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This article was published in 1968-69
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Reproduction in Beef Cattle

J. S. YOUNG, M.V.Sc., Department of Veterinary Medicine, The University of Sydney, Camden, N.S.W.

Introduction

I was employed by Sydney University under a grant from Australian Meat Committee. Commenced work in June, 1963. Aim was to examine the reproductive performance of New South Wales beef herds with particular reference to infectious causes of infertility.

TECHNIQUES EMPLOYED

(1) Pregnancy diagnosis of beef herds together with —

(a) Vaginal mucus sampling of non-pregnant cows at pregnancy

diagnosis to check on Vibrio foetus and Trichomonas infections.

(b) Follow-up check of pregnant cows to establish extent and cause of calf loss between pregnancy diagnosis and calf-marking. All wet-dry cows (those pregnant at pregnancy diagnosis but no calf at marking) blood tested for Br. abortus and L. Pomona infections.

(2) Heifers in 11 herds identified at joining to check on —

Joining age

Joining height

Joining length

Joining weight and weight gain during joining period in relation to pregnancy level and calf loss following pregnancy diagnosis with particular reference to dystocia.

(3) Survey of Br. abortus { via
Survey of L. pomona and L. hyos { via

Abattoir specimens

Veterinary inspectors

Personal collections.

(4) Closer look at dystocia in one herd to study —

(a) Weight gain during gestation and its effect on calf size.

(b) Pelvic size in relation to dystocia.

(c) Process of parturition with particular reference to uterine inertia, time elapse before giving assistance, foetal presentation, etc.

RESULTS (Illustrated by colour transparencies.-Ed.)

SLIDE 1

Total tested at pregnancy diagnosis, 16,111. Percentage pregnant, 85.9.

Generally, the fertility level was high but no northern New South Wales herds were included in data and this could have coloured the results.

SLIDE 2

Whenever poor nutrition is a cause of lowered fertility levels it is usual to find that the lactating (wet) cows show a poorer performance than the non-lactating (dry) cows. By and large the difference between the wet and dry cows is an indication of the degree of undernutrition. At its extreme limit the wet cows do not conceive while the dry cows do, a situation which produces a calf every second year.

As shown in the table below there was very little difference in the aggregate of the survey herds between wet and dry cows. This indicated that nutrition was generally good.

Class	% Pregnant
Lactating "Wets"	86.6
Non-lactating "Drys"	84.9
Heifers—Yearlings	84.0
Heifers—2-year-olds	84.0

The performance of the yearling heifers was also high—a further indication of good nutrition.

SLIDE 3

This shows the performance by age up to four years of age. The lactating two-year-old cows returned a pregnancy level of 80 per cent which again is higher than expected. When poor nutrition is causing lowered fertility levels the differences between wet and dry cows are usually most marked following the first calf, unless special treatment has been given to this group.

SLIDE 4

However, there were herds in which the wet cows returned a significantly lower pregnancy level, as in herd 7.

Other herds, as illustrated by herd 14, returned a significantly poorer performance from the dry cows. When this occurs it is an indication that nutrition is not important as a cause of lowered fertility. Under these conditions it is usual to find a much lower proportion of dry cows.

Occasionally it is found that the overall pregnancy level is low, together with a significantly poorer performance of the dry cows. When this occurs one should suspect other causes of infertility such as acute vibriosis, pasture oestrogens, bull infertility or management.

	Lactating		Non-Lactating
	No.	% Preg.	No.	% Preg.
Herd 7	1018	80.3	250	96.4
Herd 14	1541	92.4	150	80.6

SLIDE 5

This shows the pregnancy level by age in two herds — one herd having a higher level in the wet cows and one having a higher level in the dry cows. The narrowing of the difference at three years of age in the poor nutrition herd was due to special treatment of that age group.

In connection with nutrition and its relation to fertility, I wish to show two slides taken from work by Dun et al. in America. One hundred and forty days prior to expected parturition one group of heifers were kept on a high plane of nutrition and the other on a low plane. Directly following parturition the heifers were fed at three levels low, medium and high. The highest reproductive performance, as measured by the percentage of cows pregnant after 120 days and by the number of days from calving to conception was from those fed the high energy level after calving. Of particular interest is the fact that the low-high group (low prior to calving-high after) out-performed the high-high group.

