Effect of timing of pasture allocation on production, behavior, rumen function, and metabolism of early lactating dairy cows during autumn

Assessment of the current performance of grazing infrastructure across Irish dairy farms

The increased average Irish dairy herd size in a post-quota environment has put heightened pressure on grazing infrastructure. In a rotational grazing system, grazing infrastructure consists of the paddock system, which delineates the grazing areas into appropriately sized grazing parcels, and the roadway network, which connects these paddocks to the milking parlor. Where herd size has increased without corresponding adaptations to the infrastructure, farm management and roadway network performance has been affected. The links between suboptimal grazing infrastructure and roadway network efficiency are poorly understood and not widely documented. The aims of this study were to (1) analyze the effect of herd expansion and paddock size on pasture allocations per paddock, (2) identify the factors that affect the total distance walked per year, and (3) create a metric to compare the efficiency of roadway networks across farms of varying grazing platforms. A sample population of 135 Irish dairy farms with a median herd size of 150 cows was used for this analysis. Herds were split into the following 5 categories: <100 cows, 100 to 149 cows, 150 to 199 cows, 200 to 249 cows, and ≥250 cows. Herds with ≥250 cows had a greater number of paddocks per farm and rotated around the grazing paddocks more frequently, with 46% of paddocks only suitable for 12 h allocations relative to herd size, compared with just 10% to 27% of paddocks for herds with <100 cows to herds with 200-249 cows. When predicting the total distance walked per year on each study farm, the mean distance from a paddock to the milking parlor was the strongest indicator (R² = 0.8247). Other metrics, such as herd size, have failed to account for the location of the milking parlor relative to the grazing platform. The creation of the relative mean distance from a paddock to milking parlor (RMDMP) metric allowed the calculation of a farm's roadway network efficiency for moving the herd between paddocks and the milking parlor. The analyzed farms increased their efficiency in terms of RMDMP (0.34-40.74%) as they increased herd size post quota. However, the position of new additional paddocks relative to the milking parlor substantially affected their RMDMP.

Does the timing of pasture allocation affect rumen and plasma metabolites and ghrelin, insulin and cortisol profile in dairy ewes?

A study was undertaken to assess the impact of the timing of grazing on rumen and plasma metabolites and some metabolic hormones in lactating dairy sheep allocated to an Italian ryegrass (Lolium multiflorum Lam) pasture in spring for 4 h/d. Twenty-four mid lactation Sarda ewes stratified for milk yield, body weight, and body condition score, were divided into four homogeneous groups randomly allocated to the treatments (2 replicate groups per treatment). Treatments were morning (AM, from 08:00 to 12:00) and afternoon pasture allocation (PM, from 15:30 to 19:30). Samples of rumen liquor (day 39) and blood plasma (days 17 and 34 of the experimental period) were collected before and after the grazing sessions. Moreover, on days 11 and 35, grazing time was assessed by direct observation and herbage intake measured by the double weighing procedure. Grazing time was longer in PM than AM ewes (P < 0.001) but herbage intake was undifferentiated between groups. The intake of water-soluble carbohydrates at pasture was higher in PM than AM ewes (P < 0.05). The post-grazing propionic and butyric acid concentration, as measured on day 39, were higher in PM than AM ewes (P < 0.05). The basal level of glucose on day 34 and insulin (on both sampling days) were higher in PM than AM (P < 0.05). The opposite trend was detected for non-esterified fatty acids (P < 0.05, day 34) and urea (both days). Pasture allocation in the afternoon rather than in the morning decreased plasma concentration of ghrelin (P < 0.001) and cortisol (P < 0.001), with a smoothed trend on day 34 in the latter variable. To conclude, postponing the pasture allocation to afternoon increased the intake of WSC, favoring a glucogenic pattern of rumen fermentation and a rise of glucose and insulin levels in blood, although these effects were not consistent across the whole experimental period. Moreover, the afternoon grazing decreased the level of cortisol and ghrelin, suggesting a higher satiation-relaxing effect.

