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.”

Hay Quality And Heifer Performance
100 RFV 100 RFV
+ Block
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
DMI/day, lbs 9.0 9.2 9.6 9.2
Grain, lbs/day 3.7 3.7 3.8 3.7
Hay DMI, lbs/day 5.3 5.2 5.9 5.5
Feed/gain, lbs 4.7 4.6 4.6 4.3