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J. Anim. Sci. 2002. 80:2031-2035
© 2002 American Society of Animal Science

Weight necessary to change body condition scores in Angus cows1

C. J. Tennant*, J. C. Spitzer*,2, W. C. Bridges, Jr.{dagger} and J. H. Hampton*

* Animal and Veterinary Sciences Department, Clemson University, and and {dagger} Experimental Statistics, Clemson, SC 29634

2 Correspondence:
128 Poole Agricultural Center, Clemson 29634-0361 (phone: 864-656-5164; fax: 864-656-1033; E-mail:
jsptzr{at}clemson.edu).


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Weights and body condition scores (BCS) were measured and assessed on Angus females (n = 367) over 14 yr (1981 to 1994) to allow calculation of weight adjustments for different BCS. Data were collected at five time periods: prepartum, postpartum, prebreeding, postbreeding, and midgestation. Individual cows with multiple records were included in the analysis as repeated measures to yield 3,912 total observations. Body condition score was assigned on a scale of 1 = emaciated to 9 = obese. Only BCS 2 through 8 were analyzed, as there were zero recorded observations of BCS 1 or 9. The final model included age and the time period by BCS interaction as fixed effects. Year by animal within age interaction and a residual error term were treated as random effects. Animal was included to correct for repeated measures across time periods and years for individual animals. All these effects were significant (P < 0.0001). Weight adjustments for BCS were calculated for each time period. Cow weight and weight adjustments for BCS were not consistent for each time period. Overall weight adjustments to adjust cows to BCS of 5 were (kg ± SEM) BCS = 2 (68 ± 12), BCS = 3 (50 ± 4), BCS = 4 (21 ± 1), BCS = 5 (0), BCS = 6(-24 ± 2), BCS = 7(-51 ± 3), and BCS = 8 (-73 ± 7).

Key Words: Beef Cows • Body Condition • Weight


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Total body energy reserves (or body condition) have been shown to influence reproduction, milking ability, and maintenance in multiparous cows (Klosterman et al., 1968; Arnett et al., 1971; Morrison et al., 1999). Even more important may be the influence of adequate body condition on reproduction in primiparous cows (Bellows and Short, 1978; Spitzer et al., 1995; Lalman et al., 1997).

Various methods to determine body composition have been evaluated including: weight to height ratios, visually assigned condition scores, condition scores assigned by palpation, ultrasound, live weight, and heart girth (Thompson et al., 1983; Wright and Russel, 1984; Nelson et al., 1985). Assessment of a condition score has proven superior to linear measurements as a predictor of carcass energy and fat reserves (Thompson et al., 1983; Wagner et al., 1988; Houghton et al., 1990). From two data sets, Nelson et al. (1985) reported visually assigned condition scores correlated 0.71 and 0.78 with condition scores assigned by palpation. By assessing body condition score (BCS), producers can allocate cattle into nutritional feed groups to reach a desired body condition (Thompson et al., 1983). However, adjustments for BW to change BCS are corrective measures needed by producers and researchers alike as a practical tool to estimate BW changes required to obtain a desired BCS. Lalman et al. (1997) reported, on a 1-to-9 BCS scale, that each unit of BCS change required an approximate 33-kg BW change. Northcutt et al. (1992) calculated individual weight adjustments for BCS derived from condition scores and weights of Angus cows taken at or near the time of weaning.

The objective of this study was to evaluate BW adjustments for BCS in Angus cows derived from BCS and weights taken at multiple times throughout a production year, and to determine if these adjustments vary with different stages of production.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results and Discussion
 Implications
 Literature Cited
 
Over 14 yr (1981 to 1994), data on 367 winter calving Angus cows from the Clemson University Beef Physiology Herd was utilized for this study. These cows were involved in a variety of projects where body condition score was manipulated to study reproductive performance. Cow BW and BCS were recorded simultaneously at the following time periods: prepartum, and postpartum (January to March), prebreeding (April), postbreeding (June), and midgestation (October). Cows were gathered off pasture to be weighed in early morning prior to feeding (depending upon feeding and pasture conditions throughout the year). Cows were neither restricted from feed or water prior to recording BW. Cow age was ranked as 2, 3, 4, 5, 6, 7 through 10, and 11 yr or older. Body condition scores were assessed on a scale ranging from 1 = severely emaciated to 9 = very obese (Whitman, 1975; Richards et al., 1986; Spitzer, 1986) and were determined by palpation. Total observations over time contained individual cows with multiple records. These animals were included in the analysis as repeated measures to yield a total of 3,912 observations used in the analysis.

