by Don Llewellyn, Ph.D., State Livestock Specialist, Washington State University Extension
I’ve made a couple of trips across Eastern Washington in the last month or so and it is becoming apparent that our dry spell is taking its toll on the pastures in our region. Even though I’m eternally optimistic, and conditions can improve rapidly, let’s take another look at one of the tools in producers’ management toolkit to help get cows through times when grass isn’t necessarily as plentiful as we would like it to be. Given what we are seeing out there today, it seems it is rather timely to revisit the topic of early weaning.
A while back Dr. Twig Marston, some grad students, and I were thinking about doing some research into tools that producers can use when conditions are less than favorable. Early weaning came to the forefront of our discussions. Now I’m going to tell you right from the start that I’m not going to recommend early weaning as a general management practice, but I think it has its place when the conditions and circumstances are right. We conducted a research study that returned some interesting results. Here’s our thought process, what we did, and what we learned:
When we looked at the scientific literature before our project, we found that early weaning programs decrease the nutrient requirements of beef cows, increases body condition scores, and even carrying capacity of pastures. We felt like this approach could be valuable for spring-calving cows in areas with low forage quality in the mid-summer. It could also be a an option during drought conditions when forage supplies are low and producers need a strategy to maintain stocking rates and cow and calf performance. When you think about it, if you wean a calf at say 90 to 120 days of age rather than around the traditional weaning age of 210 days, there is an opportunity to increase the nutrient intake in those calves when their growth potential is high. We also found that there were some positive implications for feed efficiency and ultimately marbling of the calves by utilizing early weaning when compared with traditional weaning management.
Our study consisted of a dual approach: We looked at the effect of early weaning on summer cow body weight (BW) and body condition score (BCS) as well as the need for winter protein supplementation. The later could be significant considering the cost of protein for cows utilizing low-quality forages during the winter.
We started the summer study with 103 mature, Angus x Hereford crossbred, spring-calving cows with male calves sired by Hereford and Angus bulls. The average birth date of the calves was March 2. During the summer we randomly divided the cows into early weaned and normally weaned treatments (115 days of age and 220 days of age, respectively). On both weaning dates we collected data for BW and BCS (1 = emaciated and 9 = obese) for all cows in the study. In addition, on the normal weaning date, the external backfat of all cows (i.e., both early weaned and normal weaned cows) was determined by ultrasound.
For the winter supplementation study, we started with 96 pregnant cows from the same groups (i.e., early weaned vs. normal weaned) used in the summer study. Body weights and BCS were collected at the initiation of the study in November, every 60 days, and within 48 hours of calving. The cows were blocked by pasture (3 pastures; approximately 300 acres each), stratified by BW and BCS to ensure even distribution across treatments, and randomly assigned to one of three grazing groups within weaning treatment (i.e., early weaning or normal weaning). Two winter feeding levels were randomly assigned to the feeding groups. We used a soybean meal-grain sorghum based supplement (45% crude protein; CP; dry matter basis). The supplementation treatments were: 1) early weaning, HIGH (EWHIGH; 4.0 lbs of the supplement); 2) early weaning LOW (EWLOW; 2.78 lbs of the supplement); 3) normal fall weaning, HIGH (NWHIGH; 4.0 lbs of the supplement); and 4) normal fall weaning, LOW (NWLOW; 2.78 lbs of the supplement). In practical terms, the LOW supplementation group was fed at 70% of the HIGH group to see if a 30% reduction in supplementation level would be attainable as a result of early weaning. During the supplementation period, we gathered the cows three days/week with the amount of supplement prorated to deliver the designated daily quantity. The HIGH groups were provided supplement to meet the nutrient requirements for pregnant beef cows of the same type and physiological status as established by the NRC Nutrient Requirements of Beef Cows, 2000. Supplementation commenced on November 14, and continued until calving at which time the cows were all handled similarly with about 12 lbs of alfalfa hay per day along with dry grass until new spring growth forage was available.
