Most commercial cow herds in the Northern Plains States are bred to calve in the spring (February, March, April). Typical spring calving occurs in these states before pastures are ready to be grazed. In this scenario, late gestational and lactating females need to be fed high quality harvested forages and are usually supplemented with energy, protein, or both energy and protein, especially after calving, to meet their nutrient requirements. In most cow/calf enterprises, harvested forages account for a large portion of feed costs. Extending the grazing period in lieu of feeding harvested forages will reduce production costs and increases net returns in the cow/calf enterprise. Moving calving to late spring/early summer allows cows to meet their nutrient needs for a longer period of time while grazing dormant range with some supplementation and almost eliminates the need to harvested forages.
Spring Compared to Summer Calving
The greatest nutrient demand of beef cows is during lactation. During lactation cows need to be fed high quality hay and, sometime, supplemented to meet the energy and protein requirements. In most Northern Plains locations, much like the sandhills of Nebraska, the primary grasses available for grazing are warm-season grasses that become available in late May to June. If cows calve in March, this means they are fed a lactation diet for about 90 days before summer grass. It has been documented that the highest quality in warm-season grasses in Nebraska occurs in late May to mid- June and gradually decreases thereafter. Sequencing calving closer to the time when the grazed resource will meet the nutrient demands of the lactating female reduces feed costs and increase profit potential. Basically, this means moving “early spring” calving to “early summer” calving. Key components to changing calving time using a “systems” approach include: 1. Cows have access to vegetative forage for a short period of time prior to calving; 2. Cows meet their energy and protein needs from the pasture resource; 3. Hay and supplement costs are reduced because peak lactation now occurs when vegetative, high quality forage is available; 4. Reduced calf losses and sickness because calving occurs when the weather is warmer; 5. Less labor is needed at calving because calves weigh less at birth for June calving cows compared to February/March born calves; 6. Labor is reduced because less harvested feeds are fed; and 5. Different market alternatives are available for the calves and cull cows and bulls.
In 1993, a summer calving herd was developed at the University of Nebraska, Gudmundsen Sandhills Laboratory to compare spring and summer calving herds. In the spring herd, cows began calving in March and the breeding season began in June, and calves were weaned in October. For the summer calving herd, calving began in June, breeding season began in September, and weaning occurred in November or January. Data were collected in 1994, 1995, and 1996. Summer calving cows were fed 327 lb of hay/cow/year compared to 3,947 lb of hay/cow/year. Similar amounts of protein supplement were fed; summer calving cows were fed 154 lb/cow/yr and for spring calving 96 lb/cow/yr. The length of the grazing season went from 233 days to 357 days by adjusting the calving time from March to June. Cow reproductive performance was not different between groups. When calves were weaned at similar days of age, summer born calves were about 35 lb lighter. However, January calf prices tend to be higher for the same weight of calf sold in October; therefore, summer-born calves generate similar gross income as spring-born calves. Due to costs savings in the summer calving system, primarily due to less labor and less hay fed, the summer calving system was a more profitable even at weaning time.
Some concerns with this summer calving system include breeding season occurring at a time when the temperatures are hot. In the sandhills of Nebraska, the temperature decreases at night and the humidity is low. In areas of the United States, because of high humidity and no night cooling, a breeding season that occurs during this time period could result in lower pregnancy rates. There has also been reports by producers that have used this system of experiencing more calf scours. We did not experience that in our summer calving herd. We have experienced a lower rebreeding performance of the first-calf-cows during their second breeding season. Pregnancy rates ranged between 75% and 80% for females bred for their second pregnancy. Nebraska Sandhills upland range is dominated by warm-season grasses that decline in energy and protein in late summer and early fall. Evaluation of the forage indicated that the quality in some situations is not sufficient to meet the young females’ nutritional needs during lactation, especially energy and protein needs. Experiments have been conducted using supplementation regimes to meet the young lactating females’ nutrient needs that have resulted in acceptable rebreeding performance of these females. Pregnancy rates for the second breeding season for the supplemented cows was 95% compared to non-supplemented cows of 79%. When the experiment was repeated, pregnancy rates were not different between the two groups. Quality of the grazed forage was different in experiment 1 compared to experiment 2. In experiment 1, drought occurred early in the growing season which influenced quality during the growing season and we saw a response in pregnancy rate to supplementation. Bottom-line, it is important to evaluate the grazed forage resource, especially prior to the breeding season, for young cows in this management system.
If one studies the nutrient quality change in sandhills range, it appears that late April or early May calving may better fit to further reduce feed inputs and supplementation to young females during their second breeding season. By moving the calving time to late April, the cow requirement line shifts and nutrient needs of the beef cow are more closely met by the forage resourses. Data-bases that describe protein and energy content of grazed forages, like the ones developed for the sandhills of Nebraska, are tremendous assets to producers to help them design production systems that fit their operation and have potential to increase profit. In additions, these data-bases aid producers in designing strategic supplementation strategies.