Effect of energy level on milk production by Mossi ewes and Sahelian does

A. J. Nianogo and P.C. Ilboudo

Département de zootechnie - Université de Ouagadougou
B.P. 7021. Ouagadougou. Burkina Faso

Abstract
Introduction
Materials and methods
Results and discussions
Conclusions
References

Abstract

Two trials were conducted to evaluate the effect of energy level on milk production and composition and to establish the relationship between milk production and growth rate of suckling kids. In the first trial, 20 Sahelian does were divided into four groups to receive one of four isonitrogenous (18% crude protein (CP)) diets providing 42.2% total digestive nutrients (TDN) (diet 1a), 73.4% TDN (diets 2a and 3a) and 83.9% TDN (diet 4a). In the second trial, 18 Mossi ewes were divided into three groups to receive one of three isonitrogenous (17.4% CP) diets providing 62.1% TDN (diet 1b), 73% TDN (diet 2b) and 83.1% TDN (diet 3b). These production diets were formulated to provide subnormal (la & 1b), normal (2a, 2b and 3a), or high (3b and 4a) levels of energy; the amounts fed were constantly adjusted to milk yield. Additionally, animals were fed a basal diet satisfying all maintenance requirements. Milk production was estimated by the double weighing method, with four equally spaced weighing periods per day. In the two trials, daily dry matter intake (DMI), milk composition and production were not significantly affected by diet. It was concluded that small fluctuations in energy intake do not affect milk production in Sahelian goats or in Mossi sheep. Kid growth is correlated with milk consumption. Sorghum grain may be replaced by Dolichos lablab seeds in diets for lactating small ruminants.

Effet de l'apport énergétique sur la production laitière chez la brebis Mossi et la chèvre du Sahel

Résumé

Deux essais ont été conduits pour estimer l'effet de l'apport énergétique sur la production de lait et sa composition, et pour déterminer les relations qui existent entre la production laitière et le taux de croissance de jeunes allaités au pis. Dans le premier essai, 20 chèvres du Sahel ont été réparties en quatre lots. Chaque lot recevait une ration iso-azotée (18% de protéines brutes [PB]) apportant 42,2% de nutriments digestibles totaux (NDT) (régime la), 73,4% de NDT (régimes 2a et 3a) et 83,9% de NDT (régime 4a). Dans le second essai, 18 brebis Mossi réparties en trois lots recevaient une ration iso-azatée (17,4% de PB) apportant 62,1% de NDT (régime lb), 73% de NDT (régime 2b) ou 83,1% de NDT (régime 3b). Ces régimes avaient été formulés de manière à fournir des apports en énergie inférieurs (la et lb), conformes (2a, 2b et 3a) et supérieurs (3b et 4a) à la normale. Les quantités servies étaient constamment remaniées en fonction des quantités de lait produites par les animaux. En outre, le régime de base des animaux couvrait la totalité de leurs besoins d'entretien. La production laitière a été estimée par la méthode de la double pesée, avec quatre pesées quotidiennes espacées les unes des autres par des intervalles de durée identique. Dans les deux essais, le régime n'avait pas d'effet significatif sur l'ingestion de matière sèche, ni sur la composition et la production de lait. Il apparaît ainsi que de faibles fluctuations dans l'apport énergétique ne modifient pas la production de lait chez la chèvre du Sahel et le mouton Mossi. Il y avait une corrélation entre la croissance des jeunes et la consommation de lait. Dans les régimes des petits ruminants en lactation, on peut remplacer les grains de sorgho par des graines de Colique lablab.

Introduction

Limited information is available on the milk productivity of small ruminants in Burkina Faso. Milk from Sahelian goats is consumed by Fulani and other Sahelian livestock farmers. Milk production data is also useful for selection purposes; it is well established that females with high milk output promote faster growth and better survivability of their young.

Available data indicates that Mossi (IEMVT, 1980; Yoni, 1989) and Djallonké (Amegee, 1984a) ewes have a low milk production potential. However, preliminary studies conducted by Ouédraogo (1990) indicate that Sahelian does may produce considerable amounts of milk.

This study evaluated the effects of graded levels of dietary energy on dry matter intake (DMI), milk yield and milk composition. It was also intended to establish the relationship between milk production and the growth of suckling kids.

