Breeding and management of dairy cattle in the Sultanate of Oman

Abstract

Proc. Aust. Soc. Anim. Prod. 1994 Vol. 20 BREEDING AND MANAGEMENT OF DAIRY CATTLE IN THE SULTANATE OF OMAN P.M. RIEK and A. SRIKANDAKUMAR College of Agriculture, Sultan Qaboos University, P.O. Box 34 Al-Khod 123, Sultanate of Oman SUMMARY Pregnancy and milk production records of Holstein, Jersey and Australian Milking Zebu (AMZ) cows at the Sultan Qaboos University College Farm in Oman were evaluated for the 4 year period from 1989 through 1992. The average daily temperature humidity index varied from 63 in January to 87 in July. All animals were bred in winter except for some AMZ cows which were deliberately held back for summer breeding. The average total milk yield for Holstein, Jersey and AMZ cows calving in winter were 4707 (P c O.OS), 3162 and 3472 kg respectively while that for AMZ cows calving in summer was 3288 kg. Corresponding corrected Dairy Herd Improvement Association (DHIA) 305-day milk production adjusted for age and month of calving were 5807 (P c 0.05), 3663, 3944 and 3669 kg. The average lactation length was 266, 285, 295 and 287 days for Holstein, Jersey and AMZ cows calving in winter and AMZ cows calving in summer respectively. Average pregnancy rates were 79, 76, 92 and 39% for Holstein, Jersey and AMZ cows calving in winter and AMZ cows calving in summer respectively. Pregnancy rate for AMZ cows bred in winter was higher (P c 0.05) than the pregnancy rate for both Holstein and Jersey cows bred in winter. The pregnancy rate for AMZ cows bred in summer was lower (P < 0.05) than in winter. Therefore, management practices, particularly those related to environmental control and breeding schedules must be adjusted to maximise reproduction and milk production under extremely hot humid conditions as those found in Oman. Keywords: dairy cattle, milk production, pregnancy rate, heat stress. INTRODUCTION Hot humid weather adversely affects reproductive performance and milk production in dairy cows (Thatcher 1974; Badinga et al. 1985; Imtiaz Hussain et al. 1992; Ray et al. 1992). While all European breeds of dairy cattle are vulnerable to such heat stress, Holstein cows are more vulnerable than Jersey cows (Stott et al. 1972). In Oman, persistent, intense heat and humidity characterise the summer on the northern coastal plain from May through September. Cows that fail to conceive prior to May generally remain open until the following December. In this study, total milk yield , lactation length and pregnancy rate were evaluated for Holstein, Jersey and Australian Milking Zebu (AMZ; Hayman 1974) cows at the College Farm, with the objective of assessing the ability of these breeds in terms of milk production and reproduction. MATERIALS AND METHODS The College Farm dairy herd was established as a small teaching herd with pregnant Holstein (n = S), Jersey (24) and AMZ (9) heifers, as well as open Holstein (4) and open AMZ (15) heifers. Cows were housed by breed in open-sided, sheltered pens with approximately 25 rnz of pen space per cow. Pens were oriented north-south with approximately half of each pen under shade. The shelter roof was sheet metal covered with mats made of date palm leaves and was 8 m high. Approximately half of the floor area was concrete while the remainder was a sand and gravel. mixture. From 1989 to 1992, the average daily environmental temperature and temperature humidity index (Kibler 1964) for January were 19OC and 63. The average daily environmental temperature and temperature humidity index increased to 27OC and 75 in March, 32OC and 82 in April and 40�C and 84 in May. The average daily environmental temperature reached a high of 43OC in June with a temperature humidity index of 85. Even though the average daily environmental temperature decreased to 36OC in July, the temperature humidity index continued to increase to a high of 87. Thereafter, the average daily environmental temperature and temperature humidity index declined progressively to 32OC and 80 by October and 27OC and 75 by December. From April through October, fans provided forced air flow (35 m/s) to pens of lactating animals through an overhead duct distribution system above the concrete floor area to facilitate evaporative cooling. In addition, from May until September, lactating cows were sprayed with water twice daily for 5 minutes at 0900 and 1400 hours in a concrete floored holding area . with overhead sprinklers followed by forced air cooling. Rhodes grass hay (8% crude protein) was available ad Zibitum. Lactating cows received 1 kg of commercial dairy concentrate (18% crude protein) in the milking parlour for each 2.5 kg of milk 132 Proc. Amt. Sot. Anim. Prod. 1994 Vol. 20 produced. Non-lactating cattle received approximately 2-3 kg of dairy concentrate daily. There was free access to self-waterers in all pens. All cows received copper supplementation