The inclusion of herbage in the diet of medium yielding dairy cows offered a total mixed ration (TMR) may be beneficial. This study, which involved mid lactation dairy cows, examined the effect of partial replacement of a TMR with annual temperate pasture. Treatments were ad libitum TMR (TMR100), 75% ad libitum TMR + ryegrass (Lolium multiflorum ‘Maximus’) (TMR75), and 50% ad libitum TMR + ryegrass (TMR50). Twelve multiparous Holstein and F1 Jersey × Holstein cows were divided into six homogeneous groups, taking account of milk production (26.6 ± 4.5 kg/day), days in milk (128 ± 50) and body weight (546 ± 31 kg). Treatments were compared in a replicated 3×3 Latin square design, comprising three 21-day periods (measurements during final 5 days). Cows on TMR75 and TMR50 strip grazed between morning and afternoon milking (7 h/day), with a target pre- and post-grazing sward height of 24 and 12 cm, respectively. Herbage DM intake was estimated as the difference between pre- and post-grazing herbage mass. The TMR and herbage had a crude protein content of 150 and 303 g/kg DM, and a NDF content of 366 and 495 g/kg DM, respectively. Herbage DM intake increased from 4.8 kg/day in TMR75 to 6.7 kg/day on TMR50. Total DM intake decreased from 19.4 kg/day (TMR100), to 18.1 and 15.9 kg/day (TMR75 and TMR50, respectively). Milk production, milk fat and milk protein content were similar between treatments, averaging 25.6 kg/day, 44.6 g/kg and 33.7 g/kg, respectively. The net energy for lactation (NEL) supply was 113, 104 and 92% of NEL requirements, for cows receiving TMR100, TMR75 and TMR50, respectively. Ryegrass pastures were able to replace up to 50% of TMR offered to mid lactation dairy cows without any adverse effects on milk production and milk composition

Civiero, M.

Ferris, C. P.

Ribeiro-Filho, Henrique M. N.

Schaitz, L. H.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XXIV International Grassland Congress / XI International Rangeland Congress Annual Ryegrass Pasture for Dairy Cows Receiving Total Mixed Ration M. Civiero Universidade do Estado de Santa Catarina, Brazil L. H. Schaitz Universidade do Estado de Santa Catarina, Brazil C. P. Ferris Agri-Food and Biosciences Institute, UK Henrique M. N. Ribeiro-Filho Universidade do Estado de Santa Catarina, Brazil Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/24/3-2/9 The XXIV International Grassland Congress / XI International Rangeland Congress (Sustainable Use of Grassland and Rangeland Resources for Improved Livelihoods) takes place virtually from October 25 through October 29, 2021. Proceedings edited by the National Organizing Committee of 2021 IGC/IRC Congress Published by the Kenya Agricultural and Livestock Research Organization This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. Annual ryegrass pasture for dairy cows receiving total mixed ration Civiero, M.*; Schaitz, L.H.*, Ferris, C.P.†, Ribeiro-Filho, H.M.N.*  *Universidade do Estado de Santa Catarina, Lages, Brazil †Agri-Food and Biosciences Institute, Hillsborough, United Kingdom   Key words: intake; milk production; milk composition; Lolium multiflorum Abstract The inclusion of herbage in the diet of medium yielding dairy cows offered a total mixed ration (TMR) may be beneficial. This study, which involved mid lactation dairy cows, examined the effect of partial replacement of a TMR with annual temperate pasture. Treatments were ad libitum TMR (TMR100), 75% ad libitum TMR + ryegrass (Lolium multiflorum ‘Maximus’) (TMR75), and 50% ad libitum TMR + ryegrass (TMR50). Twelve multiparous Holstein and F1 Jersey × Holstein cows were divided into six homogeneous groups, taking account of milk production (26.6 ± 4.5 kg/day), days in milk (128 ± 50) and body weight (546 ± 31 kg).  Treatments were compared in a replicated 3×3 Latin square design, comprising three 21-day periods (measurements during final 5 days). Cows on TMR75 and TMR50 strip grazed between morning and afternoon milking (7 h/day), with a target pre- and post-grazing sward height of 24 and 12 cm, respectively. Herbage DM intake was estimated as the difference between pre- and post-grazing herbage mass. The TMR and herbage had a crude protein content of 150 and 303 g/kg DM, and a NDF content of 366 and 495 g/kg DM, respectively. Herbage DM intake increased from 4.8 kg/day in TMR75 to 6.7 kg/day on TMR50. Total DM intake decreased from 19.4 kg/day (TMR100), to 18.1 and 15.9 kg/day (TMR75 and TMR50, respectively). Milk production, milk fat and milk protein content were similar between treatments, averaging 