Beef cattle are the scavengers of the livestock business. They can turn high fiber forages and food by-product residuals into protein food at a very effective rate. For the cow herd there is seldom a period during the year when the cow cannot meet her nutritional needs with reasonable quality grass, hay, or stored forages. The exception for these nutritional needs is for the 60 days prior to calving and immediately after calving.
Why is there a challenge to the cow just prior to and after calving? There are three major reasons: the initiation of lactation, the return to a fertile reproductive state, and for the production of colostrum. Cow age will certainly have an impact on these factors, and younger cows have more critical nutritional needs.
There is considerable variation from genetics and breed type, but the average beef cow produces about 1 1/2 gallons of milk per day during a lactation. Approximately 60-75% of the total milk produced will be in the first 60 days after calving. Studies have shown there is a point of diminishing returns and additional milk production in beef cows is probably wasted because calves will not be able to efficiently utilize large quantities of milk. When we compare this result to the typical dairy cow that may produce 6-10 gallons of milk daily, the divergent nutritional needs are apparent. The dairy cow has a large outflow of protein, minerals, and water that must be replaced. The beef cow has very little loss of these nutrients from milk production. Data in Table 1. show an 1100-lb. cow eating 22 lbs. of grass hay with 11% crude protein will need to be a pretty exceptional milk producer to require additional protein in the diet. Except for small additions of protein for heavy-milking cows and young cows still growing, the key nutrient is energy. Most beef cows will be able to meet lactation needs with reasonable intake of grass, hay, and stored forages of good quality that will usually supply 1-1.2 Mcal/lb of metabolizable energy.
Table 1. Daily Nutrient Requirements of Beef Cows During Early Lactation
|Cow Weight||10 Lbs Milk|
|10 Lbs Milk|
|10 Lbs Milk|
|20 Lbs Milk|
|20 Lbs Milk|
|20 Lbs Milk|
There are reams of data to show that cows in poorer body condition at calving will have a longer postpartum interval, lower rebreeding rate, and a shorter life in the herd than cows in adequate condition. First-calf cows are the usual suspects for poor condition since they are adding growth to the stress of lactation and reproduction. Condition scores range from 1 through 9 with 1 being extremely thin to 9 being very obese. The optimum score at calving for most mature cows is 4-5 and for young cows is 5-6 (Morrison et al., 1999.) Studies show condition score at calving will have very little effect on calf birth weight, so it follows Nature is pushing the intake of nutrients to fetal growth at the expense of cow condition. When the nutritional plane is inadequate, problems occur. Results from an older-but still relevant-study in Table 2. show the results of reduced feed intake prior to calving and the subsequent loss of production from cows and calves.
Table 2a. Cow Return to Estrus and Calf Production For Adequate and Restricted 100-day Pre-Calving Feed Intake
|First-Calf Cows||100% of Requirements||67% of Requirements|
|Born alive (%)||97||90|
|Weaning wt. (lbs.)||350||324|
|40-day estrus return (%)||41||28|
|Heifer calf puberty (days)||318||337|
Table 2b. Cow Return to Estrus and Calf Production For Adequate and Restricted 100-day Pre-Calving Feed Intake
|Second-Calf Cows||100% of Requirements||50% of Requirements|
|Born alive (%)||100||90|
|Alive at weaning (%)||100||71|
|40-day estrus return (%)||48||38|
|Weaning wt. (lbs.)||320||294|
|Calf Scours rate (%)||33||50|
Corah et al., 1975.
If one calculates the economics of the above data with calf value at $1.00 per pound, it shows the restricted intake cost about $40.00 per cow (36% of calf weaning weight) in returns even with these very light weaning weights, and it does not include lost production from cows that did not rebreed.
Restricted feed intake right after calving will result in similar losses. Increased nutrient intake after calving stimulated secretion of anabolic hormones, promoted fat deposition, shortened the postpartum interval to estrus, and increased pregnancy rate at the first estrus in the study from Ciccioli et al. (2003) for cows fed to gain either 1 lb/day or 2 lbs./day for 71 days after calving.
Restricted pre-calving feed intake may also influence calf nursing behavior. Lardy and Stolenow (2001) have reported on Australian data which showed calves born to dams on a low plane of nutrition took significantly longer to nurse than calves born to dams on a maintenance or high plane of nutrition.
One of the factors often overlooked in the nutrition of beef cows is colostrum production. A Virginia Tech study (Hough et al., 1990) indicated immunoglobulin (IgG) concentration would not be changed in cows fed 100% or 57% of NRC pre-calving nutritional levels, but colostrum volumn and calf absorption of IgG would be lower from the restricted cows. A study in sheep from Swanson et al (2008) indicated improper nutrition from mid to late pregnancy in ewe lambs altered colostrum quality and quantity and reduced offspring birth weight. By association, results from Table 2 indicate calves born from dams with restricted pre-calving nutrition are more susceptible to disease from scours and have a higher mortality rate. Other studies have shown steers with restricted colostrum intake at birth had lower feedlot growth rates and lower carcass grades.
The restriction of feed intake and quality pre-calving will have significant impacts on many economically-important issues of beef production, and there will be life-long effects on calf performance.
Prepared by Dr. John Comerford. The following article originally appeared in Farming: The Journal of Northeast Agriculture.