A review of environmental and management factors affecting the reproductive performance of Holstein-Friesian dairy herds in Tunisia

M Ben Salem, M Djemali^*, C Kayouli* and A Majdoub^*

Laboratory of Animal and Forage Production, National Institute for Agricultural Research, Rue Hédi Karray, 2049 Ariana, Tunisia
lahmar.mondher@iresa.agrinet.tn
^*Institut National Agronomique de Tunisie, 43 Avenue Charles Nicole, 1082 Tunis, Tunisia

Abstract

Holstein cows are the major milk-producing cattle in Tunisia. However, under local conditions, the reproductive efficiency of these cows is low and the production and economic efficiency of dairy herds is reduced. The objective of this paper is to evaluate the reproductive performances of dairy herds, investigate major management and environmental factors that affected these performances and suggest alternative management practices that have potential to improve reproductive efficiency and productivity of dairy cows and to ensure the sustainability of dairy herds. Available information on the reproductive performance of Holstein dairy herds in Tunisia have been compiled and examined. The relation among management practices, temperature and humidity and reproductive performance is discussed.

Data showed that the reproductive performance of Holstein herds is poor. Average calving interval is in excess of 13 months and calving to conception interval can be as high as 157 days. Average services per conception often exceed 2. Cows inseminated in the summer when temperature-humidity index values are above 72 have the lowest reproductive efficiency. The culling rate for reproductive failure is more than 40% of all culled cows. These performances are the result of poor herd management and adverse summer high temperature and relative humidity. Poor feeding management of dry and early postpartum cows, inappropriate heat detection and breeding programs and the lack of heat stress relief management techniques and strategies are the major causes of the low reproductive efficiency of dairy cows. Improving this efficiency requires that reproductive management programs should be integrated into broadly based production management strategies.

Major improvements will first be associated with cycle control techniques, which will result in a thorough and accurate oestrous detection. In addition, a good nutritional program should provide dietary control of hypocalcaemia, ketosis, retained placenta, monitor dry cows and lactating cow rations, maximize feed intake and prevent nutrient deficiency problems. A reproductive health program, whereby all cows and heifers are checked and treated on a regular basis, should be followed. Practical and economical heat stress relief systems, such as shades and fans, and feeding strategies, such as dietary fiber adjustments, protected fat supplementation and feeding during the cool hours of the day, need to be adopted to reduce the negative effects of heat stress on the reproduction of dairy cows.

Key-words: Dairy cows, efficiency, environment, management, reproduction

Introduction

During the last two decades, the dairy sector in Tunisia went through major development programs, which call in most cases for increased milk production to ensure the country's self-sufficiency in milk and dairy products. Thus, numerous measures were taken in favour of the sector aiming mainly at the development of a dairy industry based on national production. These measures were particularly related to price policy and investment loans for the purchase of imported pure breed dairy heifers. They resulted in a continuous increase in the total cow population, which went from 355.000 heads in 1987 to 485.000 in 2002, and in about three fold increase in total milk production, which went from 356.000 to 940.000 tonnes during the same period. The population of cows is composed of exotic breeds (45%), native animals (37%), and their respective crossbreds (18%). Imported breeds included the Friesian-Holstein, the Brown Swiss, the Tarentaise and the Fleckvieh. Their total number increased from 88.000 to 212.000 heads between 1987 and 2002. The Holstein is by far the largest introduced breed. Its share to total milk production is more than 70%.

Today the Tunisian agriculture is confronted with decreasing world commodity prices and strong competition from overseas products, including milk and milk products. Thus, the sustainability of dairy farming requires that the dairy sector productivity growth needs to be fostered because only efficient farmers are likely to stand the competitive pressure and to remain competitive in the ever-changing world economy. This could be achieved either trough a technological progress or an increase in the reproductive efficiency of dairy farms. The latter appears to be the first logical step in a progress that leads to enhanced cattle productivity and dairy herds profitability in Tunisia. Indeed, under local conditions, productive and reproductive performances of Holstein cows remain low, while it is known that reproductive efficiency is a major contributor to profitability of dairy herds. The objectives of this paper are two fold. One is to evaluate the reproductive efficiency of Holstein dairy herds in Tunisia. The other is to address current management practices and environmental factors that affected this efficiency and to suggest alternatives that have potential to improve reproductive efficiency of dairy cows.

