Reproductive performance of rabbit does on concentrate to forage (Stylosanthes hamata) combinations

Nulliparous New Zealand White X California crossbred does were used to study the utilization of concentrate and Stylosanthes hamata (stylo) combinations by breeding does during pregnancy and lactation. The treatments comprised the following concentrate and stylo combinations (%) respectively: (1) 20:80, (2) 40:60, (3) 60:40 and (4) 80:20. The concentrate (22% CP and 2600kcal ME/kg) used was routinely fed to the rabbits. Concentrate and stylo were fed in the morning at 08.00 hour in separate feeders while clean water was supplied daily in earthen pots. The does were mated to intact bucks after a two weeks adjustment period.

Results indicated total feed intake during pregnancy was higher for treatment 40:60 than 20:80. Feed intake was lower for 20:80 and 40:60 than 60:40 treatment. Total feed intake during lactation was higher for 20:80 and 40:60 treatments than 60:40 and 20:80 treatments. Relative feed intake increased during pregnancy but decreased during lactation with increase in concentrate level. Relative feed intake was 65-81% during pregnancy and 75-59% during lactation. Doe weight gain showed progressive increase during pregnancy and lactation with periods when does maintained their weight. Kindling rate was highest on 60:40 (90%) and lowest on 20:80 and 80:20 (45%) treatments. Litter size at birth, alive at birth, litter weights, kit weight at weaning and litter gain was similar for all treatments. Percent stillbirth was higher for 60:40 and 80:20 treatments than for 20:80 and 40:60 treatments while kit mortality was high for 60:40, 40:60 and 80:20.

It is concluded from this study that does on 60:40 concentrate:stylo combination had overall better performance in terms of feed intake, kindling rate and litter size.

Key words: concentrate, kit mortality, lactation, litter size, pregnancy, stylosanthes

Introduction

Forage legumes are a dependable source of protein feed for animals. The seeds and leaves are rich in nitrogen. Forage legumes are adequately supplied with protein for livestock feeding, even when harvested at an advanced stage of maturity. When an appropriate balance of nutrients is available in forages as in alfalfa meal, the forage can replace grain in rabbit diet, and therefore, reduce concentrate need of rabbits (Aduku et al 1986). Fibre supplies an important source of dietary energy for pregnant animals (Schoknecht 1997). Dietary fibre has positive effects on gut health, welfare and reproductive performance (Johnson et al 2003).

Higher digestibility and utilization of dietary fibre showed great potential for the practical use of various fibrous feeds during gestation and had no adverse effects on reproductive performance (Danielson and Noonan 1975, Pond et al 1985 in Schoknecht 1997. Although the causal link between caloric intake and fertility is well known, precisely how nutritive resources act on reproduction remains unclear, several hormones such as leptin work together in linking growth, metabolism, energy homeostasis, and reproduction (Boiti 2004).

Stylosanthes hamata (verano stylo) is a widely used pasture legume for raising cattle, sheep and goats (Kexian Yi 2000). It is cut and fed, used to make hay and stylosanthes leaf meal (SLM) for feeding poultry, cattle, swine and rabbits. Stylo is fairly palatable to rabbits (Aduku et al 1989). Bamikole and Ezenwa (1999) and Iyeghe-Erakpotobor (2006) fed verano stylo to growing rabbits and obtained good performance. There is however, a dearth of information on performance of breeding rabbits on stylosanthes. The objective of this study was to evaluate the reproductive performance of rabbit does fed concentrate and Stylosanthes hamata combinations.

Materials and methods

Animals and experimental design

Nulliparous New Zealand White X California crossbred does were individually kept in metal cages of dimensions 120 x 60 x 50 cm. Eighty does were allocated to four treatments in a completely randomized design (n=20/treatment). The treatments comprised of concentrate and Stylosanthes hamata (stylo) combinations (%) respectively: (1) 20:80, (2) 40:60, (3) 60:40 and (4) 80:20. The concentrate (22% CP and 2600kcal ME/kg) contained (%): maize 39.24, groundnut cake 42.26, maize offal 15.00, bone meal 3.0, salt 0.25 and vitamin/mineral premix 0.25. Stylo was harvested, dried at room temperature and chopped before feeding. The concentrate and stylo (Table 1) were fed in the morning at 08.00 hour in separate feeders while clean water was supplied daily in earthen pots (Figures 1 and 2).