Materials and methods

A group of 20 Sahelian does and another of 18 Mossi ewes were paired, based on body weight and age. Each animal entered the study 48 hours after kidding. A two-week preliminary phase was observed, during which all animals received the same diet to establish initial production levels. After the preliminary phase, a separate 12-day trial was conducted for each species using different dietary treatments.

Trial 1

Paired does were randomly assigned to one of four production diets (Table 1). Three energy (E) levels were used: diet 1a (low E); diets 2a and 3a (medium E); and diet 4a (high E). Additionally, a maintenance (NRC, 1981) diet composed of 77% sorghum straw, 5% cottonseed meal and 18% wheat bran was fed to all groups. The amount of basal diet served daily was based on body weight. The amount of production diet served varied with milk yield.

Paired ewes were randomly assigned to one of three production diets (Table 2): diet 1b (low E); diet 2b (medium E); and diet 3b (high E). The ewes also received a basal diet composed of 83.9% chopped sorghum straw and 16.2% cottonseed meal (dry matter basis).

In each trial, kids were offered an ad libitum supply of sorghum straw and their mother's production diet. Body weights were monitored once a week. Feed intake of mothers was monitored daily during weeks 4,6,8,10 and 12. Milk production was estimated by weighing the kids immediately before and after suckling, four times per 24 hours, one day a week as described by Coombe et al (1960). Milk was sampled during weeks 4, 8, and 12 and preserved at 4°C with 1% of a 35% solution of formaldehyde until chemical analyses were performed.

The milk was analysed for total solids, crude protein (CP), casein and ash using methods described by AOAC (1984). Milk fat was determined by the Babcock method (AOAC, 1984). Lactose was determined by difference.

Data was statistically analysed using the SAS General Linear Models (GLM) procedures (SAS, 1982). Means were separated using Scheffe's Multiple Comparisons Test.

Results and discussions

Intake of dry matter

Dry matter intake (DMI) by goats increased with the increase in energy levels of the diets (Table 3). With ewes, DMI was depressed by the high energy diet (Table 4). Goats appeared to consume more DM than ewes.

Yield and composition of milk

Data on the yield and composition of milk are shown in Tables 5 (does) and 6 (ewes). The milk yield of does on diet 4a was significantly higher (P<0.05) than that of diet la. Peak milk yields were 1091.67, 1062.5, 1079.2 and 1275g/d for diets la, 2a, 3a and 4a respectively. Diets 2a and 3a performed similarly, indicating that Dolichos l. seeds may be a good substitute for sorghum grain.

Table 1. Composition of production diets for Trial I (goats).

Item		Diet
		1a	2a	3a	4a
Ingredient (%):
Cottonseed meal		17.00	4.00	0.00	22.00
Commercial mix*		17.60	24.00	2.00	0.00
Dolichos l. Seeds		5.00	5.00	42.20	0.00
Cottonseed		0.00	0.00	8.00	0.00
Wheat bran		14.50	28.50	23.00	0.00
Sorghum grain		17.50	36.00	10.00	72.50
Ground oyster shells		1.40	2.50	2.30	01.50
Molasses		0.00	0.00	5.00	0.00
Corn cobs		27.00	0.00	8.00	0.00
Cotton oil		0.00	0.00	0.00	4.00
Total		100.00	100.00	100.00	100.00
Expected chemical composition (%):
	TDN	62.16	73.38	73.42	83.87
crude protein (CP)		18.02	18.06	18.01	18.03
	Ca	0.62	1.01	0.63	0.62
	P	0.66	0.78	0.52	0.56

TDN = total digestible nutrients.
Cottonseed meal with 47% cottonseed hulls added.

Table 2. Composition of production diets for Trial 2 (ewes).

Item		Diet
		1b	2b	3b
Ingredient (%)
Cottonseed meal		32.50	12.00	00.00
Commercial mix1		17.00	8.00	0.00
Dolichos L. Seeds		5.00	42.00	49.50
cottonseed		0.00	3.00	7.00
Wheat bran		10.00	19.00	19.60
Sorghum grain		11.50	7.00	15.00
Ground oyster shells		2.50	3.00	1.70
Molasses		5.00	0.00	0.00
Corn cobs		8.00	27.00	0.00
Cotton oil		0.00	0.00	6.20
Urea		0.00	0.00	1.00
Total		100.00	100.00	100.00
Expected chemical composition (%):
	TDN²	62.09	73.03	83.13
crude protein (CP)		17.47	17.43	17.40
	Ca	1.04	1.68	0.70
	P	0.78	0.65	0.50

¹Cottonseed meal with 47% cottonseed hulls added.
²TDN: total digestible nutrients.