Source of information

Holstein cows are the major exotic dairy cattle introduced into the country. Their contribution to total milk production is around 73%. Thus, the data examined in this paper refers to Holstein cows. Much of the information used comes from scientific research works on the reproductive performance of dairy cows. Mainly research conducted for graduate programs and papers published in national or international scientific journals were considered. Additional information, whenever needed, is obtained from the national center for performance recording of dairy cattle. Data included calving interval, calving to conception interval, number of services per conception and culling rate for reproductive failure. The time trend of reproductive performances was examined using published yearly data and research studies covering different periods of time. The first work (Frigui 1995) looked at the 1993 reproductive performances of 196 large herds under the national program for performance recording of dairy cattle. The second work is that by Rezgui (1996), which examined the reproductive performance of 5 large dairy herds using a 7-year period data (1988-1994). The Third work was conducted recently by Ben Hamouda et al (2005). It assessed the reproductive performance recorded for dairy herds under the national program for animal performance recording between 1995 and 2001 (164.000 artificial inseminations for 49.000 lactations). The last work used long-term data to examine the effect of heat stress on reproductive performances of 4 Holstein herds located in different zones (Bouraoui et al 2002). The first part of the article is an examination of animal reproductive performances. The second part is a discussion of major management and environmental factors affecting these performances. In the last section, alternatives that have potential to improve reproductive efficiency of Holstein dairy herds in Tunisia were suggested.

Reproductive performances of Holstein cows

Various methods are used for calculating reproductive indices and assessing reproductive efficiency in dairy cows. Proposed standards for measuring dairy herd reproductive efficiency include calving to conception interval, number of services per conception, non return rate, calving interval and reproductive culling rate for infertility (Fertrow et al 1990). Available indices on dairy herds in Tunisia are given in table 1(Rezgui 1996).

Overall means for calving to first service, calving to conception and calving intervals were 73, 103 and 407 days, respectively. Average services per conception were 2.2. However, all these indices varied between herds. Calving to first service intervals were 79, 68, 73, 73 and 67 days respectively for herds A, B, C, D and E. Calving to conception intervals were 101, 103, 102, 110 and 99 days for herds A, B, C, D and E, respectively. Corresponding calving intervals were 417, 401, 399, 420 and 401 days. Similar values for the calving to first service interval and the calving interval were reported by Frigui (1995). However, using data on larger numbers of herds and animals, Ben Hamouda et al (2005) reported longer intervals for all the indices. They reported a calving to first service, calving to conception and calving intervals of 85, 157 and 417 days, respectively. This suggests a deterioration of the cow's fertility in Tunisia over the time. This is in agreement with the existence of a worldwide trend towards declining reproductive performances of dairy herds (Lucy 2001). The number of services per conception ranged between 2 in herd C and 2.5 in herd D. Recent findings by Ben Hamouda et al (2005), which indicate an average number of services per conception of 2.5, fall within previous reported results and confirms again the deterioration in fertility parameters.

Impaired reproductive performance is the predominant reason for culling in several countries. This is also true in Tunisia. The average percentage of cows culled for reproductive failure is high and represents 42.5% of all culled cows. It is almost twice the culling rate for low milk production. It can be as high as 49%. It varies with the lactation number, with the highest rates being observed for the third and fourth lactations (table 2). These values translate poor reproductive performances.