Effect of timing of paddock allocation in tropical grass on performance, nitrogen excretion, and enteric methane emissions from dairy cows

The objective of this study was to investigate the influence of timing of paddock allocation (AM or PM) in tropical grass on nutritive value of the herbage, dry matter intake (DMI), milk yield and composition, ruminal fermentation, nitrogen excretion, and enteric CH₄ emissions of dairy cows. Twenty cows were grouped in pairs and randomly distributed within pair to one of two treatments. PM herbage had greater contents of dry matter (DM), soluble carbohydrates, starch, and nonfibrous carbohydrate to protein ratio and lower contents of neutral detergent fiber and acid detergent fiber. There was no treatment effect on DMI, N excretion, milk yield, and CH₄ emissions. However, milk protein and casein yields tended to be greater for PM than AM, while milk urea nitrogen concentration was lower for PM than AM. The increase in nutritive value of the afternoon relative to the morning herbage within the framework of this study was not large enough to increase DMI and milk yield or to decrease CH₄ emission intensity by the dairy cows as hypothesized. The findings indicate that PM treatment can be a simple and useful grazing strategy that results in an herbage harvest with greater nutritional value and in lower excretion of urea N into milk.

Evaluation of Molly model predictions of ruminal fermentation, nutrient digestion, and performance by dairy cows consuming ryegrass-based diets

Several studies have been conducted to improve grazing management and supplementation in pasture-based systems. However, it is necessary to develop tools that integrate the available information linking the representation of biological processes with animal performance for use in decision making. The objective of this study was to evaluate the precision and accuracy of the Molly cow model predictions of ruminal fermentation, nutrient digestion, and animal performance by cows consuming pasture-based diets to identify model strengths and weaknesses, and to derive new digestive parameters when relevant. Model modifications for adipose tissue, protein synthesis in lean body mass and viscera representation were included. Data used for model evaluations were collected from 25 publications containing 115 treatment means sourced from studies conducted with lactating dairy cattle. The inclusion criteria were that diets contained ≥45% perennial ryegrass (Lolium perenne L.), and that dry matter intake, dietary ingredient composition, and nutrient digestion observations were reported. Animal performance and N excretion variables were also included if they were reported. Model performance was assessed before and after model reparameterization of selected digestive parameters, global sensitivity analysis was conducted after reparameterization, and a 5-fold cross evaluation was performed. Although rumen fermentation predictions were not significantly improved, rumen volatile fatty acids absorption rates were recalculated, which improved the concordance correlation coefficient (CCC) for rumen propionate and ammonia concentration predictions but decreased CCC for acetate predictions. Similar degradation rates of crude protein were observed for grass and total mixed ration diets, but rumen-undegradable protein predictions seemed to be affected by the solubility of the protein source as was the intestinal digestibility coefficient. Ruminal fiber degradation was greater after reparameterization, driven primarily by hemicellulose degradation. Predictions of ruminal and fecal outflow of neutral detergent fiber and acid detergent fiber, as well as total fecal output predictions, improved significantly after reparameterization. Blood urea N and urinary N excretion predictions resulted in similar accuracy using both sets of model parameters, whereas fecal N excretion predictions were significantly improved after reparameterization. Body weight and body condition score predictions were greatly improved after model modifications and reparameterization. Before reparameterization, yield predictions for daily milk, milk fat, milk protein, and milk lactose were greatly overestimated (mean bias of 61.0, 58.7, 73.7, and 64.6% of mean squared error, respectively). Although this problem was partially addressed by model modifications and reparameterization (mean bias of 3.2, 1.1, 1.7, and 0.4% of mean squared error, respectively), CCC values were still small. The ability of the model to predict grass digestion and animal performance in dairy cows consuming pasture-based diets was improved, demonstrating the applicability of this model to these productive systems. However, the failure to predict grass digestion based on standard model inputs without reparameterization indicates there are still fundamental challenges in characterizing feeds for this model.

Measuring seasonal and agro-ecological effects on nutritional status in tropical ranging dairy cows

Despite high numbers of cattle, milk production in many tropical countries such as Ethiopia is very low. Animals are managed traditionally, meaning they mostly depend on seasonal availability of natural pasture, grass, and crop residues with no supplementary feeds. Due to the lack of pasture management, there is overgrazing and soil erosion, and the land still must deal with extremely dry periods. All this has a negative effect on dairy cow productivity. Identification of the specific nutritional deficits would enable targeted interventions to improve milk yield performance, but nutrient and energy intakes are difficult to assess in ranging conditions. The aim of this research was, therefore, to evaluate the nutritional status of ranging dairy cows through blood metabolites, milk yield, and body condition in relation to environmental factors such as agro-ecology and season. The study was performed in a tropical region that is known to be exposed to the above-mentioned situation, the Arba Minch region in the southern Ethiopian Rift Valley. Blood samples were collected from 170 ranging dairy cows in 6 different districts, along a transect extending from the lowlands to the highlands, in both seasons (dry and rainy). Body condition score and milk yield of all cows were also determined for both seasons. Serum urea, creatinine, triglyceride, and nonesterified fatty acid concentrations were quantified spectrophotometrically. Dried serum spots were subject to quantitative electrospray tandem mass spectrometry to estimate changes in nutrient metabolism based on selected free AA and carnitine esters. Based on these measurements, nutritional status varied with season and geographical region. It can also be concluded that extensive metabolite analysis such as mass spectrometry can provide detailed insights, but the simpler spectrophotometric metabolite analysis can estimate the nutritional status of ranging animals.