twice yearly in February and September and had constant access to mineral licks. Cows were checked for oestrus at approximately 0600 and 1800 hours. In addition, KAMAR heat mount detectors were used on all cows. In general, all cows were bred by artificial insemination (AI) from January to April except for some AMZ cows that were deliberately held back for summer breeding in 1991 and 1992. Pregnancy rates were confirmed by rectal palpation approximately 90 days after last AI. Data were analysed using the general linear models procedure of the Statistical Analysis System (SAS 1985). Table 1. Pregnancy rate, average total milk yield and average lactation length for dairy cattle at Sultan Qaboos University College Farm, Sultanate of Oman Table 2. Overall milk production and reproductive performance of dairy cattle at Sultan Qaboos University College Farm, Sultanate of Oman RESULTS The average pregnancy rate, milk production (based on daily Holstein, Jersey and AMZ cows for each year from 1989 to 1992 pregnancy rate, milk production, corrected Dairy Herd Improvement production and lactation length for each breed is presented in Table were highest (92%, P < 0.05) during winter breeding and lowest records) and lactation length for are given in Table 1. The overall Association (DHIA) 305-day milk 2. Pregnancy rate for AMZ cows (39%, P c 0.05) during summer 133 Proc. Amt. Sot. Anim. Prod. 1994 Vol. 20 breeding. Pregnancy rates were similar (P > 0.05) for Holstein (79%) and Jersey (75%) cows bred in winter and were lower (P < 0.05) than those of AMZ cows bred in winter and higher (P < 0.05) than those of AMZ cows bred in the summer. There was no difference in the lactation length for the 3 breeds. The average total milk yield was highest (P < 0.05) for Holstein cows in all years. There was no difference in total milk yield between Jersey and AMZ cows calving in winter or summer. Corrected DHIA 305-day milk production adjusted for age and month of calving (Norman et al. 1974) was similar to the results for total milk yield. An example of milk production for 1991 in Figure 1 demonstrates the difference between the lactation curves for Holstein cows and the other breeds. Holstein cows produced more milk than either Jersey or AMZ cows throughout their lactation. 30 Figure 1. Lactation curves for dairy cattle bred in winter 1990 and summer 1991 at Sultan Qaboos University College Farm, Sultanate of Oman (Holstein bred in winter - open circles; Jersey, winter - closed diamonds; AMZ, winter - open squares; AMZ, summer - closed squares) DISCUSSION It is well documented that there is a negative relationship between high temperature humidity index and fertility and that Jersey cattle have a higher conception rate than Holstein cattle during periods of summer heat stress (Gwazdauskas 1985; Badinga et al. 1985). In addition, fertility in Holstein cows was depressed in summer (Ingraham et aZ. 1974; Badinga et al. 1985; Wolfenson et al. 1988). The similar pregnancy rates observed for the Holstein (79%) and Jersey (76%) cows in Oman during winter are lower than would be expected in more temperate climates. However, the AMZ cows which have been shown to be heat tolerant (Srikandakumar et al. 1993), had the highest pregnancy rate, 92%, in winter but decreased to a pregnancy rate of 39% in summer. However, this reduction in pregnancy rate was less than that for the temperate breeds in hot climates (Ingraham et aZ. 1976). The higher pregnancy rate of AMZ cows in winter may be associated with better recovery mechanisms from summer heat stress, an indication of better thermoadaptability of this breed to hot environments. The extreme heat of the Omani summer and the high thermal load associated with lactation may have resulted in cows being unable to maintain normal body temperature (Badinga et al. 1985; Srikandakumar et al. 1993) and this may explain the lowered pregnancy rate for AMZ cows bred during the summer. It has been shown that AMZ cows were shown to be the most heat tolerant, Jersey cows were intermediate and Holstein cows were the least in Oman based on rectal temperature, respiratory and sweating rates (Srikandakumar et al. 1993). Corrected DHIA 305-day milk production of 5807 kg for Holstein cows in Oman was lower than the 7815 to 8215 kg reported by Ray et al. (1992) for Holstein cows in Arizona in spite of the environmental 134 Proc. Amt. Sot. Anim. Prod. 1994 Vol. 20 modifications of shade, forced ventilation and sprinkling that were used (Thatcher 1974; Roman-Ponce et al. 1977). These data indicate that Holstein cows, while the least heat tolerant of these breeds, were the highest milk producers during winter under the management practices at the College Farm. Milk production of AMZ cows during the hot summer was similar to that during winter but with poor reproductive performance. 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