It has been previously shown that the long-term inhibition of milking-induced prolactin (PRL) release by quinagolide (QN), a dopamine agonist, reduces milk yield in dairy cows. To further demonstrate that PRL is galactopoietic in cows, we performed a short-term experiment that used PRL injections to restore the release of PRL at milking in QN-treated cows. Nine Holstein cows were assigned to treatments during three 5-d periods in a 3×3 Latin square design: 1) QN: twice-daily i.m. injections of 1mg of QN; 2) QN-PRL: twice-daily i.m. injections of 1mg of QN and twice-daily (at milking time) i.v. injections of PRL (2µg/kg body weight); and 3) control: twice-daily injections of the vehicles. Mammary epithelial cells (MEC) were purified from milk so that their viability could be assessed, and mammary biopsies were harvested for immunohistological analyses of cell proliferation using PCNA and STAT5 staining. In both milk-purified MEC and mammary tissue, the mRNA levels of milk proteins and BAX were determined using real-time reverse-transcription PCR. Daily QN injections reduced milking-induced PRL release. The area under the PRL curve was similar in the control and PRL injection treatments, but the shape was different. The QN treatment decreased milk, lactose, protein, and casein production. Injections of PRL did not restore milk yield but tended to increase milk protein yield. In mammary tissue, the percentage of STAT5-positive cells was reduced during QN but not during QN-PRL in comparison with the control treatment. The percentage of PCNA-positive cells was greater during QN-PRL injections than during the control or QN treatment and tended to be lower during QN than during the control treatment. In milk-purified MEC, κ-casein and α-lactalbumin mRNA levels were lower during QN than during the control treatment, but during QN-PRL, they were not different from the control treatment. In mammary tissue, the BAX mRNA level was lower during QN-PRL than during QN. The number of MEC exfoliated into milk was increased by QN injections but tended to be decreased by PRL injections. Injections of PRL also increased the viability of MEC harvested from milk. Although PRL injections at milking could not reverse the effect of QN treatment on milk production, their effects on cell survival and exfoliation and on gene expression suggest that the effect of QN treatment on the mammary gland is due to QN's inhibition of PRL secretion.

The aim of this study was to estimate the intake of dry matter forage (CMSf) by grazing holstein cows. The research was conducted in northern Antioquia highlands; a silvopastoral system with Tithonia diversifolia and Cenchrsus clandestinum (SSP) and a monoculture C. clandestinum were used. Were estimated the CMSf by different methodologies and kikuyu:wild sunflower consumption relation, also the interchangeability of two methodologies was determined. There were two conducted trials, in the first trail SSP was used without browsing of wild sun ower and monoculture; in the second trial the same system was applied, with the difference that for the SSP animals browsed the shrubby by themselves. Twelve random infant holstein cows were used in the two systems. CMSf was estimated by indicators (I), agronomic (A) and grazing behavior (C) methods, method I was the reference. In trial I more CMSf was observed in the SSP, with an average of 14.7 kg/day (p<0.05); trial II showed no difference in the CMSf, with an average of 13.3 kg/day (p>0.005). The kikuyu:wild sunflower consumption relation was 95:5. The correlation coefficient of concordance between the methods I and C near to 0 shown that they are not interchangeable. The results suggest that the SSP evaluated supplied sufficient forage to ensure optimal CMSf.

The aim of this study was evaluated by in vitro, the effect of mixing wild sunflower (Tithonia diversifolia), kikuyu (Cenchrus clandestinum) and concentrated feed, with the addition of polyunsaturated fatty acids (AGPI) on the production of methane (CH4 ml/g MSd), dry matter digestibility (%DIVMS) and production of volatile fatty acids (AGV). The research was conducted in NUTRILAB laboratory (Medellin, Colombia) in September 2015. Three combinations of AGPI rich lipid sources were used with a total maximum inclusion level corresponding to 3% of incubated dry matter. Combinations of lipid sources were: SAGPI1: 0.5% soya oil, 0.5% sish oil, 2% rich in omega 3 bypass fat. SAGPI2: 1% Soya oil, 0.5% fish oil, 1.5% bypass fat rich in omega 3. SAGPI3: 2.5% Soya oil, 0.5% fish oil. A source of bypass fat (GSP) was also used. The results were processed using pre-planned test comparisons through the PROC MIXED-SAS.The methane production in vitro decreased (p<0.05), while the dry matter digestibility increased (p<0.05) 24 and 48 hours after wild sunflower was include and / or AGPI or both into the mixtures. In the molar ratio of AGV (%), acetic acid showed an increased presence. The inclusion of forage like wild sunflower and sources of AGPI supplementation in cattle, could be a strategy to reduce methane emissions without causing a detriment to the ruminal fermentation.

The aim of this study was to analyze the milk production, quality and cost:benefit ratio the addition of three levels (0%, 15% and 25%) our of Tithonia diversifolia in the supplement of Holstein cows. In a bovine milk production system in a high tropic were used nine cows (70 to 120 milk days and parity two to ve). They were randomly assigned in three groups, which grazed on Kikuyo grass (Cenchrus clandestinus) in La Montaña farm, located in San Pedro de los Milagros, Antioquia, Colombia, at 2350 meters above sea level. This study was carried out during March 2015. At 56 days, T. diversifolia (wild sunflower) from a fodder bank located at 2456 masl was harvested, and dried using marquees ground for an approximate period of time of ten days, it was then minced and stored to prepare isoenergetics (1.8 Mcal NEL/kg) and isoproteics (14% CP) supplements. The study evaluated its effect on dry matter intake (DMI), corrected milk production (4% fat, FCM), milk composition (protein, fat, lactose, total solids, milk urea nitrogen –MUN), somatic cell count (SCC), produced milk: supplement intake and cost:benefit ratio. The results showed signi cant differences for the inclusion of 25% of T. diversifolia flour in the supplement for benefit:cost ratio, lactose, MUN, SCC and produced milk:supplement intake ratio, contrary to what happened with DMI, corrected 4% fat milk production, protein, fat and total solids that not differ. The addition of 25% of wild sunflower in the supplement for grazing dairy cows improved the milk quality in reference to lactose concentration, efficiency in the use of the supplement, cost:benefit ratio.

La percepción de calidad de carne es un concepto complejo y requiere de análisis multivariados para entender su estructura y conceptualización. El objetivo del estudio fue valorar la percepción de calidad de carne por parte del consumidor y la disponibilidad a pago por información de calidad. Se aplicaron 400 encuestas bajo un cuestionario estructurado. La encuesta indagó sobre el perfil socioeconómico del consumidor y la percepción sobre características intrínsecas y extrínsecas de la carne, perfil de consumo por información nutricional, estilo de vida, preferencias de cortes y frecuencia de compra, y disposición a pago por información nutricional, empleando una escala Likert. Los datos se analizaron mediante modelos de ecuaciones estructurales (SEM) y pruebas chi2. El SEM registró un ajuste satisfactorio (CFI=0,978, RMSEA=0,17). Los resultados indicaron que el consumidor conceptualiza (P < 0,05) la carne con base en aspectos intrínsecos (color, suavidad y pérdida de agua), extrínsecos (precio, bienestar animal y confianza) y la actitud de consumo saludable. El encuestado no consideró el concepto de calidad para la disposición a pago por información. Las mujeres, los consumidores entre 37-55 años y los empleados, registraron la puntuación más alta (P < 0,05) en el concepto de calidad de la carne.