25.6 kg/day, 44.6 g/kg and 33.7 g/kg, respectively. The net energy for lactation (NEL) supply was 113, 104 and 92% of NEL requirements, for cows receiving TMR100, TMR75 and TMR50, respectively. Ryegrass pastures were able to replace up to 50% of TMR offered to mid lactation dairy cows without any adverse effects on milk production and milk composition. Introduction Full time grazing systems are normally unable to supply all of the energy requirements of lactating dairy cows (Kolver and Muller 1998), and often do not provide a constant supply of herbage throughout the year (Wilkinson et al. 2020). As a result, systems involving full time housing, in which cows are often offered a total mixed ration (TMR), are common. However, giving housed cows access to grazing for part of the day may improve animal welfare (Arnott et al. 2017) and reduce feeding costs (White et al. 2002). Thus the adoption of ‘mixed systems’ (‘part housing-part grazing’) may provide a tool to help maintain individual cow total DM intakes and milk production, and overall stocking density (Wales et al. 2013). Previous studies involving dairy cows grazing annual ryegrass (Lolium multiflorum Lam.) swards in a subtropical region have observed that even when herbage allowance was high, herbage DM intake was lower than expected due to low pre-grazing herbage mass (Miguel et al. 2014, 2019). The low herbage mass of annual ryegrass has been explained by its low tiller density, especially during the first grazing cycles, in comparison to perennial species (Miguel et al. 2014). Thus, herbage DM intake appears to be predominantly limited by sward structure. Nevertheless, the effect of including this kind of pasture in dairy cow diets which are predominantly comprised of a TMR deserves further research. Thus, the aim of this study was to assess the effect of including annual ryegrass pasture in the diets of TMR-fed dairy cows, on total DM intake and milk production. We hypothesized that when a TMR comprises at least 50% of ad libitum intake, annual ryegrass pasture would allow total DM intake and milk production to be maintained.  Methods and Study Site The experiment was performed in Lages, SC, Brazil (50.18°W, 27.47°S; 920 m above sea level) from 19 June to 21 August 2019. During the experimental period the average temperature was 11.8°C and the total rainfall was 197 mm (3.1 mm/day). The 10-year climatic average temperature and rainfall during the months of the experiment were 13.9°C and 107 mm, respectively. Before the first grazing cycle, and after each experimental period, the experimental area was fertilized with 50 kg N/ha, supplied as urea. Twelve multiparous Holstein and Holstein × Jersey cows were divided in six homogeneous groups, each of two cows (experimental unit), according to milk production (26.6 ± 4.55 kg/day), days-in-milk (129 ± 50.8 days) and body weight (546 ± 30.6 kg) measured during the week prior to the experiment starting. Each pair   p. 2 of cows were distributed within two 3 × 3 Latin squares, with each experimental period 21 days: a 16-day adaptation period and a 5-day measurement period.  The treatments comprised a TMR diet offered at 100% of ad libitum intake (TMR100), TMR at 75% of ad libitum intake + access to an annual ryegrass pasture for grazing (TMR75), and TMR at 50% of ad libitum intake + access to annual ryegrass pasture for grazing (TMR50). Cows on TMR75 and TMR50 had access to pasture for 7 h/day, between morning and afternoon milking (from 08:00 h to 15:00 h), and were offered the TMR following afternoon milking. The TMR comprised corn silage (600 g/kg DM), ground corn (260 g/kg DM) and soybean meal (140 g/kg DM), and had a crude protein and neutral detergent fiber (NDF) content of 150 and 366 g/kg DM, respectively. The pasture area (approx. 3 ha) was divided into two halves (one half for each Latin square), with one third of each half assigned to TMR75 and two thirds assigned to TMR50 (4 paddocks in total, 2 cows per paddock). Paddocks were strip grazed, with target pre- and post-grazing sward height of 24 and 12 cm, respectively (a target reduction in sward height of 50%). Fresh pasture was allocated daily, with the area allocated based on allocations during the one-week pre-experimental period. As actual pre- and post-grazing sward heights were similar to the target heights, no other adjustment was necessary. Pre- and post-grazing sward heights were measured daily using a rising plate meter (F200 model, Farmworks, Feilding, New Zealand). In addition, the plate-meter was