A model was developed for cow BW that included main effects and interaction terms for age, time period, year, BCS, and animal. Age, BCS, and time period were considered fixed effects. Year, animal, and a residual error term were considered random effects. Including the animal term allowed for correction of repeated measures across time periods and years. A mixed model analysis of variance (ANOVA) was used to test for significance of the different terms in the model. The final model included the following terms: time period by BCS interaction, age, and year by animal within age interaction, all of which were significant (P < 0.0001). Least squares means (LSM) of cow BW for BCS, time period, and age were calculated using the final model. Weight adjustments were created to change BW at BCS = 2, 3, 4, 6, 7, 8 and to estimate BW for BCS = 5. Linear contrasts of time period by BCS interaction were defined to calculate BW adjustments for BCS, where each BCS LSM for BW was compared to LSM for BW at BCS = 5. Weights were adjusted to a BCS = 5. Adjustments were calculated separately for the five periods because of the interaction of time period by BCS. All calculations were performed using the MIXED procedure of SAS (SAS Inst. Inc., Cary, NC).


   Results and Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
Implications
 Literature Cited
 
Throughout the duration of the study, observations of a BCS 1 or 9 did not occur. Additionally, occurrences of BCS 2 and 8 were limited (Table 1Go). Mean cow BW (± SEM) for the present study of 502 ± 2.3 kg (Table 2Go) is lower than the mean cow BW of 548 kg reported previously in Angus cows by Northcutt et al. (1992). A mean BCS (± SEM) of 5.0 ± 0.01 is also slightly lower than the mean BCS of 5.6 reported by Northcutt et al. (1992). Lower mean cow BW and BCS reported in the current study could be a result of observations being collected at various stages of production, while all observations by Northcutt et al. (1992) were taken at or near the time of weaning.


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  		Table 1. Number of observations recorded for each body condition score (BCS) for each time perioda throughout the production year
 

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  		Table 2. Least square means (LSM) and standard error (SEM) for weight by cow age and number of observations (n) recorded for each age
 
Weight plateaued as animals reached maturity near 6 yr of age (Table 2Go). Northcutt et al. (1992) found similar results for Angus cows reaching their mature BW by 6 yr of age. In studying cows reared on extremely high nutrition, Arnett et al. (1971) reported that BW tended to increase until approximately 4 yr of age. However, Klosterman (1972) stated that, due to the effect of condition on BW, weight alone was not a good measure of the mature size of the animal.

The current study revealed cow BW was influenced by BCS (P < 0.0001). Previous research has reported condition score highly correlated with BW (Thompson et al., 1983; Buskirk et al., 1992; Lalman et al., 1997), explaining the direct relationship of BW and BCS found in the current study. Least squares means and standard errors for BW at each time period and each BCS are displayed in Table 3Go. Weight was highest at the prepartum period, and lowest during the period immediately following parturition until breeding. This period of decreased BW during the postpartum period was expected due to the loss of BW associated with parturition in addition to the nutritional stress associated with early lactation. The subsequent BW gain realized from the post-breeding period up until parturition was also expected. This time period corresponds to the season in the production year when animals are usually on lush pasture in South Carolina and experience a dry period, free from lactation, between weaning and parturition.


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  		Table 3. Least square means (LSM) and standard errors (SEM) for cow weight (kg) of each body condition score (BCS) for each time perioda throughout the production year
 
Weight adjustments for BCS (± SEM) at the five time periods are given in Table 4Go. Weights were adjusted to a BCS of 5 because the mean condition score in the current study was 5.0, and the mean BCS in the 1 to 9 system is 5. In addition, previous research has indicated a BCS = 5 at parturition adequate for reproduction in mature cows (Richards et al., 1986; Morrison et al., 1999). Large standard errors observed for the adjustments of condition scores 2 and 8 are a reflection of the limited number of observations recorded for these condition scores.


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  		Table 4. Weight needed (kg ± SEM) to adjust body condition scores (BCS) to a body condition score 5 for each time perioda throughout the production year
 
Adjustments varied among time periods of the production year. These results infer BW adjustments to shift BCS may change with differences in cow BW. The latest NRC (1996) stated that BW at which cattle reach the same chemical composition differs depending on mature size. Therefore, cows with lower BW would not be expected to require as much BW change to achieve a specified change in BCS compared to cows with a higher BW.

Northcutt et al. (1992) in Angus cows, reported BW adjustments (adjusted to a condition score 6) of 116, 91, 69, 39, 0, -40, and -86 kg for condition scores 2, 3, 4, 5, 6, 7, and 8 respectively. When adjustments reported by Northcutt et al. (1992) are converted to a condition score 5 rather than 6, adjustments for BW are 77, 52, 30, 0, -39, -79, and -125 kg for condition scores of 2, 3, 4, 5, 6, 7, and 8 respectively. Weight adjustments for BCS recorded in the current study at mid-gestation (the time period most closely corresponding to weaning) are consistently lower than adjustments reported by Northcutt et al. (1992). Although results from the current study and Northcutt et al. (1992) were all determined from records derived from Angus cows, our lower adjustments may be indicative of lower mean cow BW. These results again suggest BW adjustments for changing BCS vary with differences in cow BW. The NRC (1996) predicted standard BW to be 76.5, 81.3, 86.7, 92.9, 108.3, 118.1, 129.9, and 144.3 percent of a BCS 5 cow for BCS 1, 2, 3, 4, 6, 7, 8, and 9 respectively.