Table 3. Effect of diet on intake of dry matter (DMI) and average daily gain (ADO) of Sahelian goats.

Parameter		Diet
		1a	2a	3a	4a	SE
Does
	Number	6		4	6	4
	DMI, g/day	975.24	1122.91	1116.07	1178.47	65.63

g/kg0.75

84.88

92.57

96.13

101.16

2.96

Body weight, week:
	0	25.25	29.12	25.05	24.50	0.99
	2	26.03	28.45	25.10	24.35	0.98
	ADG, week 3-14	1.98a	17.56ab	10.71ab	39.29b	4.65
Kids
	Number	8	5	8	7
	Body weight, week:
	0	2.15	2.26	2.09	2.01	0.04
	14	8.64ab	9.78a	8.51ab	7.37b	0.39
ADG week:
	3-14	65.92	70.24	67.26	55.44	3.76
	0-14	66.20	76.74	65.56	54.67	4.22

Means in the same row with different superscripts differ significantly (P<0.05).

Average composition of the milk from does was not affected by diet (Table 5). However, diet 3a gave a higher (P<0.05) CP concentration than all other diets during week six. Milk yields obtained in this study were higher than those reported by Ouédraogo (1990) with hand-milked Sahelian does. However, Ouédraogo (1990) reported higher concentrations of solids (16.42%) and fats (6.03%).

Table 4. Effect of diet on intake of dry matter (DMI) and average daily gain (ADO) of Mossi ewes.

Parameter			Diet
			1a	2a	3a	SE
Ewes
	Number		6	6	6	-
	DMI, g/day		1051.50	1052.94	1016.00	23.20
		g/Kg0.75	85.95	87.33	79.58	1.95
Body weight, week:
	0		27.60	26.78	28.97	4.16
	2		27.47	26.57	28.97	0.94
ADG, week 3-14			5.16	17.26	12.50	3.48
Lambs
	Number		6	6	7
Body weight, week:
	0		2.76	2.33	2.41	0.43
	14		10.33	10.53	8.16	0.64
ADG week:
	3-14		76.19	80.95	54.59	6.17
	0-14		77.21ab	83.67a	58.45b	6.29

Means within the same row with different subscripts differ (P<0.05)

Table 5. Effect of diet on milk yield and milk composition of Sahelian does.

Parameter		Diet
		1a	2a	3a	4a	SE
Yield (g/d):
	week 3-14	582a	667ab	631	713b	45.72
	week 1-14	632a	700ab	675ab	735	47.98
Solids: %		13.67	12.31	13.38	13.21	0.25
	total (g/d)	102.10	106.72	110.22	120.28	8.43
Fat: %		5.22	3.81	4.76	4.47	0.23
	total (g/d)	38.66	32.46	38.53	36.95	2.49
Crude protein: %		3.83	4.05	3.76	3.62	0.07
	total (g/d)	29.06	34.96	31.12	33.20	2.52
Casein, %		3.08	3.31	3.20	3.05	0.05
Lactose, %		3.84	3.63	4.09	4.33	0.15
Minerals, %		0.77	0.78	0.81	0.77	0.01

Means in the same row with different superscript differ (P<0.05).
Body weights and ADG of all animals are shown in Tables 3 (goats) and 4 (sheep).

Milk yield (MY), milk composition and production of milk constituents by Mossi ewes (Table 6) were not affected by diet.

The MY recorded here were lower than those reported by Amegee (1984a) on Djallonké ewes for mothers of singles (547g/day) and for mothers of twins (772g/day). Amegee also reported higher concentrations of total solids (16.47%) and CP (6.02%).

Goats produced more milk than ewes and goat milk had a higher concentration of total protein, casein and minerals.

Bodyweight changes

Weight gains were low throughout both trials. Does had higher weight gain (P<0.05) on diet 4a than those on diet la

Growth of kids and correlation with milk yield

On average, lambs reached a higher body weight than goat kids at 14 weeks old. There was no effect of dietary treatments on average daily gain (ADO) or body weight of kids.

