V. Merino, O. Balocchi, and R. Pulido. 2018. Effect of daily herbage allowance restriction on pasture characteristics and milk production by grazing dairy cows. Cien. Inv. Agr. 45(1): 21-34. The cumulative effects of daily herbage allowance (DHA) restriction on pasture characteristics and the sustainability of pasture-based dairy systems were evaluated. Sixty-four dairy cows were randomly assigned to one of two grazing treatments (20 and 30 kg DM cow -1 day -1 ). Milk yield and pre-and post-grazing herbage mass were recorded for every grazing event. Botanical and chemical compositions of the pasture were evaluated. Low DHA increased the stocking rate by 0.7 cows ha -1 and consequently increased grazing efficiency from 41 to 47%. Daily herbage allowance restriction did not affect pasture characteristics or milk production per cow, but DHA restriction increased milk production per hectare (+27%). The results suggest that restriction on daily herbage allowance ensures a higher level of herbage utilization and milk output per ha than high DHA, without affecting pasture characteristics. Therefore, DHA might be a useful grazing management tool for improving the profitability and sustainability of grazing-based dairy systems.

Grazing ruminant systems can be sustainably intensified by improving efficiency while reducing their environmental impact. The objective of the present study was to examine the potential of pastures differing in water-soluble carbohydrates (WSC) and crude protein (CP) contents to affect milk production and composition as well as the behaviour of cows grazing perennial ryegrass (PRG) swards. By modifying the nitrogen (N) fertilisation rate (83 and 250 kg/ha per year) and the defoliation frequency (two or three leaves per tiller) in combination with cultivar selection (high-sugar vs. standard cultivars), we obtained two swards differing in WSC and CP contents. The two contrasting swards were each grazed by six dairy cows in nine daily strips in autumn. Pasture samples were collected to determine herbage mass and quality. Cow behaviour was recorded by direct observation. Herbage offered and apparently consumed were similar between swards (averaging 37.3 and 18.2 kg/cow, respectively), although the residual was lower in the high-sugar sward (1735 vs. 2143 kg/ha). Cows spent less time grazing in the high-sugar sward (66.9% v. 71.6%), but the rumination times was similar (14.6%). Milk production and composition were similar between groups, suggesting that high-quality pastures would require a greater difference in nutritional composition to affect animal performance.

Daily herbage allowance is recognised as the main tool to control pasture utilisation and milk production per cow. The aim of the present study was to evaluate the long-term effects of daily herbage allowance (DHA) on pasture characteristics and milk production of dairy cows. Forty-four dairy cows were randomly assigned to one of four treatments in a 2 × 2 factorial design by considering two levels of DHA (20 and 30 kg DM/cow.day) and two types of supplements (high-moisture maize and maize silage) over a 77-day period. Pre- and post-grazing herbage masses, vertical distribution of herbage mass, species density, botanical and chemical composition, sward depletion and changes in morphological components of the pasture were measured. The effect of DHA on soil compaction was evaluated on the basis of the penetration resistance. Milk production and composition levels, bodyweights and body condition scores were recorded. Post-grazing residual declined as the level of DHA decreased, while grazing efficiency increased from 39.8% to 44.8%. We found no effects of DHA on any pasture characteristics, pasture regrowth or soil compaction. Low-DHA conditions induced a faster sward-height reduction, while the herbage mass remained unaffected. Individual milk production decreased with DHA. However, milk outputs per hectare increased by 2772 L/ha. Milk composition, bodyweight and body condition score were not affected by DHA. The results showed that DHA restriction decreases milk production per cow while increasing both herbage utilisation and milk production per hectare, without affecting long-term pasture condition.

