Horacio Leandro Gonda

Evaluation of Dietary Nitrogen Utilization in Dairy Cows Based on Urea Concentrations in Blood, Urine and Milk, and on Urinary Concentration of Purine Derivatives

Abstract The effects of level and degradability of dietary protein on urea in blood, urine and milk, and on the urinary purine derivatives and creatinine in dairy cows, were studied. Diurnal variation in urinary concentration of urea, allantoin and creatinine was also studied. A total of 24 multiparous lactating dairy cows were selected from a production experiment and divided into two 12-cow groups according to their lactation stage (LG1, 14th-16th week of lactation; and LG2, 26th-30th week of lactation). Within groups, cows were fed four different rations (three cows per treatment). Four concentrate mixtures with two levels of protein [19 and 14% of crude protein on dry matter (DM) basis] and two different rumen degradabilities (72 and 52%) of the dominating protein feed rapeseed meal, were fed to the cows together with pasture silage and hay. In both groups of cows the urea concentration in plasma, urine and milk increased (p<0.05) with increasing protein intake. Based on the pooled data from both lact...

The effect of roughage to concentrate ratio in the diet on nitrogen and purine metabolism in dairy cows

Abstract Four lactating dairy cows were used in two experiments to study the effects of the roughage to concentrate ratio in the diet on nitrogen balance, plasma urea, urinary urea, milk urea and urinary purine derivatives. The use of the allantoin to creatinine ratio in spot samples of urine as an index of the urinary allantoin excretion was also evaluated. Four isoenergetic and isonitrogenous diets were formulated according to a 2 × 2 factorial arrangement. Factor I was concentrate content. The roughage to concentrate ratios were 65:35 and 35:65 for the high roughage and high concentrate diets, respectively. Factor II was fat content, which was 2.8% and 5.8% for the low and high fat diets, respectively. In Experiment 1 cows were fed diets with low fat content, and in Experiment 2 cows were fed diets with high fat content. In both experiments, diets were fed according to a change-over design. Nitrogen balance was not affected by the treatments. In cows fed high concentrate diets the amount and the proportion of nitrogen excreted in milk, as well as milk production was higher than in cows fed the high roughage diets. In both experiments, as an overall effect, the urea levels in plasma, urine and morning milk were higher, although the total urinary excretion of urea was lower, for the high concentrate diets. Urinary allantoin excretion was higher, although not significantly in Experiment 1, for the high concentrate diets. The allantoin to creatinine ratio in spot samples of urine showed the same pattern as the total allantoin excretion. Urinary creatinine excretion appeared to be affected by the diet.

From the bite to precision grazing: understanding the plant-animal interface to exploit the multi-functionality of grasslands.

Precision livestock involves innovative technologies to monitor the animal within its pastoral environment. Understanding ingestive behaviour is fundamental to management decisions based upon animal and vegetation monitoring. The way such information can be used is not yet clear. In precision agriculture, the governing principle has been to correct or manage variability so as to homogenise yield at maximized levels. If the same reasoning is applied in livestock production, it can foster classical mistakes in grazing management. However, if precision livestock production can help integrate heterogeneity in managing animals on pasture, then we have a powerful new tool for responding to the new paradigms involving the multi-functionality of grasslands. This paper discusses this concept, and presents the bite as the basic unit of the process to be monitored. A few types of equipment and their application in monitoring site use and the spatial-temporal dynamics of animal biting are presented. The discussion concludes with how to build pastoral environments with precision bite management, and how to create sward structures to influence the temporal and spatial dynamics of animal biting.

Forage Allowance as a Target of Grazing Management: Implications on Grazing Time and Forage Searching

