Irish Journal of Agricultural and Food Research Volume 41, Issue 2

Effect of rumen degradable protein with or without fermentable carbohydrate supplementation on systemic concentrations of ammonia and urea in cattle

D.A. Kenny ^1,2 †, M.P. Boland², M.G. Diskin¹ and J.M. Sreenan¹

¹ Teagasc Research Centre, Athenry, Co. Galway
² Faculty of Agriculture, University College Dublin, Belfield, Dublin 4

High systemic concentrations of ammonia and urea have been associated with poor reproductive performance in cattle. The effects of rumen degradable protein (RDP) intake and source and level of fermentable carbohydrate supplementation on systemic concentrations of ammonia and urea were examined in two experiments. In the first experiment, 18- to 24-month-old beef heifers (n = 18) were individually offered, a diet based on grass silage supplemented with one of four levels of feed-grade urea (460 g N /kg): 0 (n = 5), 80 (n = 5), 160 (n = 4) or 240 (n = 4) g head⁻¹ day ⁻¹. Blood samples were taken as appropriate for determination of plasma concentrations of ammonia and urea. In a second experiment, 80 heifers were assigned to either low RDP (0 g urea; 0U) or high RDP (240 g urea; 240U) diets based on grass silage and unsupplemented (control) or supplemented with 1.5 or 3.0 kg of either rolled barley or molassed sugar-beet pulp (MSBP). Animals were fed once daily at 1000 h. In Experiment 1, plasma concentrations of ammonia (P < 0.05) and urea (P < 0.001) were linearly related to dietary urea intake. In Experiment 2, plasma urea was higher on 240U (P < 0.001) than 0U. Plasma ammonia concentration was higher (P < 0.01) in animals on 240U in the post-feed samples v. the pre-feed samples than those on 0U. Plasma urea was lower in animals fed 3 kg MSBP than 3 kg barley on both 240U (P < 0.001) and 0U (P < 0.05). Plasma ammonia was not affected by carbohydrate supplementation (P 0.05). Increased dietary RDP increases systemic concentrations of ammonia and urea. Supplementation with fermentable carbohydrate reduces systemic concentrations of urea and is dependent on the source and level fed.

Keywords: Ammonia; cattle; fermentable energy; rumen degradable protein; urea

Measurement of vacuum stability in milking units during simulated milking

E.J. O'Callaghan†

Teagasc, Moorepark Research Centre, Fermoy, Co. Cork

The vacuum stability conditions at the teat end in the cluster of a milking unit recorded during milking are related to the flow through individual milking liners. Since a commercial flow-measurement system is not available for recording the milk flow through individual liners vacuum stability measurements are generally made using laboratory flow simulators where the flow of water through the cluster is controlled. The objective of the present study was to develop a new flow simulator with simultaneous electronic recording of vacuum stability at the apex of an artificial teat, in the claw and in the pulsation chamber with controlled flow of water through each liner. The flow simulator consisted of four artificial teats each separately connected to four reservoirs. Vacuum recordings were done in 5-s scanning periods of the four measurement channels. On completion of the 5-s scanning period of the four measurement channels, the software computes the pulsation rate, the pulsator ratio and the maximum, minimum and mean values of vacuum pressure during each of the four phases of pulsation for each channel. The measurement system was evaluated with both the ISO (1996) artificial teat and an alternative design of artificial teat.

Keywords: Milking machine; simulation; vacuum

The influence of housing system on skin lesion scores, behaviour and responses to an ACTH challenge in pregnant gilts

L.A. Boyle1†, F.C. Leonard2, P.B. Lynch1 and P. Brophy3

1T eagasc, Moorepark Research Centre, Fermoy, Co. Cork

2D epartment of Veterinary Microbiology and Parasitology, Uni _e rsity College Dublin, Ballsbridge, Dublin 4

3D epartment of Animal Science and Production, Uni _e rsity College Dublin, Belfield, Dublin 4

Pregnant gilts were assigned to stalls [ST, n=23] and to loose bedded [LB, n=15] or unbedded [LU, n=14] pens in groups of four to determine the effect of housing system on welfare. Behaviour was recorded during the first hour in the housing treatments and on days 1, 8 and 31. Skin lesions at 34 locations on the body were scored according to severity (0 to 6) prior to entering the housing treatments, on the day after entry, on days 8 and 31 and prior to entering the farrowing house (day 75) . Aggression induced scratches were counted on the same days. Six weeks after entry to the treatments, an adrenocorticotropic hormone (ACTH) challenge test was conducted. Gilts showed an acute behavioural stress response during the first hour in the stalls, which caused an increase in skin lesion scores the day after entry to the housing treatments. ST had the highest total lesion scores throughout the housing period. However, lesion scores of the front limbs did not differ between ST and LU. LB had the lowest levels of skin damage throughout the experiment. There was a low level of aggression at feeding in both loose housing treatments and these gilts had more scratches than gilts in stalls. The response to ACTH did not differ between ST and LU but was higher than the LB response. The findings suggest that gilt welfare is poor in stalls and that bedding improves gilt welfare in groups.