Simple Summary: Daily herbage allowance (defined as herbage mass × daily offered area) is recognized as the main grazing management factor to improve pasture utilization and milk output per hectare. Daily herbage allowances should balance the dual objectives of high milk output per hectare while maintaining the quality of the pasture to optimize the profitability of grazing-based dairy production systems. We tested two contrasting herbage allowances (17 and 25 kg dry matter (DM)/cow.day) and two levels of maize silage supplementation (4.5 and 9 kg DM/cow.day) in grazing dairy cows and measured a set of variables related to pasture management, sward characteristics, dynamic of herbage depletion throughout the grazing sessions, and cows grazing behavior, among others. Our results suggest that a more intensive grazing regime of 17 kg DM/cow per day of daily herbage allowance rather than a high level of supplementation with maize silage is appropriate to improve milk production and solids yield per hectare without affecting pasture quality or sward characteristics over the short-term.Abstract: The aim of this study was to evaluate the short-term effects of daily herbage allowance (DHA, defined as the product of pre-grazing herbage mass and offered area per animal) on pasture conditions and milk production of Holstein-Friesian dairy cows. Forty-four early lactation dairy cows were randomly assigned to one of four treatments in a 2 × 2 factorial design that tested two levels of DHA (17 and 25 kg DM/cow.day) and two levels of maize silage supplementation (MSS, 4.5 and 9 kg DM/cow.day) over a 77-day period. Low DHA decreased the post-grazing herbage mass from 1546 to 1430 kg DM/ha and the compressed sward height from 5 to 4.4 cm, while the grazing efficiency remained unaffected. Low DHA induced a faster herbage mass reduction, while the sward-height and pasture characteristics did not differ from the high DHA regime. Low DHA decreased the tiller production rates and daily lamina growth, while the leaf-production rate was not affected by the DHA. Daily increases of herbage mass were greater in the high DHA than in the low DHA treatments. Individual milk production and milk protein concentration decreased at a low DHA compared to high DHA, while the milk fat concentration was greater and the milk output per hectare increased by 1510 kg. Neither the MSS level nor the interaction DHA by the MSS level had any effect on the sward characteristics or the productivity of the cows. From these results, it is suggested that, Animals 2020, 10, 62 2 of 17 in a high-quality pasture, using 17 kg DM/cow.day was appropriate for improving both herbage utilization and milk production per hectare while maintaining the short-term conditions of a pasture grazed by dairy cows in the autumn.

A deeper knowledge on the effects of herbage allowance (HA) on pasture characteristics and animal performance is necessary to improve efficiency of dairy production systems based on intensive grazing of pasture. The objectives of this study were to assess the effect of two levels of HA on pasture characteristics and milk performance during a three years period. Holstein Friesian dairy cows were selected from a dairy herd owned by the Universidad Austral de Chile and randomly assigned to one of two homogeneous groups. Each group was managed with different HA (high or low), measured at ground level, in a grazing system with half day strip. Grazing management variables (pre and postgrazing herbage mass, stocking rate, and proportion of pasture harvested), and animals variables (body weight, body condition score, milk production and composition), were measured and the results were averaged for each season of the year. Pre-grazing herbage mass did not differ between treatments averaging 2,313, 2,261, 2,069 and 1,315 kg DM ha -1 , for spring, summer, autumn and winter, respectively. Cows grazing at low HA had a lower post-grazing herbage mass (-146 kg DM ha -1 ), especially in summer and spring. Consequently the proportion of pasture harvested was greater at low HA (+5.5%). Milk production per cow was not significantly reduced when a low level of HA was offered. However, due to higher stocking rate, milk production per hectare increased in low HA by 26% as average of the three-year period. Results suggest that the restriction on herbage allowance might be a useful grazing management tool to improve the profitability of dairy systems based on intensive grazing of pasture. RESUMENUn mayor conocimiento de los efectos de la oferta de pradera (OP) sobre las características de la pradera y productividad animal son necesarios para mejorar la eficiencia de los sistemas de producción de leche basados en pastoreo. Los objetivos de este estudio fueron evaluar el efecto de dos niveles de OP sobre variables de la pradera y productividad de vacas lecheras, durante un período de tres años. Se utilizaron vacas lecheras Holstein Friesian pertenecientes al rebaño de la Universidad Austral de Chile. Las vacas se separaron en dos grupos homogéneos. Cada grupo fue manejado en una oferta de pradera diferente (alta o baja), medida a ras de suelo, en un sistema de pastoreo con franjas de medio día. Las variables de manejo del pastoreo (fitomasa pre y post-pastoreo, carga animal y proporción de cosecha de la pradera) y las variables de los animales (peso vivo, condición corporal, producción y composición de la leche), fueron medidos y los resultados promediados para cada estación del año. La fitomasa pre-pastoreo no difirió entre los tratamientos promediando 2.313, 2.261, 2.069 y 1.315 kg MS ha -1 en primavera, verano, otoño e invierno, respectivamente. Las vacas que pastorearon una baja OP dejaron una fitomasa postpastoreo inferior (-146 kg ha -1 ), especialmente en verano y primavera. Consecuentemente la proporción de pradera cosechada fue m...

