THE EFFECTS OF MILLING AND THE ADDITION OF CONCENTRATES OR MOLASSES ON THE CONSUMPTION OF POOR QUALITY HAY BY MILKING COWS

350
Trop Anim Prod 1981 6:4
THE EFFECTS OF MILLING AND THE ADDITION OF CONCENTRATES OR
MOLASSES ON THE CONSUMPTION OF POOR QUALITY HAY BY MILKING COWS
M Castejon and J Combellas
Instituto de Produccion Animal, Facultad de Agronomia, Universidad
Central de Venezuela, Maracay, Venezuela
Three trials were carried out with the purpose of studying some factors which might affect the
consumption of low quality hay by dairy cows receiving concentrate supplements. The first two trials were
each carried out with 6 Holstein cows using a 3 x 3 Latin Square design with 3 levels of supplementation:
5, 7 and 9 kg/d of concentrate with 16.7% protein in the first trial and 32.7% in the second. The dry
matter (DM) consumption of the hay was less than 3 kg/d in both trials and decreased between 0.05 and
0.21 kg for each kg of DM of concentrate consumed. The supplementation increased milk production in
both experiments. The third trial was to determine the effect of the physical form of the hay (whole vs
milled) and the addition of molasses (0 vs 200 g/d) on the hay intake of cows receiving 5 kg/d of
concentrate. Eight Brown Swiss cows were used in 2 x 2 factorial design within a 4 x 4 Latin Square. Hay
intake and milk production were not affected by any of the treatments.
Key words: dairy cows, poor quality hay consumption, effect of milling, concentrates, molasses
The use of hays in animal feeds is one of the alternatives used during the the dry
season in tropical areas where the precipitation is seasonal. The hays produced and
sold under these conditions are, in general, of low quality as the ambiental limitations
during the rainy season mean that hay must be made at the beginning of the dry
season from pastures with long periods of growth.
Little is known of the nutritional value of these hays and the quality and quantity of
concentrates necessary to balance the nutrient deficiencies in these fibrous materials
when fed to milking cows. In temperate countries, cereal straws of a quality similar to
these hays (protein content less than 5% and digestibility between 35 and 50%) have
received special attention as cattle feeds. Physical and chemical methods of treatment
have also been used to improve consumption (Smith and Broster 1977; Owen 1979).
Three experiments were carried out with the objective of discovering the effect of
the level of supplementation with concentrates of different protein content, the milling
of the hay and the addition of small quantities of molasses on consumption and
productivity of dairy cows fed a basal diet of low quality Bermuda hay.
Materials and Methods
Experiments 1 and 2:
These experiments were carried out with the purpose of studying the effect of the
level of concentrate supplementation on the consumption of low quality Bermuda
grass hay and milk production. In Experiment 1 a concentrate with 16.7% crude
protein (dry weight basis; CP=N x 6.25)was fed and in Experiment 2 the concentrate
contained 32.7% CP. In each experiment six Holstein cows of 2 or more lactations
were used, At the outset of the experiment these cows had 58 ± 9 and 47 ± 10 days in
milk, were producing 15.6 ± 2.3 and 16.3 ± 1.9 kg milk/d and had liveweights of 432 ±
62 and 416 ± 31 kg in Experiments 1 and 2 respectively. The experimental design in

---

Trop Anim Prod 1981 6:4
351
the two trials was a 3 x 3 Latin Square with periods of 6 weeks, The measurements
taken in the last four weeks were used in the statistical analysis,The supplementation
levels were 5, 7 and 9 kg of concentrate daily, feeding 1.5 kg at each milking and the
rest at 0900h. In both trials Bermuda grass hay (Cynodon dactylon Pers) was fed ad
libitum, at 1100h, The composition of the hays and concentrates used are shown in
Table 1.
DM, CP and ash content were determined according to A.O.A.C (1965)
procedures and the cell wall content determined according to the method described by
Van Soest (1967). The digestibility of the hay and concentrate in Experiment 1 was
determined in an in vivo digestibility trial using 8 sheep. All were fed hay ad libitum
and four also received 0.5 kg/d concentrate. The digestibility of the organic matter of
the concentrate, estimated by the differential method (Fredriksen 1973) was 70% and
that of the hay was 43.4%. Milk production was determined daily and samples of milk
were taken once a week to determine protein content (Udy 1965). Solids not fat was
determined by density and fat by the Milko-tester. The animals were weighed twice a
week and liveweight change was estimated by regression.
Experiment 3:
This experiment was carried out with the objective of determining the effect of
milling the hay and the addition of small quantities of molasses on hay consumption
by dairy cows of average milk production receiving concentrates. Eight Brown Swiss
cows of two or more lactations were used. At the outset of the trial these had 86 ± 37
days in lactation, a milk production of 10.1 ± 1.2 kg/d and a liveweight of 460 ± 23 kg.
The experimental design was a 2 x 2 factorial design within a 4 x 4 Latin Square with
periods of 3 weeks. The results of the last week were used for this analysis. One
variable was the physical form of the hay, it being supplied both whole and milled
using a hammer mill with a screen with holes of 1 cm diameter. The other factor was