Table 1. Nutrient composition of concentrate and Stylosanthes hamata hay fed to does
	Dry matter	Ash	Ether extract	Crude fibre	Crude protein	Nitrogen free extract
Concentrate meal	96.6	6.68	12.6	10.1	21.9	48.6
Stylosanthes hay	98.1	4.04	8.18	50.5	15.1	22.2


Figure 1. Rabbit kits feeding from an earthen feeder. (The waterer is beside the feeder)	Figure 2. Nesting, feeder/waterer earthen pots used for keeping rabbits. (The big pot is the nesting pot while the smaller pots with curved mouth are the feeders and waterers)

A total feed supply of 150g air-dry feed/day was offered the does during pregnancy and 350g air-dry feed/day during lactation. Additional 100g concentrate across the treatments was offered in the second week of lactation because the initial concentrate feed was not sufficient for the does especially those on 20:80 and 40:60. Does were allowed to adjust to the treatments for two weeks before being mated to intact bucks. Feed and forage leftovers and wastage were weighed daily before feeding. Proximate composition of the concentrate diet and stylo were analyzed according to AOAC (1980). Rabbits were weighed at start, mating and at weekly intervals during pregnancy and lactation.

Pregnancy diagnosis was done by palpation and weight method. Does were supplied earthen nesting pots (Figure 2) on day 25 of pregnancy. Crude protein intake of does during pregnancy and lactation was calculated based on total feed intake (concentrate + stylo). Kindling rate of does was calculated as number of does that kindled over number of does mated multiplied by 100. Kits were counted and weighed at birth and at weekly intervals. Kits were weaned at four weeks postpartum. Parameters monitored were doe feed intake and weight gain during pregnancy and lactation, kindling rate, litter size and weights, stillbirths and kit mortality at 7 days postpartum. The study lasted four months.

Statistical analysis

Data collected were subjected to analysis of variance using general linear model procedure (PROC GLM), for completely randomized design. Litter size at weaning was adjusted by removing records of does that lost all their kits in the first week of parturition. Pair-wise difference (pdiff) method was used to separate significant means. Regression between pregnancy weight, lactation weight, birth weight and litter weaning weight and total crude protein intake, total feed intake, concentrate and stylosanthes intakes was conducted (SAS 1987).

Results and discussion

Concentrate and forage intakes (Table 2) during pregnancy and lactation increased with increase in quantity offered. Total feed intake during pregnancy was significantly affected by concentrate:stylo combinations.

Table 2. Feed intake of rabbit does fed concentrate and Stylosanthes combinations during pregnancy and lactation
Parameter	Concentrate:Stylosanthes combinations, %				Prob.	SE
Parameter	20:80	40:60	60:40	80:20	Prob.	SE
Pregnancy:
Concentrate intake, g/d	27.9^d	53.5^c	83.2^b	96.4^a	<0.01	1.87
Stylo intake, g/d	69.6^a	56.8^b	36.2^bc	26.5^c	<0.01	2.36
Total feed intake, g/d	97.6^c	110^b	119^a	123^a	<0.01	3.20
Crude protein intake, g/d	16.6^c	20.3^b	23.7^a	25.1^a	0.001	0.58
Lactation
Concentrate intake, g/d	141^c	170^b	187^a	202^a	0.001	8.55
Stylo intake, g/d	203^a	156^b	109^b	64.7^c	0.001	3.29
Total feed intake, g/d	344^a	326^a	297^b	266^c	0.001	9.59
Crude protein intake, g/d	61.5^a	60.8^a	57.5^ab	53.9^b	0.05	2.01
^abMeans with different superscripts along rows are significantly different.

