A survey of the reproductive status of cattle in Nharira-Lancashire smallholder dairy scheme, Zimbabwe

E Masama, N T Kusina, S Sibanda and C Majoni

Department of Animal Science, University of Zimbabwe, P. O. Box MP 167, Mount Pleasant, Harare
edmasama@agric.uz.ac.zw

Abstract

A 12-month study on the reproductive status of dairy cows was conducted in two adjacent areas of Nharira (communal) and Lancashire (small-scale commercial) in Zimbabwe during 1999. On-farm farmer participatory and monitoring studies were used to collect data. Palpation of the ovary through the rectum was conducted to determine ovarian cyclical activity and/or pregnancy.

Ovarian cyclical activity was related to the prevailing season with the highest number of pregnant animals (57.1% in the communal and 73.1% in the small-scale commercial area) recorded in the dry season. The highest number of anoestrus animals (56% for both the communal and small-scale areas) was recorded in the month of January. Animals attained peak body weight and body condition around May and the lowest body weight and body condition was recorded around December. The results indicate that reduced ovarian activity was observed during periods of low body weight and body condition.

It is concluded that the ovarian cyclical activity of cattle in the smallholder dairy sector in Zimbabwe is not satisfactory particularly during the dry season and early wet season. Farmers need to find ways to maintain the body weight and reproductive performance of their animals to ensure viability in the smallholder dairy sector.

Keywords: Crossbred cows, ovarian activity, rectal palpation, reproductive performance, Zimbabwe

Introduction

Before the land reform programme in the year 2000, commercial dairy producers dominated the formal market for milk with smallholder dairy farmers contributing less than 2% (Dube 2000). However the number of commercial farmers has decreased with the emergence of more newly resettled and relatively inexperienced farmers with smaller herds. Smallholder farmers typically own less than five milking cows at any one time as they build up their herds. While the potential for improved milk production is abundant, smallholder farmers face various constraints among which is poor reproductive performance of the cows (Masama et al 2003).

The seasonality of milk production in the smallholder dairy sector of Zimbabwe is linked to the availability of adequate feed resources (Dube 1995). During periods of abundant feed supply, the productivity of dairy animals improves. The nutritional status of the animal affects ovarian function, which in turn affects reproductive performance. Stevenson et al (2000), among other workers, found that there were lower levels of cyclicity in cows of low body condition score. In Nharira-Lancashire, the seasonality of milk production and poor reproductive performance due to nutrition affects viability. Feeding at a higher level throughout the year improves productivity of the dairy animals but is expensive. It is more economic to feed on-farm formulated dairy diets in order to improve milk production and reproductive performance.

The viability of dairy production critically depends on the reproductive and lactation performance of each cow. The optimum calving interval for dairy cows should be 365 days. The knowledge of basic cow physiology by farmers aids them in the successful management of their herds. However little research has been done to characterize the reproductive performance (ovarian activity) of smallholder dairy cattle. Therefore, the objective of this study was to determine the ovarian activity of cows used for dairy production by smallholder farmers in Nharira-Lancashire.

Materials and methods

Nharira is a communal crop-livestock production area, while Lancashire is a small-scale commercial farming area. Both areas supply milk to a central milk collection centre called the Nharira-Lancashire Dairy Centre. The study sites were located in a semi-arid ecological zone approximately 172 km southeast of Harare in Mashonaland East Province. Nharira-Lancashire lies 1460 m above sea level on latitude 19⁰ 2'S and longitude 30⁰ 35'E. Mean annual rainfall received in the area for the period 1988 to 1998 was 640 mm and mean maximum and minimum temperatures were 25.4⁰C and 12⁰C, respectively. The vegetation in Nharira consists of sparsely scattered trees, short un-browseable bushes and overgrazed natural veldt growing in non-arable plains. In Lancashire, trees are more abundant and tall grasses such as Heteropogon and Hyparrhenia grow in several paddocks, some of which show evidence of underutilization by becoming moribund.