Abstract This work aimed to evaluate the following hypotheses: 1) the daily grazing time (GT) and 2) forage searching are more associated with the sward structure than with the levels of daily forage allowance (FA). To this end we proposed a model that was tested through an analysis of the sward structure, grazing time, and displacement in grazing by heifers on the natural grassland of the Pampa Biome (southern Brazil), which has been managed by FA levels since 1986. For three seasons, between January 2009 and February 2010, we evaluated the effect of FA on the main descriptors of the sward structure (herbage mass, sward height, and tussocks frequency) and the effect of these on the GT, displacement rate (DR), and daily displacement (D) in grazing. The data were analyzed with the use of regression and descriptive analyses from three-dimensional contour graphs with the data of the sward structure and GT. The DR was not associated with the FA levels or sward structure; however, the DR presented a positive linear relationship with the D and GT. The incremental change in the GT was accompanied by an increase in the D. Lastly, independently of the level of the FA and season evaluated, the lower values of GT were always associated with the following structural configuration: forage mass between 1 400 and 2 200 kg DM · ha−1, sward height between 9 and 13 cm, and tussock levels not exceeding 35%. Outside these limits, a penalty occurred in the GT and displacement patterns of the heifers. We found evidence that a better understanding of the cause–effect relationships between the sward structure and the ingestive behavior of the animals demonstrates the possibility of increasing the performance of domestic herbivores with important economic and ecological consequences. Resumen El objetivo del estudio fue evaluar las siguientes hipótesis: (i) si el tiempo de pastoreo diario (TP) y (ii) la búsqueda de forraje están más estrechamente relacionados a la estructura del pasto que a los niveles diarios de oferta de forraje (OF). Con este fin, propusimos un modelo que se puso a prueba en base al análisis de la estructura del pasto, el tiempo de pastoreo y el desplazamiento en pastoreo en terneras sobre un pastizal natural del Bioma Pampa (sur de Brasil) que, desde 1986, se ha manejado con distintos niveles de OF. En tres épocas, entre Ene/2009 y Feb/2010, se evaluó el efecto de la OF sobre los principales descriptores de la estructura del pasto (biomasa de forraje, altura y frecuencia de matas) y el efecto de éstos sobre el tiempo de pastoreo (TP), la tasa de desplazamiento (TD) y el desplazamiento diario (D). Los datos fueron analizados mediante regresión y por análisis descriptivos a partir de gráficos de contorno tridimensionales en base a los datos de estructura del pasto y TP. La TD no tuvo relación con OF ni con la estructura del pasto, pero mostró una relación lineal positiva con D. Incrementos en TP estuvieron asociados a incrementos en D. El estudio demostró la importancia de la estructura del pasto al constatar que, independientemente del nivel de OF y de la época del año evaluada, los valores más bajos de TP siempre estuvieron asociados a estructuras del pasto caracterizadas por una masa de forraje de 1 400 a 2 200 kg MS · ha−1, alturas de 9 a 13 cm y frecuencia de matas en el pastizal menores al 35%. Fuera de estos límites hubo una penalización en el TP y en el patrón de desplazamiento en pastoreo de las vaquillas. Encontramos evidencias de que el mejor entendimiento de las relaciones causa-efecto entre la estructura del pasto y el comportamiento en pastoreo harían posible incrementar el rendimiento de los herbívoros domésticos, con importantes consecuencias económicas y probablemente ecológicas.

Methane Production in Dairy Cows Correlates with Rumen Methanogenic and Bacterial Community Structure

Methane (CH4) is produced as an end product from feed fermentation in the rumen. Yield of CH4 varies between individuals despite identical feeding conditions. To get a better understanding of factors behind the individual variation, 73 dairy cows given the same feed but differing in CH4 emissions were investigated with focus on fiber digestion, fermentation end products and bacterial and archaeal composition. In total 21 cows (12 Holstein, 9 Swedish Red) identified as persistent low, medium or high CH4 emitters over a 3 month period were furthermore chosen for analysis of microbial community structure in rumen fluid. This was assessed by sequencing the V4 region of 16S rRNA gene and by quantitative qPCR of targeted Methanobrevibacter groups. The results showed a positive correlation between low CH4 emitters and higher abundance of Methanobrevibacter ruminantium clade. Principal coordinate analysis (PCoA) on operational taxonomic unit (OTU) level of bacteria showed two distinct clusters (P < 0.01) that were related to CH4 production. One cluster was associated with low CH4 production (referred to as cluster L) whereas the other cluster was associated with high CH4 production (cluster H) and the medium emitters occurred in both clusters. The differences between clusters were primarily linked to differential abundances of certain OTUs belonging to Prevotella. Moreover, several OTUs belonging to the family Succinivibrionaceae were dominant in samples belonging to cluster L. Fermentation pattern of volatile fatty acids showed that proportion of propionate was higher in cluster L, while proportion of butyrate was higher in cluster H. No difference was found in milk production or organic matter digestibility between cows. Cows in cluster L had lower CH4/kg energy corrected milk (ECM) compared to cows in cluster H, 8.3 compared to 9.7 g CH4/kg ECM, showing that low CH4 cows utilized the feed more efficient for milk production which might indicate a more efficient microbial population or host genetic differences that is reflected in bacterial and archaeal (or methanogens) populations.

Portal net appearance of amino acids in growing pigs fed a barley-based diet with inclusion of three different forage meals.

