Efecto de distintas estrategias de alimentación sobre la respuesta productiva de vacas lecheras y la calidad de la leche

Tesis para obtener el grado de Doctor en Ciencias Agrarias, de la Universidad Nacional de Mar del Plata, en junio de 2020.Los sistemas pastoriles de producción de leche utilizan concentrados energéticos y raciones completamente mezcladas (TMR) cuando la tasa de crecimiento de la pastura y la cantidad de forraje disponible resultan limitantes del consumo y la producción. Los trabajos de niveles de suplementación con concentrado en primavera demostraron que el consumo creciente de concentrado genera efectos aditivos incrementando la producción de leche y el contenido de caseína hasta un 40% del total de MS consumida. Una mayor absorción de energía glucogénica no incrementó la concentración proteica de la leche, pero permitiría aumentar la producción de proteína láctea y caseínas y reducir el tenor ureico de la leche y la concentración de nitrógeno amoniacal en el rumen. La producción o concentración de grasa láctea, la digestión ruminal de la FDN de la pastura y los parámetros relacionados con el valor saludable de la grasa láctea no fueron afectados en el rango de consumo de concentrado estudiado (15 al 40% de la MS total consumida). La ecuación de respuesta marginal ajustada [Leche (kg día-1) = 25,95 + 0,774 x kg MS concentrado (P < 0,042; R2 = 0,37)] indicó que la producción de leche incrementa linealmente a medida que la cantidad de concentrado aumenta desde 2,7 a 11,6 kg MS vaca-1 día-1, con una respuesta de 0,774 kg leche kg MS concentrado adicional-1. Los trabajos de reemplazo de pastura por TMR indicaron un incremento lineal de la producción de leche y sólidos ante consumos crecientes de TMR en reemplazo de pastura cuando los mismos (TMR) representaron entre el 30 y el 100% de la MS total consumida por vacas produciendo 27,0-34,0 kg leche día-1, sin efectos sobre los contenidos de grasa y proteína. Las combinaciones de TMR y pastura evaluadas no indujeron cambios en el ambiente ruminal ni generaron efectos asociativos negativos sobre la degradación ruminal de la FDN de los forrajes. Por lo tanto, los efectos positivos del consumo de creciente de TMR sobre la producción de leche no estarían explicados por un mejor equilibrio de nutrientes a nivel ruminal. La calidad nutricional y antioxidante de la leche disminuyó a medida que la cantidad de pastura consumida fue menor debido al menor contenido de ácidos grasos saludables como el ruménico y el linolénico y la reducción en el contenido de vitaminas antioxidantes. Tomados en conjunto, los resultados confirman que el sistema pastoril con suplementación es una alternativa económicamente competitiva comparada con el sistema confinado. Una estrategia viable para vacas de parición otoñal sería utilizar una PMR (75% TMR:25% pastura) durante otoño-invierno que permita sostener altas producciones de leche y luego en primavera con vacas en etapas más avanzadas de lactancia aprovechar los menores costos del pastoreo y utilizar las pasturas con una suplementación estratégica.In dairy pasture based systems cows are strategically supplemented with energy concentrates or total mixed rations (TMR) when the rate of growth of the pasture and/or the amount of available forage are limiting DM intake and hence milk production. In the spring trials, increased levels of concentrate intake in grazing dairy cows showed additive effects on DM and energy intake. Milk production, milk protein and milk casein output where enhanced when concentrate intake represented up to 40% of total DM intake whereas fat yield or milk fat content were not affected. The putatively higher absorption of glycogenic energy did not increase milk protein content but allow to increase milk protein and caseins yields reducing milk urea content and concentration of ammonia nitrogen in the rumen. Ruminal pasture NDF digestion and parameters linked to healthy value of milk fat were not affected in the range of concentrate intake assayed (15 to 40% of the total DM intake). The response equation adjusted to concentrate feeding [Milk (kg day-1) = 25.95 + 0.774 x kg DM concentrate (P < 0.042, R2 = 0.37)] indicated that milk production increased linearly as the amount of concentrate intake increased from 2.7 to 11.6 kg MS cow-1 day-1 showing a marginal response of 0.774 kg milk per additional kg of DM concentrate. Experiments that examined the replacement of autumn-winter pastures for TRM showed linear increments in milk yield and solids as intake of TMR was increased from 30 to 100% of total DM intake in dairy cows producing from 27 to 34 kg milk day-1 without effects on milk fat or protein contents. Combinations of TMR and pasture did not induce changes in ruminal environment or negative associative effects on pasture NDF degradation. Therefore, the positive effects of increasing TMR intake on milk production would not be explained by a better nutrient balance at the ruminal level. The nutritional and antioxidant quality of milk decreased as the amount of pasture intake was lower due to a lower content of the healthy milk fatty acids (rumenic and linolenic) and the reduction in the content of antioxidant vitamins. Taken together, the results confirm that the pasture based system with strategically supplementation is an economically and competitive alternative compared to the confined system. A viable strategy for autumn calving cows would be to use a partial mixed ration (75% TMR: 25% pasture) during autumn-winter to maximize milk pic yield and later use the spring pastures with a strategic concentrate-supplementation to take advantage of the residual effects and the lower costs of grazing feeding.EEA RafaelaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentin

Recría de vaquillonas: efecto de la alimentación sobre el desarrollo de la glándula mamaria

El éxito del manejo alimenticio de las vaquillonas de reposición depende en buena medida del potencial de producción de leche de la futura vaca. La principal limitante para alcanzarlo, es el número de células secretoras de la glándula mamaria. En este artículo, se explican las distintas fases de crecimiento de la glándula mamaria y la incidencia de la alimentación en las mismas. Además, mostramos un ejemplo de ración adecuadamente formulada con alimentos habitualmente disponibles en los establecimientos lecheros para no afectar el desarrollo mamario.EEA RafaelaFil: Salado, Eloy. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina.Fil: Roskopf, Pablo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Roskopf, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Enfermedades del período de transición en vacas lecheras: monitoreo y prevención

En este artículo se presenta un enfoque práctico, a nivel de explotación lechera, para prevenir y monitorear las enfermedades del período de transición basado en el uso de óptimas estrategias nutricionales y de manejo. Este enfoque preventivo y de monitoreo se ha subdividido en 3 áreas claves: balance energético negativo, hipocalcemia puerperal y salud ruminal.EEA RafaelaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Área de Investigación en Producción animal; ArgentinaFil: Roskopf Perez, Pablo Matías. Instituto Nacional de Tecnología Agropecuaria (INTA). Becario; ArgentinaFil: Roskopf Perez, Pablo Matías. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Becario; Argentin

Sequía y deficiencia de fibra en dietas de vacas lecheras

En el contexto actual de sequía extrema, donde la mayoría de los productores lecheros está atravesando o atravesará un déficit en la disponibilidad de forraje, resulta imperioso formular raciones que cubran los requerimientos nutricionales y aseguren una adecuada salud ruminal, no sólo por cuestiones económicas, sino también por razones de bienestar animal. Investigadores del Área de Producción Animal del INTA Rafaela, brindan algunas alternativas y recomendaciones ante la escasez de fibra dietética.EEA BalcarceFil: Roskopf, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina.Fil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina

Productive Response of Dairy Cows Fed with Different Levels of Totally Mixed Ration and Pasture

Forty multiparous Holstein cows in early lactation (66 ± 19 days) were assigned to one of four treatments that consisted in different ratios of total mixed rations (TMR) and pasture at 100% TMR (T0), 75:25 (T1) 50:50 (T2) and 25:75 (T3) over 9 weeks in autumn-winter. Measures of rumen parameters and digestion were performed on 4 additional Holstein cows in late lactation (287 days postpartum) fitted with permanent ruminal fistulae and producing 22.6 (±5.4) kg milk in a 4 × 4 Latin Square design. In T1 to T3 cows were taken to the grazing plot once they finished the pre-planned TMR intake and pasture was offered at 2 times the expected forage DM intake. Milk was analyzed for chemical composition, milk fatty acid (FA) profile and antioxidant compounds. The cows were individually weighed and body condition score (BCS) was determined. After the morning milking, blood samples were taken every 2 weeks and plasma was analyzed for glucose, urea, non-esterified fatty acids (NEFA), insulin, growth hormone (GH) and insulin-like growth factor (IGF-I). Herbage mass in pre grazing strips of pasture averaged 2540 ± 343 kg DM/ha. As TMR intake increased, production variables increased linearly excepting milk fat (3.88 g/100g) and milk protein (3.43 g/100g) contents that were not affected. Milk yield (kg/cow/d) resulted maximal in T0 (34.2) and linearly decreased (p < 0.01) with pasture intake averaging 32.1 (T1), 28.4 (T2) and 26.8 (T3) as a higher energy intake and a lower energy cost associated with grazing activity. Milk fat output (kg/cow/d) resulted higher in T0 (1.35) and T1 (1.25) compared to T2 (1.10) and T3 (1.04). Milk protein yield (kg/cow/d) was also higher in T0 (1.18) and T1 (1.11) compared to T2 (0.96) and T3 (0.92). Total DM (24.09 kg/cow/d) and energy (41.95 Mcal NEL/cow/d)) intakes resulted maximal in T0 decreasing as pasture replaced TMR without effects on conversion efficiency (1.48 kg milk/kg DM). Plasma concentration of glucose, insulin and IGF-I were not affected but GH and NEFA increased as pasture replaced TMR in T3. Ruminal pH (5.91) and total or VFA proportions did not differ but NH3-N concentration resulted higher in treatments with higher proportion of pasture. Kinetic parameters of DM and NDF digestion from pasture or corn silage were not affected. Milk FA profile and milk antioxidant quality showed unfavorably changes as TMR increased by a decrease in rumenic and linolenic acids and content of antioxidant vitamins, without effect on the atherogenicity index. Results suggested a depressing effect of the pasture on total DM and energy intake probably explained by qualitative deficiencies chemical composition of the forage and/or factors that affect animal behavior that may induce losses in body condition of high yielding dairy cows.EEA RafaelaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Bretschneider, Gustavo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Agencia De Extensión Rural Necochea; ArgentinaFil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Descalzo, Adriana Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Tecnología de Alimentos; ArgentinaFil: Gagliostro, Gerardo Antonio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Area de Investigación en Producción Animal; Argentin