Weight adjustments for BCS in the current study reveal adjustments are not consistent when changing BW from one condition score to the next. This concurs with Northcutt et al. (1992) and Wagner et al. (1988) who reported BW adjustments for BCS that were not proportional from one BCS to the next. Wagner et al. (1988) reported the equation LW = 368.59 - 33.05(CS) + 7.11(CS2) for prediction of live weight (LW) from body condition score (CS). Weight adjustments that are not proportional when changing BW from one BCS to the next suggest that other changes in body composition exist when changing BCS besides changes in body energy reserves. Not only fat depletion, but also muscle depletion has been reported in cows fed a low plane of nutrition and reaching the lower BCS (Houghton et al., 1990; Perry et al., 1991). Wagner (1984) reported changes in condition for thinner cows might reflect less BW changes than do condition changes for fatter cows. The NRC (1996) states that when energy does not limit growth the empty body contains an increasingly smaller percent of body protein and an increasingly larger percent of fat, and the empty body reaches chemical maturity when additional BW increase contains little additional protein.

The current study was conducted utilizing both individual cow changes in BW and BCS, in addition to BW and BCS differences among cows. Northcutt et al. (1992) and Wagner et al. (1988) conducted their studies only using the relationship of BW and BCS differences among cows. Other previous research has also utilized this approach. However, in contrast to Northcutt et al. (1992) and Wagner et al. (1988), the NRC (1996) and Ferrell and Jenkins (1996) suggested and reported BW adjustments for BCS calculated from linear regression equations. The NRC (1996) assumed an approximate 44 kg of BW change associated with each unit of BCS for mature cows of diverse breed types. In agreement, Ferrell and Jenkins (1996) in mature cows of diverse breed types found a linear relationship between cow empty BW and BCS. They reported a 51-kg BW change associated with each unit BCS change on a 1 to 9 scale. Rather than using linear regression, the present study used linear contrasts to determine weight adjustments for BCS.

Lalman et al. (1997), Buskirk et al. (1992), and Houghton et al. (1990) also used linear regression to calculate BW changes associated with changes in BCS. However, these studies only used individual cow changes in BW and condition. Lalman et al. (1997) in Angus and Angus-sired crossbred heifers, reported cow BW change accounted for 72% of the variation in BCS change, and each unit of BCS change was associated with a 33-kg change in cow BW. Using a 1 to 5 BCS scale Buskirk et al. (1992) reported each unit BCS change was associated with a 68-kg change in cow BW for mature Angus cows. This converts to approximately a 40-kg BW change in the 1 to 9 BCS system. Houghton et al. (1990) in mature Charolais x Angus cows reported empty BW increased 56 to 99 kg (avg. = 75) per unit BCS increase using a 1 to 5 BCS system. Houghton et al. (1990) also suggested BCS 1, 3, and 5 on a 5-point system would be similar to BCS 2, 5, and 8 respectively on a 9-point system.

The BW adjustment for BCS 8 at the post-breeding time period (Table 4Go) does not coincide with adjustments of the same time period or other adjustments at BCS 8. This discrepancy is not understood. However, the low number of observations recorded for BCS 8 at the post-breeding time period should be considered.


   Implications
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
Literature Cited
 
Throughout the production cycle of the beef cow, adequate body condition is essential in ensuring optimal overall productivity and reproductive performance. Inadequate nutrition is most often the cause of poor reproductive efficiency in beef cows. Assessment of body condition can inform a producer of the effectiveness of the current feeding program. Therefore, weight adjustments for changing body condition scores are a helpful management tool to producers and researchers. Results from the current study were calculated using linear contrasts rather than linear regression and suggest weight adjustments for changing body condition scores are not proportional across the condition scores. In addition, weight adjustments for changing body condition scores are not consistent throughout all times of a production year. This realization appears to be highly weight dependent as weight of the cow is not constant year round.


   Footnotes
 
1 Technical Contribution No. 4743 of the South Carolina Agricultural Experiment Station, Clemson University. Acknowledgments: the authors would like to thank Cherylene Amidon and Sultana Alam for their help with data entry. Back

Received for publication December 17, 2001. Accepted for publication March 22, 2002.


