DOI: 10.1111/jpn.12032
ORIGINAL ARTICLE
Effect of short-term supplementation with rumen-protected fat during the late luteal phase on reproduction and metabolism of ewes N. M. Hashem1 and S. Z. El-Zarkouny1,2 1 Department of Animal Production, Faculty of Agriculture, Alexandria University Alexandria, Egypt, and 2 Department of Arid Land Agriculture, Faculty of Meteorology, Environment and Arid Land Agriculture King Abdul-Aziz University Jeddah, Saudi Arabia
Summary This study was designed to study the effect of short-term supplementation with rumen-protected fat during the late luteal phase on reproduction and metabolism of sheep during breeding season. Seventy-six ewes (Rahmani, Barki and Awassi 9 Barki) were allocated to two groups considering genotype: the control ewes (C-group) received a maintenance diet, and the fat-supplemented ewes (F-group) received the maintenance diet plus 50 g/ head/day of rumen- protected fat (Megalac) for 9 days during which oestrus was synchronized. The latter had been accomplished using double intramuscular injection of prostaglandin F2a (PGF2a) 11 days apart. Ovarian activity, serum concentration of cholesterol, glucose, insulin and reproductive performance variables were recorded. Data were analysed considering treatment (group) and genotype. Supplementation had positive effects on the overall mean serum concentrations of cholesterol (p < 0.05), glucose (p < 0.05) on day 6 of nutritional treatment and insulin (p = 0.07) on day 8. Fat supplementation did not affect the total number of follicles, follicle populations and ovulation rate. However, fat-supplemented Rahmani ewes tended to have higher ovulation rate compared with other breeds (treatment 9 breed interaction, p = 0.06). Treatment also did not affect the mean concentration of serum estradiol or progesterone. Supplemented ewes had higher conception (p = 0.06) and lambing rates (p < 0.05) compared with control. In conclusion, short-term supplementation with rumenprotected fat as a source of energy around breeding time improved metabolism, conception and lambing rates of ewes without effects on steroidogenic capacity and ovarian activity being apparent. Keywords protected fat, short-term, ovarian activity, metabolites, ewes, subtropics, flushing, reproductive performance Correspondence N. Hashem, Department of Animal Production, Faculty of Agriculture, Alexandria University, Alexandria 21545, Egypt. Tel.: +20 1111003962; Fax: +20 35922780; E-mail:
[email protected] Received: 18 September 2012; accepted: 11 December 2012
Introduction Mechanisms that control selection of the ovulatory follicles from the follicular cohort are characterized by complex interactions between intrafollicular growth factors, the hypothalamic–pituitary–ovarian feedback system and by the nutrient supply to the follicle during the final stages (late luteal phase) of follicular growth and development (Scaramuzzi et al., 2006, 2010). In the sheep industry, nutritional measures can be used to improve reproductive performance of ewes, particularly ovulation rate. The stimulatory effect of nutrition inputs on folliculogenesis and ovulation rate can be exerted through long- or shortterms supplementation (Letelier et al., 2008). Further, nutritional measures for an increasing reproductive
efficiency are considered an alternative to hormonal treatments (Martin et al., 2004). Somchit et al. (2007) enhanced folliculogenesis and subsequent ovulation rate by short-term supplementation (focus feeding) with high energy inputs during emergence of ovulatory follicle(s). Diets containing lupin, maize or soy bean have been used for this goal (Pearse et al., 1994; Letelier et al., 2008). Under subtropical conditions, the breeding season often falls in the summer associated with elevated environmental temperature and humidity (Hashem et al., 2011; Hashem and Sallam, 2012), and with scarcity of high-quality nutrients. Thus, diets with high energy density may help animals to cover a higher proportion of energy requirements of the animals under conditions like great heat and humidity where feed consumption is typically
Journal of Animal Physiology and Animal Nutrition 98 (2014) 65–71 © 2013 Blackwell Verlag GmbH
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Reproductive performance of ewes flushed with protected fat
N. M. Hashem and S. Z. El-Zarkouny
impaired. Most studies performing focus feeding illustrated a clearly positive effect of short-term nutritional input on ovarian activity. This was shown for using grains (lupin, maize), glucogenic drenches and infusion of amino acids (Mu~ noz-Guti errez et al., 2002; Scaramuzzi et al., 2010). However, the potential for increasing total energy intake in ruminants by raising the proportion of grain in the diet is limited by the occurrence of digestive and metabolic disorders (Jenkins and Palmquist, 1984). Rumen-inert fats such as Ca-saponified fatty acids have been shown to increase total energy intake without adversely affecting rumen fermentation in cows (Chalupa et al., 1986) with a net energy value being approximately three times higher than that of maize (Andrew et al., 1990). In sheep, the use of Ca-soaps from palm oil in feed improved the number and size of the pre-ovulatory follicles (El-Shahat and Abo-El maaty, 2010), as well as ovulation rate and superovulatory response (Herrera et al., 2008). However, to the authors’ knowledge, reports on the effect of supplementation of rumenprotected fat as a source of energy for short term on ovarian activity and subsequent reproductive performance are limited. The objective of this study was therefore to study reproductive and metabolic responses of genotypes of sheep indigenous to the subtropics with various genetic makeups when subjected to a 9-day focus feeding protocol based on rumen-protected fat during the breeding season. Materials and methods This study was conducted at the Agricultural Experimental Station (31° 20/N, 30°E) of the Faculty of Agriculture of the Alexandria University from June to October, 2011. The procedures imposed on the animals were carried out meeting the International Guiding Principles for Biomedical Research Involving Animals (1985). Experimental design
Seventy-six 3- to 6-year-old adult ewes were allocated into two equal groups (n = 38): a control-group (C; Follicular phase
Luteal phase
PGF2α
genotypes: Rahmani, n = 15, Barki, n = 11 and Awassi 9 Barki, n = 12) and a fat-supplemented group (F; Rahmani, n = 15, Barki, n = 10 and Awassi 9 Barki, n = 13). Mean initial body weights and body condition scores (scale ranging from 1 = emaciated to 5 = obese; Jefferies, 1961) at allocation to the groups were 47.4 0.4 kg and 2.6 0.1, 38.5 0.5 kg and 2.7 0.2 as well as 38.3 0.4 kg and 2.4 0.2 for Rahmani, Barki and Awassi 9 Barki respectively. The corresponding average values for C- and F-group animals were 41.9 0.3 kg and 2.4 0.1 as well as 40.8 0.4 and 2.6 0.2. Animals were kept outdoors with shelter during the daytime, and were housed in semiopen barns at night. The mean ambient temperature across the flushing and mating periods was 29.7 0.8 °C, and the mean relative humidity was 70.5 0.9%. All ewes were subjected to oestrous synchronization using double injections of 125 lg cloprostenol (Estrumate, 250 lg cloprostenol/ml, Schering-Plough Animal Health, Germany) 11 days apart. All ewes received feed in an amount to cover their daily maintenance requirements according to their body weights (NRC, 1985). The maintenance diet consisted of 500 g of concentrate mixture (containing in g/kg, maize grains, 365; cottonseed meal, 350; wheat bran, 250; lime stone, 20; NaCL, 10; mineral premix, 5) and wheat straw (ad libitum). The fat-supplemented ewes received additionally 50 g/head/day of protected fat (Megalac, ME = 33 MJ/KG DM, Volac Ingredients Sdn. Bhd., Malaysia) for 9 days starting at day 0 – day 8 (Fig. 1). The fatty acid composition (g/kg product) of used protected fat was, according to producer’s statement, myristic acid, 3–3–3–3–
