Condition Score - An Aid To Management
Frank Buckley, Pat Dillon, John Mee and John Murphy
Dairy Production Research Centre, Teagasc, Moorepark,
Introduction
The continuing increase in genetic merit for milk production has resulted in dairy cows that are under increasing nutritional stress, especially in early lactation. Figure 1 shows the increase in genetic merit (PD00) for milk production of milk recorded cows in Ireland (ICBF, 1999). It is likely that this trend will continue. Cows nowadays therefore, are larger and of higher genetic merit than in the 1980's. With selection on milk yield only, the correlated increase in feed intake is not large enough to cover the increase in nutrient requirement (Gravert 1985, Van Arendonk et al., 1991). This implies that selection on milk yield only is expected to increase the mobilisation of body reserves in early lactation. Even though a negative energy balance is normal in early lactation for all mammals (Robirson, 1986), the magnitude and duration of it are related to reduced health and fertility (Butler and Smith, 1989: Domecq et al 1997; Senatore et al., 1996; Villa-Goodoy et al., 1988).
Figure 1: Change in Predicted Difference (00) for milk yield in milk recorded herds in Ireland, 1988-1997. Source: (Irish Cattle Breeding Statistics, 1999)
Recent research on the influence of body condition score at calving on subsequent milk production, conducted mainly in the UK with high dry matter, high concentrate diets, offered indoors (Garnsworthy, 1988) suggests considerably less advantage in cow performance from improvements in body condition score. However with forage based diets, there is likely to be a greater advantage to cows calving in good condition (3-3.5). Cowen (1982) reported that milk production responses to feeding before calving (i.e. higher condition score) were greatest when animals were restricted in intake after calving, because of low feed availability and/or feed of low energy content. The introduction of milk quotas in the European Union in 1984 has led to a greater dependence on grazed pasture as a major source of energy yielding substrates for dairy cows in Ireland. The purpose of this paper is to issue guidelines for the high yielding Holstein-Friesian dairy cow on a pasture-based seasonal calving system of milk production.
Assessment of body fatness
A difficulty until recently has been the absence of a simple measure of the energy reserves or condition score of the cow. Live weight alone is not a good indicator of body reserves since a cow could be large and thin or small and fat. Live weight is rarely measured on commercial dairy farms; it is subject to variation due to gut fill and it usually increases before calving, due to the development of the foetus and associated uterine tissues, independently of changes in energy reserves.
Appraisal of cows through a combination of handling and visual assessment allows the subjective distinction between thin and fat cows to be made regardless of frame size. There are many condition scoring systems. The method of condition scoring used at Moorepark is that of Lowman et al. (1975), which runs from 1 to 5 (Table 1). Condition scores are allocated based on the amount of flesh covering the skeleton at the following key reference points.
- Backbone - in the area between the last rib and the hip bone.
- Loin - along the transverse processes of the short ribs.
- Tail head and pin bones.
- Ribs
- Hip bone.
Accurate condition scoring depends on handling the animal in the areas outlined. Visual scoring is not recommended unless the operator has considerable previous experience at condition scoring by touch.
Experienced assessors can differentiate between 0.25 of a condition score. In general, scores less than 2.00 and greater than 4.00, are rarely found in commercial dairy herds.
Table 1. Condition scores as defined on a scale of 1 to 5.
| Condition score | Assessment |
|---|---|
| 1 | Very thin |
| 2 | Poor |
| 3 | Good |
| 4 | Very good |
| 5 | Very fat |
Figure 2 shows a diagrammatic representation of various condition scores. A photographic representation of four key condition scores that can be used as management benchmarks are shown in Figure 3. One unit of condition score is equivalent to about 50 kg.
Condition score 2.0
As presented in Figure 3, cows in a condition score of 2.0 are in poor condition. The backbone is prominent and the individual short ribs can be seen easily and feel reasonably sharp when the hand is rubbed over them. The ribs are very obvious and feel hard as the hand is rubbed over them. The area between the pin bones and the tail head is very depressed and feels quite sharp.
Condition score 2.5
With a condition score of 2.5the backbone and the tips of the short ribs are still obvious to the eye but have increased cover, and are more rounded/smooth to touch when the hand is rubbed over then. The ribs again can be seen quite easily but offer a little suppleness as the hand runs over them. The pin bones too are still very obvious and the area between them and the tail head is still quite depressed.