Summer performance of cows is shown in Table 1. When calves reached an average of 115 days of age, there were no differences in BW and BCS of the cows, but the cows that had their calves weaned earlier were heavier at the normal fall weaning time. In addition, cows that had their calves weaned early gained 116 lbs more BW during the summer grazing season than the cows that had their calves weaned at the normal time. The results for BCS were consistent with the BW data. Cows with early weaned calves had greater BCS at the normal weaning time in the fall. The cows that had their calves weaned in the fall seemed to maintain BCS during the summer, but the cows with early weaned calved gained 1.2 BCS more than the early weaned cows during the period from early weaning to the normal fall weaning time. The ultrasound backfat measurements showed that early weaned cows had 3.3 mm more backfat at the normal fall weaning time. There were no differences between the early and normal weaned treatments for pregnancy rate at the normal fall weaning time when cows are customarily pregnancy checked.
Cow BW and BCS for the winter supplementation study are presented in Tables 2 and 3. We found that winter BW and BCS score changes were similar to those observed in our previous protein supplementation studies and those conducted by other researchers. The cows that were weaned early were heavier at the start of winter grazing. Cumulative BW losses from the start of winter grazing until calving tended to be greater for the cows that had their calves weaned at 115 day of age. Interestingly, the cows that had calves weaned early had greater final BW. These results indicate that when cows have their spring-born calves weaned at the traditional time in the fall, feeding to meet the NRC requirements results in performance comparable to cows with the calves weaned early. When we compared the HIGH vs LOW supplementation levels, cows on the HIGH treatments gained more BW during the period from November 14 to January 7. They also tended to lose less BW than the LOW treatments from November 14 to calving. We really focused in on the possibility that the BW and BCS gained during the summer from early weaning could result in protein supplement savings. We compared the NWHIGH cows (calves weaned at 220 days of age) to the EWLOW cows to determine if the increase in weight gained from early weaning would allow producers to reduce the amount of protein supplement required to support cows in adequate BW and BCS during the winter through calving. In the first period of the winter grazing season, NWHIGH had greater BW gains than EWLOW. The cumulative BW losses from the start of winter grazing to calving were about 44 lbs greater for the EWLOW cows than the NWHIGH cows. When we looked at final BW at calving, we noted that there were no differences between NWHIGH and EWLOW, which indicates that cows with early weaned calves that started winter grazing with greater BW were able to use the weight they had gained to their advantage and have good body weight at calving.
Winter BCS changes were also similar to previous studies. Cows with early weaned calves had approximately 0.9 greater BCS than the normal weaned cows. The early weaned cows lost more BCS than the normal weaned cows during the winter until calving. No significant differences in BW were observed between NWHIGH and EWLOW at calving, BCS were greater for EWLOW than for NWHIGH. Our findings suggest that even though EWLOW cattle were allowed to lose more BCS during the winter period, the ability to put on BCS during the summer utilizing early weaning more than compensated for the losses. For the subsequent calving season, only the NWLOW group tended to have a lower rebreeding rate.
We concluded that early weaning is an option to increase the BW and BCS of cows during the summer. Therefore, early weaning has the potential to be a useful tool during drought conditions or other times when grass is limited. It can be beneficial when cows enter the winter grazing season in better body condition. Allowing cows to cycle weight during periods when feed resources are limiting has been an important management tool for many years. However, it is of paramount importance that severe nutrient limitations do not take place because of the potential negative impact on the developing fetus. Together, early weaning and winter supplementation gives the possibility of allowing producers to feed less protein supplement during the winter and may represent a significant cost savings. Feeding less than 70% of the normal supplementation regimen may result in significant BW and BCS losses and reductions in reproductive performance.
Obviously, the calves from the early weaned cows must be maintained on a separate feeding regimen and there are costs and benefits to that dynamic as well. Producers will have to evaluate all of the economic implications before implementing an early weaning program to respond to whatever conditions are thrown at us.
As always, if you have questions or would like to discuss nutrition and management of your herd, please contact me at 509-335-8759 or don.llewellyn@wsu.edu.