Browsing by Author "Donaghy D"

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    Dairy Cows Grazing Plantain-Based Pastures Have Increased Urine Patches and Reduced Urine N Concentration That Potentially Decreases N Leaching from a Pastoral System
    (MDPI (Basel, Switzerland), 2023-02-02) Nguyen TT; Navarrete S; Horne D; Donaghy D; Bryant RH; Kemp P; De La Fuente G
    The objective of this study was to determine the effect of grazing plantain-based pastures on urine volume, urination frequency, and urinary nitrogen (UN) concentration of dairy cows under a typical pastoral dairy practice offering approximately 25% supplemented feeds. The experiment was a completely randomised design with three pasture treatments (perennial ryegrass-white clover (RGWC); RGWC + low plantain rate (PLL); and RGWC + high plantain rate (PLH)), five replicate plots, and repeated in two sequential grazing periods. Forty-five lactating Friesian × Jersey cows were randomly assigned into three groups of 15 animals each to graze over six days in adaptation paddocks and three days in experimental plots. Urine flow sensors were used to measure urine volume and urinary frequency, while spot urine sampling was conducted to determine nitrogen (N) concentration in cow urine. The results showed that including 25% plantain in the diet (PLH) increased daily urine volume by 44% and the daily number of urinations by 28%, compared to grazing the RGWC pasture. In addition, N concentration in cow urine was decreased by 18 and 29% when the diet contained 18% and 25% plantain, respectively. In conclusion, under a typical dairy farm practice, incorporating plantain into the RGWC pasture with the proportion of 25% plantain in the diet can increase the number of urine patches and reduce the concentration of N in the urine, thereby providing the opportunity to decrease N leaching from pastoral systems.
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    Methane emissions intensity in grazing dairy cows fed graded levels of concentrate pellets
    (Taylor and Francis Group, 2024-05-03) Bosher T; Della Rosa MM; Khan MA; Sneddon N; Donaghy D; Jonker A; Corner-Thomas R; Handcock R; Sneddon N
    The current New Zealand greenhouse gas inventory predictions assume that dairy cows consume pasture only, but the use of supplemental feeds, including concentrates, on New Zealand dairy farms has increased greatly in recent decades. The objective of this study was to evaluate the effect of feeding graded levels of concentrates on methane (CH4) emissions in lactating dairy cows within a pastoral system. Early lactation dairy cows (n = 72) were allocated (n = 18 per treatment) to receive 0, 2, 4 and 6 kg dry matter (DM) of treatment concentrates per day during milking. The cows grazed pasture ad libitum and CH4 emissions were measured in the paddocks using automated emissions monitoring systems called ‘GreenFeed’. Gross CH4 emissions (g/d) were similar for cows across the four dietary treatments, while CH4 emissions intensity (g/kg fat and protein corrected milk production (FPCM) and milk solids production) linearly decreased with increasing concentrate inclusion in the diet (P < 0.02). The CH4 intensity decreased linearly (r2 = 0.42) and quadratically (r2 = 0.53) with increasing FPCM production.
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    Nitrogen Use Efficiency and Excretion in Grazing Cows with High and Low Milk Urea Nitrogen Breeding Values
    (MDPI (Basel, Switzerland), 2021-09-01) Correa-Luna M; Donaghy D; Kemp P; Schutz M; Lopez-Villalobos N
    Milk urea nitrogen content is moderately heritable and is phenotypically related to urine nitrogen (UN). Based on this relationship, it has been suggested that genetic selection for lower milk urea nitrogen in grazing dairy cows could decrease UN concentration thereby reducing nitrogen excretions into the ground. The objective of this study was to compare the nitrogen use efficiency (NUE) and excretion in grazing cows with high and low milk urea nitrogen breeding values (MUNBV) in two farms of contrasting farming intensity. On the high-intensity farm (HIF) 68 and 70 cows with low and high MUNBV, respectively, were fed higher levels of supplementation and milked twice-daily, while on the low-intensity farm (LIF) 82 and 86 cows with low and high MUNBV, respectively, were fed lower levels of supplementation milked once-daily. Nitrogen use efficiency (g/g) was calculated as the ratio of daily milk N to daily N intake. Daily N intake (g/day) was derived from feed intake estimates based on energy requirements. The UN (g/day) was estimated by back-calculation from dietary N and subtracting milk N, faecal N, and N retained in body tissues. Irrespective of farm, cows with low MUNBV had significantly lower MY and milk urea nitrogen (p < 0.001) but this was not linked to significantly less UN. In the LIF, cows with low MUNBV had lower NUE (p < 0.001) than cows with high MUNBV, and this was explained by the reduced protein yield (p < 0.001). Selecting cows for low MUNBV was not an effective tool to reduce N losses and to increase the NUE in two dairy farms of contrasting farming intensity.
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    Regression of traits-other-than-production phenotypes for cows milked once a day on estimated breeding values obtained from cows milked twice a day
    (The New Zealand Society of Animal Production (Inc), 2019-06-17) Sneddon N; Lopez-Villalobos N; Garrick DJ; Rocha JF; Donaghy D
    The use of traits other than production (TOP) to aid selection for conformation fit-for-purpose offspring becomes more important as once-a-day (OAD) milking for whole or part season becomes more common. In 2013 Massey University Dairy 1 farm transitioned their mixed-breed herd milked twice a day (TAD) to an OAD spring-calving system. All cows on the farm were scored for 14 inspector TOP traits and four farmer-scored traits for a total of 1,163 records over five seasons (168 to 254 cows per year). The scores were adjusted for age of the cow and season. The adjusted phenotypes for all cows for each trait were then regressed on their corresponding nationally-produced TAD estimated breeding values (EBV), which had been calculated without using these phenotypes. The four farmer-scored traits had the lowest relationships with EBV. Estimates of regression coefficients near one were observed for the udder traits (udder support, rear udder, front teats, udder overall), dairy conformation and body capacity. This supports the use of national EBVs in OAD herds derived mostly from records on daughters in TAD herds.
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    The Impact of Accumulating Herbage Masses in Autumn on Perennial Ryegrass Sward Characteristics
    (MDPI (Basel, Switzerland), 2024-01-08) Looney C; Wingler A; Donaghy D; Egan M; MacAdam J
    Autumn grazing management aims to accumulate herbage for defoliation prior to a decrease in growth rates for the extension of the grazing season. The current study investigated the impact of building different target herbage masses (THMs) in autumn and imposing one of three different defoliation dates (DDs) between mid-October and late November on light transmitted to the base of the sward, free leaf lamina (FLL), leaf stage and internode elongation. Four THMs (low, medium, high and very high) and three DDs (DD1—15 October, DD2—7 November and DD3—21 November) were assigned to a 4 × 3 split plot design over two years. Light transmitted to the base of the sward was greatest in the low THM and decreased in all other THMs. Internode elongation increased in tillers in the medium to the very high THMs. Defoliation of the medium, high and, in particular, the very high THMs earlier in autumn reduced the effect of decreased light transmission on internode elongation. This study highlights that, as light transmitted to the base of the sward decreases, internode elongation increases, and this could negatively impact sward structure.