Calving interval is above 13 months, which makes the objective of one calf every year impossible. The high number of services per conception increases breeding and veterinary costs. The large calving interval results in few numbers of calves being borne per year and decreases milk production per time interval. Consequently, impaired fertility is causing economical losses and the profitability of dairy herds is reduced. One partial explanation for recorded poor reproductive performances comes from the relative distributions of cows conceiving at the first service, those requiring 3 services and more, those having a calving to first insemination interval above 90 days and cows with a calving to conception interval longer than 110 days. Data reported by Rezgui (1996) indicate that the percentage of cows that require 3 services and more is as high as 30%. That of cows having a calving to first insemination interval more than 90 days is 18.3%. The percentage of those having calving to conception intervals more than 110 days is high (33.6%). Recent data from Hemdane (2003) indicated that 52% of the cows under the national animal performance-recording program have a calving to conception interval more than 120 days. The magnitude of these values, coupled with field observations, suggests that these low performances resulted more likely from poor management practices and adverse summer climatic conditions. Management practices show that feeding of dry and early postpartum cows is not appropriate, heat detection and health programs are not efficient, and heat stress alleviating strategies are not adopted during the summer season.

Factors affecting reproductive performances

Physiological, pathological, management and environmental factors affect reproduction in cattle. If one or more of these factors is sub optimal, then both the calving interval and culling rate due to reproductive failure can increase and profitability of dairy cows decreases. The focus of this paper is to discuss only the effects of management, temperature and relative humidity on the reproductive efficiency of dairy cows.

Effect of management on reproduction

Data given in tables 1 and 2 come from 5 different large dairy herds conducted under intensive production systems. Average herd size is about 600 cows. The examination of management practices among these herds shows failures at various aspects of management. Reproductive management is not efficient. Heat detection, the single most important factor affecting reproductive efficiency, is one of the major management problems in our dairy herds. In most case, visual detection of oestrous lacks accuracy and thoroughness. The reliance on simple workers, with less specialized dairying skills and not motivated and supervised often results in heat detection errors. Common errors include identification, omission and diagnosis and inadequate or inaccurate oestrous detection, especially if either is combined with reduced inseminating competence, can prolong interval from calving to conception and increase culling due to infertility. Also, too few observations per day are being conducted in our herds to check for heat activity, where there is no substitute for frequent and systematic observation of the cow. In most cases, people involved in heat detection are only present at regular working hours when they should be present at very specific hours because the pattern of heat onset is variable, with the greatest activity occurring early morning and late evening. Moreover, too little time spent observing the cow and observing the cow at the wrong times or in the wrong place such as at feeding time or in the collecting yard at milking time are other reasons for heat detection failures in our herds. Breeding at the wrong time within the oestrous period is another important management factor associated with infertility in our dairy cows either because of a limited knowledge or unavailability of the inseminator. Another management aspect, which is of concern for our dairy herds, is the quality of reproductive records. Although all herds do have recording systems, large numbers of records are missing, incomplete, inaccurate or not updated, which limits their usefulness in measuring elements usually used when reproductive management needs to be improved. Simple, complete and accurate records about the entire reproductive life of the dairy cow are required to monitor components contributing to reproductive management.

Many specific reproductive health problems, such as, the true anoestrus, ovarian cysts, abnormalities of the puerperium, retained placenta and metritis are quite common in dairy herds. They require a good reproductive health program, which is essential for efficient reproduction not only because it generates data necessary for breeding management, but it also allows for checking normal uterine involution and return of ovarian cyclicity. Unfortunately, this type of program is lacking in many herds where veterinarians are usually called on an emergency basis.

Nutrition often directly affects reproductive capabilities. Calving intervals in excess of 12 months are often caused by nutritional stress (deficiency) at some point, either before the calving season or during the subsequent breeding season, which results in thin body condition and poor reproductive performance. The number one nutritional reason for poor reproductive performance is the lack of energy. Energy deficiency, particularly in postpartum cows, is most likely the major feeding factor involved in poor reproductive performance of dairy herds in Tunisia. It results from the feeding of poor quality forages, which in most cases, is coupled with inadequate supplementation. The end result is that follicular growth and development leading to first ovulation are affected and that cows in most negative energy balance are more likely to remain anoestrus.

