|Livestock Research for Rural Development 26 (6) 2014||Guide for preparation of papers||LRRD Newsletter||
Citation of this paper
To investigate the effects of the supplementation of Methionine Hydroxy Analog (MHA) and dietary antioxidants on milk production, forty (40) open does were mated, grazed on natural pastures and supplemented with a groundnut cake and rice bran-based concentrate until kidding. After kidding, 12 of the lactating females were penned individually and were divided in two groups balanced on number of kids /dam, body score and weight. Control animals were fed ad libitum natural pasture hay and 175 g/day of a concentrate without additional supplements (control) while animals of the supplemented group (MHA) were fed with 175 g/day of the concentrate containing a premix with MHA and dietary antioxidants. Every week does were separated from their kids, hand-milked, weighed and body conditions scored. Milk production was measured individually and samples of milk were chemically analyzed according to standardized techniques.
In control animals, peak lactation, reached after two weeks, was 298 ml/d while it was 326 ml/d after 3 weeks in MHA goats. Body condition and average daily gain fluctuated during the trial but overall were improved at the end of the experiment in both groups, with a slight advantage in MHA animals. The supplementation significantly improved milk protein and fat content. At weaning, kids of the MHA group tended to be heavier than those of the control group (6.95 kg versus 6.25 kg; p=0.079).
Key words: dairy goats, milk production, milk quality, nutrition, supplementation
In Senegal, local milk production is low and up to 66% of domestic demand was met by import in 2007 (DIREL 2009). Goats could contribute to self-sufficiency in milk and dairy products due to their high tolerance to the harsh environmental conditions prevalent in Senegal, their short production cycle and simple facilities required. However goat productivity remains low due to heavy reliance on fibrous feeds – mainly crop residues and low quality pasture – that are or may be deficient in nitrogen, minerals and vitamins (Breman and de Wit 1983). According to Vasquez-Añon et al (2008), antioxidant could improve milk production through the decrease of oxidative stress and improvement of fibrous feed digestion.
Moreover, studies carried out in recent years to identify amino acids that limit milk production in goats reported lysine and methionine to be the most limiting amino acids (Madsen et al 2005, NRC 2005). Feeding of protected methionine to lactating cows (Devillard et al 2007, Chen et al 2011) or goats (Salama et al 2003, Poljicak-Milas and Marenjak 2007, Flores et al 2009, El-Gendy et al 2012) resulted in increased milk yield and protein content.
The combination of antioxidant and methionine could be of interest in Senegal where the milk value chain is developing through the implementation of processing units, particularly of goat milk (Missohou et al 2004).The objective of the current study was to evaluate the effects of the supplementation of Methionine Hydroxy Analog (MHA) and dietary antioxidants as components of a concentrate blend on performance of lactating Sahelian goats in Senegal.
The experiment was carried out on the experimental farm of Ecole Inter-Etats des Sciences et Médecine Vétérinaires (EISMV) located in Keur Ndiaye Lo, 30 km from Dakar, Senegal. Forty (40) females, checked for pregnancy by echography, and 10 males of the Sahelian breed were purchased in June 2011at the market. They were mated, grazed on natural pastures and supplemented with a groundnut cake and rice bran- based concentrate (115 g/doe; 25:75% by weight) until kidding. After kidding 12 females were penned individually and divided in two groups balanced on number of kids /dam, body condition scores and weight.
The does were fed ad libitum natural pasture hay (Table 1) and transitioned over a 1 week period to 175 g/day of a molasses /urea/rice bran based concentrate blend (Control) or with similar concentrate with added premix containing Methionine Hydroxy Analog (MHA) and dietary antioxidants.
The concentrates were groundnut cake: rice bran: urea: sugar cane molasses: premix at a ratio of 50:35:7.5:7.5:0% and of 47.5:33.3:7.1:7.1:5% by weight, respectively, for Control and MHA animals. The premix had (% by weight): 6% MHA®, 6% Solis® anti-caking agent, 2.5% Mintrex® Zn, 1% Santoquin® Mix 6 antioxidant, 0.5% Mintrex® Cu, 0.5% Zorien SeY® (Novus International, Inc., St. Charles, MO), with calcium carbonate, dicalcium phosphate, and rice bran used as carrier (35%, 25% and 23.5%, respectively).
|Table 1. Chemical composition of diet ingredients for Sahelian goats in Senegal. All nutrients on a DM basis, except DM which is on air-dry basis|
|Dry Matter (%)||93.3||87.5||89.6||73.1|
|Crude Protein, CP (%)||5.2||54.5||12.3||2.60|
|Acid Detergent Fiber, ADF (%)||53.0||7.20||31.0||0.20|
|Neutral Detergent Fiber, NDF (%)||80.1||11.00||41.0||0.60|
|Non Fibrous Carbohydrate, NFC (%)||9.3||-||-||84.9|
|Total Digestible Nutrients, TDN (%)||52.0||84.0||74.0||72.0|
|Net Energy for Lactation (Mcal/kg)||0.98||2.37||1.71||1.81|
|Metabolizable Energy (Mcal/kg)||1.81||3.91||2.90||3.06|
|Digestible Energy (Mcal/kg)||2.24||4.31||3.30||3.48|
Body weight of the does and kids was determined at birth and on a weekly basis. Body condition scores of the does were determined according to Cissé et al (1992). Does were hand-milked weekly for 13 weeks 12 hours after withdrawing the kids and milk yield measured in the morning. Samples of milk were collected and stored for chemical analysis. Water was offered ad libitum and feed intake was calculated as the difference between the amount of feed offered and refusals. Milk dry matter (DM), ash, crude protein (CP) and ether extract (EE) were determined according to the French Association for Standardization (AFNOR 1997). Data were processed using IBM SPSS Statistics (Version 12, Chicago, IL, USA). Means were compared using the Fisher's protected least significant difference procedure (Snedecor and Cochran 1956) with significance at the 0.05 level of probability.