Milk Yield and Composition and Pasture Ruminal Digestion in Grazing Dairy Cows Receiving Three Levels of Energy Concentrate Supplementation

The objective of the experiment was to determine the effect of feeding three levels (T3.5, T7.0 and T10.5) of energy concentrate (3.5, 7.0 and 10.5 kg cow-1 day-1) on total dry matter (DM) and energy intakes, milk yield and composition, nutritional value of milk and rumen pasture neutral detergent fiber (NDF) digestion in grazing dairy cows. Twenty-one multiparous Holstein cows in early lactation (70.2 ± 13 days postpartum) producing 37.1 (±4.7) kg of milk were assigned to a 3 treatments (7 cows/treatment) × 3 periods Latin square design. Parameters of ruminal environment and pasture NDF degradation were obtained using 3 additional cows of the same breed fitted with rumen cannulae. On a wet basis, concentrate was composed by corn grain (68%), soybean meal (22%), wheat bran (8%) and a vitamin-mineral nucleus with monensin. Pasture (Medicago sativa, sp) was used in a rotational grazing system with an herbage allowance of 30 kg DM cow-1 d-1. Yield (kg cow-1 d-1) of fat corrected milk (4% FCM) resulted higher (p < 0.05) in T7.0 (29.0) compared to T3.5 (26.8) but similar to T10.5 (30.2). Milk and protein yields were linearly increased (p < 0.01) by concentrate intake. Milk fat (3.13 g/100g) and total solid contents (11.79 g/100g) did not differ whereas milk protein (p < 0.03) and casein (p < 0.01) levels (g/100g) increased linearly from 3.05 to 3.10 (protein) and from 2.42 to 2.47 (casein). Pasture intake decreased but total DM and energy consumption were enhanced showing addition effects after concentrate feeding. Body weight (BW) loss and plasmatic levels of non esterified fatty acids (NEFA) decreased with concentrate intake. Circulating levels of insulin-like growth factor-I (IGF-I) were higher (p < 0.05) in T10.5 while those of glucose, plasma urea nitrogen, insulin and somatotrophin were not affected. Ruminal pH and acetate concentration resulted lower (p < 0.05) in T10.5 when compared to T3.5. The acetate:propionate ratio decreased (p < 0.01) from 4.25 in T3.5 to 3.08 in T10.5 and ruminal ammonia nitrogen levels tended (p < 0.07) to be lower as concentrate intake increased. Kinetics parameters of NDF degradation remained unchanged. The potential hypercholesterolemic fatty acids (FA) of milk (C12:0 to C16:0.) remained unchanged as concentrate intake increased. Milk content of linolenic acid decreased and the n-6:n-3 ratio increased with concentrate intake from 1.56 (T3.5) to 2.57 (T10.5) remaining below the recommended values for human health (<4:1). Milk content of antioxidant vitamins was not significantly altered even when pasture DM intake fall in T10.5 compared to T3.5. Increased consumption of a starch-rich concentrate up to 40% of DM intake of cows showed additive effects on total DM and energy intakes improving milk yield, milk protein and casein contents without negative effects on milk fat concentration or yield. Pasture fiber digestion and nutritional parameters linked to healthy value of milk fat were not affectedEEA RafaelaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Bretschneider, Gustavo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Agencia De Extensión Rural Necochea; ArgentinaFil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Descalzo, Adriana Maria. INTA-LABINTEX-Centre de Coopération Internationale en Recherche Agronomique pour le Déeveloppement (CIRAD), Déepartement PERSYST, UMR Qualisud; FranciaFil: Gagliostro, Gerardo Antonio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Area de Investigación en Producción Animal; Argentin