Rabbit does on 40:60 consumed more total feed than 20:80. Feed intake was lower for 20:80 and 40:60 than 60:40 treatments. Crude protein intake increased with increase in concentrate:stylo levels during pregnancy. During lactation, concentrate and stylo intakes increased with increase in quantity offered as during pregnancy. Total feed and crude protein intakes decreased with increase in concentrate level. Feed intake was higher for 20:80 and 40:60 treatments than 60:40 and 20:80 treatments. This could be as a result of higher feed intake of does as concentrate level increased during pregnancy while doe intake reduced during lactation. Another reason could be the high protein content of stylo and higher intake of stylo during lactation compared with pregnancy. Iyeghe-Erakpotobor and Muhammad (2007) reported similar decrease in total feed intake as concentrate level increased by rabbit does offered concentrate-lablab combinations during the second and third weeks of lactation.

Relative feed intake (Figure 3) was 65-81% during pregnancy and 75-59% during lactation and increased during pregnancy with increase in concentrate level but decreased during lactation. This is probably as a result of the increase in concentrate offered during lactation.

Rabbit does showed progressive gain in weight (Figure 4) with periods of stagnation when they maintained their weights throughout the study period. There were however, large variations in weight gain of rabbits especially during lactation.

Reason for negative weight gain during the first week of pregnancy is not clear but could be as a result of adjustment of the does to the treatments, though two weeks adjustment period was allowed before mating. The does were fed high concentrate level prior to the study which could likely be the reason for the general loss in weight.

Kindling rate of does (Table 3) increased with increase in concentrate level up to 60:40. The highest kindling rate of 90% was obtained on 60:40 and the lowest rate (45%) was obtained for does on 20:80 and 80:20 treatments. Gestation length was similar for 20:80, 40:60 and 60:40 but shorter for does on 80:20 combinations.

Table 3. Reproductive performance of rabbit does fed concentrate-Stylosanthes combinations
Parameter	Concentrate: Stylosanthes combinations, %
Parameter	20:80	40:60	60:40	80:20	Prob.	SE
Kindling rate	45^c	60^b	90^a	45^c	0.05	0.20
Gestation length, days	29.9^a	30.2^a	30.8^a	27.0^b	0.05	1.01
Litter size at birth	4.20	5.00	4.67	4.80	0.49	0.56
Litter size alive at birth	4.00	4.67	4.50	4.60	0.80	0.68
Litter size at weaning	3.67	4.11	4.25	4.00	0.94	0.62
Litter birth weight, g	225	244	244	250	0.34	29.9
Litter weight at weaning, g	1517	1633	1487	1660	0.94	181
Total litter weight gain, g	1292	1389	1244	1410	0.92	159
Kit weight gain, g	368	363	344	357	0.75	30.1
^abMeans with different superscripts along rows are significantly different.

Aganga et al (1991) reported a reduction in gestation length with increase in dietary protein levels irrespective of source of protein fed to rabbit does while Omole (1982) reported increase in gestation length from 31.2 to 33.7 days when protein content was reduced from 18% to 10% and a progressive but non-significant decrease as protein levels increased from 18 to 26%. Litter size, litter weights, litter and kit weight gains were similar for all the treatments. Iyeghe-Erakpotobor and Muhammad (2007) did not observe significant differences in litter size at birth and alive at birth for rabbit does fed varying levels of concentrate and lablab combinations. Earlier reports seem to indicate variable response of litter size to intake of forages by animals. Johnson et al (2003) indicated out of nineteen studies, thirteen reported increase in litter size when sows received a diet high in non starch polysaccharides during the previous gestation, while six studies reported no difference or a depression in litter size.

Percent stillbirth (Figure 5) was higher (24-25%) for 60:40 and 80:20 treatments than 20:80 (9%) and 40:60 (4%) treatments. Kit mortality was 10-16% for 60:40, 40:60 and 80:20 while 20:80 treatment maintained their kits after birth to 7 days postpartum.