Table 2 shows the effects of MHA and antioxidant supplementation on growth parameters of the does. The supplementation of MHA and dietary antioxidant had no significant effect on body weight even if MHA does (30.3 kg) were heavier than Control (28.1 kg) at the end of the trial. In the last month of the trial average daily gain (ADG) was significantly higher in MHA animals (72.4 g) compared to Controls (3.3 g). ADG ranged from zero (0 g) in the first month to 3.33 g at the end of the trial in Control animals while in MHA does it was negative during the first month of lactation but quickly rose up to 72.4 g. These effects of the additives compared favorably with results reported by El-Gendy et al (2012) who attributed them to the effects of rumen protected methionine on the improvement of digestibility of nutrients and metabolism.
|Table 2. Effects of MHA and antioxidant supplementation on zootechnical traits|
|Body weight, kg|
|Average Daily Gain, g|
|Body condition score|
|Forage intake, g/d (air dry)|
|Feed efficiency (milk/feed intake)|
|ab Means within lines with different superscripts are significantly different (p<0.05)|
Feed intake and feed efficiency (milk/feed intake) did not differ between groups. These results are in accordance with results reported by El-Gendy et al (2012) in goats and by Devillard et al (2007) and Chen et al (2011) in lactating cows. Feed intake and feed efficiency were low at the beginning of the trial but increased sharply in the two groups (Figures 1a and 1b).
|Figure 1. Effects of MHA and antioxidant supplementation on feed intake and feed efficiency (milk/feed intake)|
Figure 2 shows the evolution of body score in the two groups of animals. During the first weeks of the experiment, there was a loss of body score in the two groups. However, Control animals recovered sharply while the body score loss persisted until the 7th week in MHA animals. One explanation could be the mobilization of body fat as a consequence of the imbalance between low feed intake at the beginning of the trial and increasing milk output, mainly in MHA animals.
|Figure 2. Effects of MHA and antioxidant supplementation on body score.|
As can be seen in Figure 3, milk yield quickly increased in the two groups but the peak lactation (298 ml/d in Control vs. 326 ml/d in MHA) occurred, respectively, 2 and 3 weeks postpartum. There was a slight indication (p = 0.23) that the overall average daily yield of milk was increased in the MHA and antioxidant supplemented group compared to the control. Many authors demonstrated that antioxidant (Mardalena et al 2011) and rumen protected methionine additives (Salama et al 2003, Poljicak-Milas and Marenjak 2007, Flores et al 2009, El-Gendy et al 2012) increase goat milk yield. In cattle, however, the effect of rumen protected methionine remains very controversial. For Wang et al (2010), Chen et al (2011), and Devillard et al (2007), the additives were efficient while Stokes et al (1981), Lundquist et al (1983), Huber et al (1984) and Overton et al (1996) reported no effects of rumen protected methionine on milk yield. As previously indicated, the low feed intake associated with this sharp increase in milk production during the first 3 weeks postpartum could explain the poor body condition score in that period.
|Figure 3. Effects of MHA and antioxidant supplementation on milk yield.|
Milk fat and milk protein were increased by MHA and antioxidant supplementation (Table 3). Similar results were reported by Saeed (2010) and Wang et al (2010) with antioxidants and by Yang et al (1986) with rumen protected methionine.
|Table 3. Effects of MHA and dietary antioxidant supplementation on milk chemical composition|
|Milk yield (ml/d)|
Dry matter (%)
Crude protein (%)
|Ether extract (%)|
ab Means within lines with different superscripts are different at p<0.05
The improved composition of milk from supplemented does could explain the growth rate and tendency towards higher body weights from birth (1.92 kg versus 2.11 kg; P=0.383) to weaning (6.95 kg versus 6.25 kg; P=0.079) found in kids (Figures 4a and 4b). According to Farina (1989) and Bourzat and Mian Oudanang (1994), growth rate in early youth is the consequences of mother milk capabilities (both quantity and quality).
|Figure 4. Effects of MHA and dietary antioxidant supplementation on body weight (left) and average daily weight gain or growth rate (right) of kids.|
In this study milk conversion ratios were 6.4 kg of milk/kg liveweight in control kids vs 5.8 kg of milk/kg liveweight in MHA kids. These ratios were lower than the results (15.6 kg of milk/kg liveweight) reported by Banda (1993) in small East African goat in Malawi but were comparable to results (6.0 kg of milk/kg liveweight) reported in another tropical breed of goat (Titi et al. 2011).
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Received 24 July 2013; Accepted 17 April 2014; Published 1 June 2014
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