Increasing demands for land is necessitating the optimisation of grazing land used for livestock production. Hormonal growth promoter implants (HGPI) are widely used to improve cattle performance and thus land-use efficiency. However, there is limited information on their efficacy in grazing systems. Forty grazing steers, 10 of each breed (Angus, Hereford, Holstein, Overo Colorado), had growth rates monitored for 85 days after which half received HGPI and half continued as a control. Growth rates were monitored for an additional 61 days and performance between the groups compared. Implants had a significant impact on liveweight gain (LWG; p = 0.013), and whilst breed did not (p = 0.65), there was an interaction effect of breed × treatment (p = 0.029). For three of the four breeds, the LWG was greater in the implant group (mean +14.3%). The exception was for Holstein steers which did not respond to the implant. In general, HGPI were found to be effective in increasing LWG of grazing cattle and thus has the potential to increase yield densities and relieve pressures of land use and competition. The efficacy may be affected by breed and other extraneous factors not covered in this study. Furthermore, the use of HGPI must be carefully considered in a wider context since its use might have secondary impacts.

The aim was to determine the effect of the herbage allowance (HA) and supplement type (ST) on dry matter intake (DMI), milk production and composition, grazing behavior, rumen function, and blood metabolites of grazing dairy cows in the spring season. Experiment I: 64 Holstein Friesian dairy cows were distributed in a factorial design that tested two levels of daily HA (20 and 30 kg of dry matter (DM) per cow) and two ST (high moisture maize (HMM) and cracked wheat (CW)) distributed in two daily rations (3.5 kg DM/cow/day). Experiment II: four mid-lactation rumen cannulated cows, supplemented with either HMM or CW and managed with the two HAs, were distributed in a Latin square design of 4 × 4, for four 14-d periods to assess ruminal fermentation parameters. HA had no effect on milk production (averaging 23.6 kg/day) or milk fat and protein production (823 g/day and 800 g/day, respectively). Cows supplemented with CW had greater protein concentration (+1.2 g/kg). Herbage DMI averaged 14.17 kg DM/cow.day and total DMI averaged 17.67 kg DM/cow.day and did not differ between treatments. Grazing behavior activities (grazing, rumination, and idling times) and body condition score (BCS) were not affected by HA or ST. Milk and plasma urea concentration increased under the high HA (+0.68 mmol/L and +0.90 mmol/L, respectively). Cows supplemented with HMM had lower milk and plasma urea concentrations (0.72 mmol/L and 0.76 mmol/L less, respectively) and tended (p = 0.054) to have higher plasma β-hydroxybutyrate. Ruminal parameters did not differ between treatments.

A trial was conducted to, firstly, demonstrate heavy veal or grain-fed veal production and, secondly, to examine the effect of fishmeal quality, used as part of the protein supplement, on growth and feed efficiency. Twenty-four Friesian X Holstein male calves, with an initial age of ca 100 days, were assigned to two treatments using a completely randomized experimental design, with 3 repetitions per treatment and 4 calves per replicate. After a period of adaptation of 12 days they were offered rations consisting of 3 parts corn grain and one part a protein supplement. Those in treatment 1 received a supplement "P" which included 25% "Prime" fishmeal, while the calves in treatment 2 were fed a supplement "S", which included the same level of a "standard" fishmeal, with the difference between the fishmeals being the drying temperature used in their production. Every group of calves received water and their respective rations ad libitum. The trial ended when the calves reached a live weight of around 200 kg. The total weight gains were 128.6 and 118.3 kg while the daily gains were 1.53 and 1.41 kg for treatments 1 and 2, respectively (P> 0.05). During the second half of the trial (last 42 days) calves on treatment 1 had a total gain of 73.3 kg (1.,74 kg d-¹) while those in treatment 2 gained 63.0 kg (1.50 kg d-¹) (P<0.05). No statistically significant differences were observed between treatments in total DM intake, values being 347.2 and 330.0 kg, nor in efficiency of feed conversion (2.71 and 2.84 kg kg-¹) for treatments 1 and 2 respectively. Dressing percentage of carcasses, determined in a sample