The study started by identifying the participating farmers through meetings at the Dairy Milk Centre. Twenty-one farmers were selected based on their ownership of at least two dairy animals. One hundred and fifty-three female animals, pregnant and non-pregnant, were used. For the measurement of various parameters, the number of animals varied due to absence, mortality and new additions.

The trial was run over one year. Herds of the participating farmers were weighed once every month. Cows were subjected to rectal palpation once every four months (i.e. January, April, August and December in 1999). The animals depended on native pasture and some supplements available on the farms. However, some animals in the trial were lost due to death, sales and/or slaughter by the farmers. Cows were the experimental units and were assumed not to have inherent differences, apart from breed and parity, which could affect ovarian activity.

Measurements

The following measurements were made: body weight and condition, reproduction and ovarian activity. All the cows were weighed monthly using a cattle-weigh scale (Kattleway Cattle Scale, Marondera, Zimbabwe). At the time of weighing, the body condition score was measured using a five-point scale (ADAS 1978). Rectal palpation was used to diagnose pregnancy and ovarian activity. The farmers observed animals in heat and did the routine management of the animals, with assistance from extension workers and researchers on technical issues.

Statistical analysis

The PROC MIXED procedure of SAS (SAS 1994) for repeated measures analysis, as described by Littell et al (1998), was used to describe body weight changes. Chi-square analysis and Student's 't' test were performed to compare data in the two treatment groups, using the Proc Freq and Proc Ttest procedures of SAS (1994).

Results

Breeds

The breeds identified in the study areas included Bos taurus (Friesian, Jersey and Red Dane) and Bos indicus or Sanga, also termed indigenous (Mashona), and crossbred (Mashona x Friesian; Mashona x Red Dane; Mashona x Jersey; Red Dane x Friesian). Indigenous breeds constituted 18.5% of the total number of cows in the study while the exotic breeds and crossbreds constituted 48.6% and 32.9% respectively.

Pregnancy diagnosis

Some animals used by the farmers had no reliable reproductive history, therefore, the effect of parity was not included in data analysis. The results of pregnancy diagnosis for all animals are shown in Table 1.

The pregnancy rate pattern was similar in both areas, with the highest numbers of pregnant animals occurring in the middle of the year. Conception would have taken place at the end and beginning of the year, confirming the calving pattern. The animals were further classified as milking and dry. Table 2 shows the numbers in each category.

The number of pregnant animals was significantly different (P< 0.05) between the sectors only in August.

Mortality

The losses due to mortality and sales from the dairy herds were 21.3% in the communal area, which was not significantly different (P>0.05) from 18.6% in the small-scale commercial area.

Body weight and body condition score

Body weight changes (n=140) are shown in Figure 1.

Body weight increased from February, peaked in July, and then declined thereafter. Body weights were lower in cows in the communal area compared to those in the small-scale commercial sector. Month or season, sector and breed significantly affected (P<0.05) the body weight changes of cows. The cows in Lancashire had generally better body condition score of greater than 2.5 out of a scale of 5.

Calving rate

The calving rates in the communal and small-scale commercial areas were 50% and 53.2% respectively. However, the calving rates were not significantly different (P>0.05) across the farming sectors.

Discussion

The mean body weight of cows in Nharira and Lancashire was about 350 kg and mean milk yield was about 4 kg per day. The maximum dry matter intake of the cows was about 9.15 kg per day. (Derived from the equation DM Intake = 0.025 Mass + 0.1 Yield (Topps and Oliver 1993)). The farmers supplemented the cows with about 2 kg per day of snapped corn mixed with legume or other protein source. Snapped corn contains 10.2 MJ ME/kg DM. Therefore, the animals obtained about 20.4 MJ ME/day from this source. The energy required for maintenance (MR) for such animals is 48.15 MJ ME /day. (Derived from the equation MR for energy = 10 + 0.109 Mass). The energy required for milk production was about 18 MJ ME /day (Derived from the equation Energy for lactation = 4.93 MJ ME x 0.90 x Daily milk yield). Therefore, the total energy requirement per day was about 66 MJ ME.

