Oscar Balocchi

Herbage production, nutritive value and grazing preference of diploid and tetraploid perennial ryegrass cultivars (Lolium perenne L.).

The objective of this study was to determine, under the soil and climatic conditions of Southern Chile, the effect of the ploidy of perennial ryegrass (Lolium perenne L.) cultivars on herbage production, nutritive value, grazing preference and utilization of pasture produced. This study was conducted in southern Chile, Valdivia Province, and was evaluated for 3 years. The tetraploid cultivars used were Quartet (4n), Gwendal (4n), Pastoral (4n) and Napoleon (4n). The diploid cultivars were Anita (2n), Jumbo (2n), Aries (2n), and Yatsyn 1 (2n). When the average sward height reached 20 cm, all plots were simultaneously grazed by dairy cows for a period of 24 h. Before and after grazing, sward height, dry matter availability and nutritive value were evaluated. Grazing preference was visually assessed every 5 min for a period of 2.5 h after the afternoon milking. During the 3-year period 20 grazing events were evaluated. A randomized complete block design, with eight cultivars and three replicates, was used. Diploid

Sward and tiller growth dynamics of Lolium perenne L. as affected by defoliation frequency during autumn

A mini-sward study was undertaken between January and September 2008 in Valdivia, Chile, to quantify and compare changes in the herbage production, growth dynamics and nutritive quality of a Lolium perenne sward during autumn in response to different nitrogen (N) application regimes and defoliation frequencies. The N levels used in the present study corresponded to the equivalent of an autumnal application of 0, 25 or 75 kg N/ha. The defoliation frequency was based on leaf regrowth stage, and corresponded to the time taken for 1.5, 2.5 or 3.5 leaves per tiller to expand. The growth dynamic measurements were also related to temperature. The results showed that the level of N had no effect on the studied variables. Plants defoliated at the 3.5-leaf stage showed a higher herbage production, higher tillering and a more balanced nutritional profile than plants cut at the 1.5-leaf stage. The defoliation interval had no effect on leaf elongation or leaf appearance. The leaf elongation rate was linearly related to the mean daily temperature (P < 0.01), and the accumulated leaf and tiller number showed a significant linear relationship (P < 0.01) with the thermal time expressed as growing degree days. From the defoliation frequencies tested here, we can conclude that the best time for grazing L. perenne swards during autumn is at the 3.5-leaf stage due to a higher herbage production, higher tillering rate, more balanced nutritive quality and higher reserve levels of the plant, which provide a more favourable background for subsequent growth.

Productive and metabolic response to two levels of corn silage supplementation in grazing dairy cows in early lactation during autumn

Corn (Zea mays L.) silage (CS) is a nutritious food that can be used as a supplement in dairy cows. The aim of this study was to determine the effect of supplementation with two amounts of CS on milk production and composition, live weight and body condition, as well as on some blood indicators for energy and protein metabolism on dairy cows in early lactation and grazing low mass pasture during autumn. The study was carried out in 40 Holstein Friesian cows over 57 d. Prior to experimental treatment, milk production and days of lactation averaged 24.1 ± 2.8 kg d-1 and 62 ± 14 d, respectively. The dietary treatments consisted of two levels of supplementation with CS; 4.5 and 9 kg DM cow-1 d-1 (treatments LCS and HCS, respectively). Additionally, all the cows received a pasture allowance of 21 and 3 kg DM cow-1 d-1 of concentrate. Milk composition was determined using infrared spectrophotometry, while blood indicators were obtained using an autoanalyzer. There were not differences between treatments regarding milk production or composition, total DM or energy intake. Herbage and protein intake was higher for LCS treatment (P < 0.001). Increasing supplementation decreased (P < 0.001) daily weight gain but did not affect body condition. Plasma concentrations of βOH-butyrate were lower (P = 0.038) for the LCS treatment; while urea concentrations were higher (P = 0.003), with no differences for non-esterified fatty acids (NEFA) concentrations. Supplementation with 4.5 kg d-1 of CS was sufficient to meet the production requirements of the cows.

Effect of increasing pasture allowance and concentrate supplementation on animal performance and microbial protein synthesis in dairy cows

El objetivo de este estudio fue evaluar la influencia de la oferta diaria de pradera y la suplementacion con concentrado en vacas lecheras durante el otono. El estudio tuvo una duracion de 56 dias, usando 30 vacas lecheras Frison Negro. Los tratamientos empleados fueron el resultado de la combinacion de dos ofertas de pradera (B = baja oferta, 20 kg y A = alta oferta, 30 kg de materia seca vaca-1 dia-1) y tres cantidades de concentrado (0, 3 y 6 kg MS/vaca/dia). Todas las vacas fueron suplementadas con 4,5 kg de MS de ensilaje de pradera vaca-1 dia-1. La oferta de pradera no tuvo efecto sobre la produccion de leche (P > 0,05), pero si incremento la concentracion de proteina (de 3,02% a 3.21 %) (P < 0.05), el peso vivo (0,336 a -0,121 kg) y tiempo de pastoreo (de 299 min vaca-1 dia-1 a 411 min vaca-1 dia-1, P < 0,001). La suplementacion con concentrado incremento la produccion de leche (15,1, 19,2 y 21,7 kg vaca -1 dia-1) (P < 0,05), grasa (+0,1 kg cow-1 day-1) y proteina (+0,1 kg vaca-1 dia-1), disminuyendo la concentracion de urea lactea (-0,25 mmol/L-1 day-1), (P < 0,001). Durante el experimento, la oferta de pradera o el concentrado suplementado tuvo un efecto significativo sobre las concentraciones de AGNES y urea plasmatica. La mayor oferta de pradera incremento (P < 0,05) la excrecion de derivados de purinas y el indice PD/CT, sin observarse un efecto sobre la suplementacion con concentrado. La suplementacion con concentrado tuvo un efecto positivo sobre el desempeno animal, como resultado de un mejor balance proteina-energia de la dieta

Phenotypic variability in Holcus lanatus L. in southern Chile: a strategy that enhances plant survival and pasture stability.

