By Cathy Gallivan, PhD
Sheep farmers who feed round bales are familiar with their convenience and also with the resulting high feed waste, even when round-bale feeders are used.
Many unique designs of round-bale feeders have been developed and some claim to reduce or even eliminate feed wastage. Researchers at the Norwegian University of Life Sciences conducted two experiments to investigate the effect of feeder design, roughage type and size of round bales on feed wastage in sheep.
Four indoor pens were each provided with a different type of round-bale feeder, and stocked with 10 Norwegian White ewes in early pregnancy. Ewes in each pen were given a bale of low-quality roughage (Roughage 1) that was left in the feeder for four days, followed by a bale of high-quality roughage (Roughage 2) for the next four days. Each group of 10 ewes was subjected to each type of feeder by rotating them among the pens.
Two of the round-bale feeders were circular; one had diagonal dividers (RD) and one had vertical dividers (RV). A third feeder (KR) had six sides made from linked panels that the ewes could move, with no dividers. The fourth feeder (TR) suspended the round bale in an open ‘basket’ over a square platform 18 inches off the ground. Bales were placed on the floor with round sides up in the first three feeders, and placed in the basket of the TR feeder with the round side facing sideways.
Roughage 1 (low quality) was grass silage harvested at a late stage of maturity with a dry matter (DM) content of 56.0%. Roughage 2 (high quality) was hay harvested at an early stage of maturity with 73.8% DM. Each type of roughage was baled in rounds that were approximately 47 inches tall and 52 inches in diameter. The average weight of the bales was 514 kg (288 kg DM) for Roughage 1 and 468 kg (346 kg DM) for Roughage 2. The median particle length was 7.7 inches for Roughage 1 and 3.8 inches for Roughage 2, which also had a greater leaf:stem ratio than Roughage 1.
Bales were replaced every four days, with leftover feed removed from the feeders before new bales were added. Every morning at 0800, the wasted forage on the floor surrounding the feeders was collected, weighed and sampled.
Feeding behavior of the ewes was scored by an observer at 2-minute intervals on Days 2 and 4 from 0900 to 1200, and 1500 to 1800, for each bale of Roughage 2 fed. Behavior was scored as the number of ewes eating with their whole head (both ears) inside the feeder, eating with their head partly inside the feeder (at least one ear outside the feeder), eating from the feeder while climbing with their front legs, or eating roughage from the floor outside the feeder.
Results – feed wastage
Overall, feed wastage averaged 1.1 kg DM/day per ewe. Feed waste was greatest on Day 1 (1.3 kg DM/day per ewe) and decreased gradually until Day 4 (0.9 kg DM/day per ewe). Feed wastage was almost four times as high for Roughage 1 as Roughage 2 (1.9 versus 0.5 kg DM/day per ewe). Feeder design also had significant impact on feed wastage, with more feed being wasted from the RV feeder (1.3 kg DM/day per ewe) than the KR and TR feeders (1.0 and 0.9 kg DM/day per ewe, respectively). The RD feeder (1.1 kg DM/day per ewe) was intermediate between the RV and KR or TR feeders.
Wastage from both types of round bales had lower dry matter content than the baled feeds. Wastage from Roughage 1 also had lower crude protein content compared to round bales of Roughage 1, but wastage from Roughage 2 had a similar content of crude protein as the round bales of Roughage 2.
Results – feeding behavior.
Ewes spent approximately 40% of the time during the observation periods eating. The time spent eating with the whole head inside the feeder was significantly lower for the TR-feeder than for the other feeders. Time spent eating with the head partly inside the feeder was lowest for the KR-feeder. Climbing with the front legs while eating was most prominent in the RV and TR-feeders. Time spent eating wastage from the floor was almost negligible. Interestingly, time spent eating with the whole head inside the feeder increased from 9.3% at Day 2 to 15.6% at Day 4, while time spent feeding with the head partly inside the feeder decreased from 30.3% at Day 2 to 20.8% at Day 4. Eating from the feeder while climbing with the front legs decreased only slightly from 3.6% at Day 2 to 2.8% at Day 4.
In this experiment, the ewes were offered half or whole round bales of only one roughage in each of the same four types of feeders. Roughage in this experiment was harvested at a late stage of maturity and 76.6% DM. Median particle length of the hay was 6.2 inches. Bales were fed as either half bales averaging 188 kg (145 kg DM) or whole bales weighing 419 kg (323 kg DM). Feeding behaviors were scored as in Experiment 1, but morning observations were limited to only one hour due to low feeding activity between 1000 and 1200.