---

352
Trop Anim Prod 1981 6:4
the addition or non addition of 200 g/d of molasses sprinkled over the hay. All the
animals received a fixed level of 5 kg/d of concentrate fed in equal parts during the
two milkings. The same hay and concentrates were fed as in Experiment 1.
Results
The consumption and production of the cows in Experiment 1 and 2 are presented
in Table 2. The milk production figures obtained in both trials were similar, however,
the response to supplementation on the concentrate levels used was lower with the
concentrate of 32,4% CP. The production obtained at the lower level of concentrate
(10.2 kg/d) being similar to the maximum production obtained (11.8 kg/d) . In the two
trials the lower level of supplementation caused slight weight losses, in comparison
with gains of almost 0,5 kg/d on the high concentrate levels.
The fat content of the milk dropped with supplementation. This decrease, in spite
of being appreciable, was not statistically significant, probably because of the low
number of animals used in each test. Hay consumption dropped slightly with
supplementation in the two experiments. This effect was only significant in Experiment
1 (P< 0.10). Hay consumption dropped between 0,05 and 0.21 kg DM/kg DM
concentrate fed.
The hay consumptions obtained in Experiment 3 (Table 32 were higher than those
observed in the other two trials. However, no improvement was noted in consumption
due to the effect of milling or the addition of the 200 g of molasses. The milk
production measured in the last week of each period was also not affected by these
treatments,
Discussion
The results of the three trials show very varied consumptions of the low quality
hay fed to the cows receiving concentrates. The higher consumptions obtained in

---

Trop Anim Prod 1981 6:4
353
Experiment 3 cannot be explained with the information available. The digestibility of
the hay used in this trial was not determined and it could have been superior to that
used in the other two experiments. The increase in the level of concentrate from 5 to 9
kg/d caused a slight drop in the consumption of hay (Table 2), comparable to that
obtained with similar quality straws in temperate countries (sampling and Murdoch
1966; Andrews et al 1972; Horton and Holmes 1976). The increases in the
consumption of low quality forages when feeding concentrates initially reported by
Blaxter and Wilson (1963) in sheep, were observed in cows by Campling and Murdoch
(1966) only when the supplementation level was 4 kg/d or lees. At the level of
concentrates used in these trials the drop in hay consumption could be due to a drop
in the cellulitic activity of the microorganisms of the rumen and to a drop in the flow of
digesta from the rumen, as these authors pointed out.
The evaluation of the effect of the protein content of the ration on hay
consumption in Experiment 1 and 2 is not statistically valid as different animals and
different hays were used. However, it was observed that the consumption of fibrous
material remained equally low in the second trial (Table 2), in spite of the protein
content of the concentrate being almost double that used in Experiment 1. The
inclusion of a high percentage of cottonseed cake in the concentrate in Experiment 2,
a primary material of low degradability (A.R.C. 1980), could also have decreased the
negative effect of the concentrate on the cellulosis in the rumen and on the
consumption of hay. The absence of response to the higher percentage of protein and
to the use of a primary material of low solubility in this test, is probably due to the high
ratio of concentrate to forage in the diet . The change in the composition of the
concentrate in Experiment 2 and the rise in the protein percentage does not appear to
have had an effect on milk production in comparison with the results obtained with the
low protein concentrate in Experiment 1, The protein contents obtained in the total
diets in this latter trial remained over 12% due to the low consumption of hay observed
and are theoretically sufficient for an efficient utilization of energy in the rumen (A,R.C.
1980). Milk production was limited fundamentally by the energy consumption in both
trials, At the high levels of supplementation in Experiment 2, the low response
obtained could be due to the excess of protein consumed and the energetic value
required for its elimination (Oldham and Alderman 1981). The tendency for milk fat to
decrease with the level of concentrate supplementation is probably a consequence of
the decrease in the fibre content of the total ration, when the proportion of hay in this
diet was decreased appreciably (Broster et al 1979).
The milling of the hay in Experiment 3 had no effect on consumption. The effect of
this physical treatment on consumption of straws and hays in ruminants is known
(Owen 1979), however the little published evidence shows that the processing of
forages has a small effect on consumption when the forage is fed in high concentrate
diets (sampling and Milne 1972; Greenhalgh and Wainman 1972)

