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The effect of concentrate supplements differing in ruminal
protein degradability on milk production and blood metabolite
concentrations of dairy cows grazing perennial ryegrass pasture
a ,
*
a bF.P. O’Mara
, J.J. Murphy , M. Rath
a
Teagasc, Moorepark Research and Development Centre, Fermoy, Co. Cork, Ireland
b
Department of Animal Science and Production, University College Dublin, Belfield, Dublin 4, Ireland
Received 16 February 1999; received in revised form 19 August 1999; accepted 2 September 1999
Abstract
An experiment was carried out to compare the milk production of Friesian cows grazing perennial ryegrass pastures when fed an energy supplement or supplements with high levels of undegradable protein. Eighty-seven cows were blocked on the basis of calving date and milk yield and allocated to one of three treatments. The treatments consisted of 1.25 kg / day of concentrates based predominantly on beet pulp, fishmeal or formaldehyde-treated soyabean meal (Sopralin). The cows were grazed as a single group for the duration of the 16-week experiment. Ruminal degradability was measured in three separate cows and the results showed that the fishmeal and Sopralin concentrates had similar contents of undegradable protein, and both had substantially more than the beet pulp concentrate. Milk yields were 17.3, 18.0 and 18.6 (S.E.D.50.46) kg / day, fat
yields were 0.67, 0.67 and 0.70 (S.E.D.50.021) kg / day, and protein yields were 0.58, 0.61 and 0.62 (S.E.D.50.015)
kg / day for the beet pulp, fishmeal and Sopralin treatments, respectively. The differences in milk and protein yields between
the Sopralin and beet pulp treatments were significant (P,0.05). Milk protein concentrations were 33.9, 34.3 and 33.7
(S.E.D.50.26) g / kg for the beet pulp, fishmeal and Sopralin treatments, respectively. The difference between the Sopralin
and fishmeal treatment was significant (P,0.05). These results show that supplements of undegradable protein at pasture
can result in higher milk production than when an energy supplement is fed. 2000 Elsevier Science B.V. All rights
reserved.
Keywords: Milk production; Blood metabolites; Perennial ryegrass; Supplements; Rumen degradable protein
1. Introduction
Generally responses in milk production to concen-trate supplementation at pasture are poor. Stakelum *Corresponding author. Present address: Department of Animal (1993) reported responses ranging from 0.17 to 0.70 Science and Production, Agriculture Building, University College
kg milk per kg of concentrate DM over five experi-Dublin, Belfield, Dublin 4, Ireland. Tel.: 1353-1-706-7142; fax:
ments where the concentrate feeding level ranged 1353-1-706-1103.
E-mail address: [email protected] (F.P. O’Mara) from 2.7 to 5 kg DM / cow per day. The lowest
responses were obtained from cows given a large Rulquin et al., 1993) as the two amino acids first grass allowance and when barley was the main limiting milk protein synthesis in dairy cows. How-supplementary feed. Journet and Demarquilly (1979) ever, fishmeal is an expensive feedstuff. Formalde-reported similar responses, ranging from 0 to 0.67 kg hyde-treated soyabean meal has high contents of milk per kg of concentrate, over six trials with cows undegradable protein and is less expensive than producing 23 kg milk at the start of the grazing fishmeal, but it has lower contents of lysine and season. They also reported slightly higher responses methionine (O’Mara et al., 1997a).
with cows producing 25 kg milk at the start of the The objectives of this experiment were to de-grazing season. Dillon et al. (1997) reported average termine if supplements with high contents of UDP responses over 2 years of 0.65 and 0.55 kg milk per would result in higher milk production than the same kg of concentrate when 2 and 4 kg of concentrate, amount of dry matter of an energy supplement, and respectively, were fed to cows in early lactation to determine the effect of different sources of UDP. which were grazing spring grass. Two high UDP supplements based on fishmeal or These responses are low and generally un- formaldehyde-treated soyabean meal were compared economic. However, better responses may be ob- to a beet-pulp-based supplement.