Housing arrangement, concrete floors without adequate bedding and feet and leg problems are other factors associated with lowered detection of heat and reduced fertility in our herds. Cows do not have enough space to interact with their herd mates once on heat, making detection more difficult. In many cases we have seen slippery floors in our barns without bedding because straw shortage. The excessive (more than 60% of the total ration on a dry matter basis) use of concentrate feeds in the ration of lactating cows along with the prevalence of concrete floors increase the frequency of cows with sore feet among our herds. These cows dislike being mounted on coarse floors. They will exhibit fewer stands resulting in poor heat detection. Consequently, they will have significantly longer calving to service and calving to conception intervals. Research showed that mounting activity was reduced by almost the half when cows were left on concrete as opposite to softer floors while the duration of oestrus activity was reduced by 25% (Britt et al 1986).

Effect of ambient temperature and relative humidity on reproduction

Among all environmental stressors, the temperature and the relative humidity are the major factors, which affect the reproductive performance of dairy cows. One aspect of the temperature effects is heat stress, which is caused by high ambient temperature and aggravated by high relative humidity. The temperature-Humidity Index (THI) is a widely used tool to assess the impact of heat stress on dairy cows (Johnson et al 1962). Research in Tunisia indicates negative effects of heat stress on the reproduction of dairy cows. Bouraoui et al (2003) used long-term data on Friesian-Holstein cows and calculated THI values to assess the effects of heat stress on first conception rate, calving to conception interval and calving interval. Results showed that heat stress affects days open and calving interval. The lowest conception rate at first breeding (25.8%) was observed in august when THI reaches 78, which is above the critical value of 72 reported by Johnson (1980). The highest rate (58.9%) was observed in February when THI values are well below 72. Similarly calving and calving to conception intervals were longer for cows calving during the months of May, June and July compared to those calving during December and January. Calving to conception interval varied between 130 and 167 days for cows calved in May and June against a variation between 77 to 115 days for those calving in December and January. The calving interval was in the range of 390 and 420 days for cows calved in May and June against 355 to 388 days for those calving in December and January. These results are in agreement with those reported by Du Bois and Williams (1980) and Weller and Folman (1990), which indicate larger calving to conception intervals for cows calving during hot months. In addition, the results showed that abortion and retained placenta percentages were highest for cows calving during the summer (Bouraoui et al 2003). Average abortion rates were 17.4 and 15.2%, respectively for June and July. Respective retained placenta rates were 39.1 and 21.7%. Corresponding rates for other months rarely exceeded 5% for abortion and 20% for retained placenta.

Alternatives for improving reproductive efficiency

Reproductive efficiency is a major contributor to profitability of dairy herds. Dairymen must then be concerned with its improvement. Selection favouring efficiency of reproduction would not be effective in improving reproductive efficiency because reproductive traits have low heritabilities. Rather, significant improvement in reproductive efficiency can be accomplished by the herdsman through good management. Specific attention to several management practices outlined in this paragraph should enable dairymen in Tunisia to achieve optimal reproductive efficiency. Future developments in management for successful reproduction in our herds will be associated with careful, accurate and thorough oestrus detection, excellent recording system and animal records, breeding at the right time relative to calving and onset of heat, comprehensive reproductive health program, sound nutritional program for dry and early postpartum cows and the adoption of heat stress relief strategies.