---

354
Trop Anim Prod 1981 6:4
The quantity of molasses offered was about 4% of the hay consumed and also
did not have an effect on the consumption, Preston (1972) pointed out that small
quantities of molasses added to dried, milled hay improved voluntary consumption.
This was not observed in this trial and could be due to the fact that this effect does not
occur when the animal also received an appreciable quantity of concentrates. The
results obtained in these trials show that the nutritive value of low quality hay for dairy
cows is very low when they are fed separately from the concentrates because of their
low nutritive value and low consumption. To satisfy the requirements of these animals
it is necessary to increase appreciably the concentrate level in the ration , with the
consequent negative effect on the fat content of the milk even in cows of average
production. The feeding of milled hay mixed with the concentrate in complete diets
could improve its consumption as has been demonstrated with hays in temperate
countries (Owen et al 1968; Greenhalgh and Wainman 1972), but this implies higher
capital investment in tropical countries where these resources are available,
References
Andrews R P, Escuder-Volonte J, Curran M K & Holmes W 1972 The influence of supplements of energy
and protein on the intake and performance of cattle fed on cereal straws Animal Production
15:167-176
A.O.A.C. 1965 Official methods of analysis Association of Official Agricultural Chemists Washington D C
A.R.C. 1980 The nutrient requirements of ruminant livestock Agricultural Research Council
Commonwealth Agricultural Bureaux London
Blaxter K L & Wilson R S 1963 The assessment of a crop husbandry technique in terms of animal
production Animal Production 5:27-42
Broster W H, Sutton J D & Bines J A 1979 Concentrate forage ratios for high yielding dairy cows In:
Recent Advances in Animal Nutrition 1978 Eds. W Haresing and D Lewis Butterworths London
99-126
Campling R C & Milne J A 1972 The nutritive value of processed roughages for milk cattle Proceedings of
the British Society of Animal Production 1972 53-60
Campling R C & Murdoch J C 1966 The effects of concentrates on the voluntary intake of roughages by
cows Journal of Dairy Research 33:1-11
Fredrikson J H 1973 Method studies relating to digestibility trills with ruminants Acta Agricola
Scandinavica 23:17-33
Greehalgh J F D & Wainman F W 1972 The nutritive value of processed roughages for fattening cattle
and sheep Proceedings of the British Society of Animal Production 1972 61-72
Horton G M J & Holmes W 1976 A note on the influence of a supplement of barley and dried lucerne on
the intake of barley by cattle Animal Production 22:419-421
Oldham J D & Alderman G 1981 Recent Advances in understanding protein-energy interrelationships in
intermediary metabolism of ruminants Symposium on observations on the practical we of new
sources of protein in relation to energy supply for high production of meat and milk Geneva
Switzerland
Owen E 1979 Processing of roughages In: Recent advances in Animal Nutrition 1978 Ed. W Harsing & D
Lewis Butterworths London pp 127-148
Owen J B, Miller E L & Bridge P S 1968 A study on the voluntary intake of food and water and the
lactation performance of cows given diets of varying roughage content ad libitum Journal of
Agricultural Science 70:223-235
Preston T R 1972 Molasses as an energy source for cattle World Review of Nutrition and Dietetics
17:250
Smith T & Broster W H 1977 The usee of poor quality fibrous sources of energy by young cattle World
Review of Animal Production 13:49-58
Udy D 1965 A rapid method for estimating total protein in milk Nature 178:314
Van Soest P J 1967 Use of detergents in the analysis of fibrous feeds IV Determination of plant cell wall
constituents Journal of the Association of Official Agricultural Chemists 50:50 .
Received 6 October 1981
Translated from the Spanish

---