Disease frequencies of tied zero-grazing dairy cows and of dairy cows on pasture during summer and tied during winter

Preventive Veterinary Medicine, 4 (1986) 291--306 291 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

D I S E A S E F R E Q U E N C I E S O F T I E D Z E R O - G R A Z I N G D A I R Y C O W S

A N D O F D A I R Y C O W S O N P A S T U R E D U R I N G S U M M E R A N D T I E D

D U R I N G W I N T E R

P.H. BENDIXEN, B. VILSON, I. EKESBO and D.B. ASTRAND'

Swedish University of Agricultural Sciences, Faculty of Veterinary Medicine, Department of Animal Hygiene, 53200 Skara (Sweden)

'Swedish University of Agricultural Sciences, Faculty of Agriculture, Department of Economics and Statistics, 75007 Uppsala (Sweden)

(Accepted for publication 11 August 1986)

ABSTRACT

Bendixen, P.H., Vilson, B., Ekesbo, I. and /~strand D.B., 1986. Disease frequencies of tied zero-grazing dairy cows and of dairy cows on pasture during summer and tied during winter. Prey. Vet. Med., 4: 291--306.

Disease frequencies of Swedish Red and White Breed (SRB) and Swedish Friesian Breed (SLB) in tied herds with zero-grazing management system and in tied herds with pasture periods are presented. Incidences axe compared both with respect to season and between the two systems. Figures are given for accidents and nine different diseases.

In zero-grazing cows no seasonal difference could be demonstrated except for a higher risk of ketosis and tramped teat during wintertime for SRB.

Cows of both breeds kept on pasture had lower risks of dystocia, ketosis, mastitis and tramped teat during this period, but an increased risk of accidents and inflammation of the hoof(s). SRB cows also had higher risks of retained placenta, parturient paresis and non-inflammatory diseases of the hoof(s) during pasture period.

Comparison of year-round incidence in the two management systems revealed a higher risk of retained placenta in zero-grazing cows of both breeds and higher risk of parturient paresis in zero-grazing SRB cows. The risk of accidents was decreased in zero-grazing cows of both breeds.

The relative risks of tramped teat, mastitis and diseases of the hoof(s) varied depending on the herd size distribution of the control group. Increased risk of mastitis in zero- grazing cows of both breeds and of tramped teat in zero-grazing SLB cows was found when comparing with cows from a group of mainly smaller herds with pasture feeding during summer. However, comparison with cows from a group of herds with the same herd size distribution as zero-grazing cows revealed decreased risk of tramped teat, mastitis and inflammation of the hoof(s) in zero-grazing SRB cows and decreased risk of diseases of the hoof(s) in zero-grazing SLB cows.

INTRODUCTION

E c o n o m i c c i r c u m s t a n c e s h a v e c r e a t e d a t r e n d t o w a r d s l a rger h e r d s w h i c h

m a k e s t h e use o f s u m m e r f e e d i n g on p a s t u r e i m p r a c t i c a l in m a n y t i e d

0167-5877/86/$03.50 © 1986 Elsevier Science Publishers B.V.

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herds in Sweden. Also, it has been found that the difference in feeding procedure, necessitated by alteration between pasture periods and housing periods, causes product ion losses (Burstedt, 1983).

Ekesbo (1966) found lower morbidi ty in dairy cows during pasture, but no large-scale evalution of the impact of zero-grazing management on the health of cows has yet been done. This paper presents the seasonal disease frequencies in zero-grazing cows and in tied cows with summer feeding on pasture, and a comparison of year-round incidence in the two management systems.

Data are given for the two most common dairy breeds in Sweden, Swe- dish Red and White (SRB) and Swedish Friesian (SLB).

MATERIALS AND METHODS

Data bank

During the period October 1970--September 1974 data about diseases of dairy cows were collected as a descriptive epidemiologic project for the purpose of identifying risk factors.

Herd selection was purposive in order to cover different housing systems, e.g. loose housed cows and tied cows, as well as different management practices: conf inement in closed buildings or free access to open air for loose housed cows and zero-grazing or access to pasture during summer for tied cows. All 24 counties of Sweden were represented.

Data about diseases, injuries, removals, and date of changes from pasture to housing were mailed by the farmers once a month on a survey form specially designed for the project.

