Sy.x) equal to 13.49, and an Akaike's information criterion corrected (AICC) of 3902.8. To this function, we added the multiplicative factors test day (x2, 1 to 12), the number of productive quarters (x3, 2, 3 or 4), months of age of cow (x4, 25 to 209), and days in milk (x5, 2 to 196), to adjust the decay function for their effects. The fitted model was y = [(9.65 - 3.95)e-0.03415*x1 + 3.95] (x2-0.1081) (x30.1049) (x40.1589) (x5-0.1972) with R2 of 0.3166, Sy.x = 11.38, and AICC = 3821.9. We used the adjusted decay function parameters to compute a conversion factor (CF, 0 to 1) each x1 integer value from 0 to 16 to project its actual y to that of an SCM-free udder (x = 0). Then, the CF for a x1 of 0 equals to 9.65/9.65 = 1, and for a x1 of 8 equals 8.28, so its CF would be 8.29/9.65 = 0.8588. A cow with a 5.5 kg/day milk production at an x1 score of 8 would have an SCM-free production of 5.5/0.8588 = 6.4 kg/day, and its daily milk loss would be 6.4-5.5 = 0.9 kg/day. The difference, multiplied by MX$ 5.50 (US$ 0.275), would result in an economic loss of 4.95 Mexican pesos per day. This procedure makes possible the timely on-site estimation of economic losses due to subclinical mastitis.

Segmented regression to describe cumulative milk production of grazing dual-purpose Holstein-Zebu cows.

The objective of this study was to compare the fit of seven functions to cumulative daily milk yield records of grazing F1 (Holstein × Zebu) cows in a dual-purpose cattle production unit of the Mexican tropics. Fifty-seven lactations from cows that calved from 1998 to 2001 were used. The functions were quadratic without intercept, three with two segments (both segments linear, the first segment quadratic and the second linear, and both segments quadratic), and three classical growth functions (Gompertz, logistic, and Richards). The Akaike information criterion corrected (AICC) was used as criterion of fit, being the function with the best fit the one with the lowest AICC value. The best fit was for the segmented function with both segments quadratic, followed closely by the Richards function. The derivatives of these functions give the daily milk yield curve (kg/cow/day), so the former results in a straight line per segment and the latter in the usual shape of the typical lactation. However, as cumulative records produce a monotonic increasing line, neither function can distinguish a priori the presence of a lactation peak. For this reason, it is advisable to examine the common dispersion plot of daily milk yield of each cow, and if a peak is not evident, then proceed to fit the segmented function; otherwise, the function of Richards should be used. The need to study the causes for the absence of a lactation peak in tropical dual-purpose cows is highlighted.

Rotational Grazing Modifies Rhipicephalus microplus Infestation in Cattle in the Humid Tropics.

Rotational grazing has been mentioned as a potential tool to reduce losses caused by high tick loads. This study aimed: (1) to evaluate the effect of three grazing modalities (rotational grazing with 30- and 45-day pasture rest and continuous grazing) on Rhipicephalus microplus infestation in cattle, (2) to determine population dynamics of R. microplus in cattle under the three grazing modalities mentioned in the humid tropics. The experiment was carried out from April 2021 to March 2022 and consisted of 3 treatments of grazing with pastures of African Stargrass of 2 ha each. T1 was continuous grazing (CG00), and T2 and T3 were rotational grazing with 30 (RG30) and 45 d of recovery (RG45), respectively. Thirty calves of 8-12 months of age were distributed to each treatment (n = 10). Every 14 days, ticks larger than 4.5 mm were counted on the animals. Concomitantly, temperature (°C), relative humidity (RH), and rainfall (RNFL) were recorded. Animals in the RG45 group had the lowest count of R. microplus compared to the RG30 and CG00 groups; these results suggest that RG45 days of rest could be a potential tool to control R. microplus in cattle. Yet, we also observed the highest population of ticks on the animals under rotational grazing with a 30-day pasture rest. A low tick infestation characterized rotational grazing at 45 days of rest throughout the experiment. The association between the degree of tick infestation by R. microplus and the climatic variables was nil (p > 0.05).

Effects of Three Herbs on Methane Emissions from Beef Cattle.