The energy content of veldt hay and maize stover, which were the commonest feed resources, was estimated at 5.9 MJ / kg DM (Topps and Oliver 1993). Therefore, the animals consumed about 7.6 kg DM (energy required divided by energy content of feed) off the veldt. Since the animals grazed veldt pastures, they obtained about 45 MJ ME (5.9 MJ / kg DM x 7.6 kg DM) per day from this source to support the basal level of production. The cows were then deriving 68 % of their energy requirements from the poor pasture, which was inadequate for dairy production.

Protein requirements also had to be considered, as there is a critical relationship between energy and protein utilization, especially in the rumen. The metabolizable protein system considers rumen degradable protein (RDP) and undegradable protein (UDP) and the contribution that both of these make to the tissue protein (TP) requirements of the animal. The requirement for RDP in the lactating cow depends upon the size of the animal, the yield of milk and the live weight change. The RDP requirement of a 350 kg cow was about 550.4 g/day (Derived from the equation RDP (g/day) = 8.34 x ME intake (McDonald et al 1987; Topps and Oliver 1993)). The metabolizable protein requirement for maintenance was 177.2 g/day (Derived from the equation TP for maintenance = 2.19 g/kg W^0.75 (McDonald et al 1987). The metabolizable protein requirement for milk production was 121.6 g/day (Derived from the equation TP for milk production = milk protein content x true protein nitrogen fraction of milk x daily milk yield (McDonald et al 1987). The total metabolizable protein requirement was, therefore, 298.8 g/day. However, the metabolizable protein from microbial protein was 299.6 g/day (TMP = 4.54 X ME intake), which was higher than metabolizable protein requirement, so there was no UDP requirement.

Both hay and maize stover have protein contents of about 40 g CP/kg DM (Topps and Oliver 1993). Assuming that animals consumed equal amounts of maize stover and hay, the metabolizable protein that could be supplied was 85.7 g/day (Topps and Oliver 1993). This would leave a deficit of 213.1 g/day that needed to be supplemented. In their normal practice, farmers supplied about 2 kg home-mixed supplement containing 83 g metabolisable protein, given that most supplements were based on snap corn and/or maize. This meant that the animals suffered from a deficiency of both protein and energy.

About a third of the animals in the present study were milking, not pregnant and not cycling at the pregnancy diagnosis in January 1999. According to a study by Warnick et al (1995), 5% of the cows diagnosed open calved at a time consistent with being pregnant when the diagnosis was made. In the same study, among cows diagnosed pregnant, 3.4% were subsequently bred and 1.5% were diagnosed open by palpation later. Pregnancy diagnosis by palpation per rectum can lead to pregnancy attrition where a positive pregnancy diagnosis 30 to 70 days post insemination results in a negative diagnosis in the second palpation carried out between 120 and 150 days after insemination. Labernia et al (1996) found overall proportion of pregnancy losses of 7.9% (9.6% in parous cows and 2.8% in heifers). In addition, the effect of time of pregnancy diagnosis on pregnancy attrition was significant, being higher in animals inseminated in summer than in autumn (P<0.04). Herd effect on pregnancy attrition was also significant.

In another study by Forar et al (1996) in which pregnancy was diagnosed by palpation per rectum, the cumulative incidence of foetal loss between 31 and 260 days of gestation was 10.8% overall and ranged from 7.6% to 13% among 10 herds. The interval of greatest risk of loss was between 31 and 55 days of gestation. In the present study, there were certain differences in pregnancy rate according to seasons and sectors. There is considerable inter-farm variation in fertility rates in dairy cattle due to time of service after calving and embryonic mortality (Forar et al 1996).

