Maize Silage for Milk Production

Main Findings

• Inclusion of maize silage in the forage with grass silage invariably increased forage intake but the benefit in milk production depended on the maturity (starch content) and digestibility (greenness) of the crop when harvested.
• Partially replacing a high quality grass silage with good quality maize silage (200-250 g starch/kg DM) increased forage intake, milk yield and milk protein concentration without affecting the efficiency of milk production.
• Inclusion of 33% maize silage in the forage achieved most of the increase in milk yield but a high inclusion level (67%) was required to maximise the yield of fat and protein and milk protein concentration. In practise a 50:50 mixture of maize silage and grass silage is near optimum for milk production. A mixed forage was better than all maize silage for milk production.
• Immature maize silage containing very little starch (<50 g/kg DM), when harvested in a green state with a good digestibility, was equivalent to a high quality grass silage for milk production when representing 60% of the forage. However, forage intake was increased and feed efficiency for milk production was reduced on the mixed forage compared with the grass silage based diet.
• There was no advantage in delaying harvesting of an immature maize crop from mid-October to mid-November in terms of yield, crop maturity or milk production. Later harvesting increases the risk of crop damage due to inclement weather and associated difficult harvesting conditions. If the crop is killed by a severe frost in October, it should be harvested as soon as possible.
• Delayed harvesting of immature maize crops for 3 weeks after a frost kill in October, due to a prolonged period of inclement weather, reduced the digestibility of the maize silage. When those silage were fed to partially replace a moderate quality grass silage forage intake was increased but milk yield was reduced, even though one of the maize silage contained a moderate level of starch (146 g/kg DM). However, milk composition was improved on the mixed forage diets resulting in a similar yield of fat and protein to the grass silage based diet, but the efficiency of milk production was reduced.
• The optimum level of starch in maize silage for cows in early lactation has not been firmly established. Increasing the level of starch in maize silage from a very low to a very high level (350 g/kg DM) in one experiment considerably increased forage intake and increased milk yield, fat and protein yield and milk protein concentration, but feed efficiency for milk production was reduced. However, in another experiment there was no advantage in milk production to increasing the starch level from 240 to 290 g/kg DM with cow s in mid lactation. The stage of lactation and the hardness of the grain in the mature maize silage may have affected the response. However, there was no indication that the digestibility of the diet was reduced for the high starch maize based diet. It would appear that a starch level of about 250 g/kg DM in maize silage is near optimum for milk production.
• Good quality mature maize silage produced in suitable locations, in good growing seasons for maize, can play an important part in the diet of dairy cows, particularly on farms involved in winter milk production. It can also be fed as part of the forage for spring calving cows prior to fulltime turnout or in late lactation when housed or to other stock on the dairy farm i.e replacement heifers, finishing beef cattle or weanlings. In poor growing seasons, immature maize silage harvested in a green state should be equivalent to a good grass silage for milk production.
• Continuing improvements in the breeding of maize hybrid varieties more suited to marginal areas and developments in the use of a photo degradable polythene covering to enhance early growth of maize will lead to more consistency in the yield and quality of the crop, an expansion in the acreage of maize grown and extension into areas hitherto considered less suitable for the crop, particularly in areas where liquid milk or winter milk production is established

Good quality maize silage fed with grass silage increased forage intake, milk yield and milk protein concentration.

The effect of replacing grass silage with a good quality maize silage on milk production.

The objective of this study was to examine the effect of replacing varying proportions of a good quality grass silage with a good quality maize silage on feed intake, milk production and milk composition of dairy cows in early lactation and to establish the optimum level of maize silage in the forage.