The net absorption of amino acids (AA) in young pigs fed a barley-based control diet (C) and diets where barley was replaced by 200 g/kg fresh weight of dried lucerne (Medicago sativa; L20), white clover (Trifolium repens; W20) or perennial ryegrass (Lolium perenne; PR20) meal was studied. Castrated male pigs were fitted with permanent catheters in the hepatic portal vein and mesenteric artery, and the hepatic portal net absorption of AA was estimated from the porto-arterial plasma concentration differences and the hepatic portal-vein blood flow. In general, the essential AA (EAA) concentrations in the hepatic portal vein reached peak levels 90 min after feeding and thereafter exhibited a transient decline. Maximum porto-arterial differences were reached between 1 and 3 h postprandially for most of the AA. The cumulative net absorption of non-essential AA (NEAA) and EAA did not differ significantly between the barley-based diet and diets W20 and PR20. Due to a lower intake of AA on diet L20, the cumulative net absorption of NEAA and EAA was significantly (P < 0.05) lower than diet C. With the exceptions of the EAA arginine, cystine and valine, and the NEAA glutamic acid + glutamine and glycine, there were no significant differences in the absorption coefficients for the EAA and NEAA between the diets. In addition, the pattern of the total EAA in the mixture absorbed postprandially did not differ significantly between the diets. The present study gives support to the contention that the replacement of barley AA with forage meal AA in a barley-based diet for growing pigs should be expected to result in minor differences in the net portal flux of AA.

Effects of Level and Degradability of Rapeseed Meal in Rations for Dairy Cows. 1. Animal Performance

Abstract A total of 44 dairy cows of the Swedish Red and White dual-purpose breed were divided into 4 equal groups. Two groups were fed concentrate containing approximately 19% crude protein (high level), while two groups were fed concentrate containing 14.3% crude protein (low level). The differences were obtained by mixing either 25 or 8% 00-rapeseed meal into a basic grain-dominated mixture. Within each protein level, one half of the cows were allotted untreated rapeseed meal and the other half heat-treated rapeseed meal. The heat treatment decreased the effective protein degradability of the rapeseed meal by 20 units from 72 to 52%. The experiment was commenced as a continuous experiment, where weeks 1–3 of the lactation were a preliminary period in which all cows received the same feeding. The experimental period covered lactation weeks 4–20. When the experiment was analysed, the results from the preliminary period were used as covariates. Significant treatment effects were reached both for level and...

Potencial de um método acústico em quantificar as atividades de bovinos em pastejo

The objective of this work was to evaluate the potential of an acoustic method for quantifying the duration of grazing, rumination, and other activities of beef heifers on natural pasture. To obtain sound recordings, heifers were fitted with a digital recorder and a microphone was mounted on the heifers forehead. The recordings were analyzed using audio software. Activities were discriminated, and their duration was quantified and compared with those obtained using a visual method. The acoustic method is efficient in quantifying the duration of grazing, rumination, and other activities of grazing cattle.

Plasma Levels of Energy Metabolites and Pancreatic Hormones in Relation to the Level of Intake and Intraruminal Infusions of Volatile Fatty Acids in Fed Wether Sheep

Abstract The effect of feeding level and intraruminal infusion of volatile fatty acids (VFA) on the jugular plasma concentrations of energy metabolites and insulin and glucagon was studied in wether sheep. Three animals (42 kg ± 0.5 of body weight) of the Swedish Landrace breed were fed a grass hay and barley diet (70:30 on a dry matter basis) at three levels of intake (L1, L2, L3) in a change-over design. In addition to the diet, 3 different VFA mixtures and water (control) were continuously infused into the rumen during 16 days (one mixture during 4 consecutive days). The energy content of the VFA mixtures infused was equivalent to 17% of the calculated metabolizable energy intake per day. Plasma levels of non-esterified fatty acids and citrate decreased, and plasma insulin increased with increasing energy intake. When propionate was absent from the VFA infusion mixtures, plasma citrate tended to increase with increasing energy intake. The plasma citrate levels were negatively correlated to the concentrations of glucose and insulin in plasma. The concentrations of glucose and insulin in plasma were increased by the infusion of propionate in animals fed at L3. There was a high correlation between plasma glucose and insulin. Plasma glucagon levels were not affected either by level of intake or by VFA infusions. No evidence was found to support the concept that propionate is a major regulator of insulin and glucagon secretion in fed sheep.

Effect of Level and Degradability of Rapeseed Meal in Rations for Dairy Cows: 2. Diet Digestibility, Dietary Nitrogen Partition and Urinary Purine Derivatives Excretion

Abstract The effects of level and degradability of rapeseed meal on ration digestibility, N balance, urinary purine derivatives excretion, milk production and milk composition in dairy cows were studied. A total of 24 multiparous lactating diary cows were selected from a production experiment and divided into two 12-cow groups according to their lactation stage (LG1, 14th-16th week of lactation; and LG2, 26th-30th week of lactation). Within lactation groups, cows were fed four different rations (3 cows per treatment). Four concentrate mixtures with two levels of protein (19% and 14% of CP on DM basis) and two different rumen degradabilities (72% and 52%) of the dominating protein feed rapeseed meal were fed to the cows together with pasture silage and hay. Apparent total tract digestibilities were not affected by the treatments. N balance was positive and similar between diets in both lactation groups. N partition data were similar between treatments on LG1, while on LG2 a tendency for a more efficient us...