Performance of dairy cows supplemented with by-pass fat under heat stress conditions

The objective of this study was to determine the effect of supplementation with a protected fat source on the productive response, metabolic environment and physiological indicators in Holstein cows under heat stress conditions during a 12-week experimental period. Thirty Holstein cows were distributed in 15 blocks by parity (2.0 ± 1.1), days in milk (182 ± 80) and milk production (29.4 ± 5.7 kg·day-1) at the beginning of the trial and randomly assigned within each block to the following treatments (diets): SPF: supplementation with protected fat or WPF: without supplementation with protected fat. All the cows were kept in a dry-lot where they were given a partial mixed ration (PMR) ad libitum while in the milking parlor they received individual supplementation depending on the treatment. The SPF diet contained 4.0 kg·day-1 concentrate in pellet form + 0.6 kg·day-1 ground corn grain + 0.7 kg·day-1 protected fat, while the WPF diet was similar to that offered in SPF, but the protected fat was isoenergetically replaced by ground corn grain. The fat supplement contained fats of animal and vegetable origin and microencapsulation was used for its preparation. Total dry matter and metabolic energy intakes were similar (p > 0.05) between treatments. Fat corrected milk (4% FCM) production was higher (p = 0.04), while energy corrected milk and fat productions tended (p = 0.06) to be higher in cows from the SPF group, without effects (p > 0.05) on the rest of the milk production and composition parameters. These results could be attributed to an improvement in the efficiency of the use of the energy consumed. Protected fat supplementation neither modified the metabolic profile, nor reduced the respiratory rate and body temperature of heat-stressed cows. Future research is needed to explain this latter result.EEA RafaelaFil: Roskopf, Pablo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina.Fil: Tieri, Maria Paz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina.Fil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentina.Fil: Ceron Cucchi, Maria Esperanza. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patobiologia; Argentina.Fil: Gere, Jose Ignacio. Universidad Tecnológica Nacional. División de Investigación y Desarrollo de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Salado, Eloy. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina

Relevant aspects of dietary n-3 polyunsaturated fatty acids in the adaptation of dairy cattle to the transition period

During the transition period, cows undergo a series of metabolic and immunological changes, which represent a physiological challenge that is often a risk for their production and health. During this period, dairy cows have a pro-inflammatory state associated with frequent infectious diseases and lipomobilization, and present an insulin resistance state related to fat mobilization and a high body condition score. In humans, the polyunsaturated fatty acids (PUFAs) from the omega-3 (n-3) family, which are involved in many biological systems and processes, have been shown to exert beneficial effects on health, particularly on the metabolic syndrome. Therefore, the incorporation of n-3 PUFAs in the diets of dairy cows could represent an interesting supplement for them to afford the challenge of the peripartum. This review describes the novel information and advances in the understanding of relevant aspects concerning the effects of dietary PUFAs on dairy cows, focusing on metabolic and inflammatory aspects with possible effects on the cows' physiology and adaptation to the peripartum period.Fil: Angeli, Emmanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Barcarolo, Daiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Ribas, L.. Universidad Nacional del Litoral; ArgentinaFil: Marelli, Belkis Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Roskopf Perez, Pablo Matías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Ortega, Hugo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; ArgentinaFil: Hein, Gustavo Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; Argentin

Feeding Calcium Salts of Linseed Oil on Productive Performance and Milk Fatty Acid Profile in Grazing Dairy Cows