Keywords: Behaviour; housing system; pig; skin lesions; welfare

Visual assessment of herbage mass

M. O'Donovan ¹ †, J. Connolly², P. Dillon¹, M. Rath³, G. Stakelum¹

¹ Teagasc, Moorepark Research Centre, Fermoy, Co. Cork
² Department of Statistics, University College Dublin, Belfield, Dublin 4
³ Department of Animal Science, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4

An ability to accurately and quickly estimate farm grass supply helps greatly in the management of grazing pastures to enable high cow performance. The objective of this study was to evaluate the accuracy of visual assessment of herbage mass (HM). Measurements of HM were made on 13 dairy farms from November 1995 to October 1996. HM measurements were repeated over the following 12-month period. Farms were visited monthly from October to March and bimonthly from April to September. HM was estimated for a range of herbage masses on the farm. Herbage mass was visually estimated and then harvested by cutting a square (0.25 m²) quadrat to 40 mm above ground level. The variable of interest is the ratio of actual to estimated HM. In Year 1, when HM was <750 kg dry matter (DM) /ha, the ratio of actual to estimated yield was biased upwards by between 0.06 and 0.40. The variance of the ratio declined with increasing estimated HM. The standard deviation of the ratio declined from about 0.20 to 0.12 as estimated HM increased from about 1000 to 3000 kg DM/ha. A model was fitted to the data with farm x visit as a random effect for all yields >kg DM/ha. The increase in variability as HM increased was incorporated into the analysis. One farm's predicted ratio was significantly different from unity. The months of January, July and November had a predicted ratio significantly different (P < 0.05) from unity. The accuracy of the visual assessment method was confirmed by the results from Year 2. The results indicate that there is potential for precise estimation of HM by visual assessment.

Keywords: Herbage mass; observer; visual assessment

An assessment of the potential impact of climate change on grass yield in Ireland over the next 100 years

N.M. Holden† and A.J. Brereton

Department of Agricultural and Food Engineering, University College Dublin, Earlsfort Terrace, Dublin 2

The impact of climate change on grassland agriculture may affect yield, livestock numbers, winter housing, slurry storage and land spreading, and the production system. The potential change in grass yield in Ireland due to climate change was estimated using simulation modelling. The estimation took account of the spatial variation of soil and climate. The approach adopted was to: (i) use statistically downscaled climate data derived from the Hadley HADCM3 climate model; (ii) simulate daily weather for 30 separate years from monthly climate data (baseline, 2055 and 2075) using a stochastic weather generator; (iii) simulate 30 years of grass yields for each climate period using the Johnstown Castle Grass Model; (iv) summarize the 30 yield predictions for each climate period as a mean response to climate; and (v) quantify the change in yield as a result of climate change. Grass yield was predicted to decrease in the east of the country due to summer drought stress. In the west grass yield was predicted to increase. The major impacts of yield change were considered to be: (i) grass may cease to be a viable crop in the southeast and east if it requires irrigation to compensate for drought; (ii) theoretical turnout date may become earlier in the season; (iii) stock may have to remain housed at times when currently grazed outside, thus extending storage requirements; and (iv) alternative forage crops may become more suitable for winter feed conservation. No catastrophic impacts are foreseen, but the exact implications will also depend on regional agricultural policy.

Keywords: Climate change; grass yield; Johnstown Castle Grass Model

Plant populations and row widths for diploid sugar-beet cultivars

B. Rice†

Teagasc, Oak Park Research Centre, Carlow

This work aimed to establish whether a change from triploid to diploid cultivars would require any adjustment of the conventional plant populations and row widths used in sugar-beet production. In five trials, the diploid cultivar Celt was sown at three row widths: 51, 56 and 61 cm. At each width, seed spacings were adjusted so that four seed counts, between 50 000 and 113 000 seeds/ha, were sown. In four of these trials, plant establishment was 78 to 90% and yield (root, sugar) and sugar concentration were not significantly affected by the plant population density achieved. In one trial, where plant establishment was 58%, yield and sugar concentration continued to increase up to the highest plant density of 65 000 plants/ha. There were no yield or quality differences between 51-cm and 56-cm rows. On average, there was a reduction of 3.5% in extractable sugar yield with 61-cm rows; this was highly significant in one experiment. These results suggest that no change is required to the target plant populations used in Ireland. For those currently using 61-cm rows, a small yield increase may be achieved by reducing row width.

