We have a symbiotic relationship with grazing cattle, in which they convert cellulose and other inedible fibrous material into a wholesome protein product for human consumption. There are many types of production systems, cattle breeds and available resources across the domestic cow-calf sector, but the basic nutritional demands are somewhat standard across the board.
In layman’s terms, regardless of genetics or environment, there is seldom a time throughout the production year where the cow cannot meet her nutritional needs with acceptable quality grass or available forage. However, the last 60 days prior to calving and immediately after parturition, cattle nutritional demands increase dramatically (Table 1).
[inline_image file=”1ec770dd04a3df2b2744cc14b7e355fe.png” caption=”Table 1. Annual energy requirement of a spring-calving beef cow.Adapted from Harvey Freetly, BIF Proceedings 2009.”]
These changes in basal metabolic requirements are a direct result of rapid fetal growth, the cow preparing herself for the stress of calving, initiation of the lactation process and the return to a fertile state for the subsequent breeding season.
It’s clear that spring-calving herds are currently managing cows at the peak of their nutritional demands. Producers also have groups of first-timers that are still growing and haven’t reached their mature size and weight. Optimizing nutrition at this critical wintertime point is imperative for maximizing production efficiency. Are your females nutritionally prepared?
With many producers already in the heart of calving season and others with due dates approaching, what is actually happening biologically to the females at this stage? If she is a heifer, a good portion of her nutrition is being partitioned toward growth.
However, all females are directing a large portion of their dietary nutrition toward fetal growth and preparation of parturition. During the first and second trimesters, fetal life functions such as vital organs and skeletal-muscular systems are developed. The third trimester results in nearly 75 percent of the fetal growth during the entire pregnancy and prepares the calf for extrauterine life.
If you bred your cow or heifer on time, she’s currently in the third trimester or has recently calved, so it’s important to know that the energy/protein demand for her calf should be accounted for. Additionally, the cow needs a bioavailable vitamin A and E supply, along with trace minerals such as copper, zinc and selenium to support a healthy, vigorous calf.
Some producers are reluctant to supplement their cows at this time, fearing the dogma of increased birth weights and subsequent dystocia. No doubt, calf birth weight is influenced by the maternal plane of nutrition, and a summary of research by Bellows (1993) indicates this trend (Table 2).
[inline_image file=”3df90193d938788b3ba70eddaba960c3.jpg” caption=”Table 2. Effect of low or high gestation feeding level on calving and subsequent reproduction. Adapted from Bellows, USDA-Agricultural Research Service, Miles City, MT. Range Beef Cow Symposium XIII, 1993, pp. 175-189.”]
However, this increase in birth weight does not necessarily correlate to more incidence of dystocia. It’s important to remember that birth weight is only one component of calving ease. Outside of abnormal presentations (i.e., breech), the cow’s energy status and glycogenic reserves are critical for her to physically push that calf through the birth canal. We’ve all given assistance (especially to a heifer) at calving time, and it’s exhausting on us. Think about the energy just spent by the cow!
In fact, calves that are born from mothers on a high pre-calving plane of nutrition were up and nursing their dams faster than those born from dams with a low plane of pre-calving nutrition. Bottom line, thin cows with no energy stores may in fact have a tougher time calving, regardless of calf size.
Speaking of nursing, lactation is the final step in this whole transition process, and it’s an important one. Nutritional requirements continue to rise for nearly 60 days postpartum, where nearly two-thirds of the total milk will be produced by the dam. Energy, protein, vitamins and minerals are vital for quality milk and early calf performance.
If nutritional demands for lactation cannot be met, the cow will start to mobilize her own body reserves to support lactation, resulting in loss of body condition score, metabolic disorder and immune system depression. Since we don’t really know the milking potential of each cow until she’s in production, it’s important to pay attention to cows that appear to be sick or losing weight because females who are losing weight during the breeding season have decreased conception rates.
This concept comes full circle because we need a cow to calve unassisted, wean off a heavy calf and breed back on time to maintain an economically viable production cycle. Don’t overfeed your females, but understand now is not the time to cut corners on your cow herd nutrition. — Chris Cassady, BioZyme Inc.