Rumen Fermentation and Fatty Acid Composition of Milk of Mid Lactating Dairy Cows Grazing Chicory and Ryegrass

The goals of the current study were to investigate the effects of including chicory (Cichorium intybus L.) into the traditional feeding regime of ryegrass/white clover (Lolium perenne L./Trifolium repens L.), and time of its allocation on milk production, rumen fermentation, and FA composition of milk and rumen digesta of dairy cows. Nine groups of four cows were allocated one of three replicated feeding regimes: (1) ryegrass/white clover only (RGWC), (2) ryegrass/white clover + morning allocation of chicory (CHAM), and (3) ryegrass/white clover + afternoon allocation of chicory (CHPM). One cow per group had a rumen cannulae fitted. Treatment did not affect total grazing time or estimated dry matter intake, but cows ruminated more when fed RGWC than chicory. Allocating chicory in the afternoon elevated milk production compared with RGWC and CHAM. Milk from cows grazing chicory contained greater concentrations of polyunsaturated FA (PUFA) such as C18:3 c9, 12, 15 and C18:2 c9, 12 than those on RGWC. As with milk, rumen digesta concentration of PUFA increased when cows grazed on chicory rather than RGWC, which corresponded with lower concentrations of intermediate vaccenic and biohydrogenation end-product stearic acid for cows grazing on chicory. Mean ruminal pH was lower for cows offered chicory than those on RGWC, reflecting greater rumen concentrations of volatile fatty acids (VFA) for cows fed chicory. Allocating chicory during the afternoon is a useful strategy that can translate to improved milk production. The lower rumen pH, lower concentration of vaccenic and stearic acids, and elevated concentration of PUFA in the rumen of cows fed chicory suggest reduced biohydrogenation and may explain the elevated concentration of PUFA in the milk of cows fed chicory compared with those fed RGWC.

Diurnal Concentration of Urinary Nitrogen and Rumen Ammonia Are Modified by Timing and Mass of Herbage Allocation

Simple Summary

Low nitrogen use efficiency in grazing dairy cows leads to high urinary N excretion, which contributes to greenhouse gases emission. This problem has been associated with high N and low energy intake, increasing rumen ammonia (NH₃) concentration, and thereby, increasing urinary N excretion. Under this situation, it is important to discover nutritional and grazing management strategies that allow reduced urine N excretion in the pasture. This study evaluated whether changes in time of herbage allocation and herbage mass modify the diurnal pattern of urinary nitrogen (N) concentration and ruminal NH₃ of lactating dairy cows. We found that the combination of time of herbage allocation and herbage mass modified rumen NH₃ production and urinary N concentration. Results suggest that maintaining cows in the holding pen at the milking parlor for two hours after morning and afternoon milking could allow collection of urine from cows in the slurry pit during peak N concentration, returning cows to the pasture at a time of day when urinary N concentration is decreased.

Abstract

The objective of this work was to evaluate whether changes in time of herbage allocation and herbage mass (HM) (low (L) or medium (M)) modify the diurnal pattern of urinary nitrogen (N) concentration and ruminal ammonia (NH₃) of lactating dairy cows. Four Holstein-Friesian cows fitted with rumen cannula were randomly allocated to one of four treatments: 1) low herbage mass in the morning (L-AM) (Access to new herbage allocation after morning milking with a herbage mass (HM) of 2000 kg DM/ha); 2) low herbage mass in the afternoon (L-PM) (Access to new herbage allocation after afternoon milking with a HM of 2000 kg DM/ha); 3) medium herbage mass in the morning (M-AM) (Access to new herbage allocation after morning milking with a HM of 3000 kg DM/ha); and 4) medium herbage mass in the afternoon (M-PM) (Access to new herbage allocation after afternoon milking with a HM of 3000 kg DM/ha). A four by four Latin Square design with four treatments, four cows, and four experimental periods was used to evaluate treatment effects. Rumen NH₃ concentration was greater for L-AM compared to L-PM and M-PM at 13:00 and 16:00 h. Urine urea and N concentrations were lower for M-AM compared to L-AM. Urine N concentration was greater for L-AM than other treatments at 10:00 hours and greater for M-PM compared to M-AM at 16:00 hours. Results suggest that maintaining the cows in the holding pen at the milking parlor for two hours after morning grass silage supplementation for L-AM and for two hours after afternoon grass silage supplementation for M-PM, could allow collection of urine from cows at the holding pen and storage of urine in the slurry pit during the time of peak N concentration, returning cows to the pasture at a time of day when urinary N concentration is decreased.