tained to supplements with a high content of rumen undegradable protein. Responses to degradable
pro-tein supplements (groundnut) have been similar to an 2. Materials and methods
equivalent amount of an energy supplement (Castle
et al., 1979). However Stobbs et al. (1977), Rogers 2.1. Animals, diets and treatments et al. (1980) and Minson (1981) have all reported
large responses in milk yield and milk protein Eighty-seven Friesian cows, including 15 concentration when cows were supplemented with 1 primiparous cows, were blocked on the basis of kg of formaldehyde-treated casein. The proportional calving date and milk yield in the 3 weeks preceding responses in milk yield were 0.2, 0.12 and 0.05, the experiment and randomly allocated to one of respectively, and much lower responses were ob- three treatments based on three concentrate supple-tained from untreated casein. The protein of grass is ments. The cows were calved on average 116 days highly degraded in the rumen (Cammell et al., 1983) (range 30–158) at the start of the experiment. The and these researchers demonstrated little effect of experimental concentrates were based on beet pulp, season on the extent of N degradation in early, mid fishmeal or formaldehyde-treated soyabean meal and late season perennial ryegrass (0.81, 0.85 and (Sopralin) and their ingredient composition is shown 0.84, respectively). Preduodenal loss of protein has in Table 1. The fishmeal and Sopralin concentrates previously been reported (Beever et al., 1985, 1987; were formulated to contain approximately the same Ulyatt et al., 1988). Thus supplements of UDP may amount of CP and UDP by including some beet pulp improve the protein nutrition of the cow sufficiently in the fishmeal concentrate.
to cause an increase in milk and / or milk protein The three treatment groups were grazed together
production. by day and night on predominantly perennial
rye-The quality of undegradable protein supplements
can vary. Casein is a very high quality protein and Table 1
the protein of animal feedstuffs may not be as good. Ingredient composition (kg / tonne) of the experimental concen-trates
Thus the responses to formaldehyde-treated casein
a
noted above may not be obtained with animal Beet pulp Fishmeal Sopralin feedstuffs. Fishmeal has been shown to have higher
Beet pulp 960 310
proportions of lysine and methionine in its unde- Fishmeal 600
graded amino acids than other vegetable protein Sopralin 910
Molasses 50 50
sources (O’Mara et al., 1997a). These two amino
Magnesium oxide 40 40 40
acids have often been cited (Casper and Schingoethe,
a
grass pastures for the duration of the 16-week centrifuged at 28003g for 10 min to obtain serum
experiment which began on 4th June, 1990. The samples. Plasma and serum samples were stored at overall stocking rate was 2.45 cows / ha. However, up 2208C before analysis. Ammonia concentration was until 20th May, 60% of the farm was closed for measured in blood plasma samples, and urea, non-silage, giving an effective stocking rate of 6.1 cows / esterified fatty acids (NEFA), b-hydroxybutyrate, ha. From 20th May to 7th July, 45% of the area was protein, albumin, D and L lactate, serum glutamate closed for silage, giving an effective stocking rate of pyruvate transaminase (SGPT), serum glutamate 4.5 cows / ha. Thereafter, until the end of the trial, the oxalo-acetate transaminase (SGOT), calcium, mag-cows grazed the entire area. All animals had been at nesium, and phosphorus concentrations were mea-pasture at least 3.5 weeks before the start of the sured in blood serum samples using a Cobas Mira experiment. They were divided into their experimen- biochemical analyzer (Roche Diagnostica, Basle, tal groups after the morning milking and fed their Switzerland).
appropriate concentrate at a rate of 1.25 kg / day. Concentrates were manufactured from the same Prior to the experiment, they had been supplemented batches of ingredients for the entire experiment. with 0.5 kg / day of a molassed beet-pulp-based They were sampled once per fortnight and ground mixture containing magnesium oxide. through a 1-mm screen before analysis. Dry matter was determined by drying at 1038C for 4 h. Samples 2.2. Measuring and sampling procedures and were ashed at 5508C for 16 h in a muffle furnace to
analytical methods determine ash content. Crude protein concentration
(N36.25) was determined using a Kjelfoss instru-Milk yield was recorded on 3 days per week. instru-Milk ment (Foss Electric), ether extract concentration was fat, protein and lactose concentrations were mea- determined using the Foss-let 15300 instrument sured weekly using the Milkoscan 203 instrument (Foss Electric) and crude fibre concentration was (Foss Electric, Hillerød, Denmark) on samples from determined according to A.O.A.C. (1984).