   Literature Cited
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 


Arnett, D. W., G. L. Holland, and R. Totusek. 1971. Some effects of obesity in beef females. J. Anim. Sci. 33:1129–1136.[Abstract/Free Full Text]

Bellows, R. A., and R. E. Short. 1978. Effects of precalving feed level on birth weight, calving difficulty and subsequent fertility. J. Anim. Sci. 46:1522–1528.[Abstract/Free Full Text]

Buskirk, D. D., R. P. Lemenager, and L. A. Horstman. 1992. Estimation of net energy requirements (NEm and NE{delta}) of lactating beef cows. J. Anim. Sci. 70:3867–3876.[Abstract]

Ferrell, C. L., and T. G. Jenkins. 1996. Relationships between body condition score and empty body weight, water, fat, protein, and energy percentages in mature beef cows of diverse breeds. J. Anim. Sci. 74(Suppl. 1): 245 (Abstr.).[Abstract]

Houghton, P. L., R. P. Lemenager, G. E. Moss, and K. S. Hendrix. 1990. Prediction of postpartum beef cow body composition using weight to height ratio and visual body condition score. J. Anim. Sci. 68:1428–1437.

Klosterman, E. W. 1972. Beef cattle size for maximum efficiency. J. Anim. Sci. 34:875–880.[Abstract/Free Full Text]

Klosterman, E. W., L. G. Sanford, and C. F. Parker. 1968. Effect of cow size and condition and ration protein content upon maintenance requirements of mature beef cows. J. Anim. Sci. 27:242–246.[Abstract/Free Full Text]

Lalman, D. L., D. H. Keisler, J. E. Williams, E. J. Scholljegerdes, and D. M. Mallett. 1997. Influence of postpartum weight and body condition change on duration of anestrus by undernourished suckled beef heifers. J. Anim. Sci. 75:2003–2008.[Abstract/Free Full Text]

Morrison, D. G., J. C. Spitzer, and J. L. Perkins. 1999. Influence of prepartum body condition score change on reproduction in multiparous beef cows calving in moderate body condition. J. Anim Sci. 77:1048–1054.[Abstract/Free Full Text]

Nelson, T. C., R. E. Short, W. L. Reynolds, and J. J. Urick. 1985. Palpated and visually assigned condition scores compared with weight, height and heart girth in Hereford and crossbred cows. J. Anim. Sci. 60:363–368.[Abstract/Free Full Text]

Northcutt, S. L., D. E. Wilson, and R. L. Willham. 1992. Adjusting weight for body condition score in Angus cows. J. Anim. Sci. 70:1342–1345.[Abstract]

NRC. 1996. Nutrient Requirements of Beef Cattle. 7th ed. National Acadamy Press, Washington, DC.

Perry, R. C., L. R. Corah, R. C. Cochran, W. E. Beal, J. S. Stevenson, J. E. Minton, D. D. Simms, and J. R. Brethour. 1991. Influence of dietary energy on follicular development, serum gonadotropins, and first postpartum ovulation in suckled beef cows. J. Anim. Sci. 69:3762–3773.[Abstract]

Richards, M. W., J. C. Spitzer, and M. B. Warner. 1986. Effect of varying levels of postpartum nutrition and body condition at calving on subsequent reproductive performance in beef cattle. J. Anim. Sci. 62:300–306.[Abstract/Free Full Text]

Spitzer, J. C. 1986. Influences of nutrition on reproduction in beef cattle. In: D. A. Morrow (ed.) Current Therapy in Theriogenology. 2nd ed. W. B. Saunders Co., Philadelphia.

Spitzer, J. C., D. G. Morrison, R. P. Wettemann, and L. C. Faulkner. 1995. Reproductive responses and calf birth and weaning weights as affected by body condition at parturition and postpartum weight gain in primiparous beef cows. J. Anim. Sci. 73:1251–1257.[Abstract]

Thompson, W. R., D. H. Theuninck, J. C. Meiske, R. D. Goodrich, J. R. Rust, and F. M. Byers. 1983. Linear measurements and visual appraisal as estimators of percentage empty body fat of beef cows. J. Anim. Sci. 56:755–760.[Abstract/Free Full Text]

Wagner, J. J. 1984. Carcass composition in mature Hereford cows: Estimation and influence on metabolizable energy requirements for maintenance during winter. Ph.D. dissertation, Oklahoma State Univ., Stillwater.

Wagner, J. J., K. S. Lusby, J. W. Oltjen, J. Rakestraw, R. P. Wettemann, and L. E. Walters. 1988. Carcass composition in mature Hereford cows: Estimation and effect on daily metabolizable energy requirement during winter. J. Anim. Sci. 66:603–612.[Abstract/Free Full Text]

Whitman, R. W. 1975. Weight change, body condition and beef cow reproduction. Ph.D. dissertation, Colorado State Univ., Fort Collins.

Wright, V. A., and A. J. Russel. 1984. Estimation in vivo of the chemical composition of the bodies of mature cows. Anim. Prod. 38:33–43.


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