The Order of Grass and Maize Silage Supplementation Modifies Milk Yield, Grazing Behavior and Nitrogen Partitioning of Lactating Dairy Cows

The aim of this study was to evaluate the effects of the order of grass silage (GS) and maize silage (MS) supplementation on milk yield, grazing behavior and nitrogen (N) partitioning of lactating dairy cows during autumn. Thirty-six Holstein-Friesian dairy cows were randomly assigned to one of three treatments, and cows remained on these treatments for a 62 days period: (1) MIX; cows supplemented with 3 kg of dry matter (DM) of silage containing 1.5 kg DM of MS and 1.5 kg DM of GS in both the morning and afternoon; (2) GS-MS; cows supplemented with 3 kg DM of GS in the morning and 3 kg DM of MS in the afternoon; (3) MS-GS; cows supplemented with 3 kg DM of MS in the morning and 3 kg DM of GS in the afternoon. All cows received a pasture allowance of 17 kg DM/cow/d and 3 kg DM of concentrate. Grazing time and pasture intake were unaffected by treatment; however, milk production was greater for MS-GS, while milk protein was greater for GS-MS. Urinary N excretion was greater for MS-GS than MIX. In conclusion, MS-GS resulted in high milk yield but also high urinary N excretion, while MIX resulted in low urinary N excretion but also decreased milk yield.

Interaction between herbage mass and time of herbage allocation modifies milk production, grazing behaviour and nitrogen partitioning of dairy cows

The objective of the present study was to evaluate the interaction effects between herbage mass and time of herbage allocation on milk production, grazing behaviour and nitrogen partitioning in lactating dairy cows. Forty-four Holstein Friesian cows were grouped according to milk production (24.7 ± 2.8 kg), bodyweight (580.6 ± 51.7 kg), days in milk (74 ± 17.1) and body condition score (3.1 ± 0.3), and then assigned randomly to one of four treatments: (1) L-AM: access to new herbage allocation after morning milking with herbage mass of 2000 kg DM/ha, (2) L-PM: access to new herbage allocation after afternoon milking with herbage mass of 2000 kg DM/ha, (3) M-AM: access to new herbage allocation after morning milking with herbage mass of 3000 kg DM/ha, and (4) M-PM: access to new herbage allocation after afternoon milking with herbage mass of 3000 kg DM/ha. All cows received a daily low herbage allowance of 21 kg DM measured above ground level, 3.0 kg DM of grass silage and 3.5 kg DM of concentrate. Herbage intake was similar between treatments, averaging 8.3 kg DM/day (P &gt; 0.05). Total grazing time was lower for M-PM compared with other treatments (P &lt; 0.01). Milk production was greater for M-AM and M-PM compared with L-PM (P &lt; 0.05). Urea in milk and plasma were greater for L-AM than L-PM and M-PM (P &lt; 0.01). Similarly, rumen ammonia was greater for L-AM compared with M-PM and M-AM (P &lt; 0.05). Nitrogen intake was 13.6% greater for L-AM than L-PM, and 17.5% greater for L-AM than M-PM (P &lt; 0.05). Nitrogen use efficiency was 22.1% greater for M-PM than L-AM, and 11.8% greater for M-PM than L-PM (P &lt; 0.01). In conclusion, the best management combination was observed when a medium herbage mass was delivered in the afternoon, maintaining a low nitrogen intake, low urinary nitrogen excretion and high milk production.