Condition score 2.75
A condition score of 2.75 (not shown) could be described as lean but fit. The short ribs are less obvious to the eye and require slight pressure to identify them individually. Although the ribs can be felt quite easily with slight pressure they are much flatter and smoother. The pin bones have obvious cover and are smoother to feel but the depression between them and the tail head is still present.
Condition score 3.0
A cow at a condition score of 3.0, although still quite lean, is very supple to touch. There is a distinct cover (smoothness) over all of the main reference points. The depression between the tail head and the pins although still in existence is much fuller.
Condition score 3.25
At 3.25 (not shown) there is a substantial cover over the loin area and the short ribs are not easily felt. The area between the pin bones and the tail head is quite full but firm when handled. There is a good cover over the ribs.
Condition score 3.5
At 3.5 there is a substantial cover over the loin area and the short ribs are not easily felt. The area between the pin bones and the tail head is full and there is obvious deposition of fat under the skin at this point. The area between the hip bone and the pins is well fleshed. The ribs are well covered and again these cannot easily be felt individually. Note, however, that the cover at this score is still quite firm and not very "fatty" when felt.
Condition score 4.0
When a cow reaches a score of 4.0 (not shown) she is fat, and when your hand is rubbed over the reference points the fat under the skin is obviously present. The are over the ribs and around the tail head feel particularly "jelly like" at this score.
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Figure 2. Diagrammatic representation of condition scores
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Figure 3. Photographic representation of cows at condition scores of 2.0, 2.5, 3.0 and 3.5 respectively.
Photos of cows kindly supplied by Irish Farmers Journal.
Effect of condition score on milk yield, milk composition and feed efficiency.
Information on the influence of body condition score at calving on subsequent milk production of grazing dairy cows is scarce. Hutton and Parker (1973), Rogers et al. (1979) and Grainger et al. (1982) showed clear benefits for milk production of having cows in better condition at calving, unlike Thompson et al. (1997) and Stockdale (2000) who showed no advantage. Two recent experiments carried out at Moorepark show the benefits of improved body condition score at calving on milk production in early lactation. McNamara et al. (2001) observed daily yields of 24.1, 26.2 and 28.2 kg/day during the first 8 weeks of lactation, from cows calving at condition scores of 2.60, 2.76 and 2.88 respectively (Table 2). Yields of fat and protein as well as milk fat content, were increased with no effect on milk protein content. A similar study carried out by Ryan et al. (2001) also showed the effect of improved condition score at calving on subsequent production performance. Increasing body condition score pre-calving from 2.73 to 3.00 resulted in significantly higher daily milk yield (24.2 v. 25.5 kg) during the first 4 weeks of lactation. As in the previous study, yield of milk protein was also significantly increased and yield of milk fat was increased (close to significance) during this period but there was no significant effect of increased condition score on milk composition, although fat content was numerically higher.
Table 2. Effect of pre-calving condition score on production performance over the first 8 weeks of lactation (McNamara et al. 2001).
| Significance | ||||
|---|---|---|---|---|
| Pre-calving condition score | 2.60a | 2.76ab | 2.88b | * |
| Milk Yield (kg) | 24.1a | 26.2b | 28.2c | *** |
| Fat Yield (kg) | 0.93 a | 1.06 b | 1.17 c | *** |
| Protein Yield (kg) | 0.74 a | 0.80 b | 0.87 c | *** |
| Fat content (g/kg) | 38.6a | 40.3ab | 41.5b | * |
| Protein content (g/kg) | 31.6 | 31.5 | 32.3 | NS |
Means within rows not sharing a common superscript are significantly different (P<0.05)
These results suggest that milk yield in early lactation can be increased by increasing condition score at calving up to at least 3.00. These responses in milk production to increased condition score are greater than those obtained by Garnsworthy and Topps (1982) but similar to that obtained by Frood and Croxton (1978). The general tendency for cows with a higher condition score at calving to produce milk with a higher fat content but similar protein content is in agreement with previously published results (Stockdale, 2000).
