Study shows adequate growth with low-quality alfalfa.
Weaned heifers gained more weight on high- or medium-quality alfalfa hay than on low-quality hay in a recent University of Minnesota feeding trial.
“But the hay on the lowest end of the quality spectrum still got them within an acceptable growth range,” says Hugh Chester-Jones, dairy and beef production systems specialist at the university's Southern Research & Outreach Center in Waseca.
Researchers divided 96 nine-week-old Holstein heifers into four replicated group pens (six heifers per pen) for the 112-day study. They were fed 100-relative feed value (RFV) hay, 100-RFV hay plus a free-choice molasses-protein block, 130-RFV hay or 154-RFV hay.
“The crude protein amounts were similar among the different types of hay, although RFV levels varied due to differences in NDF and ADF,” says Chester-Jones.
During the first two weeks, heifers were also fed 6 lbs/head/day of a 16%-crude protein grain mix. Then the grain allotment was reduced to 4 lbs/head/day for the rest of the trial. Hay was offered free choice throughout the study.
“If you limit concentrates, the heifers don't get overconditioned; but, by offering free-choice hay, they're able to meet their needs,” he says. “They generally limit themselves to a dry matter intake of about 3% of their body weights.”
The table shows average weights of heifers fed 130- and 154-RFV hay were 439 lbs and 441 lbs, respectively, at the end of the study. Heifers fed 100-RFV hay averaged 417 lbs, and those fed that hay plus the molasses-protein block averaged 426 lbs.
The block increased daily gain by 4% and feed efficiency by 2.3% in animals fed low-quality alfalfa hay.
“The lick block provided a response, but the cost-to-benefit ratio would have to be assessed to see if it was economical,” says Chester-Jones.
He points out that feeding 130-RFV hay compared to 100-RFV hay increased daily gain by 9% and feed efficiency by 3%. Daily gain and feed efficiency improved by 1.4% and 5.9%, respectively, when 154-RFV hay was fed instead of 130-RFV hay.
Chester-Jones was surprised that heifers fed the low-quality hay gained as much as they did. “Their growth rates were still acceptable,” he says. “That's important for dairy producers to remember if they don't have higher-quality hay on the farm or if they're buying heifer hay priced on RFV points and don't want to spend more.”
|100 RFV||100 RFV |
|130 RFV||154 RFV|
|Final weight, lbs||416.5||425.9||438.5||441.4|
|Total gain, lbs||213.4||222.8||235.4||238.3|
|Daily gain, lbs||1.9||2.0||2.1||2.1|
|Final hip height, in||44.3||44.1||45.3||44.7|
|Hay DMI, lbs/day||5.3||5.2||5.9||5.5|