calibrated to predict herbage mass at the start of each experimental period, pre- and post-grazing. Samples were cut at ground level using scissors from 18 × 0.1 m2 quadrats (4 and 5 in each of the TMR75 and TMR50 paddocks, respectively) in the ‘footprint’ of areas where the plate meter had been used to record herbage height. Individual samples were dried in an oven for 72 h at 60°C, and equations subsequently developed to predict the actual herbage mass that had been offered during the study. The chemical composition of herbage offered was determined from samples collected on days 17 and 19 of each period, and herbage nutritive value estimated from chemical composition, as described by INRA (2007). Cows were milked twice daily at 07:00 h and 16:00 h, and individual cow milk yields recorded.  Milk samples were collected during the final 5 days of each period and each individual sample analysed for fat and protein concentrations. Daily herbage intakes for each pair of cows were estimated as the difference between the pre- and post-grazing herbage mass during the last 5 days of each period. Intakes of the mixed ration offered while cows were indoors was determined daily during the last 5 days of each period, as the difference between the quantity of ration offered and the orts.  The dependent variables were subjected to an analysis of variance using the function PROC MIXED in the software SAS (2002, version 9.4, SAS Institute, Cary, NC). The animal variables (averaged per group and period (n=18)) were analyzed considering the random effect of the animal, the fixed effect of the period and the fixed effect of the treatment. The pasture variables were averaged per paddock and period (n = 12) and analysed considering the random effect of period and the fixed effect of the treatment. Animal variables were tested using an orthogonal polynomial contrast and examined for linear and quadratic effects.  Results Pre- and post-grazing herbage mass of annual ryegrass averaged 1804 and 906 kg DM/ha, respectively (Table 1). Pre- and post-grazing sward height were similar with both treatments and averaged 23.8 cm and 11.4 cm, respectively. Herbage offered with TMR75 and TMR50 was similar in composition, with an average crude protein, NDF and ADF content of 303, 495 and 199 g/kg DM. Total DM intake decreased from TMR100 to TMR50 group (Table 2). There was a quadratic reduction in concentrate DM intakes, with intakes of corn silage following the same trend. Herbage DM intake increased by 1.9 kg/day from TMR75 to TMR50, being 27 and 42% of total DM intake. For each kg of herbage DM consumed, intake of TMR with treatments TMR75 and TMR50 decreased by 1.3 and 1.6 kg DM/day, respectively. Thus, total DM intake decreased as the proportion of herbage increased. Diets TMR100, TMR75 and TMR50 supplied 113%, 104% and 92% of energy requirements. However, milk production, milk fat and milk protein content did not differ between treatments, averaging 25.6 kg/day, 44.6 g/kg and 33.7 g/kg, respectively.       p. 3 Table 1. Pre- and post-grazing characteristics, chemical composition and nutritive value of annual ryegrass (Lolium multiflorum ‘Maximus’) pastures grazed by cows on TMR75 and TMR50   Treatment1     TMR75 TMR50 SEM P-value Pre-grazing characteristics     Herbage mass, kg DM/ha 1895 1713 11.2 0.087 Sward height, cm 25.8 23.1 1.13 0.983 Post-grazing characteristics     Herbage mass, kg DM/ha 915 902 7.6 0.712 Sward height, cm 11.5 11.3 0.74 0.743 Chemical composition g/kg DM     Dry matter  112 111 0.9 0.358 Organic matter 876 867 7.2 1.733 Crude protein 300 306 1.56 0.429 NDF 494 496 1.25 0.619 ADF 198 199 1.14 0.856 Nutritive Value     OM digestibility 828 812 18.1 0.419 NEL, Mcal/kg DM 7.03 6.90 1.38 0.617 PDIN, g/kg DM 203 201 4.9 0.772 PDIE, g/kg DM 122 119 2.8 0.626             1TMR75, TMR offered at 75% of ad libitum intake + access to pasture for 7 h/d; TMR50, TMR offered at 50% of ad libitum intake + access to pasture for 7 h/d; NEL,  Net energy for lactation; PDIN, metabolizable protein when nitrogen is limiting for microbial synthesis in the rumen (INRA 2007); PDIE, metabolizable protein when energy is limiting for microbial synthesis in the rumen (INRA 2007).  Table 2. Effect of treatment on DM intake, milk production and milk composition.    