The farmers were given instructions to daily register all diseases diagnosed and treated by veterinarians as well as health disorders not requiring veterinary assistance. The following definitions were given as a guide to identifi- cation of cases: Dystocia -- calvings in which assistance was necessary to save the life of the calf or to prevent the cow from suffering; Retained placenta -- cases in which the placenta was not released spontaneously within 24 h of calving; Parturient paresis -- cases of paresis occurring in connect ion with calving which could not be related to any other cause; Ketosis -- lack of appeti te, especially for concentrates which occurred within five weeks of calving; Mastitis -- cases presenting one, some or all of the following signs: swelling, warmth, pain, redness or visible changes in the milk; Tramped teat -- injury due to crushing or swelling on the teat not explicable in any other manner. Other disorders were described in words and coded by a veterinarian who throughout the study was the only person to receive the month ly reports and check the computer files.

Only farms with twelve consecutive reports during a year were included in the study, as data from persons that did not fulfil this obligation were suspected to be incomplete. During the first year of observation 932 farms

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fulfilled this obligation, during the second year 1021 farms, during the third year 918 farms, and during the four th year 900 farms. This const i tuted more than 80% of the farms originally engaged in the project at the begin- ning of a year of observation.

Data about housing environment and management practices were collected once a year by specially trained technical assistants during a visit to the farms.

All the herds were on the official milk recording system, from which informat ion was obtained about the identi ty and milk product ion of the cows, date of calvings and sex of the calf (Swedish performance recording and AI breeding 1974/1975) . During the observation period approximately 30% of the herds in Sweden were on the official milk recording system. The herds in the study amounted to approximately 4.5% of these herds, representing about 10% of the control led cows.

The number of calvings in the observed herds during the four-year observation period was 153 991. SRB accounted for 102 312 and SLB for 34 690 calvings. Approximate ly one third of the farms had only one breed of cows, the rest had two breeds or more.

Data storage and validation

Data from the official milk recording system were delivered from computer to computer via special interface t rea tment . All other data were coded and a set of interactive compute r programs writ ten and used for data input. Manual checks were performed each month to compare all of the data in the computer files with the month ly reports mailed by the farmers to ensure the reliability of the data coding and entry routines.

Data retrieval

Herd size was outpr in ted for risk factor positive herds (tied zero-grazing management system) and risk factor negative herds (tied herds using pasture

TABLE I

Herd size distribution of risk factor positive and risk factor negative tied cows

Herd Risk factor positive herd observation years

Risk factor negative herd observation years C1 C2

0--25 46 (21%) 1692 (51%) 26--50 86 (40%) 1162 (35%) 51--75 29 (14%) 270 (8%) 76-- 53 (25%) 211 (6%)

183 (22%) 342 (40%) 115 (14%) 211 (25%)

Total 214 3335 851

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feeding during summer) for each year, and summed for all four years (Table I). Due to the uneven distribution of herd size observation years in the two groups to be compared, an additional control group, C2, was created, by random selection of herds from each herd size group in C1. C2 had the same distribution of herd size observation years as the risk factor positive group, for the maximum number of herd observation years.

Disease incidence

Cumulative incidence, CI, was used as a measure of f requency of diseases related to calving. CI for dystocia, retained placenta and parturient paresis was calculated as the number of cows developing disease divided by the number of calvings. CI for ketosis was calculated as the number of cows developing disease divided by the number of calvings at risk (e.g., the number of calvings minus half the number of withdrawals, the latter being animals wi thout ketosis being removed from the herds within two months after calving).

Incidence density, ID, was calculated for diseases not related to calving, as the number of animals with at least one episode of disease during a lactation divided by the sum of disease-free months during that lactation. The measure of first occurrence of disease per lactation was chosen to avoid definit ion of recovery periods. ID was expressed per 1200 cow-months, equal to 100 cow-years.

Disease incidence was calculated both as seasonal incidence and combined incidence. Seasonal incidence was calculated as the number of cows with disease during pasture or housing divided by the number of calvings during pasture/housing for CI, or disease-free grazing months/housing months for ID. These months were individual for each year and herd depending on weather and geographical location.