Having cows calving at a condition score of 3-3.5 and allowing them to loose condition score in early lactation and increase again in late lactation is biologically inefficient. Whether the differences in biological efficiencies can be translated into differences in economical efficiencies will depend on the relative costs of the feed used to increase condition score before calving and for milk production in early lactation. It is generally accepted that it may only be economically more efficient to have cows at a higher condition score at calving (3-3.5) when the extra condition was produced from well managed grassland or grass silage.
Reproductive performance
A 365-day calving interval is one of the key factors in achieving efficient milk production from pasture in Ireland. The most likely nutritional factor to influence reproductive performance is energy balance in early lactation, particularly at the time of first service (Butler and Smith, 1989). Garnsworthy and Topps (1982), Treacher et al. (1986), Garnsworthy and Jones (1987), and Jones and Garnsworthy (1988) reported that there was no significant relationship between condition score at calving and subsequent reproductive performance on indoor high concentrate feeding systems. In contrast, Grainger et al (1982) found that improvements in condition score reduced the anoestrus interval after calving by 5.7 days for each additional condition score at calving. Grummer (1997) showed that the rate of condition score loss after calving may be more influential on reproductive performance than the actual condition score at calving. Cows with greater condition score loss in early lactation had greater days to first insemination and lower first service and all service conception rates.
Data collected from commercial dairy farms in 1999 (Farm Fertility Study) indicate the importance of condition score as a management tool in relation to achieving good reproductive performance. Table 3 summarises the main condition score variables associated with differences in submission rate during the first three weeks of the breeding season, pregnancy rate to first service and pregnancy rate after 42 days (6 weeks) of the breeding season, respectively. The data illustrate clearly the necessity to maintain body condition score at or above the target score of 2.75 during the breeding season. Condition score loss between calving and breeding should be minimised to less than 0.5 units if a negative effect on reproductive performance is to be avoided. Equally important, is the observation in the study by McNamara et al. (2001), that cows should not calve down at excessively high condition scores (4.00). These cows will tend to lose greater than the recommended condition loss of 0.5 units.
Table 3. Condition score (CS) variables associated with differences in submission rate (Sub3wk), pregnancy rate to first service (Preg 1) and pregnancy rate after 42 days (Preg 42).
| CS variable | Category | Sub3wk | Preg 1 | Preg 42 |
|---|---|---|---|---|
| CS at 1stservice | ≤2.5 | 58 | - | 50 |
| 2.75 | 72 | - | 57 | |
| ≥3.00 | 73 | - | 66 | |
| Lowest CS recorded | ≤2.5 | - | 45 | - |
| 2.75-3.00 | - | 52 | - | |
| >3.00 | - | 50 | - | |
| CS loss calving - 1stservice | ≤ 0.25 | 95 | - | 67 |
| >0.25 to 0.50 | 72 | - | 59 | |
| > 0.50 | 41 | - | 47 |
Condition Score Targets and Guidelines
(a) Dry period to calving
At the end of lactation the recommended average condition score of the herd should be 2.75 or greater. An equally important consideration is the spread in condition score in the herd. Cows that are below this target condition score should be identified and corrective action taken to increase the body reserves of these cows over the dry period. As indicated above cows calving down in low body condition (less than 3.0) will have reduced milk production in the subsequent lactation. The target condition score at calving (3.25-3.5) can be manipulated by the level of feeding in late lactation, the silage quality during the dry period and the length of the dry period. Table 4 offers guidelines with respect to varying the length of the dry period, for first lactation or mature cows, depending on the body condition score at the end of lactation. The condition score of cows at the end of their first lactation is generally less than for mature cows. If milk quota is not limiting then condition score can be increased in late lactation with a higher level of supplementation rather than lengthening the dry period required.
Table 4. Length of dry period (weeks) for cows of varying condition scores at drying off
| Condition score at drying off | 2.0 | 2.5 | 3.0 | 3.5 |
| First lactation | 14 | 12 | 10 | 8 |
| Second lactation | 12 | 10 | 8 | 6 |
Research at Moorepark would suggest that cows should calve at a condition score of 3.25 to 3.50. Table 5 provides guidelines for dry cow feeding management over a standard 8 to 10 week dry period, based on condition score in late lactation, and the quality of silage available. The level of concentrate supplementation required by cows in low body condition score will be influenced by the silage quality. In the last eight weeks of pregnancy, cow live weight increases by almost 0.6 kg per day due to the growth of the foetus and associated tissues alone. Therefore, a daily weight gain of 1 kg for an 8-week dry period is equivalent to about 0.4 kg in actual body weight and will result in an increase of about 0.5 units in condition score.
