I hope that you are "wrapping up" your holiday shopping and getting ready to celebrate the holiday season as you read this month's issue.

In this issue, we have included an index to all of the articles in the 1998 Ranch Hand. I think you will find it is a useful reference for our past issues.

Third Trimester Important for Spring Calving Cows and Heifers

Dr. Greg Lardy

Most spring calving cows have entered, or will shortly enter, the third trimester (three months) of their pregnancy. This is an important time for the cow and her developing calf. The vast majority of fetal growth takes place in the last trimester of gestation. Consequently, proper nutrition is important to ensure a live, healthy calf at parturition. As we approach calving, additional energy, protein, and other nutrients are needed.

Research conducted at Colorado State University highlights the need for proper nutrition prior to calving (Odde, 1997). Heifers in poor condition (BSC <5) at calving had lower immunoglobulin concentration in the colostrum and calves born to these heifers had lower serum immunoglobulin levels.

Research summarized (Table 1) by Dr. Bob Bellows from the Ft. Keogh Research Center at Miles City, Montana, indicates that plane of nutrition during gestation also plays a role in dystocia (calving difficulty) and calf survival (Bellows, 1993). Even though cows fed on a high plane of nutrition during gestation had higher birth weights, dystocia was lower, scours incidence and mortality was lower, calf survival at weaning was higher, and cows had higher pregnancy rates the following breeding season.

Table 1. Effect of low or high gestation feeding level on calving and subsequent reproduction.

Literature Cited
Bellows, B. 1993. Factors affecting calving difficulty. Proc. Range Beef Cow Symposium. pp. 175-189.

Odde, K. 1997. Reproductive efficiency: precalving nutrition and improving calf survival. Proc. Bovine Connection to Profit. Williston, ND. pp. 86-91.

Bison Pastures and Grazing Management

Kevin Sedivec, Extension Rangeland Specialist

Bison ranching has emerged as a popular livestock enterprise in North America, especially North Dakota. Demand for information on managing bison as a grazing animal has grown with the industry. One key to successful bison ranching is providing abundant, good quality forage for summer grazing. Shortages during this time period result in poor conception rates. The rancher must adopt the philosophy of becoming a forage producer and manager first and a bison rancher second.

Bison are graminoid grazers, with grasses and sedges comprising over 90% of their diet on native range. They were the first rotational grazers, with 90% of the historical population migratory herds. Bison tended to graze under a large scale two-paddock seasonal grazing system. They seasonally grazed on a summer range, moving about freely in search of better forage, then migrating to winter range. Bison tended to graze in smaller herds during the summer and larger herds during the winter. They did not move around freely on winter range and only moved when forage became depleted.

The use of grazing systems for bison has been debated among many bison ranchers and range managers. Many have said rotational grazing among multiple paddocks is not needed for bison. Unless the pastures are large (>1,000 acres, for instance) and stocking rates are moderate or less (<40% use), rotational grazing will benefit the impact on natural resources, improve forage quality, and improve livestock distribution grazing patterns. The type of grazing system used must be developed to fit the needs of the operator and match the available labor on the ranch. Variables to consider when developing a grazing plan include: type of range (native vs tame), plant species composition of seeded pasture, season of grazing use, location of pasture or pastures from home base, location of water sources (first variable when developing cross-fences), future plans, level of investment, and degree of manager's involvement. Always try to develop a grazing program that involves seeded pastures with native range to maximize time on pasture and minimize use of harvested feeds.

In an attempt to optimize nutritional quality and palatability of the grazing resource, stage of plant growth has more effect on nutrition and palatability than plant species in most cases. The rancher's objective, independent of livestock class, should be to maintain plants in a vegetative state for as much of the grazing season as possible. The only method of grazing to achieve this goal is one that attempts to graze all paddocks prior to the seed set stage (mid to late July). An effective grazing system does not require a multitude of small paddocks, just a large enough stock density to graze the entire pasture in a 10-20 day period, allowing a minimum of a 30 day rest period. This system assumes a minimum of three paddocks and a maximum of five. A well-designed fencing system will provide ease in moving the herd with minimal to no handling of the animals.

Determine the carrying capacity of your pastures just as if you were determining the capacity for cattle or any other grazing animal. The carrying capacity of a bison pasture will be similar to a cattle pasture with slight differences occurring in selectivity. The animal unit equivalent of a 1,000 lb bison is equal to a 1,000 lb beef cow (with or without a calf) during summer grazing.

Bison have the ability to digest low-quality forages more completely than beef cattle. Studies have shown bison can extract from 5 - 13% more nutrients from various low quality feeds. This advantage is best seen in forages with less than 8% crude protein content. This increased efficiency in bison is explained by a higher level of nitrogen recycling, differences in rumen micro flora, and longer feed retention time in the rumen (79 hrs for bison vs 69 hrs for cattle). Forages with a protein level above 10% are digested equal to or better in cattle than bison. See Table 1 for nutrient requirements of female bison.

Bison are classified as grazers (they graze mostly grasses and sedges). Studies in the Great Plains have demonstrated bison have a preference for grasses and sedges over forbs and shrubs and are more likely to overgraze grasses than cattle. Grasses are reported at 90-100% of the bison diet, depending on availability and time of year. When upland grasses and sedges are limited, sedges and wetland grasses dominate the diet when available. Bison can adjust their diet to include as much as 20-40% shrubs, often willows, when grasses are limited. Reproductive performance usually suffers when bison are forced to excessively browse more than desired. Bison will consume some forbs, willows, and poplar leaves even when there is plenty of grass available. This is a taste factor, just as some of us may eat lefse with our Christmas supper - we like it.

Index of Articles - 1998

Bison Pastures

It appears bison will graze virtually every grass species (with some exceptions). Variability in preference is based on palatability and succulence. When selecting a grass species to plant for bison chose one that produces high yields on your soil and under your climatic conditions. Don't be afraid to incorporate alfalfa in your grass seeding mix. Although alfalfa is not a grass and some producers feel bison will not graze it, many research projects and demonstrations have proven bison will graze alfalfa, especially new growth. The lactating female bison rely and depend on a lush, high quality diet during the spring and summer grazing period to replenish body fat lost during the winter. Alfalfa maintains a high quality diet when seeded with grasses in July, August, and September. It is recommended that alfalfa comprise no more than 30-35% of the pasture mix.

Much of the information presented in this article was referenced from a publication developed by the Grazing and Pasture Technology Program entitled, "Bison pastures and grazing management." For a copy of this publication, contact the Grazing and Pasture Technology Program at Box 4752, Regina, Sask, S4P 3Y4 or (306) 757-9499.

Table 1. Estimated nutrient requirements of female bison (100% DM basis).¹