The single most important factor affecting heat detection efficiency is that those responsible for checking for heat should fully understand signs of heat and should be fully devoted to heat detection. Developing employee performance incentives and training herdsmen to recognize signs of heat and to improve heat detection methods and insemination timing may improve heat detection and conception rates. Moreover, implementing a good recording system for individual animals is essential for good breeding management and all infertility investigations. Problems in detection can, in some cases, be reduced using inexpensive appropriate detection aids. Various aids are available. However, the choice depends on whether problems are producing errors of identification, omission, or diagnosis. One option would be the use of tail painting. Research showed that efficiencies of oestrous using tail paint vary from 44 to 96% (Pennington et al; 1986; Sawyer et al; 1986). Active vasectomized bulls with chin-ball marking harness are also useful in identifying cows on heat when such animals are exposed to the herd. Other aids, which can be used for oestrous detection, include pedometers attached to the leg of the cow to measure increased walking in cows in heat over a unit of time. However, the most accurate method of oestrous detection remains careful frequent visual observation of cows by the dairyman. It is recommended that careful heat detection in the early morning and late evening should be coupled with two to three further checks during the day, at about 4 to 5 hour intervals. This will more likely ensure the detection of most of the cows in heat. In addition, dairymen should observe that cows first observed in standing heat during the morning should be bred in the afternoon of the same day, whereas cows first observed in standing heat in the afternoon should be bred in the morning of the next day. Breeding people should be well trained, very skilful and devoted to the success of the insemination. An incentive program should be implemented based on the successful rate of insemination.

Early identification and diagnosis of reproductive disorders for achieving good reproductive efficiency in a dairy herd is necessary. Thus, an appropriate reproductive health program, which involves more than regular visits, is essential. It is not sufficient to have an on-farm veterinarian. What is important is to have an applied comprehensive schedule of regular checks. Alternatively, it is recommended that an agreement between the dairyman and the veterinarian should be signed, whereby the latter checks and treats, if necessary, all cows and heifers on a regular basis, in addition to emergency calls.

Dairymen should also observe that their nutritional management program provides dietary control of hypocalcaemia, ketosis, retained placenta, carefully monitor dry cow and lactating cow rations, maximizes feed intake, ensures desired body condition scores and prevents nutrient deficiency. Obviously, the leading step toward adequate reproductive performance in lactating cows is correct ration formulation so that nutrients are adequately balanced. Deficiency in dietary minerals, improperly balanced proteins or inadequate energy in dairy rations affects reproductive function adversely. Farmers should keep the highest quality feeds to postpartum cows and make sure that their rations are adequately balanced, particularly for energy and proteins. This will not only maximizes feed intake and milk yield, but also should stimulate ovulation and may lead to important economic benefits. Unfortunately, this is not the case in most dairy herds where cows usually experience severe energy deficiency in early lactation as indicated by important weight losses and low body condition scores. One available option to combat the deleterious effects of negative energy balance, other than the use of high amounts of concentrate, is to feed protected fat, which increases the energy density of the diet, reduces energy deficiency, stimulates follicular growth and reduces the length of intervals from calving to first ovulation. Our results showed that supplementing high producing dairy cows with 700g/cow/day of calcium salts of palm oil fatty acids in early lactation significantly increased first service conception and pregnancy rates and reduced the number of services per conception.

Summer high temperature and relative humidity prevail all over the country. This exposes dairy cows to heat stress and requires that economically feasible heat stress relief techniques and feeding strategies should be implemented in our herds from mid-may to early September. Relieve techniques may include the use of fans, shades, water bathing, and adequate air circulation. Feeding strategies, which include either dietary fiber adjustment or the use of high-quality fiber forage, supplemental protected fat and feeding at cool hours (i.e. early in the morning and late in the afternoon) can greatly help in reducing the negative effect of heat stress on reproductive performance. Finally, adequate reproductive management in large dairy herds requires that cow groups according to their physiological stage should manage cows because each group has different requirements. Early postpartum cows, cows to be bred and problem lactating cows more than 100 days and not pregnant should be kept in one group. Pregnant lactating cows and pregnant non-lactating cows should constitute the two other groups. Such grouping is in fact compatible with other grouping systems based on feeding, herd health and milking management.

Conclusions

• Friesian-Holstein cows have poor reproductive performances under current herd management in Tunisia. The average calving interval is well over a year and the culling rate for reproduction failure is high compared to targeted objectives.

• Major factors associated with reproductive inefficiency of dairy herds include poor feeding management of dry and early postpartum cows, inefficient heat detection and breeding programs, inadequate reproductive health programs, and the lack in the adoption of heat stress relief systems and strategies.