In all herds with zero-grazing management the pasture period was sub- sti tuted by the months of May to September and the housing period by the months of October to April. Dry cows from zero-grazing herds were of ten kept on pasture during summert ime until some weeks before calving. A bias in incidence registration due to these cows was inevitable as no informat ion about individual cows on pasture was available.

Combined incidence was calculated as the number of cows with disease irrespective of season divided by number of calvings at risk or disease-free months.

Data analysis

Relative risk, RR was calculated as the ratio between incidence for risk factor positive cows and incidence for risk factor negative cows, age-adjusted by a modified Mantel-Haenszel procedure (Kleinbaum et al., 1982).

Hypothesising housing/winter time as a risk factor, RR w was calculated

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for all three groups as the ratio between seasonal incidences. Hypothesising zero-grazing as a risk factor, RR z was calculated as the ratio between the combined incidence for zero-grazing cows and the combined incidence for cows in C1 or C2.

Cows were chosen as the sampling unit, neglecting the effect of clus- tering by herd. Therefore, proven significant differences might be optimis- tic due to the large sample size and thus emphasis should be put on the magnitude of RR, when interpreting the results.

Statistical analyses were performed using the Mantel-Haenszel test for a summary ×2. Due to the magnitude of the material only differences of P < 0.01 were considered statistically significant.

RESULTS AND DISCUSSION

Calving related diseases

The data on dystocia, retained placenta, and parturient paresis are presented in Table IIa, b, c for zero-grazing cows and cows in C1 and C2, respectively. The data on ketosis are presented in Table III.

Zero-grazing cows had no statistically significant difference between seasonal incidences (Table IV) except for the increased risk of 1.7 for ketosis during winter time in SRB cows.

Cows on pasture had a decreased risk of dystocia (RR = 1.3--1.7). In SRB the seasonal difference, however, was only statistically significant in first calving, which can be derived from Table I I b and c. In SLB the incidence during pasture period was significantly decreased both for heifers and older cows.

Reports about seasonal variation in the incidence of dystocia are con- flicting; see Meijering (1984) for a discussion of results from the north- western part of Europe. Erb and Martin (1980) found lower incidence rates of dystocia during summer in Holstein-Friesian cows, but later observations (Dohoo and Martin, 1984) were unable to confirm this. The present findings suggest that seasonal variation occurred depending on management, breed and age.

SRB cows had significantly increased risk of retained placenta during pasture (RR = 0.7--0.8). SLB cows had no seasonal difference. Dyrendahl et al. (1977) also found an increased risk during pasture period in a Swedish study of 1702 cows, 72% of which were SRB and 25% of which were SLB.

Parturient paresis occurred with significantly increased incidence during pasture periods in SRB cows (RR = 0.8). In SLB cows the increased risk during pasture was significant only in cows from C1. Pasture feeding as a risk factor for parturient paresis was also found by Harris (1981), who observed a positive correlation between the incidence of parturient paresis and pasture length in a study of 7251 cows, 64% of which were Jerseys, and recommended restricted pasture intake as a measure of prevention.

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TABLE Ill

Number of calvings at risk (N). number of cases reported positive for ketosis (I). and average cumulative incidence (CI%) according to seaaon for tied zero-grazing cows and ~ied cows from herds with traditional outdoor grazing during summer CI and C2. (For definition of CI and C2. see Materials and Methods.)

October--April: Housing period May--September: Pasture period

N I CI% N I CI%

SRB SLB SRB SLB SRB SLB SRB SLB SRB SLB SRB SLB

Zero-grazing 4 342 2 500 265 52 6.10 2.06 2 779 1408 96 27 3.45 1.91 C1 55 698 14 177 3301 379 5,92 2.67 21 269 5973 289 34 1.35 0.57 C2 23 545 5 944 1204 177 5.11 1.96 8 246 2635 84 10 1.02 0 .38

T A B L E I V

Age-adjusted ratio between seasonal incidences (RRw) for tied zero-grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods).

