Page 22 - WCA Ketch Pen August 2020

22
Early Weaning and Cow Performance
Another Look
By Don Llewellyn, Ph.D., State Livestock Special- ist, 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 pro- ducers 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 per- formance. 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 nor- mal weaned cows) was determined by ultrasound.
For the winter supplementation study, we started with 96
pregnant cows from the
same groups (i.e., ear-
ly weaned vs. normal
weaned) used in the sum-
mer 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 pas-
tures; 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 supple- mentation 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 supple- ment prorated to deliver the designated daily quantity. The HIGH groups were provided supplement to meet the nutrient require- ments 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 dif- ferences 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.
Ketch Pen www.washingtoncattlemen.org
Don Llewellyn
August 2020