End of Project ReportThere has been increased interest in and increased usage of forages other than grass silage for feeding dairy cows during the winter period. This has arisen because of the inconsistency in making good quality grass silage and the low intake characteristics of this feed. The main objective of this project was to evaluate the effects on dairy cow intake and performance of offering fermented whole crop wheat (WCW) silage, urea-treated processed WCW and maize silage in mixtures with grass silage compared with grass silage alone. The value of these feeds as supplements to grazed grass in the Autumn for late lactation spring calving cows and their effect on dietary nitrogen (N) utilisation for milk protein production were also investigated.
The first two experiments evaluated the effects of including 67% of the forage mixture on a dry matter (DM) basis as fermented WCW, urea-treated processed WCW (also known as “Alkalage”) or maize silage in comparison to grass silage alone in the diet of autumn calving cows. The fermented WCW and urea-treated processed WCW were harvested at a stubble height of approximately 20 cm. Sixty and 95% of the grain was milled/cracked in the urea-treated processed WCW in experiments 1 and 2, respectively. Forages were supplemented with concentrates of varying crude protein (CP) concentrations so as to maintain a similar CP concentration in the total dietary dry matter across treatments. In both experiments all the feeds were well preserved. The DM (g/kg) and starch contents (g/kg DM) in the fermented WCW, urea-treated processed WCW and maize silage in experiments 1 were 406 and 282, 733 and 324, 221 and 140 and in experiment 2 were 370 and 323, 763 and 341 and 302 and 324, respectively. Results from both experiments were similar. The three forage mixtures resulted in greater DM intake and greater fat plus protein production than grass silage. The largest effect on intake was obtained with the urea-treated processed WCW which probably reflected the greater DM content of this forage mixture compared with the others. Milk protein content was generally similar across the three forage mixtures and greater than on grass silage as the sole forage.
In the third experiment short-straw urea-treated processed WCW (harvested at a stubble height of 35 cm) was evaluated in comparison to the fermented WCW (harvested at a stubble height of 20 cm), maize silage and grass silage. The DM (g/kg) and starch (g/kg DM) contents in the fermented WCW, urea-treated processed WCW and maize silage were 389 and 316, 795 and 382 and 346 and 301, respectively. Fifty nine percent of the grain was cracked/processed in the urea-treated processed UP-WCW .Level of inclusion of forages in the diets was the same as in the first two experiments and total dietary CP was again maintained at a similar concentration across treatments by offering concentrates of varying CP concentrations. The higher harvesting height of the urea-treated processed WCW resulted in a greater starch concentration in this feed in comparison to the first two experiments. The results however were very similar to those obtained in the first two experiments with the forage mixtures again increasing DM intake and fat plus protein yield. Inclusion of the short-straw urea-treated processed WCW did not result in greater fat plus protein production compared with the inclusion of fermented WCW or maize silage. The greatest efficiency of conversion of dietary nitrogen (N) to milk N was achieved with the maize silage mixture and the least efficiency with the urea-treated process WCW mixture.
In experiment 4 the nutritive value of fermented WCW, urea-treated processed WCW and maize silage were evaluated in comparison to a concentrate as supplements to grazed grass for spring calving cows in the autumn. A treatment with a high grass allowance of 24 kgDM (> 4 cm)/cow per day was also included while the grass allowance on the supplemented treatments was restricted to 17 kgDM (> 4 cm)/cow per day. All the supplemented treatments and the high grass allowance treatment gave greater milk yields than the unsupplemented restricted grass treatment. The concentrate supplement resulted in the greatest solids corrected milk yield and this was greater than any of the forage supplemented treatments which were not significantly different from one another.
In the final experiment the output of N in milk, urine and faeces was measured when grass silage, fermented WCW, urea-treated processed WCW and maize silage were fed as the sole forages plus 6 kg of a concentrate containing 338 g crude protein/kg DM. The proportion of consumed N excreted in urine and faeces was greatest on grass silage and urea-treated processed WCW with fermented WCW and maize silage resulting in the greatest proportion of consumed N being excreted in milk.
Overall, the project demonstrated that including either type of WCW or maize silage with grass silage increased fat plus protein production and protein concentration to a similar extent compared to grass silage as the sole forage. All three forages increased DM intake with the greatest increase observed with urea-treated processed WCW.
Because of this greater intake resulting in similar fat plus protein production conversion of dietary DM to milk solids was less efficient on urea-treated processed WCW based diets than on fermented WCW or maize silage based diets. Grass silage and urea-treated processed WCW based diets were least N efficient with less dietary N being incorporated into milk N than on fermented WCW or maize silage based diets. Comparing the responses on the forage mixtures relative to one another and to grass silage across experiments 1 to 3 indicates that neither degree of grain processing or harvesting height (within the ranges studied here) are of substantial importance in determining the nutritive value of urea-treated processed WCW. All of the three alternative forages gave similar solids corrected milk yield responses when used as buffer feeds for spring calved cows at pasture in the autumn but these responses were less than 50% of the response to a concentrate supplement
