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The objective of this study was to quantify the farm gate nitrogen (N) offset potential of perennial ryegrass (Lolium perenne L.; PRG) white clover (Trifolium repens L.; WC) swards by comparing the herbage and milk production from dairy farmlets that were simulations of full farming systems. A study was established where 120 cows were randomly assigned to 4 farmlets of 10.9 ha (stocking rate: 2.75 cow/ha), composed of 20 paddocks each. Cows were fed 526 kg of DM of concentrate on average each year. The 4 grazing treatments were PRG-only at 150 or 250 kg of N/ha and PRG-WC at 150 or 250 kg of N/ha. Cows remained in their treatment group for an entire grazing season and were re-randomized as they calved across treatments each year. As cows calved in the spring as standard practice in Ireland, they were rotationally grazed from early February both day and night (weather permitting) to mid-November, to a target postgrazing sward height of 4.0 cm. Mean sward WC content was 18.1% and 15.4% for the 150 and 250 kg of N/ha PRG-WC treatments, respectively over the 3-yr period. When WC was included, lowering the N rate did not reduce pregrazing yield, pregrazing height, or herbage removed, but those factors decreased significantly when WC was absent. Total annual herbage DM production was 13,771, 15,242, 14,721, and 15,667 kg of DM/ha for PRG-only swards receiving 150 or 250 kg of N/ha and PRG-WC swards receiving 150 or 250 kg of N/ha, respectively. In addition, when WC was present, compressed postgrazing sward heights were lower (4.10 vs. 4.21 cm) and herbage allowance (approximately 17 kg/cow feed allocation per cow per day) higher than the high-N control (+ 0.7 kg of DM/cow per day). There was a significant increase in milk production, both per cow and per hectare, when WC was included in PRG swards. Over the 3-yr study, cows grazing PRG-WC had greater milk (+304 kg) and milk solids (+31 kg of fat + protein) yields than cows grazing PRG-only swards. This significant increase in milk production suggests that the inclusion of WC in grazing systems can be effectively used to increase milk production per cow and per hectare and help offset nitrogen use. This result shows the potential to increase farm gate N use efficiency and reduce the N surplus compared with PRG-dominant sward grazing systems receiving 250 kg of N/ha, without negatively affecting milk solids yield or herbage production, thus increasing farm profit by €478/ha. [ABSTRACT FROM AUTHOR]

Low dietary energy and decreased intake of herbage have been attributed to the reduced performance of grazing dairy cattle. We hypothesized that grasses with inherently greater energy would interact in a complementary way with condensed tannins (CT) in birdsfoot trefoil to increase herbage intake by grazing dairy heifers. Eight pasture treatments comprising high-sugar perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus riparius Rehmann), and tall fescue [ Schendonorus arundinaceus (Schreb.) Dumort] were established in Lewiston, Utah as monocultures and binary mixtures with birdsfoot trefoil (Lotus corniculatus L.; BFT). Pasture treatments were rotationally stocked by Jersey heifers for 105 d in 2017 and 2018, and herbage samples were collected pre- and postgrazing for each 7-d grazing period and analyzed for herbage mass, nutritive value, and apparent herbage intake. We observed differences among pasture treatments in herbage quantity and nutritive value, as well as differences in herbage intake by grazing Jersey heifers. On average, grass-BFT mixtures had greater herbage intake than grass monocultures, and every grass-BFT treatment individually had greater herbage intake than their respective grass monocultures. Using multivariate analyses, we determined that approximately 50% of the variation in herbage intake was due to nutritive and physical herbage characteristics, with the most explanatory being characteristics related to fiber and energy, followed by those related to the percent of BFT in the herbage. Grass monocultures exhibited a range of inherent dietary energy, but there was indication that an imbalance of energy to crude protein (e.g., protein deficient) reduced intake of grass monocultures. Moreover, there was some evidence of a complementary effect between increased dietary energy and CT; however, low CT levels made it impossible to determine the effect of CT on herbage intake per se. This study confirmed that chemical and physical characteristics inherent to different pasture species have a large effect on herbage intake by grazing cattle. Pastures planted to binary mixtures of nutritious grasses and birdsfoot trefoil increase herbage intake of temperate pastures by grazing Jersey heifers. [ABSTRACT FROM AUTHOR]

This study examined how silages of different grass and clover species affect dry matter (DM) intake, milk production, and eating behavior in dairy cows. The primary growth of perennial ryegrass (early and late harvested), festulolium, tall fescue, red clover, and white clover swards were cut, wilted, and ensiled without additives. Thirty-six Danish Holstein cows were fed ad libitum with total mixed rations containing 70% forage on DM basis in an incomplete Latin square design. The forage source was either 1 of the 6 pure silages or late perennial ryegrass silage mixed (50:50 on DM basis) with either red clover or white clover silage. Intake of DM, milk yield, and milk lactose concentration were higher, whereas milk fat and protein concentrations were lower when cows were fed clover compared with grass. No differences in DM intake and milk composition were detected between cows fed red clover and white clover, but white clover resulted in higher milk yield than red clover. Lower body weight, probably caused by lower rumen fill, in cows fed pure white clover compared with the other treatments indicated that intake was regulated physiologically instead of physically. Cows fed early perennial ryegrass, which had the highest silage organic matter digestibility (OMD), did not produce the expected amount of energy-corrected milk (ECM) compared with the other treatments based on the amount of OM digested in the gastrointestinal tract, but the reason was unclear. Across all other grass species, ECM was related to OMD. Inclusion of 50% clover in the diet increased ECM with 2.3 kg/d, and the response to OMD was comparable to the response for the grass silages. In situ fiber degradation profile parameters indicated that fiber in festulolium differed compared with fiber in the other grass species and resembled fiber in clover. Drinking and eating behavior differed markedly in cows fed pure white clover compared with the other treatments. Water intake per drinking bout was comparable among treatments, but cows fed pure white clover had higher drinking bout duration and reduced drinking rate. Additionally, meal size was smaller for cows fed pure white clover compared with the other treatments, for which meal size was similar. In conclusion, differences in ECM between different grass species can be explained by differences in OMD, and at a given OMD level inclusion of clover in the diet increased ECM. [ABSTRACT FROM AUTHOR]