Materials and methods

Forage maize from a crop with well developed cobs (540 g/kg crop DM) was harvested in late October and ensiled without any additive e. Grass silage was made from a primary growth of perennial ryegrass in late May, and treated with a sulphuric acid additive. The maize silage was fed to replace 0, 33, 67 or 100% of the grass silage on a DM basis as the forage component of the diet of dairy cows. The grass and maize silage in the mixed forages (33% and 67% maize silage) were mixed in a feeder wagon prior to feeding. Fifty six cows in early lactation were allocated to the four treatments. Each forage was supplemented with concentrates based on barley, unmolassed beet pulp and soybean meal at 6 kg/cow/day. The level of crude protein in the concentrate increased from 160 to 300 g CP/kg fresh weight as the proportion of maize silage in the forage increased to provide a similar overall level of crude protein in the total diet (170 g CP/kg DM). The in vivo DM digestibility of the grass silage and maize silage were determined with non-lactating cows while the in vivo DM digestibility of the total experimental diets were determined with lactating cows from the experiment (4 cows/diet).

Results

The grass silage was highly digestible and was well preserved (Table 1). The maize silage was considered to be of good quality in terms of DM and starch content, digestibility and preservation. The DM digestibility of the maize silage was less than that of the grass silage and it was less extensively fermented.

Table 1 : Chemical composition and dry matter digestibility of the grass and maize silage in Experiment 1 (g/kg DM unless stated)

DMD: Dry Matter Digestibility

Forage intake increased linearly as the proportion of maize silage in the forage increased (Table 2). Milk yield increased on the mixed forage diets and reached a maximum on the 67% maize silage diet. However, most of the increase in milk yield was achieved on the forage containing 33% maize silage. Inclusion of maize silage in the forage had no effect on fat concentration or yield but did improve the yield and concentration of protein. The highest yield of fat and protein was achieved on the mixed forage containing 67% maize silage. Cows also gained most weight on the forages containing a high proportion of forage. The DM digestibility of the total diet declined as the proportion of maize silage in the diet increased.

Table 2 : Effect of maize silage in the forage on feed intake and cow performance in Experiment 1

* sem : Standard error of the mean

Feed efficiency, expressed as kg milk or kg fat and protein per kg total DM intake was reduced by 3 to 7% on the diets containing a high proportion of maize silage (67 or 100%) compared with grass silage

However, feed efficiency expressed on the basis of digestible DM intake was similar or slightly increased (1-3%) on the diets containing maize silage compared with grass silage.

Conclusions

The results of this experiment showed that good quality maize silage (>200 g starch/kg DM) has the potential to increase forage intake, improve milk production and milk protein concentration when fed to partially replace a high quality grass silage. A low proportion (33%) of maize silage in the forage achieved most of the increase in milk yield but a high proportion (67%) was needed to achieved the highest yield of fat and protein and maximise milk protein concentration.

The mixed forage diets were better for milk production than all maize silage. In practice, a 50 : 50 mixture of good quality grass silage and maize silage would achieve most of the benefit in terms of milk production.

The effect of replacing grass silage with low or moderate quality maize silage on milk production

The objective of this experiment was to examine the effect of partially replacing a moderate quality grass silage with maize silage of low or moderate quality in terms of starch content and digestibility on feed intake, milk production and milk composition of dairy cows.

Materials and methods

Two sources of maize silage were used in this study. One silage was made from immature maize with poorly developed cobs and contained very little starch (LSM) due to late sowing (16th May) and a poor growing season. The second source was made from a more mature maize with better developed cobs and contained a moderate level of starch (MSM) due to an earlier sowing date (30th April).

Both crops were affected by a severe frost in mid October and ceased growth. However, due to a prolonged period of inclement weather, the crops could not be harvested until 3-4 weeks later in November. As a result, the digestibility of the silage were much reduced. Both silage were made without an additive. The grass silage was made from a re growth of perennial ryegrass and was treated with a sulphuric acid additive.

Five forage treatments were compared in which the grass silage was fed as the sole forage or was replaced by 33% or 67% of each of the maize silage on a DM basis. Sixty cows, 45 in early lactation and 15 in mid-lactation, were allocated to the treatments for a period of 8 weeks. The cows were fed a common concentrate supplement containing 250 g crude protein/kg fresh weight at 6 kg/cow/day. The invivo DM digestibility's of the grass and maize silage as the sole feeds were determined with non-lactating cows and the invivo DM digestibility's of the total diets were determined with lactating cows from the experiment.