• However, given these constraints, a room for reproductive efficiency improvement still exists and should be targeted, if dairy farming sustainability is sought. This requires the integration of reproductive management programs into broadly based production management strategies. Major improvements will first be associated with heat control techniques, which result in a thorough oestrous detection with increased accuracy. In addition, a good nutritional management program should provide dietary control of hypocalcaemia, ketosis, metritis, retained placenta, monitor dry cows and lactating cow rations, feed intake and prevent nutrient deficiency diseases.

• An appropriate reproductive health program, which involves more than simple regular palpation visits, is also essential for efficient reproduction.

• Ultimately, large farms should implement most suitable heat relief systems and adopt appropriate management strategies and feeding adjustments to reduce the impact of summer heat stress on the reproduction of cows.

References

Ben Hamouda M, Ben Mrad M and Hemdane M 2005 Genetic analyses of fertility parameters and their relations to milk yield of Holstein-Friesian cows in Tunisia. Proceedings of the 34^th biennial session of ICAR. EAAP Publication n° 113, 71-76.

Bouraoui R, Majdoub M, Djemali M and Lahmar M 2003 Effet du stress thermique sur certains paramètres de reproduction chez la vache Frisonne conduite dans les conditions tunisiennes. Proceedings of the International Symposium Prospects for a Sustainable Dairy Sector in the Mediterranean. EAAP Publication n° 99, 317-322.

Britt J H, Schott R G, Armstrong J D and Whitacre M D 1986 Determinants of estrous behavior in lactating Holstein cows. Journal of Dairy Science 69 2195-2202.

Du Bois P R and Williams D J 1980 Increased incidence of retained placenta associated with heat stress in dairy cows. Theriogenology, 13 115-121.

Fertrow J, McClary D, Harman R, Butcher K, Weaver L D, Studer E, Ehrlich J, Etherington W, Guterbock W, Klingborg D, Reneau J and Williamson N 1990 Calculating reproductive indices: Recommendations of the American Association of bovine practitioners. Journal of Dairy Science 73 (1) 78-90. http://jds.fass.org/cgi/reprint/73/1/78

Frigui M 1995 Gestion technico-économique de l'élevage bovin laitier en Tunisie: Analyses des données du contrôle laitier, étude de cas des petites et moyennes exploitations. Mémoire de troisième cycle d'agronomie. Institut Agronomique et Vétérinaire Hassan II. Rabat.

Hemdane M 2003 Etude de la fertilité de la vache laitière en Tunisie. Mémoire de diplôme d'études approfondies de l'INAT.

Johnson H D, Ragsdale A C, Berry I L and Sanklin M D 1962 Effect of various temperature-humidity combinations on milk production of Holstein cattle. Mo. Agricultural Experimental Station Research Bulletin 791.

Johnson H D 1980 Environmental management of cattle to minimize the stress of climatic change. Biometeorology 7, Part 2 65-78.

Pennington J A, Albright J L and Callahan C J 1986 Relationships of sexual activities in estrous cows to different frequencies of observation and pedometer measurements. Journal of Dairy Science 69 2925-2934.

Lucy M C 2001 Reproductive loss in high-producing dairy cattle: Where will it end? Journal of Dairy Science 84:1277-1293. http://jds.fass.org/cgi/reprint/84/6/1277

Rezgui C 1996 Etude de la longévité de la vache Frisonne-Holstein dans quatre sociétés de développement agricole: facteurs de variation et paramètres génétiques. Mémoire de fin d'études du cycle de spécialisation de l'INAT.

Sawyer G J, Russell-Brown I D and Silcock J.K 1986 A comparison of three methods of estrus detection in commercial dairy herds verified by serum progesterone analysis. Animal Reproduction Science 10 1-10.

Weller J I and Folman Y 1990 Effects of calf value and reproductive management on optimum days to first breeding. Journal of Dairy Science 1318. http://jds.fass.org/cgi/reprint/73/5/1318

Received 27 March 2006; Accepted 31 March 2006; Published 11 April 2006

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