The calves, their management and development until conception

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CHAPTER   II MATERIAL   AND   PROCEDURE

In this investigation the effect of a high and a low nutritional level on the physical health and reproductive ability was studied in Friesland dairy animals.
Week old heifers were acquired and reared intensively. Ovarian activity and reproductive phenomena were recorded through three consecutive breeding periods while the animals were grouped and put on a high and a low nutritional level re-spectively.
All clinical symptoms were recorded and various procedures were employed to study the performance of the two groups.
Full details are now presented in chronological order on the animals and on the various procedures employed during this investigation.

The  calves,  their  management  and development  until  conception

Thirty two grade Friesland heifers were acquired from commercial dairy breeders at the age of 3 to 7 days and reared intensively at the Rumerite Experi-mental Farm, Germiston, Transvaal.
They were reared on a standard type commercial milk substitute after the usual initial access to colostral milk of their own dams. Regular feeding procedures were carried out and the usual amount of milk substitute was fed, care being taken not to exceed the prescribed level, and all calves were weaned at the age of 10 weeks.
A standard type commercial calf rearing pellet and chopped teff hay were fed ad lib from the second week and free access to drinking water was allowed.
Calves were kept individually and in the open by tying them up, with an umbrella of 1,5 meter in diameter over each one to provide shelter against the sun and to protect the hay and grain against rain.
The calves were strictly isolated from all other cattle throughout the trial and they were vaccinated against paratyphoid, contagious abortion and anaplasmosis On arrival each calf was administered a 250 mgm chloramphenicol capsule twice daily for 3 days followed by one capsule daily for a further 3 days to con-trol diarrhoea. This was necessary because calves were sometimes introduced from premises where enteritis was rife.
The  proportions  of  meal  and  teff  in  this  mixture  were  64%  and  36%  respectively  and access  was  ad  lib.Progress of the calves was uneventful and no losses occurred. The incidence of diarrhoea was mild and although the calves were kept in the open, exposure had no visible or obviously harmful effect on any calf whatsoever.

Examination  of  the  genitalia  and  inseminations

From the age of 61/2 to 7 months as soon as the heifers were sufficiently developed, each one was submitted to a rectal examination twice weekly and the ovaries, follicular development, development of corpora lutea and the uteri were described.
Estrus observations were carried out by observation of the heifers from light until dark each day. Estrus was recorded when symptoms of standing heat was observed and confirmed by the presence of a Graaffian follicle and vaginal mucus on rectal palpation, which was carried out within 12 hours of a report of the onset of estrus.
At  estrus,  additionaL rectal  examinations  were  carried  out  at  intervals of between 12 and 24 hours from the first examination, to establish the time of ovulation.
Whenever ovulation failed to take place within the normal time from the onset of estrus, daily palpations were maintained until regression of the follicle became evident, usually after one week, in which case anovulation was recorded.
Delayed ovulation was recorded when ovulation occurred later than at the second examination at estrus, and this was more than 36 hours from the onset of estrus.
Silent heat or quiescent estrus was recorded when mucus secretion and follicular development was established on rectal examination at the time when estrus was expected to occur but without any of the usual signs of overt estrus.
Inseminations were commenced with when the group average body mass was 350 kg and this was reached at an average age of 13 months. All inseminations were carried out with semen of the same bull, a Friesland of known high fertility and one that was selected for low birth weight to facilitate ease of calving.
Inseminations were carried out during the period from 12 to 24 hours from the onset of estrus. Rectal examinations for the determination of ovulation were maintained after insemination as for other cycles and until pregnancy was con-firmed.

The  level  of  feeding before  insemination

Six weeks before inseminations were commenced with, the ten heifers with the highest incidence of ovulatory failure, based on their records of anovulation delayed ovulation and abnormal cycle length, were selected out of the group and allocated to Group I. The remaining 22 heifers were divided at random and allocated to Groups II and III
The proportions of meal and teff in this mixture were 46% and 54% re-spectively and access was ad libitum. Group I therefore consisted of heifers of sus-pected potential low fertility and they were kept on a high level of concentrate feeding.
Group II and Group III consisted of heifers of suspected « normal » fertility, and they were kept on a high and a low level of concentrate feeding respectively.
The growth rate and condition of the heifers simulated that encountered so frequently under intensive systems and particularly the « high » condition in which breeding animals are frequently exhibited at shows.
During  the   second   half  of  pregnancy     the   level  of  feeding   of  Groups    I  and was reduced to that of Group Ill to avoid over-fatness at calving. All three groups also received moderate excercise by allowing them into a big paddock during the day.