Dystocia Retained Parturient Ketosis placenta paresis

SRB SLB SRB SLB SRB SLB SRB SLB

Zero-grazing 1.0 1.4 0.8 0.9 1.0 1.5 1.7"* 1.0 C1 1.3"* 1.6"* 0.7** 0.9 0.8** 0.8** 3.9** 4.1"* C2 1.3"* 1.7"* 0.8** 1.0 0.8** 0.9 4.3** 4.4**

**P< 0.01

The similar seasonal pattern for retained placenta and parturient paresis suggests an association between these diseases accounting for some of the seasonal variation in the incidence of retained placenta.

Cows of both breeds had considerably higher risk of ketosis during housing period (RR = 3.9--4.4). This observation is in accordance with the findings of Dohoo and Martin (1984), that Holstein-Friesian cows calving in January have the greatest risk of developing ketosis. GrShn et al. (1984) also found increased risk for Ayrshire cows during winter.

Diseases not related to calving

The incidence of traumatic reticuloperitonitis varied between 0.49 and 0.81 (Table V), which corresponds to approximately one case per 200 cow-years. No significant difference between seasonal incidences could be found in any group.

The risk of traumatic injuries, homing injuries and accidents was significantly increased for cows on pasture (Table VI; RR = 0.2--0.3), and identical during winter and summer for cows in zero-grazing herds. The lowest incidence was 0.21 per 100 cow-years for zero-grazing cows during

300

TABLE V

Number of cases (I) reported as traumatic reticuloperitonitis and suspected traumatic reticuloperitonitis, disease-free herd time in months (HT), the calculated average incidence density/1200 months (ID), and the ratio between seasonal incidence (RRw) for tied zero-grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.)

I HT ID RR w

Winter period Zero-grazing 45 78 690 0.68 C1 378 751 884 0.60 C2 212 313 957 0.81

Summer period Zero-grazing 23 55 428 0.50 C1 152 374 254 0.49 C2 75 151 634 0.59

1.4 1.2 1.4

RRwn.S.

TABLE VI

Number of cases (I) reported as traumatic injuries, homing injuries and accidents, disease-free herd time in months (HT), the calculated average incidence density/1200 months (ID), and the ratio between seasonal incidence (RR w) for tied zero-grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.)

I HT ID RR w



0.8 0.2** 0.3**

**P < 0.01.

w i n t e r , a n d t h e h ighes t i n c i d e n c e was 1.6"/ pe r 100 c o w - y e a r s d u r i n g sum-

m e r for cows in C2. Al l SRB cows h a d s i g n i f i c a n t l y l o w e r r isk o f t r a m p e d t e a t d u r i n g p a s t u r e

(Tab le VI Ia ; R R = 1 . 4 - - 4 . 2 ) . T h e l o w e s t i n c i d e n c e was 2 .92 cases pe r 100 c o w - y e a r s d u r i n g p a s t u r e for cows in C1, a n d t he h i ghe s t i n c i d e n c e was 17 .27 cases pe r 100 c o w - y e a r s fo r cows in C2 d u r i n g h o u s i n g . Ze ro -g raz ing cows h a d a l o w e r i n c i d e n c e d u r i n g w i n t e r t h a n c o w s in C2 d u r i n g h o u s i n g :

11 .01 cases pe r 100 cow-yea r s . SLB cows in ze ro -g raz ing h e r d s h a d n o s ea sona l d i f f e r e n c e in t he i n c i d e n c e

of t r a m p e d t ea t , b u t cows o n p a s t u r e h a d s i g n i f i c a n t l y d e c r e a s e d r isk d u r i n g

301

T A B L E VlIa

N u m b e r o f cases (I) r epo r t ed as t r a m p e d teat , disease-free herd t ime in m o n t h s (HT), the ca lcula ted average inc idence d e n s i t y / 1 2 0 0 m o n t h s (ID), and age-adjusted ra t io b e t w e e n seasonal inc idence ( R R w ) for t ied zero-grazing cows and tied cows f rom herds wi th t r ad i t iona l o u t d o o r grazing dur ing s um m er , C1 and C2. (Fo r de f in i t i on of C1 and C2, see Mater ia ls and Methods . ) SRB

I HT ID R R w

Winter per iod Zero-grazing 439 47 832 11.01 C1 5620 559 544 12.05 C2 3357 233 255 17.27

S u m m e r per iod Zero-grazing 222 33 463 7.96 C1 662 272 120 2.92 C2 442 108 147 4 .90

1 .4"* 4 .2** 3 .6**

* * P < 0,01.

