The Cow-Calf Manager

Livestock Update, December 2002

John B. Hall, Extension Animal Scientist, Beef, VA Tech

Fall-Calving Cows May Need Additional Management for Successful Breeding

The fall rains brought a welcome flush of grass to the pastures of Virginia. Although increased pasture availability helped meet the nutritional needs of lactating fall cows, pastures are beginning to decline in many locations. In addition, many fall-calving cows are milking well, but they have not gained enough body condition to ensure they will breed early in the breeding season.

Producers with fall calving herds need to do an honest assessment of feed resources and cow condition. Operations with plenty of feed and cows in good shape should use their normal management procedures for the breeding season. Herds with limited feed supplies should consider a nutrition program as we discussed in the October Cow-Calf Manager. Regardless of feed supplies, cows in low body condition (BCS<5), first calf heifers, and late calvers will need some special management.

Flushing is increasing the amount of energy fed to cows immediately before the breeding season and through first three or four weeks of the breeding season. This is the same type of procedure used in ewes, except it only works well in thin or young cows. Research from several locations demonstrated that flushing increased conception rates and decreased early embryonic mortality. Flushing increased first service pregnancy rates by 20% and final pregnancy rates by 10% to 15% in studies in South Carolina.

Producers should feed 5 to 10 lbs of corn, corn gluten, or rolled barley per cow per day for two weeks before and three weeks after the first day of the breeding season. The cost of the extra feed should be offset by increased pregnancy rates and weaning weights. Flushing cows for 6 weeks that were originally fed a low energy diet (average hay) increased weaning weights by 24 lbs. compared to calves from cows that continued on the low energy diet. The extra weaning weight should be worth $10 to $13 more per calf.

Temporary calf removal, 48-hour calf removal, is removing calves from dams for two days before the beginning of the breeding season. The reduction in energy requirements and suckling stimulus causes increased release of reproductive hormones from the brain of the cow. These hormones will begin resumption of cycles in non-cycling cows.

Calves should be removed from dams and held in a pen or lot. Dams can remain out on pasture. The lot should be as clean as possible, and plenty of clean water and hay needs to be provided. A shelter is nice, but not necessary. Research done in Kentucky and other locations clearly demonstrates no significant increase in calf sickness, and no decrease in weaning weight.

Progestins meaning progesterone or progesterone like compounds can help jump-start non-cycling cows. An increase in progesterone is part of the natural resumption of cycles after calving. Giving cows progestins or compounds that cause the ovary to produce progesterone mimics this natural process.

Feeding MGA (0.5mg/cow/day) for 7 to 10 days will turn over many non-cycling cows or heifers. Also, using GnRH-based synchronization systems such as Ov-Synch or CO-Synch will initiate cycles in cows and heifers (See VA Extension publication 400-013). The new CIDR devices release progesterone and increase cyclicity in non-cycling cows. For more information about these systems contact your veterinarian, county Extension Agent or breeding service representative.

Thin cows and anestrous (non-cycling) cows are more unusual in fall calving herds than spring calving herds. However, this year more fall calving herds will have this problems. Incorporating at least two of the management tools discussed may save you from too many open cows next spring.

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