Treatments1  P-value  TMR100 TMR75 TMR50 SEM Treatment Linear Quadr         DM intake, kg/day        Corn silage 11.7 7.9 5.5 0.08 0.001 0.001 0.001 Concentrate2 7.8 5.3 3.4 0.05 0.001 0.001 0.001 Pasture - 4.8 6.7 0.04 0.001 - - Total 19.4 18.1 15.8 0.13 0.001 0.001 0.017 NEL supply, Mcal/day 32.6 30.3 26.5 0.23 0.001 0.001 0.024 NEL balance, %3 113 104 92 2.52 0.001 0.001 0.736 Milk production, kg/day 24.8 26.7 25.2 0.87 0.273 0.712 0.120 4% FCM, kg/day4 26.5 27.9 26.7 0.81 0.437 0.868 0.206 Milk fat, g/kg 45.5 43.1 45.3 0.96 0.163 0.868 0.060 Milk protein, g/kg 34.2 33.8 33.1 0.63 0.489 0.240 0.879 Milk fat, g/day 1122 1157 1184 39.9 0.548 0.279 0.934 Milk protein, g/day 846 898 873 22.0 0.255 0.390 0.157         1TMR100, TMR offered at 100% of ad libitum intake; TMR75, TMR offered at 75% of ad libitum intake + access to pasture for 7 h/d; TMR50, TMR offered at 50% of ad libitum intake + access to pasture for 7 h/d; 2 Corn ground: soybean meal 65:35; NEL= Net energy for lactation; 3 % NEL requirements; 4 4% fat-corrected milk production.  Discussion [Conclusions/Implications] The reduction in total DM intake when cows were given access to grazing is unlikely to be due to the quality of herbage offered, as the relatively low NDF and high CP content of the herbage suggests that quality was good. Indeed, Vibart et al. (2008) found that total DM intake was not reduced when TMR-fed dairy cows had access to high-quality pastures. However, a reduction in pre-grazing herbage mass was shown to reduce herbage intake (Pérez-Prieto et al. 2013), even with good quality pastures. For example, Pérez-Prieto and Delagarde (2012) demonstrated that herbage DM intake decreases linearly when pre-grazing herbage mass (calculated above ground level) decreased from 5500 to 2500 kg DM/ha. In the current study pre-grazing   p. 4 herbage mass averaged only 1800 kg DM ha, even though pre grazing sward heights were over 23 cm, a reflection of the low tiller density of annual ryegrass. Thus, it is likely that the reduction in total DM intake with the TMR75 and TMR50 treatments is due to sward structure restricting intakes. Despite the reduction in total DM intake, the inclusion of herbage in the diet of TMR-fed dairy cow did not decrease milk production, and had no effect on milk composition, thus partially confirming the main hypothesis of this study. However, despite the reduction in intake with TMR75 (compared to TMR100) this diet supplied 104% of energy required for milk production. In contrast, TMR50 provided 92% of energy requirements for milk production, suggesting that milk production was maintained by mobilization of body tissue reserves. Given the short-term nature of the experimental periods, it was not possible to accurately assess changes in body tissue. However, previous studies have demonstrated that cows with similar energy deficiency  at mid-lactation can recovery their body condition during final third of lactation and first 4 weeks of the dry period, without any negative effect on performance and reproduction during the next lactation (Roche et al. 2006, 2017). Additionally, when the energy supply is not less than 90% of requirements, there is a reduced likelihood of metabolic disorders (Overton and Waldron 2004). In conclusion, giving cows access to fresh pasture allowed the amount of TMR offered to by reduced by 50% with no loss in milk production. However, pasture access reduced total DMI, forcing cows into negative energy balance. The lower intakes are likely due to the low tiller density and low herbage mass of annual ryegrass.  Acknowledgements This work was supported in part by Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil (CNPq; finance codes 403754/2016-0 and 308591/2019-4), Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina, Brazil (FAPESC; finance code TR 584 2019), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES; finance code 001). References Arnott, G., Ferris, C.P. and O’connell, N.E. 2017. Review: welfare of dairy cows in continuously housed and pasture-based production systems. Animal, 11: 261–273. INRA. 2007. Alimentation des bovins, ovins et caprins. Besoins des animaux - valeurs des aliments. Tables INRA 2007, 4th ed. INRA, ed QUAE Editions, Versailles, France. Kolver, E.S. and Muller, L.D. 1998. Performance and nutrient intake of high producing Holstein cows consuming pasture or a total mixed ration. J. Dairy Sci., 81: 1403–1411. Miguel, M.F., Ribeiro-Filho, H., Andrade, E., Genro, T. and Delagarde, R. 2014. 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Annual Ryegrass Pasture for Dairy Cows Receiving Total Mixed Ration

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Annual Ryegrass Pasture for Dairy Cows Receiving Total Mixed Ration

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