Seasonal differences in the number and size of antral follicles of Brahman (Bos indicus) cows have been reported (Lammoglia et al 1996). Differences in nutritional status of the cows could also account for the discrepancies. In a study by Alvarez et al (2000), ovarian follicular growth as indicated by number of follicles in all categories, growth rate of the first dominant follicle to develop during the oestrous cycle, and maximum diameter of the first dominant and ovulatory follicles was greater in Brahman (Bos indicus) than in Angus (temperate Bos taurus) cows. This concurs with the studies of Segerson et al (1984) and Simpson et al (1994), who indicated that the numbers of antral follicles are greater in Brahman than in Angus cows. In the present study, no breed distinction could be made.

According to results in Table 2, the highest percentage of animals milking and not milking classified as not pregnant and not cycling was 60% in the communal area and 42% in the small-scale commercial area during January 1999. This was a period of high temperature but improving nutrition in Nharira-Lancashire. High temperatures of up to 35⁰C (Steinfeld 1988) have been recorded in this area during the rainy season. The number of cows that were lactating but not cycling (33.3%) in the communal area was similar (32.1%) to that in the small-scale commercial area during the same period. The percentage of animals ready to breed was highest during December for both sectors (57.7% in communal area vs. 50% in smallscale area). Heat stress is a major contributing factor in low fertility in lactating dairy cows in hot environments (Wolfenson et al 2000). Heat stress affects production of progesterone (Howell et al 1994), while corpus luteum diameter and concentration of progesterone are positively correlated (Rajamahendran and Taylor 1990). The dominance of the large follicle is suppressed during heat stress and the steroidogenic capacity of theca and granulosa cells is compromised. Progesterone secretion by luteal cells is lowered during summer and in cows subjected to chronic heat stress. This is also reflected in lower plasma progesterone concentration (Wolfenson et al 2000). Therefore, reproductive performance could have been affected by seasonal differences in ambient temperature. This may be particularly so for exotic animals such as the Friesians which are less heat-tolerant than the indigenous and crossbred animals in the smallholder sector.

The high percentage of milking but anoestrous animals recorded in both sectors might have been due to inadequate nutrition. A key risk factor that causes increased incidence of metabolic disease is negative energy balance in the peri-parturient and early post-partum periods. Negative energy balance decreases LH pulse frequency, growth rate and diameter of dominant follicle, glucose and insulin concentrations and increases growth hormone and certain blood metabolites. These effects result in greater loss of body condition score and a higher percent of anoestrous cows in the herd (Roche and Diskin 1995). It is important to decrease the incidence of metabolic disease by achieving high dry matter intake and minimising the period of negative energy balance after calving. In Nharira-Lancashire, some cases of cattle dying in the early post-partum period were recorded during this study. Therefore, nutritional management of the cow has a crucial role to play in improving reproductive efficiency, because acute nutritional deprivation has immediate deleterious effects on follicular growth and ovulation.

In order for cattle to ovulate in the early post-partum period, ovarian follicular activity must be re-established. This is dependent on restoration of LH secretion following calving (Thatcher et al 1996). The post-partum restoration of pulsatile LH secretion does not occur until the maximal decrease in post-partum energy status is observed and animals begin to reverse their decrease in energy status (Thatcher et al 1996). Farmers in Nharira-Lancashire can use body condition score in practice to control post-partum reproductive performance of their animals by manipulating feeding. Kaziboni et al (2004), working in the same area, noted an improvement in conception rate with increasing body condition score. The farmers in Nharira-Lancashire could improve the productivity of their animals by using cheaper, farm-mixed supplementary feeds strategically.

