Managing feed and breeding in replacement females

Heifers, first-calvers, maiden ewes and first-lambers need to be managed properly to reduce risk in terms of productivity versus production costs. Dr Francois van de Vyver, livestock nutritionist with Voermol Feeds, offers advice on this situation.

Beef cows have a critical 100-day period in their production year.
Photo: Andre Pretorius

Some commercial livestock farmers struggle to maintain their financial position of a few years ago, despite careful management, says Dr Francois van de Vyfer, nutritionist at Voermol Feeds. The main hurdle seems to be economies of scale, he says.

The key, argues Van de Vyfer, is to improve the herd or flock’s reproduction rate as much as possible. Too often, beef and sheep producers overlook the importance of reproduction rate in the herd or flock, even more so in replacement females. Optimum reproduction should be the primary goal of any enterprise.

“Reproduction can be defined in different ways. The easiest way to express it is calving or lambing rate. When focusing on profitability, a more appropriate way to define reproduction success is weaning rate. “The best way to express it is the percentage of marketable weaners, or the marketability percentage. This is what generates income for the commercial livestock enterprise,” says Van de Vyfer.

Improving the reproduction rate and number of marketable animals in a sheep enterprise has been widely researched for many years. Firstly, sheep farmers must aim to produce more lambs per lambing season (lambing rate). This is attained by increasing fecundity, using management practices such as flush feeding and selection for multiple births.

Secondly, the number of lambing periods can be increased if the environment allows it, by considering eight-month lambing intervals or other short-season lambing systems.

Beef breeding
For a beef enterprise, it is more challenging because, at best, a breeding female only has one calving per year. Van de Vyfer explains that the average weaning rate for mature cows in South Africa’s commercial beef sector is approximately 85%. This is an acceptable average, given the country’s often challenging environmental conditions, he says.

However, the average weaning rate for South Africa’s first-calver cows is below 60%, which is suboptimal. This presents an opportunity for improvement. “We know that heifers tend to become pregnant easily when they’re in the correct body condition, but it’s often challenging to get them pregnant again within 90 days after their first calving. But certain managerial and nutritional approaches can be used to improve on reconception in first calvers,” says Van de Vyfer.

The typical calving season for South African commercial beef herds usually runs from August to September and is aimed at starting a maximum of 30 days before the first spring rains. Van de Vyfer says at least 80% of pregnant cows should calve down within this first 30 days of a commercial beef herd’s typical calving season. Cattlemen should select replacement heifers that can achieve this target.

High physical demands
He points out that a cow’s lactation period after calving places great physical demands on her body’s reserves, as she loses a great quantity of nutrients through her milk. It is therefore essential that the herd manager build up lactating cows’ condition as quickly as possible so that she can reconceive within 90 days of calving, while still having a calf at foot.

“South Africa’s commercial cattlemen should achieve an average inter-calving period (ICP) of 365 days, to have their calves weaned at an average of 182 days, and allow the pregnant cow 182 days’ rest before she calves down again.

“However, statistics indicate that only about 10% of commercial beef enterprises achieve an average ICP of less than 399 days. This is because production conditions in South Africa are generally very challenging. But if some farmers can achieve this, others can too,” Van de Vyfer says.

Cattlemen should aim for reconception 82 to 90 days after calving, and for calf weaning weights above 220kg. Those who practise backgrounding should grow their weaners to a maximum of 380kg. The ideal slaughter weight for a beef animal is at least 420kg to ensure a minimum carcass weight of 225kg that will be graded A2/A3.

Critical period
During the production year of a beef cow, there is a 100-day critical period. This is made up of the last 30 days of pregnancy and the first 70 days of lactation. During this period, cows have the highest nutrient demand and the herd manager must provide appropriate supplementary nutrition to cater for this.

“A beef cow with sufficient nutrients should have the appropriate body condition score (BCS) to enable her to calve down without any major problems and reconceive relatively easily within 90 days. A cow’s total nutrient requirement during this critical period is similar to her total nutrient requirement for the remainder of her production year. At calving, a cow is in a negative energy balance and will temporarily lose body condition.”

In addition to the nutrient requirement for calving, lactation and reconception, heifers and first-calvers require added protein, calcium, phosphorous and other minerals and vitamins in their diets as they are still growing, explains Van de Vyfer.
A herd manager has a number of management strategies available to him to improve the breeding productivity of heifers, and first-calvers in particular.

Different strategies
The first is proper fodder flow planning to ensure enough feed for the females during the critical period. Insufficient feed will contribute to poor ICPs and weaning weights. The second strategy is to manage replacement heifers and first-calvers as a separate herd from weaning age until they have calved a second time. This will allow them to receive optimal nutrition, particularly as they will not have to compete with more dominant, older cows.

They can also be given licks specifically formulated for replacement heifers. The third strategy is to effectively manage their body weight. When a heifer is first put to a bull, she should ideally weigh at least 65% of her expected mature weight. This will allow her to reach 80% to 85% of her expected mature weight when she calves down for the first time. If this strategy is applied effectively, the first-calver should be able to reconceive within 90 days of calving down.

“It’s very important to regularly conduct BCS and use the results to make the necessary adjustments to nutrition to keep breeding females in the appropriate condition for the relevant time in her production year,” says Van de Vyer.

It is more cost-effective to maintain animals at the appropriate BCS than to allow this score to see-saw and then repeatedly having to correct it. If a cow is allowed to lose excessive body condition at calving, it will result in unnecessary additional expense. The cow may also reconceive much later or even skip reconception.

Shorter breeding season
A fourth strategy is to have a shorter or 45-day breeding season, specifically for replacement heifers. This allows for more intensive management of the heifer herd, which will result in lower supplementary feed costs. It will also mean a shorter calving season for heifers.

However, it is recommended that heifers are put to a bull about 30 days earlier than mature cows. This will allow a first-calver’s calf to be weaned at least 30 days earlier than the calves of mature cows, and the first-calver will have a longer rest period between calving and being put to the bull again with the rest of the cow herd. This should therefore improve her chance of reconception.

A fifth strategy for this period is to avoid supplying excessive amounts of energy supplements at the expense of more important nutrients, such as quality protein. The still-growing heifers have high protein, calcium, phosphorous and micro-element demands. Appropriate licks that augment the nutrients deficient in grazing should be provided. The ingredients in these licks may have to be adjusted from year to year, depending on the quality of the grazing.

“First-calvers can receive flush licks from about 21 days before their next breeding season and these licks can be removed at one to two oestrus cycles into the breeding season,” Van de Vyfer says. He also points out that a first-calver female’s milk production is typically low, resulting in suboptimal growth of the first calf. Providing creep feed to a calf helps to improve its growth while taking stress off the first-calver to allow her to recover her BCS.

Separate management
“The take-home message is that heifers must be managed separately from mature cows so that their productivity is improved,” Van de Vyfer concludes.

Phone Dr Francois van de Vyver on 032 439 5879, 083 386 8378, email [email protected], or visit www.voermol.co.za.