Results – Feed wastage
Overall mean feed wastage in Experiment 2 was 2.2 kg DM/day per ewe and decreased gradually from Day 1 (3.0 kg DM/day per ewe) to Day 4 (1.4 kg DM/day per ewe). Feed wastage was almost twice as high for whole bales (2.9 kg DM/day per ewe) as for half bales (1.5 kg DM/day per ewe). Feed wastage was similar for all feeder types when feeding whole bales, but higher for the TR feeder when feeding half round bales. As in Experiment 1, the dry matter content of the wastage was lower than that of the round bales.
Results – feeding behavior.
Ewes spent approximately 70% of their time eating during the observation periods. Time spent eating with the whole head inside the feeder was much higher when feeding half bales than when feeding whole bales. Feeder design also influenced feeding behavior in that time spent eating with the whole head inside the feeder was lower for the TR-feeder. Time spent eating with the head partly inside the feeder was much higher when feeding whole bales, and also higher on the TR-feeder compared to the other feeders. Time spent eating while climbing with the front legs was significantly higher when feeding whole bales compared to half bales, but this behaviour only occurred on the TR-feeder when feeding half bales. Ewes spent more than twice as much time consuming feed wastage from the floor around the feeders when fed whole versus half bales, regardless of the type of feeder.
Effect of roughage quality
The amount of feed wasted in both experiments was generally high, ranging from 0.5–2.9 kg DM/day per ewe. The amount of feed wasted was actually more than estimates of how much ewes of this size would consume, in two of the four periods. Feed wastage was highest on the day a new bale was fed and gradually decreased over four days. Type of roughage, size of bale (half or whole), and feeder design all had significant effects, but the major factor influencing feed wastage was roughage quality.
In Experiment 1, the feed wastage was nearly four times higher for Roughage 1 than Roughage 2. Roughage 1 was harvested at a later stage of maturity and, hence, had a lower nutritive value. Late-harvested forages also have more stems in relation to leaves, which was seen in the longer particle length of Roughage 1. Ewes were selecting leaves in Roughage 1, as shown by the lower level of crude protein in the wastage compared to that in the round bale. The ewes must have pulled the long fibrous stems out of the feeders and left them as wastage on the floor around the feeder. There was no indication that leaves were being selected from Roughage 2, however, as the crude protein level in the wasted feed was the same as that in the round bale. Therefore, differences in selection may be a product of a greater leaf:stem ratio in the early- versus late-harvested roughage. Dry matter content of the roughage did not affect feed wastage in this study.
In Experiment 2, the roughage used was also harvested at a late stage of maturity, resulting in even more waste (2.9 versus 1.9 kg DM/day per ewe).
Effect of whole versus half bales
Feeding half bales rather than whole ones reduced feed waste by nearly half. Reducing the amount of feed in the feeder may have allowed the ewes to eat with their heads in a normal, downward position unlike when feeders contain whole bales, causing them to raise their heads to eat. The researchers speculated that the ewes dragged the feed out of the feeder in order to eat in a more normal position. This theory is supported by the data, which shows that the ewes spent more time (50.5%) with their heads inside the feeder when feeding on half round bales than when feeding on whole round bales (27.4%), resulting in more of the potential wastage being dropped inside the feeder and less on the ground outside.
In general, the ewes spent little time consuming wastage from the floor around the feeders. However, they spent more time doing so when eating whole bales compared to half bales in Experiment 2, which is probably related to the larger amount of feed wastage available when larger amounts are fed.
Effect of feeder design
Although there was a significant effect of feeder design on feed wastage, the real differences were small. In Experiment 1, where only whole bales were used, the TR feeder had the lowest feed wastage. In Experiment 2, there were no differences between the round-bale feeders when feeding whole bales, but the TR feeder had the highest wastage when feeding half bales. This might be because the half round bales did not fit properly in the TR-feeder design. The ranking of the other feeders also differed between Experiments 1 and 2, so there seems to be no clear effect of feeder design on feed wastage.
Although feeder design did have a small effect on feed wastage, the quality and amount of roughage delivered into the round bale feeders had the largest effect on how much feed was wasted. Low-quality forage fed in whole round bales resulted in the most waste, but producers may take some consolation in knowing that ewes are consuming the higher-protein portions of poor-quality bales before wasting the rest, and that they will waste much less hay fed in round bales if it is of better quality.
S.G. Kischel et al., 2019. The effect of round-bale feeder design and roughage type on feed wastage in sheep feeding. Animal, 13 (10): 2388-2397.