Diet selection and n-3 polyunsaturated fatty acid deposition in lambs as affected by restricted time at pasture

This study investigates the effects of restricted grazing time on forage selectivity and meat fatty acid deposition of lambs compared to a traditional grazing system. Results showed that the animals preferred to graze pasture species that were more palatable and lower in fibre, while demonstrating a partial preference for species with high protein levels. Leymus chinensis was more preferentially selected by lambs grazing pasture for shorter periods than longer periods. Lambs that grazed for 4 h per day had a high LNA (α-linolenic acid) intake. The accumulation of LNA and its elongation products in tissue was closely related to the LNA level in diet. Therefore, allowing lambs to graze for at least 4 h per day resulted in a meat fatty acid profile that is richer in health-promoting fatty acids. In particular, the highest DHA (docosahexaenoic acid) was observed in meat from lambs which grazed pasture for 4-h versus 8- and 12-h. It can be concluded that, in grassland systems, a healthier meat fatty acid profile for humans and the potential for better pasture management is achieved by limiting the grazing of lambs to 4 h per day rather than grazing over longer time periods.

Milk production and composition, nitrogen utilization, and grazing behavior of late-lactation dairy cows as affected by time of allocation of a fresh strip of pasture

Eighty late-lactation dairy cows were used to examine the effects of allocating a new pasture strip of a sward based on ryegrass (Lolium perenne L.) in the morning (a.m.; ∼0730 h) or in the afternoon (p.m.; ∼1530 h) on milk production and composition, nitrogen (N) utilization, and grazing behavior. Cows grazed the same pasture strips for 24 h and were offered the same daily herbage allowance. Herbage composition differed among treatments; p.m. herbage had greater dry matter (DM; 22.7 vs. 19.9%), organic matter (OM; 89.5 vs. 88.9%), and water-soluble carbohydrate (10.9 vs. 7.6%) concentrations and lesser crude protein (20.5 vs. 22.2%) and neutral detergent fiber (48.8 vs. 50.4%) concentrations compared with a.m. herbage. Total fatty acids (FA), α-linolenic acid, and polyunsaturated FA (PUFA) were greater in a.m. herbage, whereas monounsaturated FA were greater in p.m. herbage. Estimates of herbage DM intake did not differ among treatments. Daily milk yields and milk fat and milk protein concentrations were similar among treatments, whereas milk fat (684 vs. 627 g/cow), milk protein (545 vs. 505 g/cow), and milk solids (milk fat + milk protein) yields (1,228 vs. 1,132 g/cow) tended to be greater for cows on p.m. herbage. Rumenic acid and total PUFA in milk were greater for cows on a.m. herbage, whereas oleic acid was greater for cows on p.m. herbage. Estimates of urinary N excretion (g/d) did not differ among treatments, but urinary N concentrations were greater for cows on a.m. herbage (5.85 vs. 5.36 g/L). Initial herbage mass (HM) available (kg of DM/ha) and instantaneous HM disappearance rates (kg of DM/ha and kg of DM/h) did not differ, but fractional disappearance rates (0.56 vs. 0.74 per hour for a.m. vs. p.m., respectively) differed. Under the current conditions, timing of pasture strip allocation altered the herbage nutrient supply to cows; allocating a fresh strip of pasture later in the day resulted in moderate increases in milk and milk solids yields in late-lactation dairy cows. Conversely, a greater concentration of precursor FA in a.m. herbage resulted in a greater concentration of beneficial FA in milk, compared with cows on p.m. herbage.

Milk production and composition of dairy cows grazing two perennial ryegrass cultivars allocated in the morning and afternoon

The objective of the study was to evaluate the effect of perennial ryegrass cultivar and timing of herbage allocation on herbage nutritive value and milk production of mid-lactation dairy cows. An autumn grazing trial using 48 Friesian × Jersey spring-calving cows was conducted over 10 days. Twelve groups of four cows were allocated to three replicates of four treatments, namely, two perennial ryegrass cultivars (AberMagic or Prospect) offered either after milking in the morning (0830 hours) or afternoon (1630 hours). Cows were offered a daily herbage allowance of 30 kg DM/cow above ground level. There were no significant differences in sward structure and morphological characteristics between cultivars, except for Prospect having a lower average tiller mass (43.1 mg) than AberMagic (48.4 mg). The concentration of water-soluble carbohydrates (WSC) and organic matter digestibility in DM (DOMD) was greater in AberMagic (180 g/kg, 74.2%) than in Prospect (153 g/kg, 71.4%). Herbage DM percentage, WSC concentration and DOMD were lower in the morning than in the afternoon (18.8% vs 22.3% DM; 154 vs 179 g/kg WSC; 72.1% vs 73.5% DOMD). Herbage DM intake (12.0 kg/cow.day), milk yield (17.2 kg/cow.day) and milksolids yield (1.60 kg/cow.day) did not differ significantly among treatments. Cultivar choice and timing of allocation influenced herbage WSC concentration and digestibility, but did not alter milksolids production.