one successive morning and evening milking. Casein
content was measured in bulk composite milk sam- 2.3. Ruminal degradability study ples prepared for each treatment from one successive
morning and evening milking during the 14th week Ruminal degradability of CP and DM of the of the experiment according to IDF (1964). Only concentrates was determined using small nylon bags, milk from cows with somatic cell counts (SCC) less 3.535 cm in size (De Boer et al., 1987). Three than 500,000 / ml (measured at the morning milking non-lactating Friesian cows fitted with ruminal can-before sampling) was used in preparing these bulk nulas and fed a basal diet of grass silage plus 2 composite samples. Somatic cell counts were mea- kg / day of a concentrate containing 500 g / kg of sured using a Fossomatic 180 analyser (Foss Elec- molassed beet pulp and 500 g / kg of corn distillers tric) standardised and operated according to IDF grains were used. The basal diet used was the
(1984). standard basal diet used in degradability
determi-Liveweights of the cows were measured during the nations at this Institute. Bags were made of nylon pre-experimental week and during the final week of material with a pore size of 40mm. All samples were the trial. Liveweight change was calculated as the ground through a 1-mm screen before the bags were difference between these measurements. Blood sam- filled. Incubation times were 0, 2, 4, 8, 12, 24, and ples were taken from the coccygeal vessels into 48 h. All samples were inserted into the rumen evacuated blood collecting tubes 4–5 h after the simultaneously. After removal from the rumen, the concentrates were fed during the last week of the bags were machine washed for 25 min in cold water, experiment. Two tubes were taken for each cow. One dried at 408C for 48 h and their dry weights were tube contained heparin and plasma was prepared recorded. Their N content was subsequently ana-from this tube by centrifugation at 28003g for 10 lyzed.
proportional CP (or DM) disappearance The fishmeal and Sopralin concentrates had similar
2ct contents of UDP and both were substantially higher
5a1b(12e )
that the beet pulp concentrate. Ash content was highest in the fishmeal concentrate while the beet where a is the soluble fraction, b is the potentially
pulp concentrate had the highest crude fibre con-degradable fraction not including a, and c is the
centration. The three concentrates had low concen-fractional rate of degradation per hour of the b
trations of ether extract. fraction with time t (Ørskov and McDonald, 1979).
Effective degradability ( p) at a given fractional
3.2. Milk production rumen outflow rate per hour (r) was calculated from
the equation (Ørskov and McDonald, 1979):
According to the orthogonal contrast, feeding the
p5a1(b3c) /(c1r). high UDP supplements, fishmeal and Sopralin,
re-sulted in significantly higher milk, protein and 2.4. Statistical analysis lactose yields and lactose concentration than the beet
pulp supplement (Table 3). The increases were Data from the milk production experiment were higher for the Sopralin-fed cows than for the fis-analyzed as a randomized block design using the hmeal-fed cows. The orthogonal contrast found no GLM procedure of SAS (Statistical Analysis Ser- differences in fat yield or concentration or in the vices Institute, Cary, NC). The model used was concentration of protein in milk. Fishmeal-fed cows had a significantly higher milk protein concentration
Yij5bi1tj1eij
than cows fed Sopralin but there were no other where Yij is the observed yield for treatment j in significant differences between these two concen-block i, b is the mean yield for concen-block i, t is thei j trates in milk production. The casein contents of the treatment effect on yield for treatment j, and eij composite milk samples were 749, 755 and 742 g / kg represents the random unit variation within a block. of protein for the beet pulp, fishmeal and Sopralin Days in milk was used as a covariate in analysis of treatments, respectively.
all milk production data, and lactation number and
pre-experimental data recorded in the 3 weeks before 3.3. Liveweight gains and blood metabolites the experiment were used as covariates where
appro-priate. In addition, an orthogonal contrast was made There were no differences between the treatments between the beet pulp treatment and the two high in initial or final liveweights (Table 4). All
treat-UDP supplements. ments gained liveweight over the course of the
Ruminal CP and DM degradability constants (i.e. experiment but again, there were no significant
a, b, and c) of the concentrates were calculated using differences between them in the daily rate of the NLIN procedure of SAS with the constraint that liveweight gain. Blood metabolite data are shown in
a1b,1. Table 5. Urea concentrations were significantly
lower on the beet pulp treatment than both of the other treatments, which did not differ significantly.
3. Results Feeding supplements containing high levels of UDP
caused higher blood albumin concentrations and 3.1. Chemical composition and degradability of tended (P50.054) to cause higher total protein
the feeds concentrations than the beet pulp treatment. There
Table 2
Chemical analysis, degradability constants and undegradable protein contents of the experimental concentrates
Beet pulp Fishmeal Sopralin
Metabolisable energy. Predicted from values for ingredients taken from MAFF (1992) and MAFF (1986).
b
a is the soluble fraction; b is the potentially degradable fraction not including a; c is the fractional rate of degradation per hour of the b fraction with time t.