Keywords: Diploid; population density; row width; sugar beet

The performance of a E ucalyptus g unnii cut foliage plantation over 7 years

M. Forrest†

Department of Crop Science, Horticulture and Forestry, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4

Cut foliage is a term used to describe plant material used in the floristry industry. Eucalyptus species are grown for cut foliage in Western Europe and field trials to develop a cropping programme were established in 1990. Four planting configurations, single, double, triple and quadruple rows, were planted at a spacing of 1.75 m between and within rows, giving densities of 1937, 2432, 2657 and 2787 plants per hectare, respectively. When calculated by total weight or total number of stems the treatments did not differ significantly from each other. When calculated on a per plant basis the mean yield over 7 years varied from 2.87 to 4.79 kg (5.59 t/ha to 12.72 t/ha) or 33 to 53 stems (64/ha to 140/ha). Plant losses occurred and at the end of the 7-year period only 50% of the plants remained. This loss was attributed to severe coppicing of plants before they had become well-established and poor soil conditions on part of the site. Well-grown plants filled their allotted space and a spacing of 1.75 mX1.75 m can be recommended for the production of E ucalyptus gunnii cut foliage.

Keywords: Cut foliage; Eucalyptus gunnii

Mineral balances for the use of phosphorus and other nutrients by agriculture in Northern Ireland from 1925 to 2000 — methodology, trends and impacts of losses to water

R.H. Foy ^1,2 †, J.S. Bailey^1,2 and S.D. Lennox³

¹ Agricultural and Environmental Science Division, Department of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX
² Department of Agricultural and Environmental Science, School of Agriculture and Food Science, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX
³ Biometrics Division, Department of Agriculture and Rural Development, Newforge Lane, Belfast BT9 5PX

Annual inputs to agriculture of nutrients in fertilisers and imported animal feedstuffs and outputs in agricultural product were calculated from 1925 to 2000. Up to 1939, the phosphorus (P) surplus averaged 4.2 kg P/ha. Increases in fertiliser inputs from 1940 to 1949 and imported feedstuffs from 1945 to 1962 led to a P surplus of 24 kg P/ha in 1962. Since then P inputs have not increased and, while outputs of P have increased, this increase is small relative to input P, so that during the 1990s the P balance of 16.5 kg P/ha was only 14.5% lower than in the 1960s. Including rainfall inputs of 0.2 kg P/ha and loss to water of 1.1 kg P/ha only reduced the P surplus to 15.7 kg P/ha. Annual nitrogen balances increased from zero in 1931 to 142 kg N/ha in the 1990s. Considering aquatic transfers reduced this surplus to 132 kg N/ha. Drainage losses reduced the potassium surplus of the 1990s by 50% to 17.6 kg K/ha. For sulphur, drainage losses of 38 kg S/ha in the 1990s exceeded agricultural and precipitation inputs of 13 kg S/ha.

Keywords: Fertiliser; nitrogen; phosphorus; potassium; sulphur

A note on the effects of herbage mass at closing and autumn closing date on spring grass supply on commercial dairy farms

M. OíDonovan ^1† , P. Dillon¹, P. Reid², M. Rath³ and G. Stakelum¹

¹ Teagasc, Moorepark Research Centre, Fermoy, Co. Cork
² Teagasc, 19 Sandymount Avenue, Ballsbridge, Dublin 4
³ Department of Animal Science and Production, Faculty of Agriculture, University College Dublin, Belfield, Dublin 4

The effects of herbage mass at closing (CHM) and closing date (CD) in autumn on spring herbage mass SHM were investigated on 10 dairy farms over a 2-year period. (SHM) was regressed on CHM and CD. CD had significant (P < 0.001) effect on SHM. Each 1-day delay in closing from 1 October to 11 December reduced SHM by 15.0 kg dry matter (DM) /ha. The effect of CHM varied significantly with farm × year combination. Exponential herbage accumulation curves were fitted to the data to describe the accumulation of herbage from closing in the autumn to final measurement in spring. These models had a r.s.d. of 367 and 320 kg DM/ha for Year 1 and 2, respectively.

Keywords: Closing date; herbage growth; herbage mass