Holcus lanatus L. can colonise a wide range of sites within the naturalised grassland of the Humid Dominion of Chile. The objectives were to determine plant growth mechanisms and strategies that have allowed H. lanatus to colonise contrasting pastures and to determine the existence of ecotypes of H. lanatus in southern Chile. Plants of H. lanatus were collected from four geographic zones of southern Chile and established in a randomised complete block design with four replicates. Five newly emerging tillers were marked per plant and evaluated at the vegetative, pre-ear emergence, complete emerged inflorescence, end of flowering period, and mature seed stages. At each evaluation, one marked tiller was harvested per plant. The variables measured included lamina length and width, tiller height, length of the inflorescence, total number of leaves, and leaf, stem, and inflorescence mass. At each phenological stage, groups of accessions were statistically formed using cluster analysis. The grouping of accessions (cluster analysis) into statistically different groups (ANOVA and canonical variate analysis) indicated the existence of different ecotypes. The phenotypic variation within each group of the accessions suggested that each group has its own phenotypic plasticity. It is concluded that the successful colonisation by H. lanatus has resulted from diversity within the species.

Effect of the type of silage on milk yield, intake and rumen metabolism of dairy cows grazing swards with low herbage mass

The aim of this study was to evaluate the effect of herbage allowance (HA) and type of silage supplemented (TS) on milk yield, dry matter intake (DMI) and metabolism of dairy cows in early lactation. Thirty-six Holstein-Friesian dairy cows were allocated to four treatments derived from an arrangement of two HA (LHA = 17 or HHA = 25 kg of DM/cow/day) and two TS (grass (GS) or maize (MS)). Herbage allowance had no effect on DMI or milk yield. Rumen pH and NH3 -N concentration were not affected by HA. The efficiency of microbial protein synthesis in the rumen (microbial protein (MP)) was affected by HA with 21.5 and 23.9 g microbial nitrogen per kg ruminal digestible organic matter for LHA and HHA, respectively (P < 0.05). Supplementation with MS showed higher values of milk yield by 2.4 kg/cow/day (P < 0.001), milk protein content by 0.10 % (P < 0.023) and herbage DMI by 2.2 kg/cow/day, and showed lower values for milk urea compared to GS (P < 0.001). The former results suggest that TS had a greater effect on milk yield, total feed intake and energy intake than increase in herbage allowance; however, increase in HA had greater effects on MP than TS.

In vitro fermentation and in situ rumen degradation kinetics of summer forage brassica plants

The aim of the present study was to assess and compare the nutrient concentration, the in vitro fermentation and the in situ rumen degradation characteristics of Brassica rapa ssp. rapa L. (turnips) and Brassica napus ssp. biennis L. (forage rape). Five varieties of each species were established in three field replicates and were organised in a randomised complete-block nested design. All varieties were harvested and further analysed for chemical composition, in vitro gas-production kinetics, volatile fatty acid (VFA) production and in situ degradation kinetics of dry matter (DM) and crude protein. Turnips showed higher ash, total sugars, raffinose, sucrose, glucose and fructose concentrations (P 0.05) for total in vitro VFA production, as well as for the relative proportions of acetate, propionate, butyrate, branch chained VFA and the actetate : propionate ratio. Our study showed that most of the differences that were observed in terms of chemical composition and degradation kinetics did not result in differences in in vitro fermentation products.

Milk production, grazing behavior and nutritional status of dairy cows grazing two herbage allowances during winter

Winter grazing provides a useful means for increasing the proportion of grazed herbage in the annual diet of dairy cows. This season is characterized by low herbage growth rate, low herbage allowance, and low herbage intake and hence greater needs for supplements to supply the requirements of lactating dairy cows. The aim of this study was to determine the influence of herbage allowance (HA) offered to autumn calving dairy cows grazing winter herbage on milk production, nutritional status, and grazing behavior. The study took 63 d using 32 multiparous Holstein-Friesian dairy cows. Prior to experimental treatment, milk production averaged 20.2 ± 1.7 kg d -1 , body weight was 503 ± 19 kg, and days in milking were 103 ± 6. Experimental animals were randomly assigned to two treatments according to HA offered above ground level: low (17 kg DM cow -1 d -1 ) vs. high HA (25 kg DM cow -1 d -1 ). All cows were supplemented with grass silage supplying daily 6.25 and 4.6 kg DM of concentrate (concentrate commercial plus high corn moisture). Decreasing HA influenced positively milk production (+25%), milk protein (+20 kg), and milk fat (+17 kg) per hectare; however no effects on milk production per cow or energy metabolic status were observed in the cows. In conclusion, a low HA showed to be the most significant influencing factor on milk and milk solids production per hectare in dairy cows grazing restricted winter and supplemented with grass silage and concentrate; but no effect on the milk production per cow was found.