Observations on body temperature, heart and respiratory rates

From the age of ten months, the temperature, heart, and respiratory rates of each heifer were recorded at approximately monthly intervals for a period of six months.
Observations   were  made    in  the   morning   when   the   heifers   had   been   at   rest.It was endeavoured during observations to cause no physical exertion. This was possible because of the extreme docility of the animals at the time.
Heart rates were recorded with the aid of a stethoscope and the average of three counts each of the heart and respiratory rates were recorded.

Observations after   the   first  calving

At the time of the first calving it was obvious that there were con-siderable individual differences between heifers in respect of ovarian activity and certain other reproductive phenomena vis. uterine size, cycle length, fertility etc. It was also apparent that the high level of feeding had influenced the conception rate of the heifers as well as their heart and respiratory rates.
From these observations and from existing information on the effect of intensification and a high level of feeding on the life long performance of cattle, it was decided to proceed with observations on the performance of the animals on different levels of feeding.
For this purpose they were transferred to the Experimental Farm of the University of Pretoria, a distance of approximately 50 km.
Twenty nine of the original group of 32 animals were available for this purpose. One out of Group II had died from bloat and a further two were retained for production at the Rumevite Experimental Farm.

 Procedure  and  re-grouping  of  cows after  the  first   calving

Four  out  of  the  29  cows  available now,  had  failed  to   conceive and  one was  pregnant  on  arrival  at  Pretoria.  The  remaining  24  cows  were  all  cycling  again, Internal examination of genitalia was resumed and after it was established that ovarian activity had proceeded uneventfully over a period of 90 days, it was assumed that all cows were reproductively normal and free from any post parturient complications.
The residual effect of the previous feeding levels were considered. At the time of re-grouping, these feeding levels had been discontinued for a minimum of 325 days, all animals having been kept on the same feeding since the fourth month of their previous pregnancy. This period was considered to be sufficient for the elimination of any residual effect of the previous treatment on the data to be collected.

Rations

The cows were randomly divided into two groups, a HIGH and a LOW feeding group, and they were put on the following rations for the remainder of the lactation, the  subsequent  dry period  which  was  prolonged and  the  following  lactation until  they  were  slaughtered.
Meal  concentrate  was  measured  out  and  fed   individually. In   the   HIGH  group the  amount    of  meal  for the   two  lactating  periods  was  based on the  average  ad  libitum intake  over  the  first  58 days  after  grouping  and   for the dry period  on  the  average  adlibitum intake  over  30  days.On  subsequent  control  checks,  these  amounts  proved to be  th  true adlibitum  intake.

ACKNOWLEDGEMENTS
LIST OF TABLES
LIST’ OF FIGURES 
CHAPTER I INTRODUCTION 
Paradox in the distribution of food
The physiological regulation of food intake
Some effects of the nutritional level on the production and longevity of animals
The reproductive performance of cattle on a high level of feeding
Intensification and the erosion of dairy cows
CHAPTER II MATERIAL AND PROCEDURE
The calves, their management and development until conception
Examination of genitalia and insemination
Level of feeding before insemination
Observations on body temperature, heart and respiratory rates
Observations after the first calving
Procedures and regrouping after first calving
Rations
Body mass
Body temperature, heart and respiratory rates
Cyclic and ovarian activity during first and second lactation
Inseminations
Observations at calving
Post partum observations
Clinical
Histological
Uterine biopsies
E xaml.n atl.o n o f b1′ opsy secti. ons
Bl d 1 . . . – ·~ . . ~’\’.’ oo serum ana ys1s
Clinical observations and treatment
Final insemination and slaught~fihg
CHAPTER 3 RESULTS AND DISCUSSION 
Ovarian activity
Ovulation and ovulatory failure
Cycle length
The time of ovulation from the onset of estrus
Ovulation and estrus performance
Follicular and corpus luteum development
The respective roles of right and left ovaries
Quiescent estrus
Conception in relation to ovulatory performance .
Body mass
Temperature, heart and respiratory rates
Laminitis and arthritis
Milk production
The process of parturition
The first calving . .
The second calving . .
The duration of parturition and uterine involution Uterine inertia
Histological examination of the endometrium
The morphology of the non pregnant 11 tcrine wall ..
The epithelium
The lamina propria
The stratum compactum
The caruncles
The stratum spongiosum  ..
The uterine gland .
Wandering cells
Neutrophiles
Lymphocytes
Eosinophiles .
Plasma cells
Histiocytes
Mast cells
Involutional changes in the bovine uterus after
parturitio
Cyclic changes in the endometrium
Discussion
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