T A B L E VIIb

N u m b e r o f cases (I) r epo r t ed as t r a m p e d teat , disease-free herd t ime in m o n t h s (HT), the ca lcula ted average inc idence d e n s i t y / 1 2 0 0 m o n t h s (ID), and age-adjusted ra t io be tween seasonal inc idence ( R R w ) for t ied zero-grazing cows and t ied cows f rom herds wi th t r ad i t iona l o u t d o o r grazing dur ing s um m er , C1 and C2. (Fo r de f in i t ion of C1 and C2, see Materials and Methods . ) SLB

I HT ID R R w

Winter per iod Zero-grazing 400 23 482 20 .44 C1 1992 133 743 17.87 C2 1069 56 671 22.63

S u m m e r per iod Zero-grazing 214 15 457 16.61 C1 272 66 862 4 .88 C2 146 29 128 6.01

1.2 3 .7** 3 .8**

* * P < 0.01.

this period (Table VIIb; RR = 3.7--3.8). The lowest incidence was 4.88 cases per 100 cow-years during pasture period for cows in C1, and the highest incidence was 22.63 cases per 100 cow-years during housing period in C2. Again zero-grazing cows had a lower incidence during winter than cows in C2 during housing: 20.44 cases per 100 cow-years.

Cows in zero-grazing herds had no seasonal difference in the incidence of mastitis, but cows on pasture had significantly decreased risk (Table VIIIa, b; RR = 1.2--1.4). In SRB the lowest incidence was 10.69 cases per 100 cow-years during pasture period for cows in C1 and the highest 18.43 cases per 100 cow-years during housing for cows in C2. The cor-

302

TABLE VIIIa

Number of cows (I) reported positive for mastitis at least once during a lactation, disease-free herd time in months (HT), the calculated average incidence density/1200 months (ID), and age-adjusted ratio between seasonal incidence (RRw) for tied zero- grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.)SRB

I HT ID RR w



1.0 1.3"* 1.2"*

**P< 0.01.

TABLE VIIIb

Number of cows (I) reported positive for mastitis at least once during a lactation, disease-free herd time in months (HT), the calculated average incidence density/1200 months (ID), and age-adjusted ratio between seasonal incidence (RRw) for tied zero- grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.)SLB

I HT ID RR w

Winter period Zer0-grazing 443 22 879 23.23 C1 2356 127 750 22.13 C2 1328 53 689 29.70


0.9 1.4"* 1.3"*

**P< 0.01.

r e s p o n d i n g f igures for SLB cows were 1 6 . 2 2 a n d 2 9 . 7 0 cases per 100 cow- years , r e spec t i ve ly .

The i n c i d e n c e of mas t i t i s pa ra l l e l l ed the i n c i d e n c e of t r a m p e d t ea t , in t h a t ze ro -g raz ing cows had l o w e r i n c i d e n c e o f mas t i t i s d u r i n g w i n t e r t h a n cows in C2 d u r i n g h o u s i n g , 1 4 . 8 5 a n d 2 3 . 2 3 cases per 100 c ow - ye a r s for SRB a n d SLB, r e spec t i ve ly .

No seasona l d i f f e r e n c e in t he i n c i d e n c e o f i n f l a m m a t i o n o f t he hoo f ( s ) c o u l d be f o u n d in ze ro -g raz ing cows , b u t cows of b o t h b reeds o n p a s t u r e had s i g n i f i c a n t l y i n c r e a s e d r isk ( T a b l e IXa ; R R = 0 . 3 - - 0 . 4 ) . T h e l o w e s t

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TABLE IXa

Number of cows (I) reported positive for inflammation of the hoof(s) at least once during a lactation period, disease-free herd time in months (HT), calculated average ID/1200 months (ID), and age-adjusted ratio between seasonal incidence (RRw) for tied zero-grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.) SRB and SLB

I HT ID RR w


Winter period Zero-grazing 38 50 51 264 26 873 0.88 2.23 C1 312 226 599 917 145 904 0.62 1.85 C2 203 126 249 989 60 655 0.97 2.49