Results

The grass silage was of moderate digestibility and was reasonably well preserved (Table 3). The maize silage differed in DM content and starch content but were similar in digestibility. They were well preserved and were less fermented than the grass silage. The digestibility of the maize silage were low and much less than the grass silage due to the long delay in harvesting the crops after the frost kill.

Table 3 : Chemical composition and digestibility of the grass and maize silage in Experiment 2 (g/kg DM unless stated)

DMD = Dry matter digestibility
DOMD = Digestible organic matter in the dry matter

Despite the low digestibility of the maize silage, their inclusion in the forage increased forage intake, particularly for the MSM silage (Table 4). However, milk yield declined as the proportion of maize silage in the forage increased, particularly with the LSM silage. The concentrations of milk fat and protein increased on the mixed forage diets, consequently the yields of fat and protein were similar on the mixed forage diets to that obtained on the grass silage diet. Cows gained weight to a similar extent on all treatments. The DM digestibility of the total diet was similar for both types of maize silage and declined as the proportion of maize silage in the diet increased.

The efficiency with which feed was converted into milk was reduced on the mixed forage diets, by 7-16% on the basis of total DM intake and by 4-1 1% based on digestible DM intake, compared with the grass silage diet. However, feed efficiency was reduced to a lesser extent (3-4%) on the mixed forage diets when expressed on the basis of milk solids production (kg fat + protein/kg digestible DM intake)

Table 4 : Effect of maize silage in the forage on feed intake and cow performance in Experiment 2

sem: Standard error of the mean
GS = Grass silage, LSM = Low starch maize milage, MSM = Medium starch maize silage

Conclusion

The results of this experiment highlight the adverse effect that late harvesting of maize after a frost kill had on the digestibility of the ensiled material and consequently on its feeding value for milk production compared with a moderate quality grass silage, even though one of the maize silage was reasonably mature and contained a moderate level of starch. Despite the low digestibility of the maize silage, intakes of the mixed forages were increased and intakes of digestible DM were similar to that of the grass silage based diet.

While the yield of milk was reduced on the mixed forage diets, the yield of fat and protein was similar to the grass silage diet. Consequently, maize silage with a low or moderate level of starch but with a reduced digestibility was equivalent for milk solids production to a moderate quality grass silage, but the efficiency of the mixed forage diets for milk production was reduced, particularly with the high inclusion level of maize silage (67%).

Effect of low or high starch maize silage compared with grass silage on milk production

In Experiment 2 the adverse effect that delayed harvesting had on the digestibility and feeding value of maize silage for milk production was established. In this experiment, the effect of harvesting an immature maize crop in a "green" state shortly after a frost kill on its feeding value for milk production was examined when the digestibility of the crop remained high compared with a high quality grass silage. The effect of increasing the starch content of the maize silage on intake and milk production was also examined.

Materials and methods

A crop of maize (cv Diabolo) sown on May 7th was harvested in late October and ensiled in a green state within a week following a frost kill. The crop was very immature, with a low DM content and poorly developed cobs. The grass silage was made from a primary cut of perennial ryegrass harvested in late May and was treated with a sulphuric acid additive. To obtain information on the effect on milk production of increasing the level of starch in the maize silage to that in a very mature maize crop grown in a good season, ground maize grain was incorporated into the low starch maize silage in one treatment to produce a high starch maize silage (>300 g starch/kg DM). Three types of forage were compared :

GS- all grass silage

LSM- low starch maize silage and grass silage (60:40 DM basis)

HSM- high starch maize silage and grass silage (60:40 DM basis)

Maize grain represented 40% of the DM of the HSM silage or 24% of the DM of the mixed HSM forage. Concentrates containing 250 g crude protein/kg fresh weight were fed at three levels (4, 6 and 8 kg/cow) with the GS and LSM forages and at one level (4 kg/cow) with the HSM forage. The maize silage and grass silage were mixed in a feeder wagon prior to feeding. Fifty six cows, consisting of 28 cows in early lactation and 28 cows in mid lactation, were allocated to the treatments (8 cows/treatment) for a period of 7 weeks. The in vivo digestibility of the total diets were determined with lactating cows from the experiment (4 cows/diet).