The objectives of the present work were to evaluate the in vivo antimethanogenic effects of Cymbopogon citratus (CC), Matricaria chamomilla (MC) and Cosmos bipinnatus (CB) on beef cattle fed a high in concentrate diet (forage-to-concentrate ratio [F:C] of 19.4:80.6), and the effects of increasing levels of CC (0%, 2%, 3%, and 4% of the daily DM intake (DMI)) on enteric CH4 emissions by beef cattle fed a ration low in concentrate (F:C ratio of 49.3:50.7). Two experiments were conducted to address the objectives. For the first experiment, eight Charolais × Brown Swiss steers distributed in a replicated 4 × 4 Latin square experimental design were used. Four treatments were evaluated: (1) control diet (CO), (2) CO + 365 g dry matter (DM)/d CB, (3) CO + 365 g DM/d MC, (4) CO + 100 g DM/d CC. For Experiment 2, four Charolais x Brown Swiss steers distributed in a single 4 × 4 Latin square design were used. It was concluded that 100 g DM per day CC and 365 g DM per day CB (Experiment 1) reduced CH4 yield of beef cattle. In Experiment 2, CC supplementation levels exceeding 2% of DMI reduced daily CH4 emissions but at the expense of decreasing digestibility of DM.

Effect of Gliricidia sepium leaves intake on larval establishment of Cooperia punctata in calves and bio-guided fractionation of bioactive molecules.

The aims of this study were: 1) to assess the anthelmintic effect of Gliricidia sepium on the establishment of C. punctata third-stage larvae (L3) in calves, and 2) to isolate and to elucidate an anti-exsheathment phytochemical from the plant offered during the trial. Twelve ¾ Holstein × Zebu calves were divided in two experimental groups: control (T1) and treatment (T2) (n = 6). After adaptation, each calf was infected with an oral dose of 400 C. punctata L3/Kg LW. Basal diet consisted of Digitaria decumbens hay (6.27% CP) and commercial concentrate (12% CP). In addition, during the experimental period T2 received fresh G. sepium leaves (26.88% CP) ad libitum. On day 9 post-infection, three calves per treatment were randomly selected for slaughter, and worm counts were performed. Larval establishment rates obtained were 13.44 ±â€¯0.13% and 3.1 ±â€¯1.42% for T1 and T2, respectively (P < .05). The reduction of larval establishment was 76.9%. The total length of worms recovered from the animals was also affected by the intake of G. sepium (P < .05). Phytochemicals present in G. sepium leaves offered to calves were isolated through silica gel columns and elucidated through Magnetic Nuclear Resonance (1H and 13C). Bio-guided isolation procedures lead to the elucidation of Oxytroside (Kaempferol 3-O-rhamnopyranosyl-(1 → 6)-ß-D-glucopyranoside-7-O-rhamnopyranoside), which fully inhibited the C. punctata exsheathment process (2400 µg mL-1). Gliricidia sepium represents an alternative to prevent severe C. punctata infections by reducing larval establishment in cattle.

Elucidation of Leucaena leucocephala anthelmintic-like phytochemicals and the ultrastructural damage generated to eggs of Cooperia spp.

Leucaena leucocephala is a tropical forage legume suggested as an alternative method to control gastrointestinal parasitism in ruminants. This study: (1) performed a bio-guided fractionation of an aqueous extract of L. leucocephala using the egg hatch assay (EHA) to identify the anthelmintic (AH)-like phytochemicals present in fresh leaves, and (2) assessed the ultrastructural damage to eggs of Cooperia spp. after incubation with the final fraction. Phytochemicals were isolated using silica gel columns and identified using high performance liquid chromatography and standards for comparison. The final fraction was evaluated using EHA at 0.06, 0.125, 0.250, 0.500 and 1.1 mg ml(-1). The lethal concentration to inhibit 50% of Cooperia spp. egg hatching (LC50) was calculated using a Probit analysis. Scanning and transmission electron microscopy revealed the ultrastructural changes present in Cooperia spp. eggs. Bio-guided isolation procedures led to the recognition of an active fraction (LlC1F3) mainly composed of quercetin (82.21%) and caffeic acid (13.42%) which inhibited 90.49 ± 2.8% of Cooperia spp. egg hatching (P<0.05), and an LC50 of 0.06 ± 0.14 mg ml(-1). Scanning electron microscopy (SEM) showed eggs exposed to the active fraction had an irregular external layer with small projections and ruptures of lateral eggshell walls. Transmission electron microscopy (TEM) showed changes to Cooperia spp. eggs in electro-density, including the thickness of the eggshell layers and fractures after incubation with the final fraction (LlC1F3). Changes in bioactivity after purification suggest synergistic interactions between quercetin and caffeic acid.