Research has indicated the effect of high nutrient and feed level on kit mortality. A positive correlation between viability of kits and feed intake of does during the three days prior to parturition was reported by Lebas (1974). Protein level of the diet of does during gestation has also been shown to affect kit mortality (Omole 1982).

Relationship between pregnancy weight, lactation weight, birth weight and litter weaning weight and total crude protein intake, total feed intake, concentrate and stylo intakes (Table 4) was not significant.

Table 4. Regression between pregnancy weight, lactation weight, birth weight and litter weaning weight and total crude protein intake, total feed intake, concentrate and stylosanthes intakes
Parameter	Constant	Coefficient	No.	Adjusted R²	Prob.
Pregnancy weight gain ,g
Total crude protein intake	-2.406	1.439	196	0.0001	0.313
Total feed intake	-14.002	0.054	196	0.0029	0.212
Concentrate intake	23.397	0.0118	196	-0.0046	0.342
Stylosanthes intake	16.649	0.039	196	-0.0012	0.380
Lactation weight gain, g
Total crude protein intake	20.225	-0.138	112	-0.0089	0.891
Daily total feed intake	15.438	-0.0109	112	-0.0091	0.954
Total concentrate intake	1222.443	-0.082	112	-0.008	0.779
Birth weight, g
Total feed intake	141.137	0.012	28	-0.0133	0.429
Litter weaning weight, g
Total feed intake	1340.9	0.028	28	-0.0345	0.760
No. – sample size. Prob.= level of significance.

The adjusted R² values were also very low. The same trend was observed when quadratic, cubic and exponential functions were fitted indicating the possibility of the fact that other factors apart from intake influence weight gain during pregnancy and lactation and also birth and litter weights. Factors such as ambient temperature and age especially for adult animals, and mothering ability of the doe also have effect on doe and litter performance. Though nutrition is a very important factor affecting doe and litter performance, other factors that also have important effect are season and maternal environment.

This study indicates that though feeding rabbit does concentrate:stylo combination of 20:80 did not appear to affect doe performance adversely, does on 60:40 concentrate:stylo combination had overall better performance in terms of feed intake, kindling rate and litter size. Rabbit does on 80:20 combination performed least compared with the other treatments.

References

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Aduku A O, Okoh P N, Njoku P C, Orjichie E A, Aganga A A and Dim N I 1986 Evaluation of cowpea (Vigna unguiculata) and peanut (Arachis hypogaea) haulms as feedstuffs for weanling rabbits in a tropical environment (Nigeria). Journal of Applied Rabbit Research 9:178-179

Aganga A A, Aduku A O, Abdulmalik M and Sekoni A 1991 Effect of different protein sources and their levels on the reproduction of breeding rabbits. Journal of Applied Rabbit Research 14:30-33

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Iyeghe-Erakpotobor G T 2006 Performance of grower rabbits fed concentrate and Stylosanthes (verano) combinations under tropical conditions. Animal Science Journal. 77(1):71-78.

Iyeghe-Erakpotobor G T and Muhammad I R 2007 Performance of breeding does fed concentrate and lablab combinations during pregnancy and lactation. Journal of Animal and Veterinary Advances 6(3):358-363

Kexian Yi 2000 Commercial leaf meal production from stylosanthes in China. Stylo International. September 2000. CSIRO, ACIAR. 4pp.

Pond W G, Yen J T and Varel V H 1985 Effects of level and source of dietary fiber in gestation on reproductive performance and nutrient digestibility in gilts. Nutrition reports international 32:505-514.

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Reproductive performance of rabbit does on concentrate to forage (Stylosanthes hamata) combinations

**G T Iyeghe-Erakpotobor, Y G Adeosun*, A A Sekoni and L O Esievo**

National Animal Production Research Institute, Ahmadu Bello University, PMB 1096, Shika-Zaria, Nigeria

*Department of Animal Science, Ahmadu Bello University, Samaru-Zaria, Nigeria

gtierak@yahoo.com

Abstract

Introduction

Materials and methods

Animals and experimental design

Statistical analysis

Results and discussion

References