The proportion of indigenous animals used specifically for dairy was low in this study, despite the fact that they are common on resource-poor farms in the communal area. In the smallscale commercial sector, the only Bos indicus breed used for dairy was the Brahman, which is a dual-purpose breed. Earlier work in Nharira-Lancashire (Mandibaya et al 1999) showed that farmers did not prefer the Friesian cows despite their high milk yield potential because they required higher levels of good quality feeding, had poor reproductive performance and were susceptible to diseases. During peak milk production, that is, up to three months post-partum, dry matter intake is not at its maximum and the cow will be losing weight (Schingoethe 1991). However, since appetite lags behind nutritional requirements, the peak milk production phase is a period of negative energy balance. During this phase of lactation, the objective is to increase feed intake as rapidly as possible to minimize the nutritional deficit, but not to cause digestive upsets. Supplementary feeding during early lactation has been shown to improve condition score at mating and so reduce infertility induced by acute energy deficiency in lactating cattle (Rogers 1985).

The mortality rate for cows observed in this study was unacceptably high, especially for smallholder farmers who cannot afford to purchase replacement animals. Thorough studies of the causes of deaths and strategies to reduce mortality in this sector are required.

Conclusion

• The study showed that animals lose body weight and body condition during the dry season culminating in unsatisfactory ovarian activity.

• The viability of the smallholder dairy farming depends on optimal reproductive and lactation performance by the cows. Therefore farmers should ensure that their animals do not lose weight during certain periods by monitoring the body condition of the animals. The use of pregnancy diagnosis would further ensure that only those cows with high productivity are kept on the farm.

Acknowledgement

We would like to thank the Danish International Development Agency (DANIDA) for funding this study, and workers and colleagues in the Department of Animal Science of the University of Zimbabwe for their support. We also acknowledge the farmers in Nharira-Lancashire for the use of their cattle for this study and their patience.

References

ADAS 1978 Condition scoring of dairy cows. Leaflet 612. Ministry of Agriculture, Fisheries and Food, London.

http://www.defra.gov.uk/animalh/welfare/farmed/cattle/booklets/pb6492.pdf

Alvarez P, Spicer L J, Chase Jr C C, Payton M E, Hamilton T D, Stewart R E, Hammond A C, Olson T A and Wettemann R P 2000 Ovarian and endocrine characteristics during an oestrus cycle in Angus, Brahman and Senepol cows in a subtropical environment. Journal of Animal Science 78: 1291-1302. http://jas.fass.org/cgi/reprint/78/5/1291

Dube D M J 1995 The role of high quality dry season forage from mixed crop silages in the small holder dairy farming sector of Zimbabwe-Dairy Development Programme Perspective: Paper presented at the proposed Rockefeller Funded Mixed Crop Silage Regional Project Workshop. Faculty of Agriculture, University of Zimbabwe.

Dube D 2000 Smallholder dairying in Zimbabwe - where are we? Proceedings of a review workshop held in Harare, Zimbabwe, 10-13 January 2000. Edited by S Sibanda and N T Kusina.

Forar A L, Gay J M, Hancock D D and Gay C C 1996 Featal loss frequency in ten Holstein dairy herds. Theriogenology 54 (8): 1505-1513.

Howell J L, Fuquay J W and Smith A E 1994 Corpus luteum growth and function in lactating Holstein cows during spring and summer. Journal of Dairy Science 71: 735-739. http://jds.fass.org/cgi/reprint/77/3/735

Kaziboni S, Kusina N T, Sibanda S, Makuza S, Nyoni O and Bhebhe E 2004 Performance of artificial insemination in smallholder dairies in Nharira-Lancashire in Zimbabwe. Livestock Research for Rural Development Volume 16, Article # 25 Retrieved March 23, 2006, from http://www.cipav.org.co/lrrd/lrrd16/4/kazi16025.htm

Labernia J, Lopez-Gatius F, Santolaria P, Lopez-Bejar M and Rutllant J 1996 Influence of management factors on pregnancy attrition in dairy cattle. Theriogenology 45(6): 1247-1253.