Results

The grass silage was highly digestible and was well preserved (Table 5). Harvesting the maize crop in a green state produced a silage with a good digestibility but with a low DM content and with very little starch but it was well preserved. Including ground maize grain with the LSM silage to produce the HSM silage increased the DM, starch content and digestibility of the silage.

Table 5 : Chemical composition and digestibility of the grass and maize silage in Experiment 3 (g/kg DM unless stated)

When averaged across the three levels of concentrate supplementation, intake of the LSM forage was 18% higher than that of the GS silage (Table 6). However, milk production was similar for both types of forage. Milk fat concentration and yield were similar for both types of forage. Milk protein concentration was higher for the LSM forage, resulting in a marginal increase in protein yield compared with the GS silage. Cows gained weight to a similar extent on both types of forage. The DM digestibility of the total diet was less for the LSM diet compared with the GS diet.

Compared with the GS and LSM forages supplemented with the low level of concentrates (4 kg/day), increasing the level of starch in the HSM forage considerably increased forage intake and increased the yields of milk, fat and protein. The HSM forage slightly reduced milk fat concentration but increased milk protein concentration. Cows tended to gain more weight on the HSM forage. The digestibility of the total diet was increased for the HSM treatment compared with the LSM forage and was similar to the GS diet. Feed efficiency for milk production was less for the LSM forage compared with the GS forage, by 8-1 0% on the basis of total DM intake and by 6-8% in term s of digestible DM intake. The increase in intake for the HSM diet was not matched by a corresponding increase in milk production, consequently feed efficiency for milk production was reduced by 1 0% compared with the GS diet. Nevertheless, the value of the additional milk more than compensated for the higher intake of forage on the HSM diet.

Table 6 : Effect of the starch level in maize silage on forage intake and on milk production in Experiment 3.

sem = Standard Error of the Mean, GS = grass silage,
LSM = Low starch maize silage + grass silage (60:40 DM mix),
HSM = High starch maize silage + grass silage (60:40 DM mix)

Conclusions

The results of this study show that in a poor season for growing maize, immature maize silage containing very little starch is equivalent for milk production to a high quality grass silage when harvested in a green state soon after a frost kill. However, intake of the maize based forage was higher, consequently feed efficiency for milk production was reduced by about 10% compared with the grass silage based diet. Maize silage with a high starch content (30% starch) has the potential to considerably increase forage intake and milk production compared with grass silage or low starch maize silage.

Effect of date of harvesting an immature maize crop on silage quality and on milk production

Mature maize crops with well developed cobs are normally harvested in mid to late October, or earlier if the grain is well developed. However, with immature crops there is a tendency to let the crop grow on for as long as possible, e.g. into November in the hope of increasing the yield, grain and starch content of the crop. There is, however, an increased risk from delayed harvesting due to inclement weather as the season advances (as occurred in Experiment 2) with a consequent loss of nutrients and a reduction in the digestibility and feeding value of the crop. The main objective of this study was to determine the effect of harvesting an immature crop of maize either early (mid-October) or late (mid-November) on its feeding value for milk production compared with grass silage.

Materials and Methods

An immature maize crop (cv Janna) with poorly developed cobs was grown at Johnstown Castle. It was harvested and ensiled either in mid-October (ECM) or was allowed to grow on and harvested as late cut maize (LCM) in mid-November. The resulting maize silage were fed as the major part of the forage (70%) in combination with grass silage and were compared with all grass silage (GS) when fed to spring calved cows in early lactation. Each forage was supplemented with concentrates (7 kg/cow/day) containing high starch or low starch ingredients. The cows were group fed (14 cows/diet) on their respective diets for a period of 40 days from 2 week s after calving until turned out to pasture.

Results

Samples of maize harvested at weekly intervals showed no improvement in crop yield, DM content or cob development from mid October to early November. The crop was not affected by frost during this period. The DM content of the crop harvested in mid October was very low (125 g/kg) and produced a considerable amount of effluent when ensiled. The late harvested crop had a higher DM content at ensiling (166 g/kg) but otherwise was similar in composition to the early harvested crop. The silage from the two harvests were very similar in composition and digestibility (Table 7). The grass silage was of moderate digestibility but was poorly preserved. Forage intake or milk composition were not measured in this study. Milk yields were similar for the mixed forages containing the maize silage and for the grass silage. Cows gained in weight and in body condition to a similar extent on the three types of forage.