Table 6. Effect of diet on milk yield and milk composition of Mossi ewes.

Parameter		Diet
		1b	2b	3b	SE
Yield (g/d):
	week 3-14	395.31	387.50	396.35	27.50
	week 1-14	444.20	449.29	442.71	26.73
Solids: %		13.06	13.06	12.90	0.31
	total (g/d)	89.40	81.55	80.11	7.39
Fat: %		4.94	5.33	4.65	0.21
	total (g/d)	27.78	27.78	23.18	1.80
Crude protein: %		5.38	5.05	4.95	0.14
	total (g/d)	33.16	29.01	28.40	2.69
Casein, %		4.69	4.16	4.27	0.12
Lactose, %		4.12	3.70	4.18	0.25
Minerals, %		0.86	0.84	0.82	0.01

Correlation analyses indicated that milk consumption (MC) by a suckling kid is best estimated when the weights of the kid at birth (W_o) and at six weeks of age (W₆) are included in the equation (MC in g, W_o and W₆ in Kg):

e.g.	For kids (R2 = 0.9375)
MC =	-327.1092 Wo + 38.3492 W6 + 53.9617
	Wo x W6 + 1039.4727;
	For lambs (R2 = 0.8619):
MC =	-366.92 - 58.40 Wo + 37.96 W6 + 13.70
	Wo x W6.

Good correlations were also obtained between average daily MC in the first 13 weeks (91 days) of lactation, W_o and body weight at 13 weeks of age (W₁₃); (MC in g, W_o and W₁₃ in kg):

	For goats (R2 = 0.897):
MC =	-51.8991 Wo + 4.7041 W13 + 14.3734
	Wo x W13 ± 469.2035;
	For lambs (R2 = 0.7934):
MC =	-118.8236 Wo + 7.7736 W13 + 11.3062
	Wo x W13 ± 503.0907.

Multiple factor correlations provide a better estimate of milk production than those established between milk consumption and a single parameter (ADO, birth weight or body weight at 30 or 40 days) by Amegee (1984a,b).

Conclusions

Minor fluctuations in energy intake do not affect milk production in Sahelian goats or in Mossi ewes. Kid growth is highly correlated with milk consumption.

References

Amegee Y. 1984a. Etude de la production laitière de la brebis Djallonké en relation avec la croissance des agneaux. Revue d'élevage et de médecine vétérinaire des pays tropicaux 37(3):331-335.

Amegee Y. 1984b. Le mouton de Vogan (croisé Djallonké x sahélien) au Togo. La production lactée et ses relations avec la croissance des agneaux. Revue d'élevage et de médecine vétérinaire des pays tropicaux 37(1):82-90.

AOAC (Association of Official Analytical Chemists). 1984. Official methods of analysis of the Association of Official Analytical Chemists. 14th ed. AOAC, Washington DC, USA.

Coombe J B. Wardrop I D and Tribe D E. 1960. A study of milk production of the grazing ewe, with emphasis on the experimental technique employed. Journal of Agricultural Science 54:353-359.

IEMVT (Institut d'élevage et de médecine vétérinaire des pays tropicaux). 1980. Les petite ruminants d'Afrique centrale et d'Afrique de l'Ouest. Synthèse des connaissances actuelles. IEMVT, Maisons-Alfort, France. 295 pp.

NRC (National Research Council). 1981. Nutrient requirements of goats. National Academy Press, Washington DC, USA. 91 pp.

Ouédraogo Z. 1990. Aptitudes de la chèvre du Sahel burkinabé a la production laitière. Influence du rang de mise-bas, de l'alimentation et de la saison. Mémoire de fin d'études. IDR (Institut du développement rural), Université de Ouagadougou, Burkina Faso. 136 pp.

SAS (Statistical Analysis System). 1982. SAS User's guide: Statistics. SAS Inst. Inc., Cary, North Carolina, USA.

Yoni T. 1989. Influence du taux de concentré sur la production laitière des brebis mossi et la croissance des agneaux allaités. Mémoire de fin d'études. IDR (Institut du développement rural), Université de Ouagadougou, Burkina Faso. 80 pp.