SLIDES 6 AND 7

The key to these slides is that it is prior to joining and probably immediately post-partum, which is the important period.

In good nutrition herds the performance of the dry cows can be improved by grazing hard during the winter months and lifting up the nutritional plane six to eight weeks prior to joining.

In any examination of the beef herd for fertility it is necessary to look for all the causes and not just one cause, to keep accurate records, to pregnancy test at least three successive years and examine herds at and prior to joining. When examining bulls prior to joining take the opportunity to look at pastures and management.

SLIDE 8

Let us now consider the calf losses which occur between the time cows are diagnosed as pregnant and the calves are marked.

The survey results are outlined below.

TOTAL LOSS — Calves

Pregnancy Diagnosis — Calf Marking

Heifer 17.4% (Range 10.7%-41.9%)

Cow 3.5% (Range 0.5%-14.2%)

The wide difference between losses in the heifers and losses in the cows is obvious. Dystocia caused the very high loss in the heifers.

The herd with 14.2 per cent loss in the cows showed no evidence of genital infection. These cows were snowed in for approximately one week under extremely cold conditions. It was my belief that the abortions which occurred were due to starvation and cold — really an acute shock. Abortions continued for one month after the privation period.

This outlines the heifer dystocia loss. There were no significant differences between yearlings and two-year-olds.

DYSTOCIA DEATHS - Calves only
Yearling	12-15 m.	16.1%
	Range	6.7-42.8%
	14-17 m.	19.6%
	Range	0-24.1%
2-year-old	24-27 m.	12.7%
	Range	0-23.7%

SLIDE 10

Dystocia in heifers is at present under more intensive study. The recommendations below must be considered as subject to further confirmation.

DYSTOCIA CONTROL

Leave no longer than 4 hrs. after seeing "water-bag".

Posterior presentations — highest death rate.

Heavier calves - high weight gain dams during pregnancy.

As calving season advances calves heavier.

Cull heifers with small pelves or join to known low birth weight inherent bull.

The results of serology are recorded in Slides 11, 12 and 13 below.

TABLE 1
Proportion of Reactors to Br. abortus Antigen

Herd Status	Herds, No. of	%	No. of Sera		%
			Pos.	Total
Positive * Non-vaccinated	59	23.6	347	1728	20.1
Positive * Unknown history	12	4.8	39	340	11.5
Positive † Weaner Vaccinated	7	2.8	22	168	13.1
Positive † Adult Vaccinated	8	3.2	24	428	5.6
Negative ‡ Vaccinated and non-vaccinated	164	65.6	-	4168	0.0
TOTAL	250	100.0	.	6832	.
* Sera containing 100 i.u./ml or greater.
† Sera containing 200 i.u./ml or greater.
‡ Sera containing < 100 i.u./ml.

TABLE 2
Results of Agglutination Lysis Tests for L. pomona on 234 Properties

Herd Status	Herds, No. of	%	No. of Sera		%
			Pos.	Total
Positive * Non-vaccinated	45	19.3	211	1525	13.8
Positive * Vaccinated	1	0.4	16	194	8.2
Negative	188	80.3	-	4800	0.0
TOTAL	234	100.0	.	6519	.
* Titres of 1:200 or greater.

TABLE 3
Results of Agglutination Lysis Tests for L. hyos on 225 Properties

Herd Status	Herds, No. of	%	No. of Sera		%
			Pos.	Total
Positive *	64	28.4	272	2303	11.9
Negative	161	71.6	-	4032	0.0
TOTAL	225	100.0	.	6519	.
* Titres of 1:200 or greater.

REFERENCE

Dun, I. G., Wiltbank, J. M., Ingalls, J. E, Zimmerman, D. R. (1964).- Energy level and reproduction in beef animals. Proc. Am. Soc. anim. Sci. 15:U1-U6