Table 7 : Effect of harvesting date of immature maize silage on silage composition and milk production compared with grass silage in Experiment 4

sem = Standard error of the mean

Conclusion

Delaying harvesting of an immature maize crop from mid-October to mid November was of no benefit in terms of crop yield, extra maturity, chemical composition or digestibility of the silage or in terms of milk production or weight gain of the cows. It is therefore recommended to harvest immature maize in October while weather conditions are good, but effluent production may be high and must be contained.

Effect of maize silage with a good or high level of starch in mixed forages on milk production

This study examined the effect of including mature maize silage containing a good or high level of starch, when grown in a good season for maize, in a mixed forage on milk production compared with a good quality grass silage.

Materials and methods

Maize crops (cv Melody and Hussar) were grown conventionally or under a photo degradable polythene film to enhance crop growth in spring. Following a good season for growing maize the crops were harvested in late September when they were deemed to be sufficiently mature with well developed cobs and the grain was either at the soft dough or hard dough stage. The polythene covering considerably increased the yield, DM content and cob content of the crop. The grass silage was harvested from a perennial ryegrass sward in late May and was treated with a formic acid based additive. Three types of forage were compared

GS- high quality grass silage

MSM- moderate starch maize silage and grass silage (60:40 DM basis)

HSM - high starch maize silage and grass silage (60:40 DM basis)

Each forage was supplemented with concentrates at two levels of feeding (4 or 8 kg/cow/day). The concentrates were based on either low starch or high starch ingredients and contained 230 g crude protein/kg fresh weight. Forty eight autumn calved cows in mid lactation were allocated to the three types of forage for a period of 10 weeks.

Results

The grass silage was of high quality and was well preserved (Table 8). The maize silage were mature, with a high DM content, a good to high level of starch, good digestibility and were well preserved.

Table 8 : Chemical composition and digestibility of the grass silage and maize silage in Experiment 5 (g/kg DM unless stated)

Compared with the GS silage intake of the MSM forage was much higher (+2.2 kg DM/day) and resulted in a higher yield of milk (+1.9 kg/d) and protein (+0.07 kg/d), (Table 9). Milk composition and weight gain of the cows was similar for both types of forage. Intake of the HSM forage was also much higher than the GS silage (+2.8 kg DM/day) and was marginally higher than the MSM forage. However, the yield of milk and milk constituents were intermediate between those obtained with the GS and MSM forages and were not significantly different from either of them. Milk protein concentration was better on the HSM forage and the cows tended to gain more weight and body condition on the HSM forage. The digestibility of the total diet was less for the diets containing maize silage compared with the GS diet.

Feed efficiency for milk production was reduced on the diets containing the maize silage compared with the grass silage based diet, by 10-12% on a total DM intake basis. However, on the basis of digestible DM intake, feed efficiency was similar for the GS and MSM based diets but was reduced by 7% on the HSM based diet.

Table 9 : Effect of forage type on feed intake and cow performance in Experiment 5

Sem = Standard error of the mean

CONCLUSION

In this study the MSM silage containing 240 g/kg DM of starch was superior to a high quality grass silage in terms of forage intake and milk production. The results are in agreement with those of previous studies (Experiments 1 and 3) that maize silage with a good level of starch has the potential to increase forage intake and milk production when partially replacing good quality grass silage in the diet of dairy cows. However, in this study there was no further advantage in milk production to including maize silage with a high starch content compared with the MSM silage and feed efficiency was reduced.

The cows in this study were in mid lactation and may not be as responsive to additional starch in the forage as cows producing more milk in early lactation. Some of the starch in the grain of the HSM silage may not have been fully digested. However, there was no difference in the DM digestibility of the total diets containing MSM or HSM silage. The results of this study indicate that maize silage containing about 250 g starch / kg DM is a good forage for milk production.