Milk production of cows fed the three experimental concentrates
c d
Beet pulp Fishmeal Sopralin F-test S.E.D. Contrast
a ab b
Milk yield, kg / day 17.3 18.0 18.6 0.051 0.460 0.031
Fat yield, kg / day 0.666 0.671 0.704 0.174 0.0209 0.257
a ab b
Protein yield, kg / day 0.582 0.611 0.622 0.047 0.0154 0.018
a ab b
Lactose yield, kg / day 0.777 0.81 0.844 0.024 0.0226 0.018
Concentration
Fat, g / kg 38.3 37.5 37.7 0.486 0.687 0.258
ab b a
Protein, g / kg 33.9 34.3 33.7 0.116 0.262 0.641
a ab b
Lactose, g / kg 44.5 44.9 45.3 0.050 0.302 0.025
ab
Means within a row without the same letter differ significantly (P,0.05).
c
S.E.D., standard error of the difference.
d
Beet pulp treatment compared to the other two treatments.
Table 4
Initial and final liveweights and liveweight gain of cows fed the three experimental concentrates
a b
Beet pulp Fishmeal Sopralin F-test S.E.D. Contrast
Initial liveweight, kg 527 516 511 0.585 14.6 0.333
Final liveweight, kg 544 542 541 0.979 12.9 0.868
Liveweight gain, kg / day 0.15 0.22 0.25 0.473 0.079 0.244
a
S.E.D., standard error of the difference.
b
Beet pulp treatment compared to the other two treatments. Table 5
Blood metabolite concentrations of cows fed the three experimental concentrates
c d
Beet pulp Fishmeal Sopralin F-test S.E.D. Contrast
Total protein, g / l 65.0 67.2 66.1 0.092 0.933 0.054
a ab b
Albumin, g / l 28.7 29.2 29.8 0.033 0.419 0.037
Globulin, g / l 36.3 38.0 36.3 0.227 1.098 0.393
a b b
Urea, mmol / l 3.65 4.42 4.59 0.003 0.275 0.001
Ammonia,mmol / l 120 112 105 0.137 7.35 0.081
b-hydroxy butyrate, mmol / l 0.54 0.55 0.55 0.848 0.025 0.570
a a b
Non esterified fatty acids, meq / l 0.167 0.172 0.20 0.0001 0.008 0.006
a b ab
D-lactate, mmol / l 0.90 1.08 1.00 0.026 0.061 0.013
L-lactate, mmol / l 3.10 2.76 2.67 0.233 0.252 0.097
SGPT, U / l 31.2 31.3 31.8 0.915 1.401 0.791
SGOT, U / l 78.2 78.4 81.3 0.689 4.028 0.640
ab a b
Calcium, mmol / l 2.35 2.37 2.32 0.016 0.017 0.622
Magnesium, mmol / l 1.11 1.12 1.14 0.698 0.041 0.474
a b a
Phosphorus, mmol / l 2.15 2.33 2.05 0.0002 0.061 0.505
ab
Means within a row without the same letter differ significantly (P,0.05).
c
S.E.D., standard error of the difference.
d
Beet pulp treatment compared to the other two treatments.
reached statistical significance. Phosphorus concen- hmeal sample is unknown. However O’Mara et al. trations were significantly higher in cows fed fishme- (1997a) examined two fishmeal samples from the al than both of the other treatments. same source as the sample used in this study and found amino acid disappearance to be 0.981 and 0.972 after 12 h of ruminal incubation followed by
4. Discussion transit through the intestines.
4.1. Ruminal degradability 4.2. Effect of supplement type on milk production
to the response to concentrates per se for grazing Overall, supplement type had no effect on milk fat cows (e.g. Journet and Demarquilly (1979) reported concentration or yield. This is in contrast to the responses to concentrates ranging from 0 to 0.67 kg results of Stakelum (1993) who reported that Sop-milk / kg concentrate DM over six experiments), and ralin-fed cows had significantly lower milk fat they were obtained in cows at moderate yield levels concentrations than either barley- or soyabean-meal-in mid to late-lactation. Grass supply was considered fed cows. There was a significant difference between adequate throughout the experiment although grass the UDP supplements in milk protein concentration growth measured at this Institute during the period of with fishmeal-fed cows having the highest concen-this trial was 15% lower than the average growth tration. However, the biological significance of a from 1982 to 1996. Cumulative grass growth during difference of 0.6 g / kg is small and there was no the trial was 5971 kg DM / ha compared to 7070 kg difference in milk protein yield because of the DM / ha for the average of 1982 to 1996. However, numerically higher milk yield of the Sopralin-fed milk yields averaged 20.3 kg / day in the first 2 weeks cows. Previous studies have also found that sopralin of the experiment and 13.95 kg / day in the final 2 reduces milk protein concentration but not yield weeks which corresponds to an incremental rate of (Stakelum, 1993). Both supplements supplied similar decline of 0.0265 / week. This and the increase in amounts of UDP in this experiment but the amino liveweight of the cows support our opinion that grass acid profile would differ, with the fishmeal supple-supply was adequate for the level of milk production ment supplying greater amounts of lysine and
being achieved. methionine (O’Mara et al., 1997a). Lysine and