Summer period Zero-grazing 20 27 36 577 18 409 0.66 1.76 C1 516 271 296 273 73 829 2.08 4.40 C2 354 190 117 883 31 497 3.60 7.24

1.3 1.3 0.3** 0.4** 0.3** 0.4**

**P<0.01.

TABLE IXb

Number of cows (I) reported positive for disease of the hoof(s) of non-inflammatory character at least once during a lactation period, disease-free herd time in months (HT), calculated average ID]1200 months (ID), and age-adjusted ratio between seasonal incidence (RRw) for tied zero-grazing cows and tied cows from herds with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.) SRB and SLB

I HT ID RR w


Winter period Zero-grazing 74 56 50 952 26 743 1.71 2.51 C1 647 360 597 906 145 148 1.29 2.97 C2 345 215 250 038 60 242 1.66 4.28

Summer period Zero-grazing 34 33 36 293 18 299 1.12 2.16 C1 413 189 295 141 73 262 1.67 3.09 C2 242 118 117 921 31 243 2.45 4.53

1.6 1.2 0.8** 1.0 0.7** 1.0

**P< 0.01.

i n c i d e n c e for SRB cows d u r i n g h o u s i n g was 0 .62 cases per 100 cow-yea r s a n d t he h ighes t d u r i n g p a s t u r e was 3 .60 cases pe r 100 cow-yea r s . T h e cor- r e s p o n d i n g f igures for SLB were 1 .85 a n d 7 . 2 4 cases pe r 100 cow-yea r s , r e s p e c t i v e l y . M o s t diseases in th i s g r o u p were d i a g n o s e d as i n t e r d i g i t a l

p h l e g m o n ( a c u t e f o o t ro t ) . E n v i r o n m e n t a l f ac to r s have b e e n i m p l i c a t e d

304

as c o m p o n e n t causes for this disease (Monrad et al., 1983) , and cows on pas tu re were a p p a r e n t l y expos ed to fac tors t ha t r educed the res is tance of the hoof ( s ) to bacter ia l infect ions .

No seasonal d i f fe rence in the incidence of n o n - i n f l a m m a t o r y diseases of the hoof ( s ) cou ld be f o u n d in SLB cows or in zero-grazing SRB cows, bu t SRB cows on pas tu re had s ignif icant ly increased risk (Table IXb; R R = 0 .7- -0 .8) . The incidences var ied be t ween 1.12 and 2 .45 per 100 cow- years for SRB and be t ween 2 .16 and 4.53 per 100 cow-years for SLB.

R R z was ca lcu la ted as the age-adjusted ra t io b e t w e e n the c o m b i n e d inc idence in zero-grazing cows and the c o m b i n e d incidence in cows f r o m C1 or C2. R R z indicates which kind o f m a n a g e m e n t sy s t em had the highest yea r - round disease f r equency .

No d i f fe rence in the f r e q u e n c y of dys toc i a could be d e m o n s t r a t e d be tween the two m a n a g e m e n t sys t ems (Table X), but cows of b o t h breeds in zero- grazing m a n a g e m e n t had be t ween 10 and 20% higher risk of re ta ined placenta. A large n u m b e r of obse rva t ions is requi red to m a k e such d i f fe rences s ta t is t ical ly s ignif icant in diseases wi th low incidences . Whe the r or no t a 10% increase in risk is biological ly i m p o r t a n t is a m a t t e r o f j u d g e m e n t . The risk of p a r t u r i e n t paresis was 20% increased fo r SRB cows in zero-grazing m a n a g e m e n t . T h e risk of ke tos is was ident ical fo r SLB cows, bu t increased for zero-grazing SRB cows w h e n c o m p a r i n g to C2, and was ident ical when c o m p a r i n g to C1.

