3 results
Responses to supplementation by dairy cows given low pasture allowances in different seasons 2. Milk production
- J. W. Penno, K. A. Macdonald, C. W. Holmes, S. R. Davis, G. F. Wilson, I. M. Brookes, E. R. Thom
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- Journal:
- Animal Science / Volume 82 / Issue 5 / October 2006
- Published online by Cambridge University Press:
- 09 March 2007, pp. 671-681
- Print publication:
- October 2006
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Two factorial experiments were designed to determine the effects of stage of lactation, and season of the year, on cow responses to supplementary feeding. These experiments were conducted over consecutive years with 128 high genetic merit multiparous Holstein-Friesian cows in early, mid and late lactation in spring, summer, autumn and winter. At each stage of lactation, and in each season of the year, cows were offered a restricted pasture allowance (25 to 35 kg dry matter (DM) per cow per day), either unsupplemented (control) or with supplement at 50 MJ metabolizable energy (ME) per cow per day in experiment 1 and 80 MJ ME per cow per day in experiment 2. The two supplements given in both years were rolled maize grain (MG) and a mixture of foods formulated to nutritionally balance the diet (BR). In experiment 2, another treatment, of a generous pasture allowance (60 to 75 kg DM per cow per day) (AP), was imposed on an additional group of early lactation cows during each season. Direct milk solids (MS) (milk fat plus milk protein) responses in experiment 1 to MG were 169, 279, 195 and 251 g MS per cow per day in spring, summer, autumn and winter, respectively, while those to BR were 107, 250, 192, 289 g MS per cow per day. In experiment 2, however, milk solids responses to both supplements during spring were slightly below the control treatment, with values similar to those in experiment 1 in summer and autumn for cows on the BR but not the MG supplement. Milk solids responses to supplementary foods were largest during seasons of the year when the quantity and quality of pasture on offer resulted in the lowest milk solids yield from unsupplemented cows. When carry-over effects of feeding MG and BR on milk solids production were detected, they were only about half the magnitude of the direct effects. Serum urea concentrations were higher in control cows than those offered MG with a similar effect for BR in all but summer in experiment 1, while serum glucose concentrations were highest in winter and lowest in summer. The most important factor influencing milk solids responses was the relative food deficit (RFD) represented by the decline in milk solids yield of the respective control groups after changing from a generous pasture allowance to restricted allowance when the feeding treatments were imposed. Total milk solids responses (direct and carry-over) to supplements were greatest when severe food restrictions, relative to the cows' current food demand, resulted in large reductions in milk solids yield of the control groups. The RFD was the best predictor of milk solids response to supplementary foods. Therefore, it is likely that cows are most responsive to supplementary foods during or immediately after the imposition of a severe food restriction.
Responses to supplementation by dairy cows given low pasture allowances in different seasons 1. Pasture intake and substitution
- J. W. Penno, K. A. Macdonald, C. W. Holmes, S. R. Davis, G. F. Wilson, I. M. Brookes, E. R. Thom
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- Journal:
- Animal Science / Volume 82 / Issue 5 / October 2006
- Published online by Cambridge University Press:
- 09 March 2007, pp. 661-670
- Print publication:
- October 2006
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- Article
- Export citation
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Two factorial experiments were designed to determine the effects of stage of lactation, and season of the year, on cow responses to supplementary feeding. These experiments were conducted over consecutive years with 128 high genetic merit multiparous Holstein-Friesian cows in early, mid and late lactation in spring, summer, autumn and winter. At each stage of lactation, and in each season of the year, cows were offered a restricted pasture allowance (25 to 35 kg dry matter (DM) per cow per day), either unsupplemented (control) or supplemented with 50 MJ metabolizable energy (ME) per cow per day in experiment 1 and 80 MJ ME per cow per day in experiment 2. Two different supplements were offered, namely, rolled maize grain (MG) and a mixture of foods (BR) formulated to nutritionally balance the diet. In experiment 2, a fourth treatment consisting solely of a generous pasture allowance (60 to 75 kg DM per cow per day, AP) was introduced. Offering MG and BR increased DM intake (DMI). At the restricted pasture allowance, increasing total ME allowance (MEA) by offering supplementary foods increased ME intake (MEI) by 0·68 (s.e. 0·047) MJ per extra MJ ME offered. This highly significant (P<0·001) linear relationship was consistent across seasons, and did not diminish at higher MEA. In experiment 2, cows in early lactation had lower substitution rates than mid and late lactation cows irrespective of season. Substitution rate was higher when higher pasture allowance or quality of pasture on offer enabled the unsupplemented cows to achieve higher DMI from pasture than at other times of the year. These results suggest that one of the key factors determining the intake response to supplementary foods is pasture allowance. Within spring calving dairying systems, the largest increases in total DMI per kg of supplement offered is likely when offering supplements to early lactation cows grazing restricted allowances of high quality pasture.
Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application
- S. F. LEDGARD, J. W. PENNO, M. S. SPROSEN
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- Journal:
- The Journal of Agricultural Science / Volume 132 / Issue 2 / March 1999
- Published online by Cambridge University Press:
- 01 March 1999, pp. 215-225
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Nitrogen (N) inputs and outputs were measured over 3 years in a trial with four farmlets (each with 16 randomly-allocated 0·4 ha paddocks) on permanent white clover/ryegrass pastures which were grazed throughout the year by dairy cows near Hamilton, New Zealand. Three farmlets were stocked at 3·3 cows/ha and received nominal rates of N fertilizer (urea in 8–10 split applications) of 0, 200 or 400 kg N/ha per year. A fourth farmlet with 4·4 cows/ha received 400 kg N/ha per year and was supplemented with maize grain during the first two years.
Nitrogen balances were calculated, with [sum ]N inputs[ape ][sum ]N outputs. Annual inputs from N2 fixation were 99–231 kg N/ha in the 0 N farmlet, but declined to 15–44 kg N/ha in the 400 N farmlets. The main N outputs (in kg N/ha per year) were in milk (72–126), nitrate leaching (20–204), and transfer of N via cow excreta from pastures to lanes and milking shed (54–92). Gaseous losses by denitrification (3–34) and volatilization (15–78) were smaller than the other N outputs but increased significantly with N fertilizer application. In the maize-supplemented farmlet, N outputs in milk were 31% higher than in the corresponding non-supplemented 400 N farmlet, whereas leaching losses averaged 17% lower during the 2 years of supplementation.
In the N-fertilized farmlets, estimated N balances were influenced by inclusion of the transitional N processes of immobilization of fertilizer N into the soil organic N pool (estimated using 15N at 42–94 kg N/ha per year) and the contribution from mineralization of residual clover-fixed N in soil not accounted for in the current estimates of N2 fixation (estimated at up to 70% of measured N2 fixation or 46 kg N/ha per year). However, these processes were counteracting and together were calculated to have only a small net effect on total N balances.
The output of N in products (milk, meat and feed) relative to the total N input averaged 26% in the 400 N farmlets, and is compared to that measured for commercial intensively-managed dairy farms in England and the Netherlands (14–20%). The 0 N farmlet, which was reliant on N2 fixation as the sole N input, was relatively very N-efficient with the milk production being 83% of that in the 400 N farmlet (at 3·3 cows/ha) and the N output in products relative to total N input averaging 52%.