The objective of this study was to determine the effect of supplying calcium salts of linseed oil (Ca-FA) rich in omega-3 (α-linolenic acid) on the production and chemical composition of milk and its nutraceutical value in dairy cows in early lactation. The trial lasted 12 weeks (2 weeks for adaptation to lipids and 10 weeks of data collection). A total of 36 Holstein dairy cows with 58.0 ± 17.0 days in milk (DIM), 594.1 ± 92.4 kg BW, 2.6 ± 1.5 parity and 38.9 ± 9.3 kg milk day-1 were used in a randomized complete block design. The treatments were: 1) Omega-3 (O3): 5.2 kg DM day-1 of concentrate including 0.7 kg DM of Ca-FA + 13.5 kg DM day-1 of partial mixed ration (PMR) + 12 kg DM day-1 of alfalfa pasture (Medicago sativa) and 2) Control (C): diet similar to O3 but lipid supplementation was replaced by cracked corn grain so that the diets were isoenergetic. No treatment effect was detected (P > 0.05) for any milk production and composition variables, except for urea in milk that was slightly higher in O3 (P = 0.02). The treatment × week interaction was significant (P 0.05) between treatments. Concentrate intake was higher (P 0.05) in rumen environment parameters. Supplementation with Ca-FA reduced (P < 0.05) the hypercholesterolemic fraction of milk (C12:0, C14:0 and C16:0, -13.6%, -7.4% and -9.0%, respectively). The concentration of α-linolenic acid (C18:3n-3) increased (108%, P < 0.01) in O3 group compared with group C. The absence of negative effects of lipids on the fat content of milk and ruminal fermentation suggests that protection by saponification was effective. The supplementation with Ca-FA (0.85 kg·day-1) improved the healthy value of the milk.EEA RafaelaFil: Moreno González, Yaliska. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Iorio, Jesica. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Olmeda, María Florencia. Universidad Nacional de Lomas de Zamora. Facultad de Ciencias Agrarias; ArgentinaFil: Curletto, Dino. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Scandolo Lucini, Daniel Edgardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Maciel, Martin Guillermo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Palladino, Rafael Alejandro. Universidad Nacional de Lomas de Zamora. Facultad de Ciencias Agrarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Perez, Carolina Daiana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto Tecnología de Alimentos; ArgentinaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentin

Effects of supplementation with increasing levels of energy concentrate on the productive response and ruminal digestion of dairy cows grazing lucerne pasture

The aim of the study was to determine the effect of three levels of energy concentrate intake on dry matter (DM) and energy intake, milk yield and composition, rumen environment and pasture neutral detergent fiber (NDF) digestion. Twelve Holstein multiparous cows in early lactation (69.0 ± 5 days postpartum) producing 32.8 (±4.0) kg milk were assigned to three treatments at (kg/cow day) 3.5 (T3.5), 7.0 (T7.0) and 10.5 (T10.5) kg concentrate in a 3 × 3 Latin Square design. Parameters of ruminal environment and neutral detergent fiber (NDF) digestion were obtained using 3 additional rumen cannulated cows. Concentrate was composed (as fed) by corn grain (68%), soybean meal (22%), wheat bran (8%) and a vitamin-mineral premix including monensin and thoroughly consumed. Yields (kg/cow day-1) of milk, 4% fat corrected milk (4% FCM 4%) and energy corrected milk (ECM) resulted higher (p < 0.05) in T7.0 (29.6, 26.1 and 25.7) compared to T3.5 (27.7, 24.5 and 24.2) but similar to those obtained in T10.5 (30.6, 26.2 and 26.0). Milk protein yield increased linearly (p < 0.01) from 0.82 to 0.92 kg/cow day-1 without effects on yield of milk fat. Concentrations (g/100 g) of milk fat (3.19), protein (2.97), total solids (11.75), non-fat solids (8.60) and casein (2.40) did not differ. Milk lactose content (g/100 g) was linearly increased (p < 0.02) from 4.91 to 4.98 whereas milk urea decreased (p < 0.01) from 0.048 to 0.043. Intakes of DM and energy increased with concentrate level without effects on conversion efficiency. Changes in live weight (LW), body condition score (BCS) and concentrations of plasma non-esterified fatty acids (NEFA), glucose, insulin, somatotrophin (GH) and insulin-like growth factor (IGF-I) were not affected. Plasma urea levels resulted lower (p < 0.05) in T10.5. Ruminal pH and ammonia nitrogen (N-NH3) resulted lower (p < 0.05) in T10.5 compared to T3.5. Concentration of total volatile fatty acids (VFA) was higher (p < 0.05) in T3.5 due to the increase in acetate and butyrate while the acetate: Propionate ratio remained unchanged. Pasture NDF digestion was affected as concentrate intake increased. To increase milk protein yield and reduce concentrations of N-NH3 in rumen and milk, feeding an energy concentrate at 41% of total DM intake resulted an effective tool.EEA RafaelaFil: Salado, Eloy Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Bretschneider, Gustavo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce. Agencia De Extensión Rural Necochea; ArgentinaFil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela. Area de Investigación en Producción Animal; ArgentinaFil: Gagliostro, Gerardo Antonio. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Area de Investigación en Producción Animal; Argentin