Lammoglia M A, Willard S T, Oldham J R and Randel R D 1996 Effects of dietary fat and season on steroid hormonal profiles before parturition and on hormonal, cholesterol, triglycerides, follicular patterns and post-partum reproduction in Brahman cows. Journal of Animal Science 74: 2253-2262. http://jas.fass.org/cgi/reprint/74/9/2253

Littell R C, Henry P R and Ammerman C B 1998 Statistical analysis of repeated measures data using SAS procedures. Journal of Animal Science 76:1216-1231. http://jas.fass.org/cgi/reprint/76/4/1216

Mandibaya W, Mutisi C, Hamudikuwanda H and Titterton M 1999 The nutritive value, intake, digestibility and nitrogen balance of farm-grown and prepared sunflower-based dairy calf meals. Tropical Animal Health and Production 31(5): 321-331.

Masama E, Kusina N T, Sibanda S and Majoni C 2003 Reproduction and lactational performance of cattle in a smallholder dairy system in Zimbabwe. Tropical Animal Health and Production 35(2): 117-129.

McDonald P, Edwards R A and Greenhalgh J F D 1987 Animal Nutrition. Fourth Edition. Longman Group UK Ltd. p426.

Rajamahendran R and Taylor C 1990 Characterization of ovarian activity in post- partum dairy cows using ultrasound imaging and progesterone profiles. Animal Reproduction Science 22: 171-180.

Roche J F and Diskin M D 1995 Hormonal regulation of reproduction and interactions with nutrition in female ruminants. In: Ruminant physiology: Digestion, Metabolism, Growth and Reproduction. Edited by W V Engelhardt, S Leonhard-Marek, G Breves and D Gresecke. pp 409-428.

Rogers G L 1985 Pasture and supplements in the temperate zones. In: The Challenge: Efficient Dairy Production. Australian and New Zealand Societies of Animal Production.

SAS (Statistical Analysis Systems) Institute 1994 SAS Guide for Personal Computers. SAS Institute, Cary, North Carolina, USA.

Schingoethe D J 1991 Feeding dairy cows. In: Livestock feeds and feeding. Third edition. Editor: D C Church. Prentice-Hall International Editions. 278-293.

Segerson E C, Hansen T R, Libby D W, Randel R D and Getz W R 1984 Ovarian and uterine morphology and function in Angus and Brahman cows. Journal of Animal Science 59:1026.

Simpson E, Chase C C Jr, Spicer L J, Vernon R K, Hammond A C and Rae D O 1994 Effect of exogenous insulin on particular insulin-like growth factor I, insulin-like growth factor binding protein activity, follicular oestradiol and follicular growth in superovulated Angus and Brahman cows. Journal of Reproductive Fertility 102: 483-489.

Steinfeld H 1988 Livestock development in mixed farming systems: A study of smallholder livestock production systems in Zimbabwe. Farming systems and resource economics in the tropics, Volume 3, Wissenschaftsverlag Vauk Kiel KG, Berlin, Germany. 244p.

Stevenson J S, Thompson K E, Forbes W L, Lamb G C, Grieger D M and Corah L R 2000 Synchronizing estrus and (or) ovulation in beef cows after combinations of GnRH, Norgestomet, and prostaglandin F₂ with or without timed inseminations. Journal of Animal Science 78:1747-1758. http://jas.fass.org/cgi/reprint/78/7/1747

Thatcher W W, de la Sota R L, Schimitt E J P, Diaz T C, Badinga L, Simmen F A, Staples C R and Drost M 1996 Control and management of ovarian follicles in cattle to optimize fertility. Reproductive Fertility Development 8: 203-217.

Topps J H and Oliver J 1993 Animal foods of Central Africa. Zimbabwe Agricultural Journal Technical Handbook No. 2 .154pp.

Warnick L D, Mohammed H O, White M E, Erb H N 1995 The relationship between the intervals from breeding to uterine palpation for pregnancy diagnosis with calving outcomes in Holstein cows. Theriogenology 44:(6) 811-825.

Wolfenson D, Roth Z and Meidan R 2000 Impaired reproduction in heat stressed cattle: basic and applied aspects. Animal Reproduction Science 60-61(1-4): 535-547.

Received 22 March 2006; Accepted 22 July 2006; Published 6 September 2006

Go to top