From: 1994 Proceedings of the Cornell Nutrition Conference:

FURTHER OBSERVATIONS ON FEEDING HIGHLY PRODUCTIVE SHEEP
D.E. Hogue
Department of Animal Science
Cornell University

At last year's Cornell Nutrition Conference (1), we discussed some feeding strategies for highly productive sheep. These sheep are generally described as those managed to lamb frequently, produce multiple lambs at each lambing and after weaning the ewes should be capable of re-breeding and the lambs growing rapidly. We have concentrated on those performing well when managed on the STAR system as meeting this description. Most of the ewes are of moderate size and are of Dorset, Finn or Finn Dorset breeding and may be bred either to rams of the same breed to produce replacement females or to large terminal cross rams to produce rapidly growing market lambs.

We generally divide the STAR managed flock into 3 distinct groups and consider the nutrition or feeding of each group individually. These are (1) the breeding and pregnant group, (2) the lambing and lactating group, and (3) the weaned growing lambs.

The breeding and pregnant group will not have unreasonably high requirements even if considerable numbers of ewes in the group are pregnant with 3 or 4 lambs. The lambing and lactating ewes will have the highest requirements, particularly those suckling multiple lambs. The weaned growing lamb's requirements can be generally met with most traditional recommendations. As most pregnant ewes join the lambing group 2 to 6 weeks prior to lambing, increased requirements for late pregnancy with multiple lambs can be met at that time.

In 1975 (2), the author extended the then NRC (1968) (3) requirements and estimated some values for ewes pregnant with more than 2 lambs, ewe lambs bred at 7 months of age, ewes lactating with 3 or 4 lambs and ewes lambing more frequently than once a year. Since that time, the latest NRC publication (1985) (4) has expanded estimated requirements to include pregnancy and lactation for ewe lambs at different lambing rates and also for ewes pregnant at different expected lambing rates. No estimates are given for ewes with more than 2 lambs.

It is important to recognize that the requirements for ewes published by NRC should be especially useful because they identify and define the expected body weight gain or loss of the ewes at each stage of production. These changes in body weight are set so that the ewes end each production year at the same body weight (and presumably the same body composition or condition score) as at the beginning. Furthermore, these weight changes are minimized with the ewes only losing weight during early lactation and theoretically recovering that loss in late lactation.

It is thereby implied that ewes during early lactation are expected to lose body weight (and presumably body condition). It is usually considered that ewes rearing twins cannot consume sufficient nutrients to prevent weight loss at this time. It was suggested at last year's conference that changing the feeding strategy for ewes with triplets to full-feeding a concentrate portion of the diet might be a possible method of minimizing weight loss in ewes suckled by 2 or more lambs.

Data are presented in Table 1 on observed feed intake and body weight changes of triplet-rearing ewes and their lambs. In the first trial, Finn ´ Dorset ewes weighing 144 lb and rearing triplets were fed 2.0 lb of average quality hay per day each and allowed ad lib consumption of a high energy complete lamb pellet (Agway). One lamb was lost at the end of the 30-day trial and was omitted from the data. The trial was started when the ewes were 2 to 3 weeks postpartum. In this trial, the ewes consumed 6.9 lb of the pellets daily in addition to the 2 lb of hay for a total consumption of 8.9 lb of air dry feed or about 8 lb of dry matter. The lambs also had access to the pellets in a creep. This compares to the NRC expected dry matter intake of 6 lb for ewes of this weight rearing twins during early lactation. Furthermore, although digestibility data are not available, the available energy fed in this trial most probably exceeds that anticipated in the NRC table.

Now look at the gain data in Table 1 on trial 1. The ewes actually gained 0.29 lb (130 g) per day during the trial and their 3 lambs averaged 0.49 lb (222 g) per day or a total lamb daily gain of 1.47 lb (666 g). Is it really obligatory that ewes be in negative energy balance during early lactation? Apparently not!

In a second trial (Table 1), ewes were again limit fed average quality hay (3.3 lb/day) and fed the pelleted diet ad lib. Fourteen ewes rearing 42 lambs were used and continued from 1 to 2 weeks postpartum for 41 days. In this trial, all lambs were sired by large black-faced rams. Again, the ewes consumed feed at a great rate eating 3.3 lb of hay and 7.6 lb of pellets daily. This totals 10.9 lb of feed or about 9.8 lb of dry matter. The ewe's initial weight averaged 143 lb so this amounts to a dry matter intake of almost 7% of body weight. The lambs could have consumed some of the hay, but the ewe pellet feeder was elevated to prevent lambs from consuming pellets other than in the creep.

In this trial, the ewes gained 0.55 lb (250 g) per day and the lambs gained 0.71 lb (322 g/day) for a total lamb daily gain of 2.13 lb (966 9).

Clearly, it is possible to reach levels of intake and animal performance far above what we consider "normal" as indicated in many of our 'requirement" tables. To do this may necessitate changing our feeding strategies and expectations. Whether or not these levels of intake and animal performance are economic and should be used as recommendations remains to be seen. However, it is clear that we should not be restricted by recommendations or requirements that are normally in use.

REFERENCES

1. Hogue, D.E. 1993. Feeding strategies for highly productive sheep. Proc. Cornell Nutr. Conf. pp 121-125.
2. Hogue, D.E. 1975. Nutritional requirements of highly productive sheep. Proc. SID Symposium "Sheep Breeding & Feeding for Profit" pp. 34-48.
3. NRC. 1968. Nutrient requirements of sheep. 4th edition.
4. NRC. 1985. Nutrient requirements of sheep. 6th edition.