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Thin cattle doesn't mean they won't reproduce.
April 5, 2023
Drought conditions this last growing season, limited hay supply, and a wet winter have been very challenging to beef producers. This created a situation where many cows at this point were thinner than normal years. In addition, we couple that with limited hay and lower-quality hay with the potential of having a late green up or delayed turn out to grass. With that in mind, we have to think about how to increase energy in the diet to meet the lactational requirements while gaining BCS and doing that past our traditional turn out to grass.
Body condition scoring (BCS) is an effective management tool to estimate the energy reserves of a cow. If monitored multiple times across the production year, BCS is a good indicator of direction of body weight change. Body condition score of beef cows at the time of calving has an impact on subsequent rebreeding performance; however, direction of body weight gain can be just as important (Table 1). Traditional recommendations suggest cows need to be nutritionally managed at a BCS 5 or greater at breeding for optimal reproductive performance. However, the response is not absolute; some cows are capable of rebreeding at BCS less than 5.
Although calving BCS can influence rebreeding and performance of cows, it doesn’t mean thin cows will always result in decreased reproductive performance. A large impact on reproduction is direction and magnitude of body weight change after calving and through breeding. Houghton et al. (1990) showed that thin cows gaining condition increased the probability of cows becoming pregnant; however, fleshy (fat) cows losing body condition improved pregnancy rate (Table 1). The effects of poor body condition (less than 4) can be overcome by improved nutrition. The goal is to shorten the period of weight loss by increased nutrient supply so that positive gain can be initiated, and the cows can start cycling.
Table 1. Effect of body condition score change on pregnancy rate
Fleshy (> 5) and increasing BCS
Fleshy (> 5) and decreasing BCS
Moderate (4.5 - 5.5) and maintaining
Adapted from Houghton et al. (1990)
Because of the nutritional demands of lactation, it can be difficult to get cows to gain body weight economically after calving. This is really due to nutrient requirements being the greatest up to approximately day 60 after calving, which also coincides with the start of breeding. A lactating cow at peak lactation has an energy demand of 15 – 16 lb of TDN per day depending on milk production level.
So, what do we do if we have thin cows? Additional energy will be required to restore their body condition to a moderate level. The problem with this management scheme is that nutrient demands at this time are high and the additional nutrition supplied may be used to increase milk production rather than body weight gain.
Related:Fertilizer at Half Price!
Controlling hay waste:
Controlling or minimizing feed waste is essential to stretching hay resources. With any feed or feeding method, we always have waste associated with it. Understanding how much waste is occurring is essential for meeting nutrient needs of livestock. Method and amount of hay being fed can have feed waste greater than 25%. Some studies have shown up to 39% hay waste by method of feeding hay. Hay waste is highly influenced by hay feeder design that is used to feed ad libitum amount to beef cows. Ring feeders with sheeted bottoms and basket feeders with sheeted bottoms generally have lower waste percentages of 5 to 10%.
If you are feeding hay through a processor or rolling bales out, it is important to only feed enough so that cows can eat all that they need for one day and not overfeeding. Overfeeding can lead to increased waste due to cows urinating and defecating on the excess hay.
One method to control waste is to control access to hay feeders. Segregating feeding area and only allowing cattle to access hay for 3 to 12 hours a day. Limit feeding or restricting access to hay can reduce intake and waste by ~20%. However, it is important to know hay quality and having adequate feeders/bales available so that cows have equal access to hay during the feeding times.
In situations where hay is being limit fed to stretch forage resources, grazing behavior and overall grazing intake may decrease due to cows waiting for hay to be delivered. If cows are already thin, this may cause an overall decrease in energy intake. Feeding the same quality of hay but done infrequently can help decrease the chance of cows waiting at the gate for hay to arrive.
Utilization of an ionophore for grazing livestock and livestock consuming hay can increase energy value of the overall diet and reduce the need for hay. Research has shown that hay intake can be reduced by approximately 10% with the addition of rumensin in the diet. In addition, studies have shown that rumensin improves body weight gain and BCS.
Feeding a starch-based supplement (i.e., corn) can substitute for hay intake. For instance, 3 lb of corn can decrease hay intake by 3 lbs. Starch-based energy supplements would have to be fed every day, and to minimize waste, it should be fed in a bunk. If corn or corn-based supplements are utilized, then protein supplementation would be needed to meet protein requirements. The impact of feeding corn on forage intake and digestibility has been shown to be dependent on the level of protein in the diet. In digestion studies, increasing energy in diets containing low levels of protein has decreased intake and digestibility of low-quality roughage; however, with greater levels of supplemental protein, increasing energy typically has little effect on intake or digestibility of low-quality roughage.
Other management considerations:
If possible, sort and manage cows by BCS groups (i.e., thin versus fleshy). This will allow you to be more strategic on providing high-quality feedstuffs to thin cows, while not over conditioning any fleshy cows.
Use reproductive technologies. Even if artificial insemination is not utilized, estrus synchronization can help increase the number of thin cows to cycle earlier in the breeding season. Refer to a past BeefWatch article to learn more about how to move cows up in the breeding season: https://beef.unl.edu/beefwatch/2021/managing-postpartum-anestrus-beef-cows-successful-breeding-season.
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