Complementos con base en melaza-urea para vacas de doble propósito del trópico veracruzano / Molasses-urea based supplements for dual-purpose cows in the tropics of Veracruz

El objetivo de esta investigación fue determinar qué tipo de suplementos con base en melaza y urea es el más apropiado para vacas de doble-propósito, cuando los suplementos se dan ad libitum durante el tiempo de ordeno, en el trópico húmedo del estado de Veracruz. En el primer experimento, la producción diaria de leche disminuyó al aumentar el nivel de melaza ofrecido, lo cual resultó de una disminución en la digestibilidad de la dieta causado por el alto consumo de melaza en tiempos cortos. En el segundo experimento se observó que, para producir leche y mejorar la ganancia de peso, la melaza-urea al 3 por ciento resultó más económica que un concentrado "casero". El tercer estudio indicó que la inclusión de harina de sangre en la mezcla melaza-urea mejoró significativamente la producción de leche por vaca, así como la condición corporal y la ganancia de peso de los animales. Se concluye que la mejor forma de aumentar la producción diaria de leche de las vacas de doble propósito es mediante la complementación con una mezcla de melaza, urea y harina de sangre

Efecto del nivel de complementación sobre la ganancia de peso de corderos Pelibuey estabulados / Effect of supplement level on average daily gains of Pelibuey ram lambs in the feedlot

El presente estudio se llevó a cabo con el fin de estimar el desempeño productivo del corderos Pelibuey, del destete al peso de comercialización, en función del nivel de complemento recibido. El estudio se realizó en un sitio con clima cálido (23.5ºC de temperatura media anual) y húmedo (1991 mm anuales), con lluvias todo el año, clasificado como Af(m) w'(e) que posee suelos ultisoles ácidos (pH de 4.5 a 5.2) de baja fertilidad (deficientes en N y P). La investigación duró 98 días; se utilizaron 84 corderos Pelibuey de 3 meses de edad sin castrar, con peso de 12.5 ñ 3.1 kg que se asignaron al azar dentro de cuatro grupos de 21 borregos. Los animales fueron alimentados con forraje fresco y picado de pasto Taiwán (Pennisetum purpureum) de aproximadamente 90 días de rebrote más concentrado 17.8 por ciento de proteína cruda y 11.5 MJ/kg MS de energía metabolizable, a razón de 0 por ciento, 1 por ciento, 2 por ciento y 3 por ciento del peso del animal. Las ganancias diarias de peso (GDP) por grupo fueron 0.006, 0.048, 0.094 y 0.144 kg/cordero. El consumo del materia seca del concentrado (CMS) fue de 0, 0.143, 0.324, y 0.525 kg/cordero/día y el forraje (CMS) de 0.412, 0.376, 0.344 y 0.321 kg/cordero/día. En el mismo orden, las conversiones alimenticias fueron 68.7, 8.9, 7.0 y 5.9 kg de MS/kg de GDP. Los meses para alcanzar el peso de mercado (30 kg) fueron 97.5, 9.9 5.9 y 4.0, respectivamente. La regresión lineal entre consumo total de materia seca (CMS Y) y GDP (X) mostró que el CMS cuando la GDP=0 fue 0.368 kg/cordero día (ordenada al origen) y que cada 0.1 kg de aumento en GDP requirió de un aumento de 0.319 kg/cordero/día en el CMS (coeficiente de regresión). El consumo de proteína cruda a cero GDP fue de 0.024 kg/cordero/día (ordenada al origen) y cada 0.1 kg de aumento de GDP requirió un aumento en el consumo de proteína cruda de 0.053 kg/cordero/día (coeficiente de regresión). La tasa de retorno directo [(ingreso bruto-costo de alimentación/costo de alimentación)x100] fue de: -77 por ciento, 66 por ciento, 104 por ciento y 139 por ciento para los niveles de complementación de 0 por ciento, 1 por ciento, 2 por ciento y 3 por ciento, respectivamente. Se concluyó que los animales pudieron haber consumido más materia seca y ganado más peso, dada la respuesta scendente a la complementación...