TABLE X

Age-adjusted ratio between combined incidence for tied zero-grazing cows and combined incidence for tied cows with traditional outdoor grazing during summer, C1 and C2. (For definition of C1 and C2, see Materials and Methods.) SRB and SLB

Dystocia Retained Parturient Ketosis placenta paresis


Zero-grazing/C1 1.0 1.1 1.2"* 1.1"* 1.2"* 1.0 1.1 1.0 Zero-grazing/C2 1.2 1.2 1.1"* 1.2"* 1.2"* 1.1 1.3"* 1.4

**P< 0.01.

T h e risk of acc idents and injuries was highly r educed in zero-grazing cows (Table XI) . T h e risk of t r a m p e d t ea t was ident ical (SRB) or increased (SLB) w h e n c o m p a r i n g zero-grazing cows to cows in C1, bu t decreased (SRB) or was ident ical (SLB) w h e n c o m p a r i n g to cows in C2. The risk of mast i t i s paral lel led the p ic tu re o f t r a m p e d t ea t wi th increased risk for cows in zero-grazing m a n a g e m e n t when c o m p a r i n g to cows in C1, and decreased (SRB) or ident ical (SLB) w h e n c o m p a r i n g to cows in C2. T h e risk of in- f l a m m a t o r y diseases o f the hoof ( s ) was lower in zero-grazing cows than in cows in C2, and ident ical w h e n c o m p a r i n g to cows in C1. The risk of

305

TABLE XI

Age-adjtmted ratio between combined incidence for tied zero-grazing cows and combined incidence for tied cows with traditional ou tdoor grazing during summer, C1 and C2. (For definition of C1 and C2. see Materials and Methods.) SRB and SLB

Traumatic Accidents Tramped Mut i t i s Inflamma- Non-inflamma- reticulo- and inju- teat tion o f tory diseases peritonitis ries hoof(s ) o f hoof(s) SRB + SLB SRB + SLB


Zero-grazing/Cl i . I 0 .4"* I . I 1.4"* 1.2"* 1.2"* 0.7 0.8 I . I 0.8 Zel-o-grazing/C2 0,8 0.3** 0.8** 1.1 0.9** 0.9 0.7** 0.5** 0.8 0.6**

**P < 0.01.

non-inflammatory diseases of the hoof was identical for all SRB cows, but lower for SLB cows in zero-grazing management when comparing to cows in C2 and identical when comparing to cows in C1.

CONCLUSION

The analyses confirmed the observations of Ekesbo (1966) that cows on pasture during this period had the lowest incidence of frequent and important diseases, such as tramped teat and mastitis. However, year-round incidences were lower (SRB) or identical (SLB) for zero-grazing cows when compared to cows from herds with similar herd size distribution, and pasture feeding during summer.

The explanation for this finding could be the better housing environment in zero-grazing herds, or that farmers who are the first to follow new management practices in a tradition-bound profession are skilled in- dividuals. The use of transportable milking units would allow cows from larger herds to be kept on pasture during summer. Provided overcrowding and muddy pastures can be avoided, in order to reduce the risk of accidents and inflammation of the hoof(s), pasture feeding during summer should decrease morbidi ty in dairy cows.

REFERENCES

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Dohoo, I.R. and Martin, S.W., 1984. Disease, production and culling in Holstein-Friesian cows. II. Age, season and sire effects. Prey. Vet. Med., 2: 655--670.

Dyrendahl, I., Mattson, J. and Pehrson, B., 1977. Retained placenta in cattle -- Incidence, clinical data and effects on fertility. Zbl. Vet. Med., A., 24: 529--541.

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GrShn, Y., Thompson, J.R. and Bruss, M.L., 1984. Epidemiology and genetic basis of ketosis in Finnish Ayrshire cattle. Prey. Vet. Med., 3: 66--77.

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Harris, D.J., 1981. Factors predisposing to parturient paresis. Aust. Vet. J., 57: 357-- 361.

Kleinbaum, D.G. Kupper, L.L. and Morgenstern, H., 1982. Epidemiologic Research. Principles and quantitative methods. Lifetime Learning Publications, Belmont, CA, p. 345.

Meijering, A., 1984. Dystocia and stillbirth in cattle -- a review of causes, relations and implications. Livest. Prod. Sci., 11: 143--177.

Monrad, J., Kassuku, A.A., Nansen, P. and Willeberg, P., 1983. An epidemiological study of foot rot in pastured cattle. Acta Vet. Scand., 24: 403--417.

Swedish performance recording and AI breeding, 1974/75. Svensk HusdjursskStsel ek. f6r., t-l~llsta, Eskilstuna, Sweden, Report 78.

Documents

Disease frequencies of tied zero-grazing dairy cows and of dairy cows on pasture during summer and tied during winter