Table 5. Guidelines for feeding during the dry period based on condition score in late lactation and silage quality.
| Condition score in late lactation | ||||
|---|---|---|---|---|
| Silage DMD % | <2.5 | 2.5 | 2.75 | 3.0+ |
| >72 | S + 1 kg Conc. | S | SR | SR |
| 68-72 | S + 2 kg Conc. | S + 1 kg Conc. | S | SR |
| <68 | S + 3 kg Conc. | S + 2 kg Conc. | S + 1 kg Conc. | S |
S = Silage ad libitum, SR = Silage restriced
Research at Moorepark investigating the effect of genetic merit on the performance of spring-calving Holstein-Friesian cows (Buckley et al. 2000) has shown that high merit cows tend to have lower condition score at the end of lactation (Table 6). This is due to the fact that the high producing cows have a greater tendency to mobilise body reserves in early lactation and to partition a greater proportion of energy to milk production rather than body tissue restoration in late lactation. However, in the same study it was observed that with high quality grass silage offered ad libitum during the dry period, higher live weight/condition score gain were achieved with the high genetic merit cows (+1.27kg/day) compared to the medium genetic merit cows (+1.01kg/day).
Table 6. Effect of genetic merit on condition score at the end of first lactation and 305-day milk production performance.
| *HM | MM | |
|---|---|---|
| Condition score (end of lactation) | 2.52 | 2.97 |
| Milk Yield (kg) | 6,441 | 5,496 |
| Fat Yield (kg) | 241 | 222 |
| Protein Yield (kg) | 222 | 193 |
*HM = High genetic merit; MM = medium genetic merit
(b) Calving to AI
Early lactation (0-12 weeks after calving) is a critical period with regard to the nutrition of the dairy cow. Peak yield occurs around week 6-8 of lactation while peak intake does not occur until week 8 or later. The focus in early lactation should be to minimise condition score loss. A loss of approximately 0.50 of a unit of condition score between calving and first insemination is considered acceptable and will have no detrimental effect on reproductive performance. Table 7 shows the recommended concentrate feeding levels for a herd yielding up to 6,000 kg (1300 gals) per lactation with and EBI(00) of 0 to 10 when grass silage is the forage source. Early lactation concentrate supplementation should be increased by 2 to 3 kg per day with higher yielding cows (6,550 to 8,000 kg).
Table 7. Recommended levels of concentrate supplementation with silage of varying quality (DMD %) for herds yielding up to 6,000 kg per lactation.
| Silage DMD (%) | Supplement (kg/cow/day) |
|---|---|
| 75 | 6 |
| 70 | 7 |
| 65 | 8 |
| 60 | 9 |
Grazed grass, however, should become part of the diet of the spring calving cow in early lactation, where feasible. Table 8 highlights the benefit of early grass in the diet of the high genetic merit spring-calving cow. A daily intake of 6 to 8 kg of grass DM in early lactation has a concentrate sparing effect of 3 to 4 kg of concentrates and has major benefits with regard to production and live weight and condition score loss.
Table 8. The effect of early turnout to pasture on production performance, level of concentrate supplementation and daily live weight loss.
| Grazed Grass | Grass Silage | |
|---|---|---|
| Milk Yield (kg/day) | 42.3 | 39.6 |
| Concentrate (kg/day) | 5 | 9 |
| Grass DM intake (kg/day) | 17.2 | - |
| Silage DM intake (kg/day) | - | 10.4 |
| Total DM intake (kg/day) | 21.5 | 18.2 |
| Live weight change (kg/day) | -0.30 | -1.0 |
Summary
The results of the Moorepark studies highlight the importance of condition score as an aid to management of spring calving grass-based systems in Ireland. Target a condition score of at least 2.75 at dry off and a condition score 3.25-3.5 at calving. The results of the "Farm Fertility Study" indicate that condition score should be close to 2.75 at the start of the breeding season and that condition score loss from calving to first insemination should be less than 0.5 units.
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