As noted previously, responses to UDP supple- methionine have often been reported as the first two ments at pasture have been reported (Stobbs et al., amino acids limiting protein synthesis (Casper and 1977; Rogers et al., 1980; Minson, 1981) but those Schingoethe, 1989; Fraser et al., 1991; Munneke et experiments did not investigate if an equivalent al., 1991). Thus, a possible explanation for the amount of an energy supplement could support the higher protein concentration on the fishmeal diet same level of milk production. Stakelum (1993) could be a better profile of amino acids in the UDP compared the milk production of cows fed 3.0–3.2 fraction. However, Younge et al. (1996) obtained no kg of supplement based either on barley, soyabean significant effect on milk protein yield and con-meal or Sopralin in a two-period experiment, broken centration when they supplemented grazing dairy by a period of drought. In the first period, milk yield cows with rumen protected lysine and methionine. of cows fed soyabean meal or Sopralin was 0.5 An increase in lactose synthesis on Sopralin diets, kg / day higher than cows fed the barley supplement causing a dilution of milk protein is another explana-but the difference was not statistically significant. In tion for the result obtained in this experiment. the second period, there was little difference in the However, it is unclear why feeding sopralin would milk yield of the barley- and soyabean-meal-fed stimulate lactose synthesis. Lactose yield and con-cows but the Sopralin-fed con-cows produced 1.25 kg / centration were highest on the Sopralin treatment but day more milk than the barley-fed cows and 1.04 the differences compared to the fishmeal treatment kg / day more milk than the soyabean-meal-fed cows. were not statistically significant.
Only the former difference was statistically
signifi-cant. The increase due to the Sopralin in the second 4.3. Effect of supplement type on blood metabolite period was similar to that obtained from the high concentrations
UDP supplements in this experiment but almost 2
energy needs of the animal, NEFA are released into 1992), the three supplements would have had similar the blood plasma. It has been suggested (Ørskov et magnesium concentrations due to the inclusion of 40 al., 1987) that undegraded protein can stimulate the g / kg of magnesium oxide in each. This was reflected use of body fat reserves for milk production. NEFA in the similar blood magnesium concentrations of the levels were low on all treatments in comparison to three groups of cows. Both phosphorus and mag-mean values for dairy cows of 0.226 mmol / l re- nesium concentrations in all three groups were well ported by Topps and Thompson (1984). Levels are above the standard values (1.8 and 0.74 mmol / l, highest in early lactation and decline as fat mobiliza- respectively) of Ward et al. (1995).
tion decreases. The low levels measured in this experiment are consistent with the increase in liveweight of the cows during the experiment.
Beta-5. Conclusions
hydroxy butyrate is another indicator of energy status and levels on all treatments in this experiment were
The results of this experiment demonstrate that well within the normal range (0.48 mmol / l, S.D.
moderate yielding cows in mid to late-lactation 0.20) quoted by Topps and Thompson (1984).
produce more milk and protein when fed supple-The high UDP supplements increased the amount
ments high in UDP than when fed an equivalent of circulating albumin and the increase in total
amount of DM of an energy supplement. The blood protein almost reached statistical significance (P5
results confirm that the protein status of the cows 0.054). This is most likely due to greater amino acid
was improved by the UDP supplements, and this is availability for protein synthesis in the liver. Hewett
likely the mechanism for the increased milk and (1974) demonstrated a positive correlation between
protein yields. estimated digestible protein intake and serum
al-bumin concentration in 14 dairy herds. Urea con-centrations were also higher for cows fed the high
Acknowledgements
UDP supplements. Blood urea levels have often been related to degradable protein intake (Cody et al.,
The authors express their thanks to Irish dairy 1990) and the fishmeal and Sopralin supplements
farmers who partially funded this study through the supplied more RDP than the beet pulp supplement
Irish Dairy Levy. They also thank J. Hyland, J. (Table 2). It has also been reported that 3 kg / day of
Dwyer, J.J. Cahill, and N. Byrne for technical molassed beet pulp reduced the rumen ammonia
assistance. concentrations of cows zero-grazing perennial
rye-grass from 4.2 to 3.3 mmol / l (O’Mara et al., 1997b). However, urea in blood can also arise from the
deamination of excess amino acids in the liver. This, References and the higher intake of degradable protein are
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